[PATCH tty-next 0/2] serial: Add driver for National Instruments UARTs

[PATCH tty-next 0/2] serial: Add driver for National Instruments UARTs

[Brenda Streiff]

This patch series adds a driver for the 16550-like UARTs on National
Instruments (NI) embedded controller hardware.

These UARTs have an interface that is compatble with the TL16C550C (for
which we build on top of 8250_core) but also has extra registers for
the embedded RS-232/RS-485 tranceiver control circuitry.

Brenda Streiff (2):
  dt-bindings: serial: ni,ni16650: add bindings
  serial: 8250: add driver for NI UARTs

 .../bindings/serial/ni,ni16550.yaml           |  53 +++
 MAINTAINERS                                   |   7 +
 drivers/tty/serial/8250/8250_ni.c             | 447 ++++++++++++++++++
 drivers/tty/serial/8250/Kconfig               |   9 +
 drivers/tty/serial/8250/Makefile              |   1 +
 5 files changed, 517 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/serial/ni,ni16550.yaml
 create mode 100644 drivers/tty/serial/8250/8250_ni.c

-- 
2.30.2

[PATCH tty-next 1/2] dt-bindings: serial: ni,ni16650: add bindings

[Brenda Streiff]

Add bindings for the NI 16550 UART.

Signed-off-by: Brenda Streiff <brenda.streiff@ni.com>
Cc: Gratian Crisan <gratian.crisan@ni.com>
Cc: Jason Smith <jason.smith@ni.com>
---
 .../bindings/serial/ni,ni16550.yaml           | 53 +++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/serial/ni,ni16550.yaml

diff --git a/Documentation/devicetree/bindings/serial/ni,ni16550.yaml b/Documentation/devicetree/bindings/serial/ni,ni16550.yaml
new file mode 100644
index 000000000000..4ac1c96726f8
--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/ni,ni16550.yaml
@@ -0,0 +1,53 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/serial/ni,ni16550.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NI 16550 asynchronous serial interface (UART)
+
+maintainers:
+  - Brenda Streiff <brenda.streiff@ni.com>
+
+allOf:
+  - $ref: serial.yaml#
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - ni,ni16550
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clock-frequency: true
+
+  transceiver:
+    items:
+      - enum:
+          - RS-232
+          - RS-485
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clock-frequency
+
+unevaluatedProperties: false
+
+examples:
+  - |
+      serial@80000000 {
+        compatible = "ni,ni16550", "ns16550a";
+        reg = <0x80000000 0x8>;
+        interrupts = <0 30 4>;
+        clock-frequency = <58824000>;
+        transceiver = "RS-485";
+      };
+
+...
-- 
2.30.2

Re: [PATCH tty-next 1/2] dt-bindings: serial: ni,ni16650: add bindings

[Rob Herring]

On Wed, 29 Mar 2023 10:42:34 -0500, Brenda Streiff wrote:
> Add bindings for the NI 16550 UART.
> 
> Signed-off-by: Brenda Streiff <brenda.streiff@ni.com>
> Cc: Gratian Crisan <gratian.crisan@ni.com>
> Cc: Jason Smith <jason.smith@ni.com>
> ---
>  .../bindings/serial/ni,ni16550.yaml           | 53 +++++++++++++++++++
>  1 file changed, 53 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/serial/ni,ni16550.yaml
> 

My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check'
on your patch (DT_CHECKER_FLAGS is new in v5.13):

yamllint warnings/errors:

dtschema/dtc warnings/errors:
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/serial/ni,ni16550.example.dtb: serial@80000000: compatible: ['ni,ni16550', 'ns16550a'] is too long
	From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/serial/ni,ni16550.yaml
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/serial/ni,ni16550.example.dtb: serial@80000000: Unevaluated properties are not allowed ('compatible' was unexpected)
	From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/serial/ni,ni16550.yaml
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/serial/ni,ni16550.example.dtb: serial@80000000: compatible: 'oneOf' conditional failed, one must be fixed:
	['ni,ni16550', 'ns16550a'] is too long
	['ni,ni16550', 'ns16550a'] is too short
	'ns8250' was expected
	'ns16450' was expected
	'ns16550' was expected
	'ns16550a' was expected
	'ns16850' was expected
	'aspeed,ast2400-vuart' was expected
	'aspeed,ast2500-vuart' was expected
	'intel,xscale-uart' was expected
	'mrvl,pxa-uart' was expected
	'nuvoton,wpcm450-uart' was expected
	'nuvoton,npcm750-uart' was expected
	'nvidia,tegra20-uart' was expected
	'nxp,lpc3220-uart' was expected
	'ni,ni16550' is not one of ['exar,xr16l2552', 'exar,xr16l2551', 'exar,xr16l2550']
	'ni,ni16550' is not one of ['altr,16550-FIFO32', 'altr,16550-FIFO64', 'altr,16550-FIFO128', 'fsl,16550-FIFO64', 'fsl,ns16550', 'andestech,uart16550', 'nxp,lpc1850-uart', 'opencores,uart16550-rtlsvn105', 'ti,da830-uart']
	'ni,ni16550' is not one of ['ns16750', 'cavium,octeon-3860-uart', 'xlnx,xps-uart16550-2.00.b', 'ralink,rt2880-uart']
	'ni,ni16550' is not one of ['nuvoton,npcm845-uart']
	'ni,ni16550' is not one of ['ralink,mt7620a-uart', 'ralink,rt3052-uart', 'ralink,rt3883-uart']
	'ni,ni16550' is not one of ['mediatek,mt7622-btif', 'mediatek,mt7623-btif']
	'mrvl,mmp-uart' was expected
	'ni,ni16550' is not one of ['nvidia,tegra30-uart', 'nvidia,tegra114-uart', 'nvidia,tegra124-uart', 'nvidia,tegra210-uart', 'nvidia,tegra186-uart', 'nvidia,tegra194-uart', 'nvidia,tegra234-uart']
	'ralink,rt2880-uart' was expected
	'mediatek,mtk-btif' was expected
	From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/serial/8250.yaml
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/serial/ni,ni16550.example.dtb: serial@80000000: Unevaluated properties are not allowed ('compatible', 'transceiver' were unexpected)
	From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/serial/8250.yaml

doc reference errors (make refcheckdocs):

See https://patchwork.ozlabs.org/project/devicetree-bindings/patch/20230329154235.615349-2-brenda.streiff@ni.com

The base for the series is generally the latest rc1. A different dependency
should be noted in *this* patch.

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure 'yamllint' is installed and dt-schema is up to
date:

pip3 install dtschema --upgrade

Please check and re-submit after running the above command yourself. Note
that DT_SCHEMA_FILES can be set to your schema file to speed up checking
your schema. However, it must be unset to test all examples with your schema.

Re: [PATCH tty-next 1/2] dt-bindings: serial: ni,ni16650: add bindings

[Krzysztof Kozlowski]

On 29/03/2023 17:42, Brenda Streiff wrote:
> Add bindings for the NI 16550 UART.
> 
> Signed-off-by: Brenda Streiff <brenda.streiff@ni.com>
> Cc: Gratian Crisan <gratian.crisan@ni.com>
> Cc: Jason Smith <jason.smith@ni.com>
> ---
>  .../bindings/serial/ni,ni16550.yaml           | 53 +++++++++++++++++++
>  1 file changed, 53 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/serial/ni,ni16550.yaml
> 
> diff --git a/Documentation/devicetree/bindings/serial/ni,ni16550.yaml b/Documentation/devicetree/bindings/serial/ni,ni16550.yaml
> new file mode 100644
> index 000000000000..4ac1c96726f8
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/serial/ni,ni16550.yaml
> @@ -0,0 +1,53 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/serial/ni,ni16550.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: NI 16550 asynchronous serial interface (UART)
> +
> +maintainers:
> +  - Brenda Streiff <brenda.streiff@ni.com>
> +
> +allOf:
> +  - $ref: serial.yaml#
> +
> +properties:
> +  compatible:
> +    items:

You have one item, so remove item.

> +      - enum:
> +          - ni,ni16550

As Rob pointed out - you did not test it at all.

> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  clock-frequency: true
> +
> +  transceiver:

Missing description, type and maybe vendor prefix if this is not a
common property. Explain what's this.

> +    items:

Not a list.

> +      - enum:
> +          - RS-232
> +          - RS-485
> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +  - clock-frequency
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +      serial@80000000 {

Broken indentation.

Use 4 spaces for example indentation.

> +        compatible = "ni,ni16550", "ns16550a";
> +        reg = <0x80000000 0x8>;
> +        interrupts = <0 30 4>;
> +        clock-frequency = <58824000>;
> +        transceiver = "RS-485";
> +      };
> +
> +...

Best regards,
Krzysztof

Re: [PATCH tty-next 1/2] dt-bindings: serial: ni,ni16650: add bindings

[Brenda Streiff]

On 3/30/23 02:28, Krzysztof Kozlowski wrote
>> +      - enum:
>> +          - ni,ni16550
> 
> As Rob pointed out - you did not test it at all.
> 

I did, with dt-schema 2023.1 and the 'make dt_binding_check' command as
described in Documentation/devicetree/bindings/writing-schema.rst
(with no DT_CHECKER_FLAGS, because I was unaware of it until Rob's post)

Is this a documentation gap, or is the DT_CHECKER_FLAGS option slated to
become the default for 'make dt_binding_check' in the future?

Re: [PATCH tty-next 1/2] dt-bindings: serial: ni,ni16650: add bindings

[Krzysztof Kozlowski]

On 31/03/2023 19:59, Brenda Streiff wrote:
> 
> 
> On 3/30/23 02:28, Krzysztof Kozlowski wrote
>>> +      - enum:
>>> +          - ni,ni16550
>>
>> As Rob pointed out - you did not test it at all.
>>
> 
> I did, with dt-schema 2023.1 and the 'make dt_binding_check' command as
> described in Documentation/devicetree/bindings/writing-schema.rst
> (with no DT_CHECKER_FLAGS, because I was unaware of it until Rob's post)

No need to use it...

> 
> Is this a documentation gap, or is the DT_CHECKER_FLAGS option slated to
> become the default for 'make dt_binding_check' in the future?

You shouldn't need any flags. Regular testing shows errors:

ni,ni16550.example.dtb: serial@80000000: compatible: 'oneOf' conditional
failed, one must be fixed:
	['ni,ni16550', 'ns16550a'] is too long
	['ni,ni16550', 'ns16550a'] is too short


Best regards,
Krzysztof

[PATCH tty-next 2/2] serial: 8250: add driver for NI UARTs

[Brenda Streiff]

The National Instruments (NI) 16550 is a 16550-like UART with larger
FIFOs and embedded RS-232/RS-485 transceiver control circuitry. This
patch adds a driver that can operate this UART, which is used for
onboard serial ports in several NI embedded controller designs.

Portions of this driver were originally written by Jaeden Amero and
Karthik Manamcheri, with extensive cleanups and refactors since.

Signed-off-by: Brenda Streiff <brenda.streiff@ni.com>
Cc: Gratian Crisan <gratian.crisan@ni.com>
Cc: Jason Smith <jason.smith@ni.com>
---
 MAINTAINERS                       |   7 +
 drivers/tty/serial/8250/8250_ni.c | 447 ++++++++++++++++++++++++++++++
 drivers/tty/serial/8250/Kconfig   |   9 +
 drivers/tty/serial/8250/Makefile  |   1 +
 4 files changed, 464 insertions(+)
 create mode 100644 drivers/tty/serial/8250/8250_ni.c

diff --git a/MAINTAINERS b/MAINTAINERS
index d8ebab595b2a..c5283a7385fa 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14322,6 +14322,13 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git nand/next
 F:	drivers/mtd/nand/
 F:	include/linux/mtd/*nand*.h
 
+NATIONAL INSTRUMENTS SERIAL DRIVER
+M:	Brenda Streiff <brenda.streiff@ni.com>
+L:	linux-serial@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/serial/ni,ni16550.yaml
+F:	drivers/tty/serial/8250/8250_ni.c
+
 NATIVE INSTRUMENTS USB SOUND INTERFACE DRIVER
 M:	Daniel Mack <zonque@gmail.com>
 L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
diff --git a/drivers/tty/serial/8250/8250_ni.c b/drivers/tty/serial/8250/8250_ni.c
new file mode 100644
index 000000000000..8bd9768576a7
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_ni.c
@@ -0,0 +1,447 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NI 16550 UART Driver
+ *
+ * The National Instruments (NI) 16550 is a UART that is compatible with the
+ * TL16C550C and OX16C950B register interfaces, but has additional functions
+ * for RS-485 transceiver control. This driver implements support for the
+ * additional functionality on top of the standard serial8250 core.
+ *
+ * Copyright 2012-2023 National Instruments Corporation
+ */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/property.h>
+
+#include "8250.h"
+
+/* Extra bits in UART_ACR */
+#define NI16550_ACR_AUTO_DTR_EN			BIT(4)
+
+/* TFS - TX FIFO Size */
+#define NI16550_TFS_OFFSET	0x0C
+/* RFS - RX FIFO Size */
+#define NI16550_RFS_OFFSET	0x0D
+
+/* PMR - Port Mode Register */
+#define NI16550_PMR_OFFSET	0x0E
+/* PMR[1:0] - Port Capabilities */
+#define NI16550_PMR_CAP_MASK			0x03
+#define NI16550_PMR_NOT_IMPL			0x00 /* not implemented */
+#define NI16550_PMR_CAP_RS232			0x01 /* RS-232 capable */
+#define NI16550_PMR_CAP_RS485			0x02 /* RS-485 capable */
+#define NI16550_PMR_CAP_DUAL			0x03 /* dual-port */
+/* PMR[4] - Interface Mode */
+#define NI16550_PMR_MODE_MASK			0x10
+#define NI16550_PMR_MODE_RS232			0x00 /* currently 232 */
+#define NI16550_PMR_MODE_RS485			0x10 /* currently 485 */
+
+/* PCR - Port Control Register */
+#define NI16550_PCR_OFFSET	0x0F
+#define NI16550_PCR_RS422			0x00
+#define NI16550_PCR_ECHO_RS485			0x01
+#define NI16550_PCR_DTR_RS485			0x02
+#define NI16550_PCR_AUTO_RS485			0x03
+#define NI16550_PCR_WIRE_MODE_MASK		0x03
+#define NI16550_PCR_TXVR_ENABLE_BIT		BIT(3)
+#define NI16550_PCR_RS485_TERMINATION_BIT	BIT(6)
+
+/* flags for ni16550_device_info */
+#define NI_HAS_PMR		BIT(0)
+
+struct ni16550_device_info {
+	unsigned int uartclk;
+	uint8_t prescaler;
+	unsigned int flags;
+};
+
+struct ni16550_data {
+	int line;
+};
+
+static int ni16550_enable_transceivers(struct uart_port *port)
+{
+	uint8_t pcr;
+
+	pcr = port->serial_in(port, NI16550_PCR_OFFSET);
+	pcr |= NI16550_PCR_TXVR_ENABLE_BIT;
+	dev_dbg(port->dev, "enable transceivers: write pcr: 0x%02x\n", pcr);
+	port->serial_out(port, NI16550_PCR_OFFSET, pcr);
+
+	return 0;
+}
+
+static int ni16550_disable_transceivers(struct uart_port *port)
+{
+	uint8_t pcr;
+
+	pcr = port->serial_in(port, NI16550_PCR_OFFSET);
+	pcr &= ~NI16550_PCR_TXVR_ENABLE_BIT;
+	dev_dbg(port->dev, "disable transceivers: write pcr: 0x%02x\n", pcr);
+	port->serial_out(port, NI16550_PCR_OFFSET, pcr);
+
+	return 0;
+}
+
+static int ni16550_rs485_config(struct uart_port *port,
+				struct ktermios *termios,
+				struct serial_rs485 *rs485)
+{
+	uint8_t pcr;
+	struct uart_8250_port *up = container_of(port, struct uart_8250_port,
+						 port);
+
+	/* "rs485" should be given to us non-NULL. */
+	if (WARN_ON(rs485 == NULL))
+		return -EINVAL;
+
+	pcr = serial_in(up, NI16550_PCR_OFFSET);
+	pcr &= ~NI16550_PCR_WIRE_MODE_MASK;
+
+	if (rs485->flags & SER_RS485_ENABLED) {
+		/* RS-485 */
+		dev_vdbg(port->dev, "2-wire Auto\n");
+		pcr |= NI16550_PCR_AUTO_RS485;
+		up->acr |= NI16550_ACR_AUTO_DTR_EN;
+	} else {
+		/* RS-422 */
+		dev_vdbg(port->dev, "4-wire\n");
+		pcr |= NI16550_PCR_RS422;
+		up->acr &= ~NI16550_ACR_AUTO_DTR_EN;
+	}
+
+	dev_dbg(port->dev, "config rs485: write pcr: 0x%02x, acr: %02x\n", pcr, up->acr);
+	serial_out(up, NI16550_PCR_OFFSET, pcr);
+	serial_icr_write(up, UART_ACR, up->acr);
+
+	return 0;
+}
+
+static bool is_pmr_rs232_mode(struct uart_8250_port *up)
+{
+	uint8_t pmr = serial_in(up, NI16550_PMR_OFFSET);
+
+	/*
+	 * If the PMR is not implemented, then by default NI UARTs are
+	 * connected to RS-485 transceivers
+	 */
+	if ((pmr & NI16550_PMR_CAP_MASK) == NI16550_PMR_NOT_IMPL)
+		return false;
+
+	if ((pmr & NI16550_PMR_CAP_MASK) == NI16550_PMR_CAP_DUAL)
+		/*
+		 * If the port is dual-mode capable, then read the mode bit
+		 * to know the current mode
+		 */
+		return ((pmr & NI16550_PMR_MODE_MASK)
+					== NI16550_PMR_MODE_RS232);
+	else
+		/*
+		 * If it is not dual-mode capable, then decide based on the
+		 * capability
+		 */
+		return ((pmr & NI16550_PMR_CAP_MASK) == NI16550_PMR_CAP_RS232);
+}
+
+static void ni16550_config_prescaler(struct uart_8250_port *up,
+				     uint8_t prescaler)
+{
+	/*
+	 * Page in the Enhanced Mode Registers
+	 * Sets EFR[4] for Enhanced Mode.
+	 */
+	uint8_t lcr_value;
+	uint8_t efr_value;
+
+	lcr_value = serial_in(up, UART_LCR);
+	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
+
+	efr_value = serial_in(up, UART_EFR);
+	efr_value |= UART_EFR_ECB;
+
+	serial_out(up, UART_EFR, efr_value);
+
+	/* Page out the Enhanced Mode Registers */
+	serial_out(up, UART_LCR, lcr_value);
+
+	/* Set prescaler to CPR register. */
+	serial_out(up, UART_SCR, UART_CPR);
+	serial_out(up, UART_ICR, prescaler);
+}
+
+static const struct serial_rs485 ni16550_rs485_supported = {
+	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND,
+};
+
+static void ni16550_rs485_setup(struct uart_port *port)
+{
+	port->rs485_config = ni16550_rs485_config;
+	port->rs485_supported = ni16550_rs485_supported;
+	/*
+	 * The hardware comes up by default in 2-wire auto mode and we
+	 * set the flags to represent that
+	 */
+	port->rs485.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND;
+}
+
+static int ni16550_port_startup(struct uart_port *port)
+{
+	int ret;
+
+	ret = serial8250_do_startup(port);
+	if (ret)
+		return ret;
+
+	return ni16550_enable_transceivers(port);
+}
+
+static void ni16550_port_shutdown(struct uart_port *port)
+{
+	ni16550_disable_transceivers(port);
+
+	serial8250_do_shutdown(port);
+}
+
+static int ni16550_get_regs(struct platform_device *pdev,
+			    struct uart_port *port)
+{
+	struct resource *regs;
+
+	regs = platform_get_resource(pdev, IORESOURCE_IO, 0);
+	if (regs) {
+		port->iotype = UPIO_PORT;
+		port->iobase = regs->start;
+
+		return 0;
+	}
+
+	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (regs) {
+		port->iotype  = UPIO_MEM;
+		port->mapbase = regs->start;
+		port->mapsize = resource_size(regs);
+		port->flags   |= UPF_IOREMAP;
+
+		port->membase = devm_ioremap(&pdev->dev, port->mapbase,
+					     port->mapsize);
+		if (!port->membase)
+			return -ENOMEM;
+
+		return 0;
+	}
+
+	dev_err(&pdev->dev, "no registers defined\n");
+	return -EINVAL;
+}
+
+static int ni16550_read_fifo_size(struct uart_8250_port *uart, int reg)
+{
+	/*
+	 * Very old implementations don't have the TFS or RFS registers
+	 * defined, so we may read all-0s or all-1s. For such devices,
+	 * assume a FIFO size of 128.
+	 */
+	int value = serial_in(uart, reg);
+
+	if (value == 0x00 || value == 0xFF)
+		return 128;
+
+	return value;
+}
+
+static void ni16550_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+	mctrl |= UART_MCR_CLKSEL;
+
+	serial8250_do_set_mctrl(port, mctrl);
+}
+
+static int ni16550_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct uart_8250_port uart = {};
+	struct ni16550_data *data;
+	const struct ni16550_device_info *info;
+	int ret = 0;
+	int irq;
+	int rs232_property = 0;
+	unsigned int prescaler;
+	const char *transceiver;
+	int txfifosz, rxfifosz;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	spin_lock_init(&uart.port.lock);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	ret = ni16550_get_regs(pdev, &uart.port);
+	if (ret < 0)
+		return ret;
+
+	/* early setup so that serial_in()/serial_out() work */
+	serial8250_set_defaults(&uart);
+
+	info = device_get_match_data(dev);
+
+	uart.port.dev		= dev;
+	uart.port.irq		= irq;
+	uart.port.irqflags	= IRQF_SHARED;
+	uart.port.flags		|= UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
+					| UPF_FIXED_PORT | UPF_FIXED_TYPE;
+	uart.port.startup	= ni16550_port_startup;
+	uart.port.shutdown	= ni16550_port_shutdown;
+
+	/*
+	 * Hardware instantiation of FIFO sizes are held in registers.
+	 */
+	txfifosz = ni16550_read_fifo_size(&uart, NI16550_TFS_OFFSET);
+	rxfifosz = ni16550_read_fifo_size(&uart, NI16550_RFS_OFFSET);
+
+	dev_dbg(dev, "NI 16550 has TX FIFO size %d, RX FIFO size %d\n",
+		txfifosz, rxfifosz);
+
+	uart.port.type		= PORT_16550A;
+	uart.port.fifosize	= txfifosz;
+	uart.tx_loadsz		= txfifosz;
+	uart.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10;
+	uart.capabilities	= UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR;
+
+	/*
+	 * OF device-tree and NIC7A69 ACPI can declare clock-frequency,
+	 * but may be missing for other instantiations, so this is optional.
+	 * If present, override what we've defined in this driver.
+	 */
+	if (info->uartclk)
+		uart.port.uartclk = info->uartclk;
+	device_property_read_u32(dev, "clock-frequency", &uart.port.uartclk);
+	if (!uart.port.uartclk) {
+		dev_err(dev, "unable to determine clock frequency!\n");
+		return -ENODEV;
+	}
+
+	if (info->prescaler)
+		prescaler = info->prescaler;
+	device_property_read_u32(dev, "clock-prescaler", &prescaler);
+
+	if (prescaler != 0) {
+		uart.port.set_mctrl = ni16550_set_mctrl;
+		ni16550_config_prescaler(&uart, (uint8_t)prescaler);
+	}
+
+	/*
+	 * The determination of whether or not this is an RS-485 or RS-232 port
+	 * can come from the "transceiver" device property (if present), or it
+	 * can come from the PMR (if it is present), and otherwise we're solely
+	 * an RS-485 port.
+	 */
+	if (!device_property_read_string(dev, "transceiver", &transceiver)) {
+		rs232_property = strncmp(transceiver, "RS-232", 6) == 0;
+
+		dev_dbg(dev, "port is in %s mode (via device property)",
+			(rs232_property ? "RS-232" : "RS-485"));
+	} else if (info->flags & NI_HAS_PMR) {
+		rs232_property = is_pmr_rs232_mode(&uart);
+
+		dev_dbg(dev, "port is in %s mode (via PMR)",
+			(rs232_property ? "RS-232" : "RS-485"));
+	} else {
+		rs232_property = 0;
+
+		dev_dbg(dev, "port is fixed as RS-485");
+	}
+
+	if (!rs232_property) {
+		/*
+		 * Neither the 'transceiver' property nor the PMR indicate
+		 * that this is an RS-232 port, so it must be an RS-485 one.
+		 */
+		ni16550_rs485_setup(&uart.port);
+	}
+
+	ret = serial8250_register_8250_port(&uart);
+	if (ret < 0)
+		return ret;
+
+	data->line = ret;
+
+	platform_set_drvdata(pdev, data);
+
+	return 0;
+}
+
+static int ni16550_remove(struct platform_device *pdev)
+{
+	struct ni16550_data *data = platform_get_drvdata(pdev);
+
+	serial8250_unregister_port(data->line);
+	return 0;
+}
+
+static const struct ni16550_device_info ni16550_default = { };
+
+static const struct of_device_id ni16550_of_match[] = {
+	{ .compatible = "ni,ni16550", .data = &ni16550_default },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ni16550_of_match);
+
+/* NI 16550 RS-485 Interface */
+static const struct ni16550_device_info nic7750 = {
+	.uartclk = 33333333,
+};
+
+/* NI CVS-145x RS-485 Interface */
+static const struct ni16550_device_info nic7772 = {
+	.uartclk = 1843200,
+	.flags = NI_HAS_PMR,
+};
+
+/* NI cRIO-904x RS-485 Interface */
+static const struct ni16550_device_info nic792b = {
+	/* Sets UART clock rate to 22.222 MHz with 1.125 prescale */
+	.uartclk = 25000000,
+	.prescaler = 0x09,
+};
+
+/* NI sbRIO 96x8 RS-232/485 Interfaces */
+static const struct ni16550_device_info nic7a69 = {
+	/* Set UART clock rate to 29.629 MHz with 1.125 prescale */
+	.uartclk = 29629629,
+	.prescaler = 0x09,
+};
+
+static const struct acpi_device_id ni16550_acpi_match[] = {
+	{ "NIC7750",	(kernel_ulong_t)&nic7750 },
+	{ "NIC7772",	(kernel_ulong_t)&nic7772 },
+	{ "NIC792B",	(kernel_ulong_t)&nic792b },
+	{ "NIC7A69",	(kernel_ulong_t)&nic7a69 },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, ni16550_acpi_match);
+
+static struct platform_driver ni16550_driver = {
+	.driver = {
+		.name = "ni16550",
+		.of_match_table = ni16550_of_match,
+		.acpi_match_table = ACPI_PTR(ni16550_acpi_match),
+	},
+	.probe = ni16550_probe,
+	.remove = ni16550_remove,
+};
+
+module_platform_driver(ni16550_driver);
+
+MODULE_AUTHOR("Jaeden Amero <jaeden.amero@ni.com>");
+MODULE_AUTHOR("Karthik Manamcheri <karthik.manamcheri@ni.com>");
+MODULE_DESCRIPTION("NI 16550 Driver");
+MODULE_LICENSE("GPL");
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 5313aa31930f..c0f3aec51d13 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -565,6 +565,15 @@ config SERIAL_8250_BCM7271
 	  including DMA support and high accuracy BAUD rates, say
 	  Y to this option. If unsure, say N.
 
+config SERIAL_8250_NI
+	tristate "NI 16550 based serial port"
+	depends on SERIAL_8250
+	help
+	  This driver supports the integrated serial ports on National
+          Instruments (NI) controller hardware. This is required for all NI
+          controller models with onboard RS-485 or dual-mode RS-485/RS-232
+          ports.
+
 config SERIAL_OF_PLATFORM
 	tristate "Devicetree based probing for 8250 ports"
 	depends on SERIAL_8250 && OF
diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
index 4fc2fc1f41b6..58dc1b5ff054 100644
--- a/drivers/tty/serial/8250/Makefile
+++ b/drivers/tty/serial/8250/Makefile
@@ -45,6 +45,7 @@ obj-$(CONFIG_SERIAL_8250_PERICOM)	+= 8250_pericom.o
 obj-$(CONFIG_SERIAL_8250_PXA)		+= 8250_pxa.o
 obj-$(CONFIG_SERIAL_8250_TEGRA)		+= 8250_tegra.o
 obj-$(CONFIG_SERIAL_8250_BCM7271)	+= 8250_bcm7271.o
+obj-$(CONFIG_SERIAL_8250_NI)		+= 8250_ni.o
 obj-$(CONFIG_SERIAL_OF_PLATFORM)	+= 8250_of.o
 
 CFLAGS_8250_ingenic.o += -I$(srctree)/scripts/dtc/libfdt
-- 
2.30.2

Re: [PATCH tty-next 2/2] serial: 8250: add driver for NI UARTs

[Greg Kroah-Hartman]

On Wed, Mar 29, 2023 at 10:42:35AM -0500, Brenda Streiff wrote:
> The National Instruments (NI) 16550 is a 16550-like UART with larger
> FIFOs and embedded RS-232/RS-485 transceiver control circuitry. This
> patch adds a driver that can operate this UART, which is used for
> onboard serial ports in several NI embedded controller designs.

People are still making new 8250-like variants with different ways of
controlling them these days?  That's the design pattern that will not
die, or at least, it keeps getting a "value-add" :(

> 
> Portions of this driver were originally written by Jaeden Amero and
> Karthik Manamcheri, with extensive cleanups and refactors since.
> 
> Signed-off-by: Brenda Streiff <brenda.streiff@ni.com>
> Cc: Gratian Crisan <gratian.crisan@ni.com>
> Cc: Jason Smith <jason.smith@ni.com>
> ---
>  MAINTAINERS                       |   7 +
>  drivers/tty/serial/8250/8250_ni.c | 447 ++++++++++++++++++++++++++++++
>  drivers/tty/serial/8250/Kconfig   |   9 +
>  drivers/tty/serial/8250/Makefile  |   1 +
>  4 files changed, 464 insertions(+)
>  create mode 100644 drivers/tty/serial/8250/8250_ni.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d8ebab595b2a..c5283a7385fa 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -14322,6 +14322,13 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git nand/next
>  F:	drivers/mtd/nand/
>  F:	include/linux/mtd/*nand*.h
>  
> +NATIONAL INSTRUMENTS SERIAL DRIVER
> +M:	Brenda Streiff <brenda.streiff@ni.com>
> +L:	linux-serial@vger.kernel.org
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/serial/ni,ni16550.yaml
> +F:	drivers/tty/serial/8250/8250_ni.c
> +
>  NATIVE INSTRUMENTS USB SOUND INTERFACE DRIVER
>  M:	Daniel Mack <zonque@gmail.com>
>  L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
> diff --git a/drivers/tty/serial/8250/8250_ni.c b/drivers/tty/serial/8250/8250_ni.c
> new file mode 100644
> index 000000000000..8bd9768576a7
> --- /dev/null
> +++ b/drivers/tty/serial/8250/8250_ni.c
> @@ -0,0 +1,447 @@
> +// SPDX-License-Identifier: GPL-2.0+

Do you really mean "+"?  Sorry, I have to ask.

> +/*
> + * NI 16550 UART Driver
> + *
> + * The National Instruments (NI) 16550 is a UART that is compatible with the
> + * TL16C550C and OX16C950B register interfaces, but has additional functions
> + * for RS-485 transceiver control. This driver implements support for the
> + * additional functionality on top of the standard serial8250 core.
> + *
> + * Copyright 2012-2023 National Instruments Corporation

Um, 2012 and every year since then?  You all have had an out-of-tree
driver for 11+ years that has been constantly updated every year?

> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/device.h>
> +#include <linux/io.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/property.h>
> +
> +#include "8250.h"
> +
> +/* Extra bits in UART_ACR */
> +#define NI16550_ACR_AUTO_DTR_EN			BIT(4)
> +
> +/* TFS - TX FIFO Size */
> +#define NI16550_TFS_OFFSET	0x0C
> +/* RFS - RX FIFO Size */
> +#define NI16550_RFS_OFFSET	0x0D
> +
> +/* PMR - Port Mode Register */
> +#define NI16550_PMR_OFFSET	0x0E
> +/* PMR[1:0] - Port Capabilities */
> +#define NI16550_PMR_CAP_MASK			0x03
> +#define NI16550_PMR_NOT_IMPL			0x00 /* not implemented */
> +#define NI16550_PMR_CAP_RS232			0x01 /* RS-232 capable */
> +#define NI16550_PMR_CAP_RS485			0x02 /* RS-485 capable */
> +#define NI16550_PMR_CAP_DUAL			0x03 /* dual-port */
> +/* PMR[4] - Interface Mode */
> +#define NI16550_PMR_MODE_MASK			0x10
> +#define NI16550_PMR_MODE_RS232			0x00 /* currently 232 */
> +#define NI16550_PMR_MODE_RS485			0x10 /* currently 485 */
> +
> +/* PCR - Port Control Register */
> +#define NI16550_PCR_OFFSET	0x0F
> +#define NI16550_PCR_RS422			0x00
> +#define NI16550_PCR_ECHO_RS485			0x01
> +#define NI16550_PCR_DTR_RS485			0x02
> +#define NI16550_PCR_AUTO_RS485			0x03
> +#define NI16550_PCR_WIRE_MODE_MASK		0x03
> +#define NI16550_PCR_TXVR_ENABLE_BIT		BIT(3)
> +#define NI16550_PCR_RS485_TERMINATION_BIT	BIT(6)
> +
> +/* flags for ni16550_device_info */
> +#define NI_HAS_PMR		BIT(0)
> +
> +struct ni16550_device_info {
> +	unsigned int uartclk;
> +	uint8_t prescaler;

Please use proper kernel types, u8.

> +	unsigned int flags;

And that's a horrible packing, do you mean to have those offsets?

And why "unsigned int", don't you mean "u64" or "u32"?

> +};
> +
> +struct ni16550_data {
> +	int line;
> +};
> +
> +static int ni16550_enable_transceivers(struct uart_port *port)
> +{
> +	uint8_t pcr;
> +
> +	pcr = port->serial_in(port, NI16550_PCR_OFFSET);
> +	pcr |= NI16550_PCR_TXVR_ENABLE_BIT;
> +	dev_dbg(port->dev, "enable transceivers: write pcr: 0x%02x\n", pcr);
> +	port->serial_out(port, NI16550_PCR_OFFSET, pcr);
> +
> +	return 0;
> +}
> +
> +static int ni16550_disable_transceivers(struct uart_port *port)
> +{
> +	uint8_t pcr;
> +
> +	pcr = port->serial_in(port, NI16550_PCR_OFFSET);
> +	pcr &= ~NI16550_PCR_TXVR_ENABLE_BIT;
> +	dev_dbg(port->dev, "disable transceivers: write pcr: 0x%02x\n", pcr);
> +	port->serial_out(port, NI16550_PCR_OFFSET, pcr);
> +
> +	return 0;
> +}
> +
> +static int ni16550_rs485_config(struct uart_port *port,
> +				struct ktermios *termios,
> +				struct serial_rs485 *rs485)
> +{
> +	uint8_t pcr;
> +	struct uart_8250_port *up = container_of(port, struct uart_8250_port,
> +						 port);
> +
> +	/* "rs485" should be given to us non-NULL. */
> +	if (WARN_ON(rs485 == NULL))

Can this ever happen?  If not, don't check for it, otherwise you just
rebooted a machine that has panic-on-warn enabled :(

> +		return -EINVAL;

Or better yet, handle the case and return the error, why the WARN_ON()?

> +
> +	pcr = serial_in(up, NI16550_PCR_OFFSET);
> +	pcr &= ~NI16550_PCR_WIRE_MODE_MASK;
> +
> +	if (rs485->flags & SER_RS485_ENABLED) {
> +		/* RS-485 */
> +		dev_vdbg(port->dev, "2-wire Auto\n");

Why "dev_vdbg()"?  Why not just "dev_dbg()"?  When are you going to
rebuild this code to enable the "dev_vdbg()" lines?

> +		pcr |= NI16550_PCR_AUTO_RS485;
> +		up->acr |= NI16550_ACR_AUTO_DTR_EN;
> +	} else {
> +		/* RS-422 */
> +		dev_vdbg(port->dev, "4-wire\n");
> +		pcr |= NI16550_PCR_RS422;
> +		up->acr &= ~NI16550_ACR_AUTO_DTR_EN;
> +	}
> +
> +	dev_dbg(port->dev, "config rs485: write pcr: 0x%02x, acr: %02x\n", pcr, up->acr);
> +	serial_out(up, NI16550_PCR_OFFSET, pcr);
> +	serial_icr_write(up, UART_ACR, up->acr);
> +
> +	return 0;
> +}
> +
> +static bool is_pmr_rs232_mode(struct uart_8250_port *up)
> +{
> +	uint8_t pmr = serial_in(up, NI16550_PMR_OFFSET);

Again, proper kernel types everywhere please "u8".

> +
> +	/*
> +	 * If the PMR is not implemented, then by default NI UARTs are
> +	 * connected to RS-485 transceivers
> +	 */
> +	if ((pmr & NI16550_PMR_CAP_MASK) == NI16550_PMR_NOT_IMPL)
> +		return false;
> +
> +	if ((pmr & NI16550_PMR_CAP_MASK) == NI16550_PMR_CAP_DUAL)
> +		/*
> +		 * If the port is dual-mode capable, then read the mode bit
> +		 * to know the current mode
> +		 */
> +		return ((pmr & NI16550_PMR_MODE_MASK)
> +					== NI16550_PMR_MODE_RS232);
> +	else
> +		/*
> +		 * If it is not dual-mode capable, then decide based on the
> +		 * capability
> +		 */
> +		return ((pmr & NI16550_PMR_CAP_MASK) == NI16550_PMR_CAP_RS232);
> +}
> +
> +static void ni16550_config_prescaler(struct uart_8250_port *up,
> +				     uint8_t prescaler)
> +{
> +	/*
> +	 * Page in the Enhanced Mode Registers
> +	 * Sets EFR[4] for Enhanced Mode.
> +	 */
> +	uint8_t lcr_value;
> +	uint8_t efr_value;
> +
> +	lcr_value = serial_in(up, UART_LCR);
> +	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
> +
> +	efr_value = serial_in(up, UART_EFR);
> +	efr_value |= UART_EFR_ECB;
> +
> +	serial_out(up, UART_EFR, efr_value);
> +
> +	/* Page out the Enhanced Mode Registers */
> +	serial_out(up, UART_LCR, lcr_value);
> +
> +	/* Set prescaler to CPR register. */
> +	serial_out(up, UART_SCR, UART_CPR);
> +	serial_out(up, UART_ICR, prescaler);
> +}
> +
> +static const struct serial_rs485 ni16550_rs485_supported = {
> +	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND,
> +};
> +
> +static void ni16550_rs485_setup(struct uart_port *port)
> +{
> +	port->rs485_config = ni16550_rs485_config;
> +	port->rs485_supported = ni16550_rs485_supported;
> +	/*
> +	 * The hardware comes up by default in 2-wire auto mode and we
> +	 * set the flags to represent that
> +	 */
> +	port->rs485.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND;
> +}
> +
> +static int ni16550_port_startup(struct uart_port *port)
> +{
> +	int ret;
> +
> +	ret = serial8250_do_startup(port);
> +	if (ret)
> +		return ret;
> +
> +	return ni16550_enable_transceivers(port);
> +}
> +
> +static void ni16550_port_shutdown(struct uart_port *port)
> +{
> +	ni16550_disable_transceivers(port);
> +
> +	serial8250_do_shutdown(port);
> +}
> +
> +static int ni16550_get_regs(struct platform_device *pdev,
> +			    struct uart_port *port)
> +{
> +	struct resource *regs;
> +
> +	regs = platform_get_resource(pdev, IORESOURCE_IO, 0);
> +	if (regs) {
> +		port->iotype = UPIO_PORT;
> +		port->iobase = regs->start;
> +
> +		return 0;
> +	}
> +
> +	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (regs) {
> +		port->iotype  = UPIO_MEM;
> +		port->mapbase = regs->start;
> +		port->mapsize = resource_size(regs);
> +		port->flags   |= UPF_IOREMAP;
> +
> +		port->membase = devm_ioremap(&pdev->dev, port->mapbase,
> +					     port->mapsize);
> +		if (!port->membase)
> +			return -ENOMEM;
> +
> +		return 0;
> +	}
> +
> +	dev_err(&pdev->dev, "no registers defined\n");
> +	return -EINVAL;
> +}
> +
> +static int ni16550_read_fifo_size(struct uart_8250_port *uart, int reg)

Why not return "u8"?

> +{
> +	/*
> +	 * Very old implementations don't have the TFS or RFS registers
> +	 * defined, so we may read all-0s or all-1s. For such devices,
> +	 * assume a FIFO size of 128.
> +	 */
> +	int value = serial_in(uart, reg);

Again, u8?


> +
> +	if (value == 0x00 || value == 0xFF)
> +		return 128;
> +
> +	return value;
> +}
> +
> +static void ni16550_set_mctrl(struct uart_port *port, unsigned int mctrl)
> +{
> +	mctrl |= UART_MCR_CLKSEL;
> +
> +	serial8250_do_set_mctrl(port, mctrl);
> +}
> +
> +static int ni16550_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct uart_8250_port uart = {};
> +	struct ni16550_data *data;
> +	const struct ni16550_device_info *info;
> +	int ret = 0;
> +	int irq;
> +	int rs232_property = 0;
> +	unsigned int prescaler;
> +	const char *transceiver;
> +	int txfifosz, rxfifosz;
> +
> +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	spin_lock_init(&uart.port.lock);
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0)
> +		return irq;
> +
> +	ret = ni16550_get_regs(pdev, &uart.port);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* early setup so that serial_in()/serial_out() work */
> +	serial8250_set_defaults(&uart);
> +
> +	info = device_get_match_data(dev);
> +
> +	uart.port.dev		= dev;
> +	uart.port.irq		= irq;
> +	uart.port.irqflags	= IRQF_SHARED;
> +	uart.port.flags		|= UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
> +					| UPF_FIXED_PORT | UPF_FIXED_TYPE;
> +	uart.port.startup	= ni16550_port_startup;
> +	uart.port.shutdown	= ni16550_port_shutdown;
> +
> +	/*
> +	 * Hardware instantiation of FIFO sizes are held in registers.
> +	 */
> +	txfifosz = ni16550_read_fifo_size(&uart, NI16550_TFS_OFFSET);
> +	rxfifosz = ni16550_read_fifo_size(&uart, NI16550_RFS_OFFSET);
> +
> +	dev_dbg(dev, "NI 16550 has TX FIFO size %d, RX FIFO size %d\n",
> +		txfifosz, rxfifosz);
> +
> +	uart.port.type		= PORT_16550A;
> +	uart.port.fifosize	= txfifosz;
> +	uart.tx_loadsz		= txfifosz;
> +	uart.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10;
> +	uart.capabilities	= UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR;
> +
> +	/*
> +	 * OF device-tree and NIC7A69 ACPI can declare clock-frequency,
> +	 * but may be missing for other instantiations, so this is optional.
> +	 * If present, override what we've defined in this driver.
> +	 */
> +	if (info->uartclk)
> +		uart.port.uartclk = info->uartclk;
> +	device_property_read_u32(dev, "clock-frequency", &uart.port.uartclk);
> +	if (!uart.port.uartclk) {
> +		dev_err(dev, "unable to determine clock frequency!\n");
> +		return -ENODEV;
> +	}
> +
> +	if (info->prescaler)
> +		prescaler = info->prescaler;
> +	device_property_read_u32(dev, "clock-prescaler", &prescaler);
> +
> +	if (prescaler != 0) {
> +		uart.port.set_mctrl = ni16550_set_mctrl;
> +		ni16550_config_prescaler(&uart, (uint8_t)prescaler);
> +	}
> +
> +	/*
> +	 * The determination of whether or not this is an RS-485 or RS-232 port
> +	 * can come from the "transceiver" device property (if present), or it
> +	 * can come from the PMR (if it is present), and otherwise we're solely
> +	 * an RS-485 port.
> +	 */
> +	if (!device_property_read_string(dev, "transceiver", &transceiver)) {
> +		rs232_property = strncmp(transceiver, "RS-232", 6) == 0;
> +
> +		dev_dbg(dev, "port is in %s mode (via device property)",
> +			(rs232_property ? "RS-232" : "RS-485"));
> +	} else if (info->flags & NI_HAS_PMR) {
> +		rs232_property = is_pmr_rs232_mode(&uart);
> +
> +		dev_dbg(dev, "port is in %s mode (via PMR)",
> +			(rs232_property ? "RS-232" : "RS-485"));
> +	} else {
> +		rs232_property = 0;
> +
> +		dev_dbg(dev, "port is fixed as RS-485");
> +	}
> +
> +	if (!rs232_property) {
> +		/*
> +		 * Neither the 'transceiver' property nor the PMR indicate
> +		 * that this is an RS-232 port, so it must be an RS-485 one.
> +		 */
> +		ni16550_rs485_setup(&uart.port);
> +	}
> +
> +	ret = serial8250_register_8250_port(&uart);
> +	if (ret < 0)
> +		return ret;
> +
> +	data->line = ret;
> +
> +	platform_set_drvdata(pdev, data);
> +
> +	return 0;
> +}
> +
> +static int ni16550_remove(struct platform_device *pdev)
> +{
> +	struct ni16550_data *data = platform_get_drvdata(pdev);
> +
> +	serial8250_unregister_port(data->line);
> +	return 0;
> +}
> +
> +static const struct ni16550_device_info ni16550_default = { };
> +
> +static const struct of_device_id ni16550_of_match[] = {
> +	{ .compatible = "ni,ni16550", .data = &ni16550_default },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, ni16550_of_match);
> +
> +/* NI 16550 RS-485 Interface */
> +static const struct ni16550_device_info nic7750 = {
> +	.uartclk = 33333333,
> +};
> +
> +/* NI CVS-145x RS-485 Interface */
> +static const struct ni16550_device_info nic7772 = {
> +	.uartclk = 1843200,
> +	.flags = NI_HAS_PMR,
> +};
> +
> +/* NI cRIO-904x RS-485 Interface */
> +static const struct ni16550_device_info nic792b = {
> +	/* Sets UART clock rate to 22.222 MHz with 1.125 prescale */
> +	.uartclk = 25000000,
> +	.prescaler = 0x09,
> +};
> +
> +/* NI sbRIO 96x8 RS-232/485 Interfaces */
> +static const struct ni16550_device_info nic7a69 = {
> +	/* Set UART clock rate to 29.629 MHz with 1.125 prescale */
> +	.uartclk = 29629629,
> +	.prescaler = 0x09,
> +};
> +
> +static const struct acpi_device_id ni16550_acpi_match[] = {
> +	{ "NIC7750",	(kernel_ulong_t)&nic7750 },
> +	{ "NIC7772",	(kernel_ulong_t)&nic7772 },
> +	{ "NIC792B",	(kernel_ulong_t)&nic792b },
> +	{ "NIC7A69",	(kernel_ulong_t)&nic7a69 },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(acpi, ni16550_acpi_match);
> +
> +static struct platform_driver ni16550_driver = {
> +	.driver = {
> +		.name = "ni16550",
> +		.of_match_table = ni16550_of_match,
> +		.acpi_match_table = ACPI_PTR(ni16550_acpi_match),
> +	},
> +	.probe = ni16550_probe,
> +	.remove = ni16550_remove,
> +};
> +
> +module_platform_driver(ni16550_driver);
> +
> +MODULE_AUTHOR("Jaeden Amero <jaeden.amero@ni.com>");
> +MODULE_AUTHOR("Karthik Manamcheri <karthik.manamcheri@ni.com>");
> +MODULE_DESCRIPTION("NI 16550 Driver");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
> index 5313aa31930f..c0f3aec51d13 100644
> --- a/drivers/tty/serial/8250/Kconfig
> +++ b/drivers/tty/serial/8250/Kconfig
> @@ -565,6 +565,15 @@ config SERIAL_8250_BCM7271
>  	  including DMA support and high accuracy BAUD rates, say
>  	  Y to this option. If unsure, say N.
>  
> +config SERIAL_8250_NI
> +	tristate "NI 16550 based serial port"
> +	depends on SERIAL_8250
> +	help
> +	  This driver supports the integrated serial ports on National
> +          Instruments (NI) controller hardware. This is required for all NI
> +          controller models with onboard RS-485 or dual-mode RS-485/RS-232
> +          ports.

Module name if built as a module?

thanks,

greg k-h

Re: [PATCH tty-next 2/2] serial: 8250: add driver for NI UARTs

[Brenda Streiff]

On 3/29/23 11:30, Greg Kroah-Hartman wrote:

Hi Greg, thanks for looking at this so quickly.

> On Wed, Mar 29, 2023 at 10:42:35AM -0500, Brenda Streiff wrote:
>> The National Instruments (NI) 16550 is a 16550-like UART with larger
>> FIFOs and embedded RS-232/RS-485 transceiver control circuitry. This
>> patch adds a driver that can operate this UART, which is used for
>> onboard serial ports in several NI embedded controller designs.
> 
> People are still making new 8250-like variants with different ways of
> controlling them these days?  That's the design pattern that will not
> die, or at least, it keeps getting a "value-add" :(
> 

This design has been on NI devices in some form since at least around
2009, so I hesitate to call it "new". But yes, it does seem like if you
let a hardware engineer be bored for too long you'll end up with a new
8250, a new SPI controller, or a new I2C controller. Sometimes all three!

>> +++ b/drivers/tty/serial/8250/8250_ni.c
>> @@ -0,0 +1,447 @@
>> +// SPDX-License-Identifier: GPL-2.0+
> 
> Do you really mean "+"?  Sorry, I have to ask.

It sits atop 8250_core.c which is marked as GPL-2.0+, and has been marked
as 'any later version' since it had been added to our tree [1] in the
pre-SPDX times.

[1] https://github.com/ni/linux/commit/6bf16de92cc9

>> +/*
>> + * NI 16550 UART Driver
>> + *
>> + * The National Instruments (NI) 16550 is a UART that is compatible with the
>> + * TL16C550C and OX16C950B register interfaces, but has additional functions
>> + * for RS-485 transceiver control. This driver implements support for the
>> + * additional functionality on top of the standard serial8250 core.
>> + *
>> + * Copyright 2012-2023 National Instruments Corporation
> 
> Um, 2012 and every year since then?  You all have had an out-of-tree
> driver for 11+ years that has been constantly updated every year?

It's been in _a_ tree-- NI's-- in some form for that long. But... yes,
this is correct.

I can't defend having it out of mainline for so long as having been a
good or wise choice, but that is the state of things.

>> +/* flags for ni16550_device_info */
>> +#define NI_HAS_PMR		BIT(0)
>> +
>> +struct ni16550_device_info {
>> +	unsigned int uartclk;
>> +	uint8_t prescaler;
> 
> Please use proper kernel types, u8.

Okay, did a scrub to remove C99 types.

> 
>> +	unsigned int flags;
> 
> And that's a horrible packing, do you mean to have those offsets?

I wasn't thinking about struct packing here, but yes these can be
reordered.

> 
> And why "unsigned int", don't you mean "u64" or "u32"?

For "uartclk" it was because struct uart_port::uartclk is an "unsigned
int" in include/linux/serial_8250.h.

For "flags" it was because there are loads of other places under
drivers/tty/serial/8250/* that use "flags" as an "unsigned int" or an
"unsigned long". Using a width-named types would be clearer (and I
don't mind making the change), but I tried to adhere to the convention
in nearby code.


>> +static int ni16550_rs485_config(struct uart_port *port,
>> +				struct ktermios *termios,
>> +				struct serial_rs485 *rs485)
>> +{
>> +	uint8_t pcr;
>> +	struct uart_8250_port *up = container_of(port, struct uart_8250_port,
>> +						 port);
>> +
>> +	/* "rs485" should be given to us non-NULL. */
>> +	if (WARN_ON(rs485 == NULL))
> 
> Can this ever happen?  If not, don't check for it, otherwise you just
> rebooted a machine that has panic-on-warn enabled :(
> 
>> +		return -EINVAL;
> 
> Or better yet, handle the case and return the error, why the WARN_ON()?

I'm not sure if this was ever possible, but it doesn't look like any of
the other drivers supporting rs485_config do this check today. Into the
dustbin it goes.

Re: [PATCH tty-next 2/2] serial: 8250: add driver for NI UARTs

[kernel test robot]

Hi Brenda,

I love your patch! Perhaps something to improve:

[auto build test WARNING on tty/tty-testing]
[also build test WARNING on tty/tty-next tty/tty-linus linus/master v6.3-rc4 next-20230330]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Brenda-Streiff/serial-8250-add-driver-for-NI-UARTs/20230330-010726
base:   https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git tty-testing
patch link:    https://lore.kernel.org/r/20230329154235.615349-3-brenda.streiff%40ni.com
patch subject: [PATCH tty-next 2/2] serial: 8250: add driver for NI UARTs
config: powerpc-allyesconfig (https://download.01.org/0day-ci/archive/20230330/202303301456.qfo36qC0-lkp@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project 67409911353323ca5edf2049ef0df54132fa1ca7)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install powerpc cross compiling tool for clang build
        # apt-get install binutils-powerpc-linux-gnu
        # https://github.com/intel-lab-lkp/linux/commit/6c50983e6760b2db288e3f8b7254cea537c0f052
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Brenda-Streiff/serial-8250-add-driver-for-NI-UARTs/20230330-010726
        git checkout 6c50983e6760b2db288e3f8b7254cea537c0f052
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=powerpc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash drivers/tty/serial/8250/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202303301456.qfo36qC0-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/tty/serial/8250/8250_ni.c:423:36: warning: unused variable 'ni16550_acpi_match' [-Wunused-const-variable]
   static const struct acpi_device_id ni16550_acpi_match[] = {
                                      ^
   1 warning generated.


vim +/ni16550_acpi_match +423 drivers/tty/serial/8250/8250_ni.c

   422	
 > 423	static const struct acpi_device_id ni16550_acpi_match[] = {
   424		{ "NIC7750",	(kernel_ulong_t)&nic7750 },
   425		{ "NIC7772",	(kernel_ulong_t)&nic7772 },
   426		{ "NIC792B",	(kernel_ulong_t)&nic792b },
   427		{ "NIC7A69",	(kernel_ulong_t)&nic7a69 },
   428		{ },
   429	};
   430	MODULE_DEVICE_TABLE(acpi, ni16550_acpi_match);
   431	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests

Re: [PATCH tty-next 2/2] serial: 8250: add driver for NI UARTs

[Krzysztof Kozlowski]

On 29/03/2023 17:42, Brenda Streiff wrote:
> The National Instruments (NI) 16550 is a 16550-like UART with larger
> FIFOs and embedded RS-232/RS-485 transceiver control circuitry. This
> patch adds a driver that can operate this UART, which is used for
> onboard serial ports in several NI embedded controller designs.


> +
> +static const struct acpi_device_id ni16550_acpi_match[] = {
> +	{ "NIC7750",	(kernel_ulong_t)&nic7750 },
> +	{ "NIC7772",	(kernel_ulong_t)&nic7772 },
> +	{ "NIC792B",	(kernel_ulong_t)&nic792b },
> +	{ "NIC7A69",	(kernel_ulong_t)&nic7a69 },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(acpi, ni16550_acpi_match);

Looks like should spark warnings on allyesconfig with !ACPI.

Best regards,
Krzysztof

Re: [PATCH tty-next 2/2] serial: 8250: add driver for NI UARTs

[Ilpo Järvinen]

On Wed, 29 Mar 2023, Brenda Streiff wrote:

> The National Instruments (NI) 16550 is a 16550-like UART with larger
> FIFOs and embedded RS-232/RS-485 transceiver control circuitry. This
> patch adds a driver that can operate this UART, which is used for
> onboard serial ports in several NI embedded controller designs.
> 
> Portions of this driver were originally written by Jaeden Amero and
> Karthik Manamcheri, with extensive cleanups and refactors since.
> 
> Signed-off-by: Brenda Streiff <brenda.streiff@ni.com>
> Cc: Gratian Crisan <gratian.crisan@ni.com>
> Cc: Jason Smith <jason.smith@ni.com>
> ---
>  MAINTAINERS                       |   7 +
>  drivers/tty/serial/8250/8250_ni.c | 447 ++++++++++++++++++++++++++++++
>  drivers/tty/serial/8250/Kconfig   |   9 +
>  drivers/tty/serial/8250/Makefile  |   1 +
>  4 files changed, 464 insertions(+)
>  create mode 100644 drivers/tty/serial/8250/8250_ni.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d8ebab595b2a..c5283a7385fa 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -14322,6 +14322,13 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git nand/next
>  F:	drivers/mtd/nand/
>  F:	include/linux/mtd/*nand*.h
>  
> +NATIONAL INSTRUMENTS SERIAL DRIVER
> +M:	Brenda Streiff <brenda.streiff@ni.com>
> +L:	linux-serial@vger.kernel.org
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/serial/ni,ni16550.yaml
> +F:	drivers/tty/serial/8250/8250_ni.c
> +
>  NATIVE INSTRUMENTS USB SOUND INTERFACE DRIVER
>  M:	Daniel Mack <zonque@gmail.com>
>  L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
> diff --git a/drivers/tty/serial/8250/8250_ni.c b/drivers/tty/serial/8250/8250_ni.c
> new file mode 100644
> index 000000000000..8bd9768576a7
> --- /dev/null
> +++ b/drivers/tty/serial/8250/8250_ni.c
> @@ -0,0 +1,447 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * NI 16550 UART Driver
> + *
> + * The National Instruments (NI) 16550 is a UART that is compatible with the
> + * TL16C550C and OX16C950B register interfaces, but has additional functions
> + * for RS-485 transceiver control. This driver implements support for the
> + * additional functionality on top of the standard serial8250 core.
> + *
> + * Copyright 2012-2023 National Instruments Corporation
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/device.h>
> +#include <linux/io.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/property.h>
> +
> +#include "8250.h"
> +
> +/* Extra bits in UART_ACR */
> +#define NI16550_ACR_AUTO_DTR_EN			BIT(4)
> +
> +/* TFS - TX FIFO Size */
> +#define NI16550_TFS_OFFSET	0x0C
> +/* RFS - RX FIFO Size */
> +#define NI16550_RFS_OFFSET	0x0D
> +
> +/* PMR - Port Mode Register */
> +#define NI16550_PMR_OFFSET	0x0E
> +/* PMR[1:0] - Port Capabilities */
> +#define NI16550_PMR_CAP_MASK			0x03
> +#define NI16550_PMR_NOT_IMPL			0x00 /* not implemented */
> +#define NI16550_PMR_CAP_RS232			0x01 /* RS-232 capable */
> +#define NI16550_PMR_CAP_RS485			0x02 /* RS-485 capable */
> +#define NI16550_PMR_CAP_DUAL			0x03 /* dual-port */
> +/* PMR[4] - Interface Mode */
> +#define NI16550_PMR_MODE_MASK			0x10
> +#define NI16550_PMR_MODE_RS232			0x00 /* currently 232 */
> +#define NI16550_PMR_MODE_RS485			0x10 /* currently 485 */
> +
> +/* PCR - Port Control Register */
> +#define NI16550_PCR_OFFSET	0x0F
> +#define NI16550_PCR_RS422			0x00
> +#define NI16550_PCR_ECHO_RS485			0x01
> +#define NI16550_PCR_DTR_RS485			0x02
> +#define NI16550_PCR_AUTO_RS485			0x03
> +#define NI16550_PCR_WIRE_MODE_MASK		0x03
> +#define NI16550_PCR_TXVR_ENABLE_BIT		BIT(3)
> +#define NI16550_PCR_RS485_TERMINATION_BIT	BIT(6)
> +
> +/* flags for ni16550_device_info */
> +#define NI_HAS_PMR		BIT(0)
> +
> +struct ni16550_device_info {
> +	unsigned int uartclk;
> +	uint8_t prescaler;
> +	unsigned int flags;
> +};
> +
> +struct ni16550_data {
> +	int line;
> +};
> +
> +static int ni16550_enable_transceivers(struct uart_port *port)
> +{
> +	uint8_t pcr;
> +
> +	pcr = port->serial_in(port, NI16550_PCR_OFFSET);
> +	pcr |= NI16550_PCR_TXVR_ENABLE_BIT;
> +	dev_dbg(port->dev, "enable transceivers: write pcr: 0x%02x\n", pcr);
> +	port->serial_out(port, NI16550_PCR_OFFSET, pcr);
> +
> +	return 0;
> +}
> +
> +static int ni16550_disable_transceivers(struct uart_port *port)
> +{
> +	uint8_t pcr;
> +
> +	pcr = port->serial_in(port, NI16550_PCR_OFFSET);
> +	pcr &= ~NI16550_PCR_TXVR_ENABLE_BIT;
> +	dev_dbg(port->dev, "disable transceivers: write pcr: 0x%02x\n", pcr);
> +	port->serial_out(port, NI16550_PCR_OFFSET, pcr);
> +
> +	return 0;
> +}
> +
> +static int ni16550_rs485_config(struct uart_port *port,
> +				struct ktermios *termios,
> +				struct serial_rs485 *rs485)
> +{
> +	uint8_t pcr;
> +	struct uart_8250_port *up = container_of(port, struct uart_8250_port,
> +						 port);

Reverse declaration order.

> +
> +	/* "rs485" should be given to us non-NULL. */
> +	if (WARN_ON(rs485 == NULL))
> +		return -EINVAL;
> +
> +	pcr = serial_in(up, NI16550_PCR_OFFSET);
> +	pcr &= ~NI16550_PCR_WIRE_MODE_MASK;
> +
> +	if (rs485->flags & SER_RS485_ENABLED) {
> +		/* RS-485 */
> +		dev_vdbg(port->dev, "2-wire Auto\n");
> +		pcr |= NI16550_PCR_AUTO_RS485;
> +		up->acr |= NI16550_ACR_AUTO_DTR_EN;
> +	} else {
> +		/* RS-422 */
> +		dev_vdbg(port->dev, "4-wire\n");
> +		pcr |= NI16550_PCR_RS422;
> +		up->acr &= ~NI16550_ACR_AUTO_DTR_EN;
> +	}
> +
> +	dev_dbg(port->dev, "config rs485: write pcr: 0x%02x, acr: %02x\n", pcr, up->acr);
> +	serial_out(up, NI16550_PCR_OFFSET, pcr);
> +	serial_icr_write(up, UART_ACR, up->acr);
> +
> +	return 0;
> +}
> +
> +static bool is_pmr_rs232_mode(struct uart_8250_port *up)
> +{
> +	uint8_t pmr = serial_in(up, NI16550_PMR_OFFSET);
> +
> +	/*
> +	 * If the PMR is not implemented, then by default NI UARTs are
> +	 * connected to RS-485 transceivers
> +	 */
> +	if ((pmr & NI16550_PMR_CAP_MASK) == NI16550_PMR_NOT_IMPL)
> +		return false;
> +
> +	if ((pmr & NI16550_PMR_CAP_MASK) == NI16550_PMR_CAP_DUAL)
> +		/*
> +		 * If the port is dual-mode capable, then read the mode bit
> +		 * to know the current mode
> +		 */
> +		return ((pmr & NI16550_PMR_MODE_MASK)
> +					== NI16550_PMR_MODE_RS232);

Extra parenthesis.

> +	else
> +		/*
> +		 * If it is not dual-mode capable, then decide based on the
> +		 * capability
> +		 */
> +		return ((pmr & NI16550_PMR_CAP_MASK) == NI16550_PMR_CAP_RS232);

Extra parenthesis.

Wouldn't it be easier to add do the anding only once into the local 
variable rather than 4 times?


> +}
> +
> +static void ni16550_config_prescaler(struct uart_8250_port *up,
> +				     uint8_t prescaler)
> +{
> +	/*
> +	 * Page in the Enhanced Mode Registers
> +	 * Sets EFR[4] for Enhanced Mode.
> +	 */
> +	uint8_t lcr_value;
> +	uint8_t efr_value;
> +
> +	lcr_value = serial_in(up, UART_LCR);
> +	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
> +
> +	efr_value = serial_in(up, UART_EFR);
> +	efr_value |= UART_EFR_ECB;
> +
> +	serial_out(up, UART_EFR, efr_value);
> +
> +	/* Page out the Enhanced Mode Registers */
> +	serial_out(up, UART_LCR, lcr_value);
> +
> +	/* Set prescaler to CPR register. */
> +	serial_out(up, UART_SCR, UART_CPR);
> +	serial_out(up, UART_ICR, prescaler);
> +}
> +
> +static const struct serial_rs485 ni16550_rs485_supported = {
> +	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND,
> +};
> +
> +static void ni16550_rs485_setup(struct uart_port *port)
> +{
> +	port->rs485_config = ni16550_rs485_config;
> +	port->rs485_supported = ni16550_rs485_supported;
> +	/*
> +	 * The hardware comes up by default in 2-wire auto mode and we
> +	 * set the flags to represent that
> +	 */
> +	port->rs485.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND;
> +}
> +
> +static int ni16550_port_startup(struct uart_port *port)
> +{
> +	int ret;
> +
> +	ret = serial8250_do_startup(port);
> +	if (ret)
> +		return ret;
> +
> +	return ni16550_enable_transceivers(port);
> +}
> +
> +static void ni16550_port_shutdown(struct uart_port *port)
> +{
> +	ni16550_disable_transceivers(port);
> +
> +	serial8250_do_shutdown(port);
> +}
> +
> +static int ni16550_get_regs(struct platform_device *pdev,
> +			    struct uart_port *port)
> +{
> +	struct resource *regs;
> +
> +	regs = platform_get_resource(pdev, IORESOURCE_IO, 0);
> +	if (regs) {
> +		port->iotype = UPIO_PORT;
> +		port->iobase = regs->start;
> +
> +		return 0;
> +	}

Do you need the port io?

> +	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (regs) {
> +		port->iotype  = UPIO_MEM;
> +		port->mapbase = regs->start;
> +		port->mapsize = resource_size(regs);
> +		port->flags   |= UPF_IOREMAP;
> +
> +		port->membase = devm_ioremap(&pdev->dev, port->mapbase,
> +					     port->mapsize);
> +		if (!port->membase)
> +			return -ENOMEM;
> +
> +		return 0;
> +	}
> +
> +	dev_err(&pdev->dev, "no registers defined\n");
> +	return -EINVAL;
> +}
> +
> +static int ni16550_read_fifo_size(struct uart_8250_port *uart, int reg)
> +{
> +	/*
> +	 * Very old implementations don't have the TFS or RFS registers
> +	 * defined, so we may read all-0s or all-1s. For such devices,
> +	 * assume a FIFO size of 128.
> +	 */
> +	int value = serial_in(uart, reg);
> +
> +	if (value == 0x00 || value == 0xFF)
> +		return 128;
> +
> +	return value;
> +}
> +
> +static void ni16550_set_mctrl(struct uart_port *port, unsigned int mctrl)
> +{
> +	mctrl |= UART_MCR_CLKSEL;
> +
> +	serial8250_do_set_mctrl(port, mctrl);
> +}
> +
> +static int ni16550_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct uart_8250_port uart = {};
> +	struct ni16550_data *data;
> +	const struct ni16550_device_info *info;
> +	int ret = 0;

Unecessary = 0.

> +	int irq;
> +	int rs232_property = 0;
> +	unsigned int prescaler;
> +	const char *transceiver;
> +	int txfifosz, rxfifosz;

Try to follow reverse xmas-tree order.

> +
> +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	spin_lock_init(&uart.port.lock);
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0)
> +		return irq;
> +
> +	ret = ni16550_get_regs(pdev, &uart.port);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* early setup so that serial_in()/serial_out() work */
> +	serial8250_set_defaults(&uart);
> +
> +	info = device_get_match_data(dev);
> +
> +	uart.port.dev		= dev;
> +	uart.port.irq		= irq;
> +	uart.port.irqflags	= IRQF_SHARED;
> +	uart.port.flags		|= UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
> +					| UPF_FIXED_PORT | UPF_FIXED_TYPE;

Why |= ?


-- 
 i.

Re: [PATCH tty-next 2/2] serial: 8250: add driver for NI UARTs

[Brenda Streiff]

On 3/31/23 06:46, Ilpo Järvinen wrote:
> On Wed, 29 Mar 2023, Brenda Streiff wrote:
> 
>> +static int ni16550_get_regs(struct platform_device *pdev,
>> +			    struct uart_port *port)
>> +{
>> +	struct resource *regs;
>> +
>> +	regs = platform_get_resource(pdev, IORESOURCE_IO, 0);
>> +	if (regs) {
>> +		port->iotype = UPIO_PORT;
>> +		port->iobase = regs->start;
>> +
>> +		return 0;
>> +	}
> 
> Do you need the port io?

Yes; on our x86_64 hardware this UART IP is in logic connected to LPC,
and the registers lie in I/O port space.


>> +	int irq;
>> +	int rs232_property = 0;
>> +	unsigned int prescaler;
>> +	const char *transceiver;
>> +	int txfifosz, rxfifosz;
> 
> Try to follow reverse xmas-tree order.

Is reverse xmas tree also the rule in the tty subsystem? I was aware of
it for netdev but I thought that was a netdev-specific rule (since it
only shows up in maintainer-netdev.rst and not more broadly)

Re: [PATCH tty-next 2/2] serial: 8250: add driver for NI UARTs

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 1001 bytes --]

On Fri, 31 Mar 2023, Brenda Streiff wrote:

> On 3/31/23 06:46, Ilpo Järvinen wrote:
> > On Wed, 29 Mar 2023, Brenda Streiff wrote:
> 
> > > +	int irq;
> > > +	int rs232_property = 0;
> > > +	unsigned int prescaler;
> > > +	const char *transceiver;
> > > +	int txfifosz, rxfifosz;
> > 
> > Try to follow reverse xmas-tree order.
> 
> Is reverse xmas tree also the rule in the tty subsystem? I was aware of
> it for netdev but I thought that was a netdev-specific rule (since it
> only shows up in maintainer-netdev.rst and not more broadly)

I'd say that not as strictly as e.g. netdev does so if e.g. due to 
initialization order it cannot be fully achieved no special trickery is 
required (in contrast to what you'd get from e.g. netdev telling to put
them out of line).

It seems generally useful for declarations, especially when they're as 
many as in the one I picked up above (I think might be due to less eye 
movement required when looking for a particular variable by its name).


-- 
 i.

[PATCH v2 tty-next 0/2] serial: Add driver for National Instruments UARTs

[Brenda Streiff]

This patch series adds a driver for the 16550-like UARTs on National
Instruments (NI) embedded controller hardware.

These UARTs have an interface that is compatble with the TL16C550C (for
which we build on top of 8250_core) but also has extra registers for
the embedded RS-232/RS-485 tranceiver control circuitry.

Changes from v1 -> v2:
- Schema fixes:
  - Fix schema to now pass "make DT_CHECKER_FLAGS=-m dt_binding_check"
  - Rename unprefixed "transceiver" to "ni,serial-port-mode" with a
    description. Describing this as a "mode" rather than a "transceiver"
    seems more semantically correct in comparison to other DTs; other
    schemas with a "transceiver" property (isp1301, lpc32xx-udc) have
    phandle values, which is not the case here.
- Driver fixes:
  - replace C99 integer types with kernel types
  - reverse christmas tree
  - stuff PMR mode/cap masks into locals to avoid repetition
  - wrap ACPI match table in #ifdef CONFIG_ACPI to avoid build error on
    non-ACPI platforms
  - NI 16550s are only on x86 and Zynq-7000 NI devices, so constrain the
    Kconfig "depends" to only present it as an option to users on those
    architectures, to prevent it from being needlessly built on platforms
    that would not possibly have them.
  - document module name
  - add check for "ni,serial-port-mode" property; "transceiver" remains
    for sake of compatibility with _DSD ACPI objects for NI controller
    BIOSes currently in-field (but also DSD-properties-rules.rst says
    that _DSD properties don't have to be identical to DT bindings.)

Brenda Streiff (2):
  dt-bindings: serial: ni,ni16650: add bindings
  serial: 8250: add driver for NI UARTs

 .../bindings/serial/ni,ni16550.yaml           |  51 ++
 MAINTAINERS                                   |   7 +
 drivers/tty/serial/8250/8250_ni.c             | 454 ++++++++++++++++++
 drivers/tty/serial/8250/Kconfig               |  13 +
 drivers/tty/serial/8250/Makefile              |   1 +
 5 files changed, 526 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/serial/ni,ni16550.yaml
 create mode 100644 drivers/tty/serial/8250/8250_ni.c

-- 
2.30.2

[PATCH v2 tty-next 1/2] dt-bindings: serial: ni,ni16650: add bindings

[Brenda Streiff]

Add bindings for the NI 16550 UART.

Signed-off-by: Brenda Streiff <brenda.streiff@ni.com>
Cc: Gratian Crisan <gratian.crisan@ni.com>
Cc: Jason Smith <jason.smith@ni.com>
---
 .../bindings/serial/ni,ni16550.yaml           | 51 +++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/serial/ni,ni16550.yaml

diff --git a/Documentation/devicetree/bindings/serial/ni,ni16550.yaml b/Documentation/devicetree/bindings/serial/ni,ni16550.yaml
new file mode 100644
index 000000000000..13928e89f5aa
--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/ni,ni16550.yaml
@@ -0,0 +1,51 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/serial/ni,ni16550.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NI 16550 asynchronous serial interface (UART)
+
+maintainers:
+  - Brenda Streiff <brenda.streiff@ni.com>
+
+allOf:
+  - $ref: serial.yaml#
+
+properties:
+  compatible:
+    const: ni,ni16550
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clock-frequency: true
+
+  ni,serial-port-mode:
+    description: Indicates whether this is an RS-232 or RS-485 serial port.
+    $ref: /schemas/types.yaml#/definitions/string
+    enum: [ RS-232, RS-485 ]
+    default: RS-485
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clock-frequency
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    serial@80000000 {
+      compatible = "ni,ni16550";
+      reg = <0x80000000 0x8>;
+      interrupts = <0 30 4>;
+      clock-frequency = <58824000>;
+      ni,serial-port-mode = "RS-232";
+    };
+
+...
-- 
2.30.2

Re: [PATCH v2 tty-next 1/2] dt-bindings: serial: ni,ni16650: add bindings

[Krzysztof Kozlowski]

On 10/04/2023 23:11, Brenda Streiff wrote:
> Add bindings for the NI 16550 UART.
> 
> Signed-off-by: Brenda Streiff <brenda.streiff@ni.com>
> Cc: Gratian Crisan <gratian.crisan@ni.com>
> Cc: Jason Smith <jason.smith@ni.com>

Thank you for your patch. There is something to discuss/improve.

> ---
>  .../bindings/serial/ni,ni16550.yaml           | 51 +++++++++++++++++++
>  1 file changed, 51 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/serial/ni,ni16550.yaml
> 
> diff --git a/Documentation/devicetree/bindings/serial/ni,ni16550.yaml b/Documentation/devicetree/bindings/serial/ni,ni16550.yaml
> new file mode 100644
> index 000000000000..13928e89f5aa
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/serial/ni,ni16550.yaml
> @@ -0,0 +1,51 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/serial/ni,ni16550.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: NI 16550 asynchronous serial interface (UART)
> +
> +maintainers:
> +  - Brenda Streiff <brenda.streiff@ni.com>
> +
> +allOf:
> +  - $ref: serial.yaml#
> +
> +properties:
> +  compatible:
> +    const: ni,ni16550
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  clock-frequency: true

I missed it last time - why do you need this property? You do not have
any clock input, so which clock's frequency is it?

Best regards,
Krzysztof

Re: [PATCH v2 tty-next 1/2] dt-bindings: serial: ni,ni16650: add bindings

[Brenda Streiff]

On 4/11/23 00:44, Krzysztof Kozlowski wrote:
> On 10/04/2023 23:11, Brenda Streiff wrote:
>> +
>> +  interrupts:
>> +    maxItems: 1
>> +
>> +  clock-frequency: true
> 
> I missed it last time - why do you need this property? You do not have
> any clock input, so which clock's frequency is it?
> 

This is the clock frequency of the UART; on our x86-based platforms this
comes from the LPC clock, on Zynq-7000 it's derived from a clock in the
FPGA. This is used to set struct uart_port::uartclk in the serial core,
as it is for other UARTs.

This clock frequency can vary based on board design (especially on the
x86 side, due to different LPC clocks) but for a given design is fixed-
frequency.

Would you prefer this be documented further? I was following 8250.yaml's
lead here with the simple `true`.

Re: [PATCH v2 tty-next 1/2] dt-bindings: serial: ni,ni16650: add bindings

[Krzysztof Kozlowski]

On 13/04/2023 00:24, Brenda Streiff wrote:
> On 4/11/23 00:44, Krzysztof Kozlowski wrote:
>> On 10/04/2023 23:11, Brenda Streiff wrote:
>>> +
>>> +  interrupts:
>>> +    maxItems: 1
>>> +
>>> +  clock-frequency: true
>>
>> I missed it last time - why do you need this property? You do not have
>> any clock input, so which clock's frequency is it?
>>
> 
> This is the clock frequency of the UART; on our x86-based platforms this
> comes from the LPC clock, on Zynq-7000 it's derived from a clock in the
> FPGA. This is used to set struct uart_port::uartclk in the serial core,
> as it is for other UARTs.
> 
> This clock frequency can vary based on board design (especially on the
> x86 side, due to different LPC clocks) but for a given design is fixed-
> frequency.

So you must have clock input - clocks property. Once you add this, use
assigned-clocks to get the rate you want.

> 
> Would you prefer this be documented further? I was following 8250.yaml's
> lead here with the simple `true`.

I prefer to drop it. It is not correct and a legacy property. Without
clock inputs how can you even configure some clock?

Best regards,
Krzysztof

Re: [PATCH v2 tty-next 1/2] dt-bindings: serial: ni,ni16650: add bindings

[Brenda Streiff]

On 4/13/23 02:39, Krzysztof Kozlowski wrote:
> On 13/04/2023 00:24, Brenda Streiff wrote:
>> On 4/11/23 00:44, Krzysztof Kozlowski wrote:
>>> On 10/04/2023 23:11, Brenda Streiff wrote:
>>>> +
>>>> +  interrupts:
>>>> +    maxItems: 1
>>>> +
>>>> +  clock-frequency: true
>>>
>>> I missed it last time - why do you need this property? You do not have
>>> any clock input, so which clock's frequency is it?
>>>
>>
>> This is the clock frequency of the UART; on our x86-based platforms this
>> comes from the LPC clock, on Zynq-7000 it's derived from a clock in the
>> FPGA. This is used to set struct uart_port::uartclk in the serial core,
>> as it is for other UARTs.
>>
>> This clock frequency can vary based on board design (especially on the
>> x86 side, due to different LPC clocks) but for a given design is fixed-
>> frequency.
> 
> So you must have clock input - clocks property. Once you add this, use
> assigned-clocks to get the rate you want.
> 
>>
>> Would you prefer this be documented further? I was following 8250.yaml's
>> lead here with the simple `true`.
> 
> I prefer to drop it. It is not correct and a legacy property. Without
> clock inputs how can you even configure some clock?

Configure in what respect? Software can't change this clock; it's
effectively a fixed oscillator.

In practice, this would always be pointing at a compatible="fixed-clock"
which declares a clock-frequency; this seems like "clock-frequency but
more steps". I can add that, but I'm not clear on what value that adds.

We also have shipping devices with ACPI tables using "clock-frequency",
so independent of support for "clocks" and "assigned-clocks" for
devicetree-using systems, I would still have to keep support in the
driver for a "clock-frequency" device property for ACPI-using systems.

(Is there documentation on a standalone clock-property being a legacy
property that I've missed? I don't see anything of the sort in
writing-bindings.rst or in dt-schema and I want to make sure that I
haven't missed the proper guidance here.)

Re: [PATCH v2 tty-next 1/2] dt-bindings: serial: ni,ni16650: add bindings

[Krzysztof Kozlowski]

On 13/04/2023 22:44, Brenda Streiff wrote:
> 
> 
> On 4/13/23 02:39, Krzysztof Kozlowski wrote:
>> On 13/04/2023 00:24, Brenda Streiff wrote:
>>> On 4/11/23 00:44, Krzysztof Kozlowski wrote:
>>>> On 10/04/2023 23:11, Brenda Streiff wrote:
>>>>> +
>>>>> +  interrupts:
>>>>> +    maxItems: 1
>>>>> +
>>>>> +  clock-frequency: true
>>>>
>>>> I missed it last time - why do you need this property? You do not have
>>>> any clock input, so which clock's frequency is it?
>>>>
>>>
>>> This is the clock frequency of the UART; on our x86-based platforms this
>>> comes from the LPC clock, on Zynq-7000 it's derived from a clock in the
>>> FPGA. This is used to set struct uart_port::uartclk in the serial core,
>>> as it is for other UARTs.
>>>
>>> This clock frequency can vary based on board design (especially on the
>>> x86 side, due to different LPC clocks) but for a given design is fixed-
>>> frequency.
>>
>> So you must have clock input - clocks property. Once you add this, use
>> assigned-clocks to get the rate you want.
>>
>>>
>>> Would you prefer this be documented further? I was following 8250.yaml's
>>> lead here with the simple `true`.
>>
>> I prefer to drop it. It is not correct and a legacy property. Without
>> clock inputs how can you even configure some clock?
> 
> Configure in what respect? Software can't change this clock; it's
> effectively a fixed oscillator.

So where is the clock located? Physically.

> 
> In practice, this would always be pointing at a compatible="fixed-clock"
> which declares a clock-frequency; this seems like "clock-frequency but
> more steps". I can add that, but I'm not clear on what value that adds.

Aren't we talking about two different things? Based on limited
informamtion, I claimed you have clock input. If you have clock input,
then you miss clocks property.

What value would that add? I don't know... the rules that bindings
describe hardware?

> 
> We also have shipping devices with ACPI tables using "clock-frequency",
> so independent of support for "clocks" and "assigned-clocks" for
> devicetree-using systems, I would still have to keep support in the
> driver for a "clock-frequency" device property for ACPI-using systems.

I don't care about ACPI and ACPI has nothing to do with Bindings. We do
not write bindings for ACPI.

What your driver has or has not to do, it's also separate question. I2C
camera sensors solved it long time ago. I don't see why this must be
special.

> 
> (Is there documentation on a standalone clock-property being a legacy
> property that I've missed? 
> I don't see anything of the sort in
> writing-bindings.rst or in dt-schema and I want to make sure that I

dtschema:
  # Legacy clock properties
  clock-frequency:
    description: Legacy property ...

> haven't missed the proper guidance here.)

Best regards,
Krzysztof

[PATCH v2 tty-next 2/2] serial: 8250: add driver for NI UARTs

[Brenda Streiff]

The National Instruments (NI) 16550 is a 16550-like UART with larger
FIFOs and embedded RS-232/RS-485 transceiver control circuitry. This
patch adds a driver that can operate this UART, which is used for
onboard serial ports in several NI embedded controller designs.

Portions of this driver were originally written by Jaeden Amero and
Karthik Manamcheri, with extensive cleanups and refactors since.

Signed-off-by: Brenda Streiff <brenda.streiff@ni.com>
Cc: Gratian Crisan <gratian.crisan@ni.com>
Cc: Jason Smith <jason.smith@ni.com>
---
 MAINTAINERS                       |   7 +
 drivers/tty/serial/8250/8250_ni.c | 455 ++++++++++++++++++++++++++++++
 drivers/tty/serial/8250/Kconfig   |  13 +
 drivers/tty/serial/8250/Makefile  |   1 +
 4 files changed, 476 insertions(+)
 create mode 100644 drivers/tty/serial/8250/8250_ni.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 90abe83c02f3..4d44622da6cb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14323,6 +14323,13 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git nand/next
 F:	drivers/mtd/nand/
 F:	include/linux/mtd/*nand*.h
 
+NATIONAL INSTRUMENTS SERIAL DRIVER
+M:	Brenda Streiff <brenda.streiff@ni.com>
+L:	linux-serial@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/serial/ni,ni16550.yaml
+F:	drivers/tty/serial/8250/8250_ni.c
+
 NATIVE INSTRUMENTS USB SOUND INTERFACE DRIVER
 M:	Daniel Mack <zonque@gmail.com>
 L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
diff --git a/drivers/tty/serial/8250/8250_ni.c b/drivers/tty/serial/8250/8250_ni.c
new file mode 100644
index 000000000000..65203b27c74a
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_ni.c
@@ -0,0 +1,455 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NI 16550 UART Driver
+ *
+ * The National Instruments (NI) 16550 is a UART that is compatible with the
+ * TL16C550C and OX16C950B register interfaces, but has additional functions
+ * for RS-485 transceiver control. This driver implements support for the
+ * additional functionality on top of the standard serial8250 core.
+ *
+ * Copyright 2012-2023 National Instruments Corporation
+ */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/property.h>
+
+#include "8250.h"
+
+/* Extra bits in UART_ACR */
+#define NI16550_ACR_AUTO_DTR_EN			BIT(4)
+
+/* TFS - TX FIFO Size */
+#define NI16550_TFS_OFFSET	0x0C
+/* RFS - RX FIFO Size */
+#define NI16550_RFS_OFFSET	0x0D
+
+/* PMR - Port Mode Register */
+#define NI16550_PMR_OFFSET	0x0E
+/* PMR[1:0] - Port Capabilities */
+#define NI16550_PMR_CAP_MASK			0x03
+#define NI16550_PMR_NOT_IMPL			0x00 /* not implemented */
+#define NI16550_PMR_CAP_RS232			0x01 /* RS-232 capable */
+#define NI16550_PMR_CAP_RS485			0x02 /* RS-485 capable */
+#define NI16550_PMR_CAP_DUAL			0x03 /* dual-port */
+/* PMR[4] - Interface Mode */
+#define NI16550_PMR_MODE_MASK			0x10
+#define NI16550_PMR_MODE_RS232			0x00 /* currently 232 */
+#define NI16550_PMR_MODE_RS485			0x10 /* currently 485 */
+
+/* PCR - Port Control Register */
+#define NI16550_PCR_OFFSET	0x0F
+#define NI16550_PCR_RS422			0x00
+#define NI16550_PCR_ECHO_RS485			0x01
+#define NI16550_PCR_DTR_RS485			0x02
+#define NI16550_PCR_AUTO_RS485			0x03
+#define NI16550_PCR_WIRE_MODE_MASK		0x03
+#define NI16550_PCR_TXVR_ENABLE_BIT		BIT(3)
+#define NI16550_PCR_RS485_TERMINATION_BIT	BIT(6)
+
+/* flags for ni16550_device_info */
+#define NI_HAS_PMR		BIT(0)
+
+struct ni16550_device_info {
+	u32 uartclk;
+	u8 prescaler;
+	u8 flags;
+};
+
+struct ni16550_data {
+	int line;
+};
+
+static int ni16550_enable_transceivers(struct uart_port *port)
+{
+	u8 pcr;
+
+	pcr = port->serial_in(port, NI16550_PCR_OFFSET);
+	pcr |= NI16550_PCR_TXVR_ENABLE_BIT;
+	dev_dbg(port->dev, "enable transceivers: write pcr: 0x%02x\n", pcr);
+	port->serial_out(port, NI16550_PCR_OFFSET, pcr);
+
+	return 0;
+}
+
+static int ni16550_disable_transceivers(struct uart_port *port)
+{
+	u8 pcr;
+
+	pcr = port->serial_in(port, NI16550_PCR_OFFSET);
+	pcr &= ~NI16550_PCR_TXVR_ENABLE_BIT;
+	dev_dbg(port->dev, "disable transceivers: write pcr: 0x%02x\n", pcr);
+	port->serial_out(port, NI16550_PCR_OFFSET, pcr);
+
+	return 0;
+}
+
+static int ni16550_rs485_config(struct uart_port *port,
+				struct ktermios *termios,
+				struct serial_rs485 *rs485)
+{
+	struct uart_8250_port *up = container_of(port, struct uart_8250_port,
+						 port);
+	u8 pcr;
+
+	/* "rs485" should be given to us non-NULL. */
+	if (WARN_ON(rs485 == NULL))
+		return -EINVAL;
+
+	pcr = serial_in(up, NI16550_PCR_OFFSET);
+	pcr &= ~NI16550_PCR_WIRE_MODE_MASK;
+
+	if (rs485->flags & SER_RS485_ENABLED) {
+		/* RS-485 */
+		dev_dbg(port->dev, "2-wire Auto\n");
+		pcr |= NI16550_PCR_AUTO_RS485;
+		up->acr |= NI16550_ACR_AUTO_DTR_EN;
+	} else {
+		/* RS-422 */
+		dev_dbg(port->dev, "4-wire\n");
+		pcr |= NI16550_PCR_RS422;
+		up->acr &= ~NI16550_ACR_AUTO_DTR_EN;
+	}
+
+	dev_dbg(port->dev, "config rs485: write pcr: 0x%02x, acr: %02x\n", pcr, up->acr);
+	serial_out(up, NI16550_PCR_OFFSET, pcr);
+	serial_icr_write(up, UART_ACR, up->acr);
+
+	return 0;
+}
+
+static bool is_pmr_rs232_mode(struct uart_8250_port *up)
+{
+	u8 pmr = serial_in(up, NI16550_PMR_OFFSET);
+	u8 pmr_mode = pmr & NI16550_PMR_MODE_MASK;
+	u8 pmr_cap = pmr & NI16550_PMR_CAP_MASK;
+
+	/*
+	 * If the PMR is not implemented, then by default NI UARTs are
+	 * connected to RS-485 transceivers
+	 */
+	if (pmr_cap == NI16550_PMR_NOT_IMPL)
+		return false;
+
+	if (pmr_cap == NI16550_PMR_CAP_DUAL)
+		/*
+		 * If the port is dual-mode capable, then read the mode bit
+		 * to know the current mode
+		 */
+		return pmr_mode == NI16550_PMR_MODE_RS232;
+	/*
+	 * If it is not dual-mode capable, then decide based on the
+	 * capability
+	 */
+	return pmr_cap == NI16550_PMR_CAP_RS232;
+}
+
+static void ni16550_config_prescaler(struct uart_8250_port *up,
+				     u8 prescaler)
+{
+	/*
+	 * Page in the Enhanced Mode Registers
+	 * Sets EFR[4] for Enhanced Mode.
+	 */
+	u8 lcr_value;
+	u8 efr_value;
+
+	lcr_value = serial_in(up, UART_LCR);
+	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
+
+	efr_value = serial_in(up, UART_EFR);
+	efr_value |= UART_EFR_ECB;
+
+	serial_out(up, UART_EFR, efr_value);
+
+	/* Page out the Enhanced Mode Registers */
+	serial_out(up, UART_LCR, lcr_value);
+
+	/* Set prescaler to CPR register. */
+	serial_out(up, UART_SCR, UART_CPR);
+	serial_out(up, UART_ICR, prescaler);
+}
+
+static const struct serial_rs485 ni16550_rs485_supported = {
+	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND,
+};
+
+static void ni16550_rs485_setup(struct uart_port *port)
+{
+	port->rs485_config = ni16550_rs485_config;
+	port->rs485_supported = ni16550_rs485_supported;
+	/*
+	 * The hardware comes up by default in 2-wire auto mode and we
+	 * set the flags to represent that
+	 */
+	port->rs485.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND;
+}
+
+static int ni16550_port_startup(struct uart_port *port)
+{
+	int ret;
+
+	ret = serial8250_do_startup(port);
+	if (ret)
+		return ret;
+
+	return ni16550_enable_transceivers(port);
+}
+
+static void ni16550_port_shutdown(struct uart_port *port)
+{
+	ni16550_disable_transceivers(port);
+
+	serial8250_do_shutdown(port);
+}
+
+static int ni16550_get_regs(struct platform_device *pdev,
+			    struct uart_port *port)
+{
+	struct resource *regs;
+
+	regs = platform_get_resource(pdev, IORESOURCE_IO, 0);
+	if (regs) {
+		port->iotype = UPIO_PORT;
+		port->iobase = regs->start;
+
+		return 0;
+	}
+
+	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (regs) {
+		port->iotype  = UPIO_MEM;
+		port->mapbase = regs->start;
+		port->mapsize = resource_size(regs);
+		port->flags   |= UPF_IOREMAP;
+
+		port->membase = devm_ioremap(&pdev->dev, port->mapbase,
+					     port->mapsize);
+		if (!port->membase)
+			return -ENOMEM;
+
+		return 0;
+	}
+
+	dev_err(&pdev->dev, "no registers defined\n");
+	return -EINVAL;
+}
+
+static u8 ni16550_read_fifo_size(struct uart_8250_port *uart, int reg)
+{
+	/*
+	 * Very old implementations don't have the TFS or RFS registers
+	 * defined, so we may read all-0s or all-1s. For such devices,
+	 * assume a FIFO size of 128.
+	 */
+	u8 value = serial_in(uart, reg);
+
+	if (value == 0x00 || value == 0xFF)
+		return 128;
+
+	return value;
+}
+
+static void ni16550_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+	mctrl |= UART_MCR_CLKSEL;
+
+	serial8250_do_set_mctrl(port, mctrl);
+}
+
+static int ni16550_probe(struct platform_device *pdev)
+{
+	const struct ni16550_device_info *info;
+	struct device *dev = &pdev->dev;
+	struct uart_8250_port uart = {};
+	struct ni16550_data *data;
+	const char *portmode;
+	unsigned int prescaler;
+	int txfifosz, rxfifosz;
+	int rs232_property;
+	int ret;
+	int irq;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	spin_lock_init(&uart.port.lock);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	ret = ni16550_get_regs(pdev, &uart.port);
+	if (ret < 0)
+		return ret;
+
+	/* early setup so that serial_in()/serial_out() work */
+	serial8250_set_defaults(&uart);
+
+	info = device_get_match_data(dev);
+
+	uart.port.dev		= dev;
+	uart.port.irq		= irq;
+	uart.port.irqflags	= IRQF_SHARED;
+	uart.port.flags		= UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
+					| UPF_FIXED_PORT | UPF_FIXED_TYPE;
+	uart.port.startup	= ni16550_port_startup;
+	uart.port.shutdown	= ni16550_port_shutdown;
+
+	/*
+	 * Hardware instantiation of FIFO sizes are held in registers.
+	 */
+	txfifosz = ni16550_read_fifo_size(&uart, NI16550_TFS_OFFSET);
+	rxfifosz = ni16550_read_fifo_size(&uart, NI16550_RFS_OFFSET);
+
+	dev_dbg(dev, "NI 16550 has TX FIFO size %d, RX FIFO size %d\n",
+		txfifosz, rxfifosz);
+
+	uart.port.type		= PORT_16550A;
+	uart.port.fifosize	= txfifosz;
+	uart.tx_loadsz		= txfifosz;
+	uart.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10;
+	uart.capabilities	= UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR;
+
+	/*
+	 * OF device-tree and NIC7A69 ACPI can declare clock-frequency,
+	 * but may be missing for other instantiations, so this is optional.
+	 * If present, override what we've defined in this driver.
+	 */
+	if (info->uartclk)
+		uart.port.uartclk = info->uartclk;
+	device_property_read_u32(dev, "clock-frequency", &uart.port.uartclk);
+	if (!uart.port.uartclk) {
+		dev_err(dev, "unable to determine clock frequency!\n");
+		return -ENODEV;
+	}
+
+	if (info->prescaler)
+		prescaler = info->prescaler;
+	device_property_read_u32(dev, "clock-prescaler", &prescaler);
+
+	if (prescaler != 0) {
+		uart.port.set_mctrl = ni16550_set_mctrl;
+		ni16550_config_prescaler(&uart, (u8)prescaler);
+	}
+
+	/*
+	 * The determination of whether or not this is an RS-485 or RS-232 port
+	 * can come from a device property (if present), or it can come from
+	 * the PMR (if present), and otherwise we're solely an RS-485 port.
+	 *
+	 * This is a device-specific property, and thus has a vendor-prefixed
+	 * "ni,serial-port-mode" form as a devicetree binding. However, there
+	 * are old devices in the field using "transceiver" as an ACPI device
+	 * property, so we have to check for that as well.
+	 */
+	if (!device_property_read_string(dev, "ni,serial-port-mode",
+					 &portmode) ||
+	    !device_property_read_string(dev, "transceiver", &portmode)) {
+		rs232_property = strncmp(portmode, "RS-232", 6) == 0;
+
+		dev_dbg(dev, "port is in %s mode (via device property)",
+			(rs232_property ? "RS-232" : "RS-485"));
+	} else if (info->flags & NI_HAS_PMR) {
+		rs232_property = is_pmr_rs232_mode(&uart);
+
+		dev_dbg(dev, "port is in %s mode (via PMR)",
+			(rs232_property ? "RS-232" : "RS-485"));
+	} else {
+		rs232_property = 0;
+
+		dev_dbg(dev, "port is fixed as RS-485");
+	}
+
+	if (!rs232_property) {
+		/*
+		 * Neither the 'transceiver' property nor the PMR indicate
+		 * that this is an RS-232 port, so it must be an RS-485 one.
+		 */
+		ni16550_rs485_setup(&uart.port);
+	}
+
+	ret = serial8250_register_8250_port(&uart);
+	if (ret < 0)
+		return ret;
+
+	data->line = ret;
+
+	platform_set_drvdata(pdev, data);
+
+	return 0;
+}
+
+static int ni16550_remove(struct platform_device *pdev)
+{
+	struct ni16550_data *data = platform_get_drvdata(pdev);
+
+	serial8250_unregister_port(data->line);
+	return 0;
+}
+
+static const struct ni16550_device_info ni16550_default = { };
+
+static const struct of_device_id ni16550_of_match[] = {
+	{ .compatible = "ni,ni16550", .data = &ni16550_default },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ni16550_of_match);
+
+/* NI 16550 RS-485 Interface */
+static const struct ni16550_device_info nic7750 = {
+	.uartclk = 33333333,
+};
+
+/* NI CVS-145x RS-485 Interface */
+static const struct ni16550_device_info nic7772 = {
+	.uartclk = 1843200,
+	.flags = NI_HAS_PMR,
+};
+
+/* NI cRIO-904x RS-485 Interface */
+static const struct ni16550_device_info nic792b = {
+	/* Sets UART clock rate to 22.222 MHz with 1.125 prescale */
+	.uartclk = 25000000,
+	.prescaler = 0x09,
+};
+
+/* NI sbRIO 96x8 RS-232/485 Interfaces */
+static const struct ni16550_device_info nic7a69 = {
+	/* Set UART clock rate to 29.629 MHz with 1.125 prescale */
+	.uartclk = 29629629,
+	.prescaler = 0x09,
+};
+
+#ifdef CONFIG_ACPI
+static const struct acpi_device_id ni16550_acpi_match[] = {
+	{ "NIC7750",	(kernel_ulong_t)&nic7750 },
+	{ "NIC7772",	(kernel_ulong_t)&nic7772 },
+	{ "NIC792B",	(kernel_ulong_t)&nic792b },
+	{ "NIC7A69",	(kernel_ulong_t)&nic7a69 },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, ni16550_acpi_match);
+#endif
+
+static struct platform_driver ni16550_driver = {
+	.driver = {
+		.name = "ni16550",
+		.of_match_table = ni16550_of_match,
+		.acpi_match_table = ACPI_PTR(ni16550_acpi_match),
+	},
+	.probe = ni16550_probe,
+	.remove = ni16550_remove,
+};
+
+module_platform_driver(ni16550_driver);
+
+MODULE_AUTHOR("Jaeden Amero <jaeden.amero@ni.com>");
+MODULE_AUTHOR("Karthik Manamcheri <karthik.manamcheri@ni.com>");
+MODULE_DESCRIPTION("NI 16550 Driver");
+MODULE_LICENSE("GPL");
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 5313aa31930f..c650566fc71d 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -565,6 +565,19 @@ config SERIAL_8250_BCM7271
 	  including DMA support and high accuracy BAUD rates, say
 	  Y to this option. If unsure, say N.
 
+config SERIAL_8250_NI
+	tristate "NI 16550 based serial port"
+	depends on SERIAL_8250
+	depends on (X86 && ACPI) || (ARCH_ZYNQ && OF) || COMPILE_TEST
+	help
+	  This driver supports the integrated serial ports on National
+          Instruments (NI) controller hardware. This is required for all NI
+          controller models with onboard RS-485 or dual-mode RS-485/RS-232
+          ports.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called 8250_ni.
+
 config SERIAL_OF_PLATFORM
 	tristate "Devicetree based probing for 8250 ports"
 	depends on SERIAL_8250 && OF
diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
index 4fc2fc1f41b6..58dc1b5ff054 100644
--- a/drivers/tty/serial/8250/Makefile
+++ b/drivers/tty/serial/8250/Makefile
@@ -45,6 +45,7 @@ obj-$(CONFIG_SERIAL_8250_PERICOM)	+= 8250_pericom.o
 obj-$(CONFIG_SERIAL_8250_PXA)		+= 8250_pxa.o
 obj-$(CONFIG_SERIAL_8250_TEGRA)		+= 8250_tegra.o
 obj-$(CONFIG_SERIAL_8250_BCM7271)	+= 8250_bcm7271.o
+obj-$(CONFIG_SERIAL_8250_NI)		+= 8250_ni.o
 obj-$(CONFIG_SERIAL_OF_PLATFORM)	+= 8250_of.o
 
 CFLAGS_8250_ingenic.o += -I$(srctree)/scripts/dtc/libfdt
-- 
2.30.2

[PATCH v3 tty-next 0/2] serial: Add driver for National Instruments UARTs

[Brenda Streiff]

Changes from v2 -> v3;
- Schema fixes:
  - add "clocks" and "clock-names" properties, comment legacy use of
    "clock-frequency".
- Driver fixes:
  - get clock rate as a clock consumer, if available

Changes from v1 -> v2:
- Schema fixes:
  - Fix schema to now pass "make DT_CHECKER_FLAGS=-m dt_binding_check"
  - Rename unprefixed "transceiver" to "ni,serial-port-mode" with a
    description. Describing this as a "mode" rather than a "transceiver"
    seems more semantically correct in comparison to other DTs; other
    schemas with a "transceiver" property (isp1301, lpc32xx-udc) have
    phandle values, which is not the case here.
- Driver fixes:
  - replace C99 integer types with kernel types
  - reverse christmas tree
  - stuff PMR mode/cap masks into locals to avoid repetition
  - wrap ACPI match table in #ifdef CONFIG_ACPI to avoid build error on
    non-ACPI platforms
  - NI 16550s are only on x86 and Zynq-7000 NI devices, so constrain the
    Kconfig "depends" to only present it as an option to users on those
    architectures, to prevent it from being needlessly built on platforms
    that would not possibly have them.
  - document module name
  - add check for "ni,serial-port-mode" property; "transceiver" remains
    for sake of compatibility with _DSD ACPI objects for NI controller
    BIOSes currently in-field (but also DSD-properties-rules.rst says
    that _DSD properties don't have to be identical to DT bindings.)

Brenda Streiff (2):
  dt-bindings: serial: ni,ni16650: add bindings
  serial: 8250: add driver for NI UARTs

 .../bindings/serial/ni,ni16550.yaml           |  64 +++
 MAINTAINERS                                   |   7 +
 drivers/tty/serial/8250/8250_ni.c             | 467 ++++++++++++++++++
 drivers/tty/serial/8250/Kconfig               |  13 +
 drivers/tty/serial/8250/Makefile              |   1 +
 5 files changed, 552 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/serial/ni,ni16550.yaml
 create mode 100644 drivers/tty/serial/8250/8250_ni.c

-- 
2.30.2

[PATCH v3 tty-next 1/2] dt-bindings: serial: ni,ni16650: add bindings

[Brenda Streiff]

Add bindings for the NI 16550 UART.

Signed-off-by: Brenda Streiff <brenda.streiff@ni.com>
Cc: Gratian Crisan <gratian.crisan@ni.com>
Cc: Jason Smith <jason.smith@ni.com>
---
 .../bindings/serial/ni,ni16550.yaml           | 64 +++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/serial/ni,ni16550.yaml

diff --git a/Documentation/devicetree/bindings/serial/ni,ni16550.yaml b/Documentation/devicetree/bindings/serial/ni,ni16550.yaml
new file mode 100644
index 000000000000..93b88c8206b9
--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/ni,ni16550.yaml
@@ -0,0 +1,64 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/serial/ni,ni16550.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NI 16550 asynchronous serial interface (UART)
+
+maintainers:
+  - Brenda Streiff <brenda.streiff@ni.com>
+
+allOf:
+  - $ref: serial.yaml#
+
+properties:
+  compatible:
+    const: ni,ni16550
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    items:
+      - const: baudclk
+
+  # legacy clock property; prefer 'clocks' instead
+  clock-frequency: true
+
+  ni,serial-port-mode:
+    description: Indicates whether this is an RS-232 or RS-485 serial port.
+    $ref: /schemas/types.yaml#/definitions/string
+    enum: [ RS-232, RS-485 ]
+    default: RS-485
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    serial@80000000 {
+      compatible = "ni,ni16550";
+      reg = <0x80000000 0x8>;
+      interrupts = <0 30 4>;
+      clock-names = "baudclk";
+      clocks = <&clk_uart>;
+      ni,serial-port-mode = "RS-232";
+    };
+
+    clk_uart: clock {
+      compatible = "fixed-clock";
+      #clock-cells = <0>;
+      clock-frequency = <58824000>;
+    };
+...
-- 
2.30.2

Re: [PATCH v3 tty-next 1/2] dt-bindings: serial: ni,ni16650: add bindings

[Krzysztof Kozlowski]

On 19/04/2023 00:37, Brenda Streiff wrote:
> Add bindings for the NI 16550 UART.

Do not attach (thread) your patchsets to some other threads (unrelated
or older versions). This buries them deep in the mailbox and might
interfere with applying entire sets.

> 
> Signed-off-by: Brenda Streiff <brenda.streiff@ni.com>
> Cc: Gratian Crisan <gratian.crisan@ni.com>
> Cc: Jason Smith <jason.smith@ni.com>
> ---
>  .../bindings/serial/ni,ni16550.yaml           | 64 +++++++++++++++++++
>  1 file changed, 64 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/serial/ni,ni16550.yaml
> 
> diff --git a/Documentation/devicetree/bindings/serial/ni,ni16550.yaml b/Documentation/devicetree/bindings/serial/ni,ni16550.yaml
> new file mode 100644
> index 000000000000..93b88c8206b9
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/serial/ni,ni16550.yaml
> @@ -0,0 +1,64 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/serial/ni,ni16550.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: NI 16550 asynchronous serial interface (UART)
> +
> +maintainers:
> +  - Brenda Streiff <brenda.streiff@ni.com>
> +
> +allOf:
> +  - $ref: serial.yaml#
> +
> +properties:
> +  compatible:
> +    const: ni,ni16550
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  clocks:
> +    maxItems: 1
> +
> +  clock-names:
> +    items:
> +      - const: baudclk

No need for names for one clock entry.

> +
> +  # legacy clock property; prefer 'clocks' instead
> +  clock-frequency: true

Drop it, we do not want legacy or deprecated properties on new bindings.
It's not a legacy binding...

> +
> +  ni,serial-port-mode:
> +    description: Indicates whether this is an RS-232 or RS-485 serial port.
> +    $ref: /schemas/types.yaml#/definitions/string
> +    enum: [ RS-232, RS-485 ]
> +    default: RS-485
> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    serial@80000000 {
> +      compatible = "ni,ni16550";
> +      reg = <0x80000000 0x8>;
> +      interrupts = <0 30 4>;

I still wonder what are these. Flags? Then use common defines.

> +      clock-names = "baudclk";
> +      clocks = <&clk_uart>;
> +      ni,serial-port-mode = "RS-232";
> +    };
> +
> +    clk_uart: clock {

Drop node, not related to your code. You are not documenting usage of
fixed-clock as it is obvious and already documented in other place.


Best regards,
Krzysztof

[PATCH v3 tty-next 2/2] serial: 8250: add driver for NI UARTs

[Brenda Streiff]

The National Instruments (NI) 16550 is a 16550-like UART with larger
FIFOs and embedded RS-232/RS-485 transceiver control circuitry. This
patch adds a driver that can operate this UART, which is used for
onboard serial ports in several NI embedded controller designs.

Portions of this driver were originally written by Jaeden Amero and
Karthik Manamcheri, with extensive cleanups and refactors since.

Signed-off-by: Brenda Streiff <brenda.streiff@ni.com>
Cc: Gratian Crisan <gratian.crisan@ni.com>
Cc: Jason Smith <jason.smith@ni.com>
---
 MAINTAINERS                       |   7 +
 drivers/tty/serial/8250/8250_ni.c | 468 ++++++++++++++++++++++++++++++
 drivers/tty/serial/8250/Kconfig   |  13 +
 drivers/tty/serial/8250/Makefile  |   1 +
 4 files changed, 489 insertions(+)
 create mode 100644 drivers/tty/serial/8250/8250_ni.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 90abe83c02f3..4d44622da6cb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14323,6 +14323,13 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git nand/next
 F:	drivers/mtd/nand/
 F:	include/linux/mtd/*nand*.h
 
+NATIONAL INSTRUMENTS SERIAL DRIVER
+M:	Brenda Streiff <brenda.streiff@ni.com>
+L:	linux-serial@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/serial/ni,ni16550.yaml
+F:	drivers/tty/serial/8250/8250_ni.c
+
 NATIVE INSTRUMENTS USB SOUND INTERFACE DRIVER
 M:	Daniel Mack <zonque@gmail.com>
 L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
diff --git a/drivers/tty/serial/8250/8250_ni.c b/drivers/tty/serial/8250/8250_ni.c
new file mode 100644
index 000000000000..92e8912c4875
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_ni.c
@@ -0,0 +1,468 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NI 16550 UART Driver
+ *
+ * The National Instruments (NI) 16550 is a UART that is compatible with the
+ * TL16C550C and OX16C950B register interfaces, but has additional functions
+ * for RS-485 transceiver control. This driver implements support for the
+ * additional functionality on top of the standard serial8250 core.
+ *
+ * Copyright 2012-2023 National Instruments Corporation
+ */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/property.h>
+#include <linux/clk.h>
+
+#include "8250.h"
+
+/* Extra bits in UART_ACR */
+#define NI16550_ACR_AUTO_DTR_EN			BIT(4)
+
+/* TFS - TX FIFO Size */
+#define NI16550_TFS_OFFSET	0x0C
+/* RFS - RX FIFO Size */
+#define NI16550_RFS_OFFSET	0x0D
+
+/* PMR - Port Mode Register */
+#define NI16550_PMR_OFFSET	0x0E
+/* PMR[1:0] - Port Capabilities */
+#define NI16550_PMR_CAP_MASK			0x03
+#define NI16550_PMR_NOT_IMPL			0x00 /* not implemented */
+#define NI16550_PMR_CAP_RS232			0x01 /* RS-232 capable */
+#define NI16550_PMR_CAP_RS485			0x02 /* RS-485 capable */
+#define NI16550_PMR_CAP_DUAL			0x03 /* dual-port */
+/* PMR[4] - Interface Mode */
+#define NI16550_PMR_MODE_MASK			0x10
+#define NI16550_PMR_MODE_RS232			0x00 /* currently 232 */
+#define NI16550_PMR_MODE_RS485			0x10 /* currently 485 */
+
+/* PCR - Port Control Register */
+#define NI16550_PCR_OFFSET	0x0F
+#define NI16550_PCR_RS422			0x00
+#define NI16550_PCR_ECHO_RS485			0x01
+#define NI16550_PCR_DTR_RS485			0x02
+#define NI16550_PCR_AUTO_RS485			0x03
+#define NI16550_PCR_WIRE_MODE_MASK		0x03
+#define NI16550_PCR_TXVR_ENABLE_BIT		BIT(3)
+#define NI16550_PCR_RS485_TERMINATION_BIT	BIT(6)
+
+/* flags for ni16550_device_info */
+#define NI_HAS_PMR		BIT(0)
+
+struct ni16550_device_info {
+	u32 uartclk;
+	u8 prescaler;
+	u8 flags;
+};
+
+struct ni16550_data {
+	int line;
+	struct clk *clk;
+};
+
+static int ni16550_enable_transceivers(struct uart_port *port)
+{
+	u8 pcr;
+
+	pcr = port->serial_in(port, NI16550_PCR_OFFSET);
+	pcr |= NI16550_PCR_TXVR_ENABLE_BIT;
+	dev_dbg(port->dev, "enable transceivers: write pcr: 0x%02x\n", pcr);
+	port->serial_out(port, NI16550_PCR_OFFSET, pcr);
+
+	return 0;
+}
+
+static int ni16550_disable_transceivers(struct uart_port *port)
+{
+	u8 pcr;
+
+	pcr = port->serial_in(port, NI16550_PCR_OFFSET);
+	pcr &= ~NI16550_PCR_TXVR_ENABLE_BIT;
+	dev_dbg(port->dev, "disable transceivers: write pcr: 0x%02x\n", pcr);
+	port->serial_out(port, NI16550_PCR_OFFSET, pcr);
+
+	return 0;
+}
+
+static int ni16550_rs485_config(struct uart_port *port,
+				struct ktermios *termios,
+				struct serial_rs485 *rs485)
+{
+	struct uart_8250_port *up = container_of(port, struct uart_8250_port,
+						 port);
+	u8 pcr;
+
+	/* "rs485" should be given to us non-NULL. */
+	if (WARN_ON(rs485 == NULL))
+		return -EINVAL;
+
+	pcr = serial_in(up, NI16550_PCR_OFFSET);
+	pcr &= ~NI16550_PCR_WIRE_MODE_MASK;
+
+	if (rs485->flags & SER_RS485_ENABLED) {
+		/* RS-485 */
+		dev_dbg(port->dev, "2-wire Auto\n");
+		pcr |= NI16550_PCR_AUTO_RS485;
+		up->acr |= NI16550_ACR_AUTO_DTR_EN;
+	} else {
+		/* RS-422 */
+		dev_dbg(port->dev, "4-wire\n");
+		pcr |= NI16550_PCR_RS422;
+		up->acr &= ~NI16550_ACR_AUTO_DTR_EN;
+	}
+
+	dev_dbg(port->dev, "config rs485: write pcr: 0x%02x, acr: %02x\n", pcr, up->acr);
+	serial_out(up, NI16550_PCR_OFFSET, pcr);
+	serial_icr_write(up, UART_ACR, up->acr);
+
+	return 0;
+}
+
+static bool is_pmr_rs232_mode(struct uart_8250_port *up)
+{
+	u8 pmr = serial_in(up, NI16550_PMR_OFFSET);
+	u8 pmr_mode = pmr & NI16550_PMR_MODE_MASK;
+	u8 pmr_cap = pmr & NI16550_PMR_CAP_MASK;
+
+	/*
+	 * If the PMR is not implemented, then by default NI UARTs are
+	 * connected to RS-485 transceivers
+	 */
+	if (pmr_cap == NI16550_PMR_NOT_IMPL)
+		return false;
+
+	if (pmr_cap == NI16550_PMR_CAP_DUAL)
+		/*
+		 * If the port is dual-mode capable, then read the mode bit
+		 * to know the current mode
+		 */
+		return pmr_mode == NI16550_PMR_MODE_RS232;
+	/*
+	 * If it is not dual-mode capable, then decide based on the
+	 * capability
+	 */
+	return pmr_cap == NI16550_PMR_CAP_RS232;
+}
+
+static void ni16550_config_prescaler(struct uart_8250_port *up,
+				     u8 prescaler)
+{
+	/*
+	 * Page in the Enhanced Mode Registers
+	 * Sets EFR[4] for Enhanced Mode.
+	 */
+	u8 lcr_value;
+	u8 efr_value;
+
+	lcr_value = serial_in(up, UART_LCR);
+	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
+
+	efr_value = serial_in(up, UART_EFR);
+	efr_value |= UART_EFR_ECB;
+
+	serial_out(up, UART_EFR, efr_value);
+
+	/* Page out the Enhanced Mode Registers */
+	serial_out(up, UART_LCR, lcr_value);
+
+	/* Set prescaler to CPR register. */
+	serial_out(up, UART_SCR, UART_CPR);
+	serial_out(up, UART_ICR, prescaler);
+}
+
+static const struct serial_rs485 ni16550_rs485_supported = {
+	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND,
+};
+
+static void ni16550_rs485_setup(struct uart_port *port)
+{
+	port->rs485_config = ni16550_rs485_config;
+	port->rs485_supported = ni16550_rs485_supported;
+	/*
+	 * The hardware comes up by default in 2-wire auto mode and we
+	 * set the flags to represent that
+	 */
+	port->rs485.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND;
+}
+
+static int ni16550_port_startup(struct uart_port *port)
+{
+	int ret;
+
+	ret = serial8250_do_startup(port);
+	if (ret)
+		return ret;
+
+	return ni16550_enable_transceivers(port);
+}
+
+static void ni16550_port_shutdown(struct uart_port *port)
+{
+	ni16550_disable_transceivers(port);
+
+	serial8250_do_shutdown(port);
+}
+
+static int ni16550_get_regs(struct platform_device *pdev,
+			    struct uart_port *port)
+{
+	struct resource *regs;
+
+	regs = platform_get_resource(pdev, IORESOURCE_IO, 0);
+	if (regs) {
+		port->iotype = UPIO_PORT;
+		port->iobase = regs->start;
+
+		return 0;
+	}
+
+	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (regs) {
+		port->iotype  = UPIO_MEM;
+		port->mapbase = regs->start;
+		port->mapsize = resource_size(regs);
+		port->flags   |= UPF_IOREMAP;
+
+		port->membase = devm_ioremap(&pdev->dev, port->mapbase,
+					     port->mapsize);
+		if (!port->membase)
+			return -ENOMEM;
+
+		return 0;
+	}
+
+	dev_err(&pdev->dev, "no registers defined\n");
+	return -EINVAL;
+}
+
+static u8 ni16550_read_fifo_size(struct uart_8250_port *uart, int reg)
+{
+	/*
+	 * Very old implementations don't have the TFS or RFS registers
+	 * defined, so we may read all-0s or all-1s. For such devices,
+	 * assume a FIFO size of 128.
+	 */
+	u8 value = serial_in(uart, reg);
+
+	if (value == 0x00 || value == 0xFF)
+		return 128;
+
+	return value;
+}
+
+static void ni16550_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+	mctrl |= UART_MCR_CLKSEL;
+
+	serial8250_do_set_mctrl(port, mctrl);
+}
+
+static int ni16550_probe(struct platform_device *pdev)
+{
+	const struct ni16550_device_info *info;
+	struct device *dev = &pdev->dev;
+	struct uart_8250_port uart = {};
+	struct ni16550_data *data;
+	const char *portmode;
+	unsigned int prescaler;
+	int txfifosz, rxfifosz;
+	int rs232_property;
+	int ret;
+	int irq;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	spin_lock_init(&uart.port.lock);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	ret = ni16550_get_regs(pdev, &uart.port);
+	if (ret < 0)
+		return ret;
+
+	/* early setup so that serial_in()/serial_out() work */
+	serial8250_set_defaults(&uart);
+
+	info = device_get_match_data(dev);
+
+	uart.port.dev		= dev;
+	uart.port.irq		= irq;
+	uart.port.irqflags	= IRQF_SHARED;
+	uart.port.flags		= UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
+					| UPF_FIXED_PORT | UPF_FIXED_TYPE;
+	uart.port.startup	= ni16550_port_startup;
+	uart.port.shutdown	= ni16550_port_shutdown;
+
+	/*
+	 * Hardware instantiation of FIFO sizes are held in registers.
+	 */
+	txfifosz = ni16550_read_fifo_size(&uart, NI16550_TFS_OFFSET);
+	rxfifosz = ni16550_read_fifo_size(&uart, NI16550_RFS_OFFSET);
+
+	dev_dbg(dev, "NI 16550 has TX FIFO size %d, RX FIFO size %d\n",
+		txfifosz, rxfifosz);
+
+	uart.port.type		= PORT_16550A;
+	uart.port.fifosize	= txfifosz;
+	uart.tx_loadsz		= txfifosz;
+	uart.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10;
+	uart.capabilities	= UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR;
+
+	/*
+	 * Declaration of the base clock frequency can come from one of:
+	 * - static declaration in this driver (for older ACPI IDs)
+	 * - a "clock-frquency" ACPI or OF device property
+	 * - an associated OF clock definition
+	 */
+	if (info->uartclk)
+		uart.port.uartclk = info->uartclk;
+	if (device_property_read_u32(dev, "clock-frequency",
+				     &uart.port.uartclk)) {
+		data->clk = devm_clk_get_optional_enabled(dev, "baudclk");
+		if (data->clk)
+			uart.port.uartclk = clk_get_rate(data->clk);
+	}
+
+	if (!uart.port.uartclk) {
+		dev_err(dev, "unable to determine clock frequency!\n");
+		ret = -ENODEV;
+		goto err;
+	}
+
+	if (info->prescaler)
+		prescaler = info->prescaler;
+	device_property_read_u32(dev, "clock-prescaler", &prescaler);
+
+	if (prescaler != 0) {
+		uart.port.set_mctrl = ni16550_set_mctrl;
+		ni16550_config_prescaler(&uart, (u8)prescaler);
+	}
+
+	/*
+	 * The determination of whether or not this is an RS-485 or RS-232 port
+	 * can come from a device property (if present), or it can come from
+	 * the PMR (if present), and otherwise we're solely an RS-485 port.
+	 *
+	 * This is a device-specific property, and thus has a vendor-prefixed
+	 * "ni,serial-port-mode" form as a devicetree binding. However, there
+	 * are old devices in the field using "transceiver" as an ACPI device
+	 * property, so we have to check for that as well.
+	 */
+	if (!device_property_read_string(dev, "ni,serial-port-mode",
+					 &portmode) ||
+	    !device_property_read_string(dev, "transceiver", &portmode)) {
+		rs232_property = strncmp(portmode, "RS-232", 6) == 0;
+
+		dev_dbg(dev, "port is in %s mode (via device property)",
+			(rs232_property ? "RS-232" : "RS-485"));
+	} else if (info->flags & NI_HAS_PMR) {
+		rs232_property = is_pmr_rs232_mode(&uart);
+
+		dev_dbg(dev, "port is in %s mode (via PMR)",
+			(rs232_property ? "RS-232" : "RS-485"));
+	} else {
+		rs232_property = 0;
+
+		dev_dbg(dev, "port is fixed as RS-485");
+	}
+
+	if (!rs232_property) {
+		/*
+		 * Neither the 'transceiver' property nor the PMR indicate
+		 * that this is an RS-232 port, so it must be an RS-485 one.
+		 */
+		ni16550_rs485_setup(&uart.port);
+	}
+
+	ret = serial8250_register_8250_port(&uart);
+	if (ret < 0)
+		goto err;
+	data->line = ret;
+
+	platform_set_drvdata(pdev, data);
+	return 0;
+
+err:
+	clk_disable_unprepare(data->clk);
+	return ret;
+}
+
+static int ni16550_remove(struct platform_device *pdev)
+{
+	struct ni16550_data *data = platform_get_drvdata(pdev);
+
+	clk_disable_unprepare(data->clk);
+	serial8250_unregister_port(data->line);
+	return 0;
+}
+
+static const struct ni16550_device_info ni16550_default = { };
+
+static const struct of_device_id ni16550_of_match[] = {
+	{ .compatible = "ni,ni16550", .data = &ni16550_default },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ni16550_of_match);
+
+/* NI 16550 RS-485 Interface */
+static const struct ni16550_device_info nic7750 = {
+	.uartclk = 33333333,
+};
+
+/* NI CVS-145x RS-485 Interface */
+static const struct ni16550_device_info nic7772 = {
+	.uartclk = 1843200,
+	.flags = NI_HAS_PMR,
+};
+
+/* NI cRIO-904x RS-485 Interface */
+static const struct ni16550_device_info nic792b = {
+	/* Sets UART clock rate to 22.222 MHz with 1.125 prescale */
+	.uartclk = 25000000,
+	.prescaler = 0x09,
+};
+
+/* NI sbRIO 96x8 RS-232/485 Interfaces */
+static const struct ni16550_device_info nic7a69 = {
+	/* Set UART clock rate to 29.629 MHz with 1.125 prescale */
+	.uartclk = 29629629,
+	.prescaler = 0x09,
+};
+
+#ifdef CONFIG_ACPI
+static const struct acpi_device_id ni16550_acpi_match[] = {
+	{ "NIC7750",	(kernel_ulong_t)&nic7750 },
+	{ "NIC7772",	(kernel_ulong_t)&nic7772 },
+	{ "NIC792B",	(kernel_ulong_t)&nic792b },
+	{ "NIC7A69",	(kernel_ulong_t)&nic7a69 },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, ni16550_acpi_match);
+#endif
+
+static struct platform_driver ni16550_driver = {
+	.driver = {
+		.name = "ni16550",
+		.of_match_table = ni16550_of_match,
+		.acpi_match_table = ACPI_PTR(ni16550_acpi_match),
+	},
+	.probe = ni16550_probe,
+	.remove = ni16550_remove,
+};
+
+module_platform_driver(ni16550_driver);
+
+MODULE_AUTHOR("Jaeden Amero <jaeden.amero@ni.com>");
+MODULE_AUTHOR("Karthik Manamcheri <karthik.manamcheri@ni.com>");
+MODULE_DESCRIPTION("NI 16550 Driver");
+MODULE_LICENSE("GPL");
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 5313aa31930f..c650566fc71d 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -565,6 +565,19 @@ config SERIAL_8250_BCM7271
 	  including DMA support and high accuracy BAUD rates, say
 	  Y to this option. If unsure, say N.
 
+config SERIAL_8250_NI
+	tristate "NI 16550 based serial port"
+	depends on SERIAL_8250
+	depends on (X86 && ACPI) || (ARCH_ZYNQ && OF) || COMPILE_TEST
+	help
+	  This driver supports the integrated serial ports on National
+          Instruments (NI) controller hardware. This is required for all NI
+          controller models with onboard RS-485 or dual-mode RS-485/RS-232
+          ports.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called 8250_ni.
+
 config SERIAL_OF_PLATFORM
 	tristate "Devicetree based probing for 8250 ports"
 	depends on SERIAL_8250 && OF
diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
index 4fc2fc1f41b6..58dc1b5ff054 100644
--- a/drivers/tty/serial/8250/Makefile
+++ b/drivers/tty/serial/8250/Makefile
@@ -45,6 +45,7 @@ obj-$(CONFIG_SERIAL_8250_PERICOM)	+= 8250_pericom.o
 obj-$(CONFIG_SERIAL_8250_PXA)		+= 8250_pxa.o
 obj-$(CONFIG_SERIAL_8250_TEGRA)		+= 8250_tegra.o
 obj-$(CONFIG_SERIAL_8250_BCM7271)	+= 8250_bcm7271.o
+obj-$(CONFIG_SERIAL_8250_NI)		+= 8250_ni.o
 obj-$(CONFIG_SERIAL_OF_PLATFORM)	+= 8250_of.o
 
 CFLAGS_8250_ingenic.o += -I$(srctree)/scripts/dtc/libfdt
-- 
2.30.2

Re: [PATCH v3 tty-next 2/2] serial: 8250: add driver for NI UARTs

[Ilpo Järvinen]

On Tue, 18 Apr 2023, Brenda Streiff wrote:

> The National Instruments (NI) 16550 is a 16550-like UART with larger
> FIFOs and embedded RS-232/RS-485 transceiver control circuitry. This
> patch adds a driver that can operate this UART, which is used for
> onboard serial ports in several NI embedded controller designs.
> 
> Portions of this driver were originally written by Jaeden Amero and
> Karthik Manamcheri, with extensive cleanups and refactors since.
> 
> Signed-off-by: Brenda Streiff <brenda.streiff@ni.com>
> Cc: Gratian Crisan <gratian.crisan@ni.com>
> Cc: Jason Smith <jason.smith@ni.com>
> ---
>  MAINTAINERS                       |   7 +
>  drivers/tty/serial/8250/8250_ni.c | 468 ++++++++++++++++++++++++++++++
>  drivers/tty/serial/8250/Kconfig   |  13 +
>  drivers/tty/serial/8250/Makefile  |   1 +
>  4 files changed, 489 insertions(+)
>  create mode 100644 drivers/tty/serial/8250/8250_ni.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 90abe83c02f3..4d44622da6cb 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -14323,6 +14323,13 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git nand/next
>  F:	drivers/mtd/nand/
>  F:	include/linux/mtd/*nand*.h
>  
> +NATIONAL INSTRUMENTS SERIAL DRIVER
> +M:	Brenda Streiff <brenda.streiff@ni.com>
> +L:	linux-serial@vger.kernel.org
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/serial/ni,ni16550.yaml
> +F:	drivers/tty/serial/8250/8250_ni.c
> +
>  NATIVE INSTRUMENTS USB SOUND INTERFACE DRIVER
>  M:	Daniel Mack <zonque@gmail.com>
>  L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
> diff --git a/drivers/tty/serial/8250/8250_ni.c b/drivers/tty/serial/8250/8250_ni.c
> new file mode 100644
> index 000000000000..92e8912c4875
> --- /dev/null
> +++ b/drivers/tty/serial/8250/8250_ni.c
> @@ -0,0 +1,468 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * NI 16550 UART Driver
> + *
> + * The National Instruments (NI) 16550 is a UART that is compatible with the
> + * TL16C550C and OX16C950B register interfaces, but has additional functions
> + * for RS-485 transceiver control. This driver implements support for the
> + * additional functionality on top of the standard serial8250 core.
> + *
> + * Copyright 2012-2023 National Instruments Corporation
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/device.h>
> +#include <linux/io.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/property.h>
> +#include <linux/clk.h>
> +
> +#include "8250.h"
> +
> +/* Extra bits in UART_ACR */
> +#define NI16550_ACR_AUTO_DTR_EN			BIT(4)
> +
> +/* TFS - TX FIFO Size */
> +#define NI16550_TFS_OFFSET	0x0C
> +/* RFS - RX FIFO Size */
> +#define NI16550_RFS_OFFSET	0x0D
> +
> +/* PMR - Port Mode Register */
> +#define NI16550_PMR_OFFSET	0x0E
> +/* PMR[1:0] - Port Capabilities */
> +#define NI16550_PMR_CAP_MASK			0x03

Ah, checking the comment, this is GENMASK(1, 0). Remember to add the 
include for it too.

> +#define NI16550_PMR_NOT_IMPL			0x00 /* not implemented */
> +#define NI16550_PMR_CAP_RS232			0x01 /* RS-232 capable */
> +#define NI16550_PMR_CAP_RS485			0x02 /* RS-485 capable */
> +#define NI16550_PMR_CAP_DUAL			0x03 /* dual-port */
> +/* PMR[4] - Interface Mode */
> +#define NI16550_PMR_MODE_MASK			0x10
> +#define NI16550_PMR_MODE_RS232			0x00 /* currently 232 */
> +#define NI16550_PMR_MODE_RS485			0x10 /* currently 485 */
> +
> +/* PCR - Port Control Register */
> +#define NI16550_PCR_OFFSET	0x0F
> +#define NI16550_PCR_RS422			0x00
> +#define NI16550_PCR_ECHO_RS485			0x01
> +#define NI16550_PCR_DTR_RS485			0x02
> +#define NI16550_PCR_AUTO_RS485			0x03
> +#define NI16550_PCR_WIRE_MODE_MASK		0x03

GENMASK()

> +#define NI16550_PCR_TXVR_ENABLE_BIT		BIT(3)
> +#define NI16550_PCR_RS485_TERMINATION_BIT	BIT(6)
> +
> +/* flags for ni16550_device_info */
> +#define NI_HAS_PMR		BIT(0)
> +
> +struct ni16550_device_info {
> +	u32 uartclk;
> +	u8 prescaler;
> +	u8 flags;
> +};
> +
> +struct ni16550_data {
> +	int line;
> +	struct clk *clk;
> +};
> +
> +static int ni16550_enable_transceivers(struct uart_port *port)
> +{
> +	u8 pcr;
> +
> +	pcr = port->serial_in(port, NI16550_PCR_OFFSET);
> +	pcr |= NI16550_PCR_TXVR_ENABLE_BIT;
> +	dev_dbg(port->dev, "enable transceivers: write pcr: 0x%02x\n", pcr);
> +	port->serial_out(port, NI16550_PCR_OFFSET, pcr);
> +
> +	return 0;
> +}
> +
> +static int ni16550_disable_transceivers(struct uart_port *port)
> +{
> +	u8 pcr;
> +
> +	pcr = port->serial_in(port, NI16550_PCR_OFFSET);
> +	pcr &= ~NI16550_PCR_TXVR_ENABLE_BIT;
> +	dev_dbg(port->dev, "disable transceivers: write pcr: 0x%02x\n", pcr);
> +	port->serial_out(port, NI16550_PCR_OFFSET, pcr);
> +
> +	return 0;
> +}
> +
> +static int ni16550_rs485_config(struct uart_port *port,
> +				struct ktermios *termios,
> +				struct serial_rs485 *rs485)
> +{
> +	struct uart_8250_port *up = container_of(port, struct uart_8250_port,
> +						 port);

Just put these on the same line.

> +	u8 pcr;
> +
> +	/* "rs485" should be given to us non-NULL. */
> +	if (WARN_ON(rs485 == NULL))
> +		return -EINVAL;

Remove this sanity check.

> +	pcr = serial_in(up, NI16550_PCR_OFFSET);
> +	pcr &= ~NI16550_PCR_WIRE_MODE_MASK;
> +
> +	if (rs485->flags & SER_RS485_ENABLED) {
> +		/* RS-485 */
> +		dev_dbg(port->dev, "2-wire Auto\n");
> +		pcr |= NI16550_PCR_AUTO_RS485;
> +		up->acr |= NI16550_ACR_AUTO_DTR_EN;
> +	} else {
> +		/* RS-422 */
> +		dev_dbg(port->dev, "4-wire\n");
> +		pcr |= NI16550_PCR_RS422;
> +		up->acr &= ~NI16550_ACR_AUTO_DTR_EN;
> +	}

Does this difference also mean the UART's RS485 could support 
SER_RS485_RX_DURING_TX? (half-duplex vs full-duplex RS-485)

> +
> +	dev_dbg(port->dev, "config rs485: write pcr: 0x%02x, acr: %02x\n", pcr, up->acr);
> +	serial_out(up, NI16550_PCR_OFFSET, pcr);
> +	serial_icr_write(up, UART_ACR, up->acr);
> +
> +	return 0;
> +}
> +
> +static bool is_pmr_rs232_mode(struct uart_8250_port *up)
> +{
> +	u8 pmr = serial_in(up, NI16550_PMR_OFFSET);
> +	u8 pmr_mode = pmr & NI16550_PMR_MODE_MASK;
> +	u8 pmr_cap = pmr & NI16550_PMR_CAP_MASK;
> +
> +	/*
> +	 * If the PMR is not implemented, then by default NI UARTs are
> +	 * connected to RS-485 transceivers
> +	 */
> +	if (pmr_cap == NI16550_PMR_NOT_IMPL)
> +		return false;
> +
> +	if (pmr_cap == NI16550_PMR_CAP_DUAL)
> +		/*
> +		 * If the port is dual-mode capable, then read the mode bit
> +		 * to know the current mode
> +		 */
> +		return pmr_mode == NI16550_PMR_MODE_RS232;
> +	/*
> +	 * If it is not dual-mode capable, then decide based on the
> +	 * capability
> +	 */
> +	return pmr_cap == NI16550_PMR_CAP_RS232;
> +}
> +
> +static void ni16550_config_prescaler(struct uart_8250_port *up,
> +				     u8 prescaler)
> +{
> +	/*
> +	 * Page in the Enhanced Mode Registers
> +	 * Sets EFR[4] for Enhanced Mode.
> +	 */
> +	u8 lcr_value;
> +	u8 efr_value;
> +
> +	lcr_value = serial_in(up, UART_LCR);
> +	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
> +
> +	efr_value = serial_in(up, UART_EFR);
> +	efr_value |= UART_EFR_ECB;
> +
> +	serial_out(up, UART_EFR, efr_value);
> +
> +	/* Page out the Enhanced Mode Registers */
> +	serial_out(up, UART_LCR, lcr_value);
> +
> +	/* Set prescaler to CPR register. */
> +	serial_out(up, UART_SCR, UART_CPR);
> +	serial_out(up, UART_ICR, prescaler);
> +}
> +
> +static const struct serial_rs485 ni16550_rs485_supported = {
> +	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND,

The driver does not seem to change anything based on the value of
SER_RS485_RTS_ON_SEND, was this an oversight or is RTS on/off on/after 
send not supported?

> +};
> +
> +static void ni16550_rs485_setup(struct uart_port *port)
> +{
> +	port->rs485_config = ni16550_rs485_config;
> +	port->rs485_supported = ni16550_rs485_supported;
> +	/*
> +	 * The hardware comes up by default in 2-wire auto mode and we
> +	 * set the flags to represent that
> +	 */
> +	port->rs485.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND;
> +}
> +
> +static int ni16550_port_startup(struct uart_port *port)
> +{
> +	int ret;
> +
> +	ret = serial8250_do_startup(port);
> +	if (ret)
> +		return ret;
> +
> +	return ni16550_enable_transceivers(port);
> +}
> +
> +static void ni16550_port_shutdown(struct uart_port *port)
> +{
> +	ni16550_disable_transceivers(port);
> +
> +	serial8250_do_shutdown(port);
> +}
> +
> +static int ni16550_get_regs(struct platform_device *pdev,
> +			    struct uart_port *port)
> +{
> +	struct resource *regs;
> +
> +	regs = platform_get_resource(pdev, IORESOURCE_IO, 0);
> +	if (regs) {
> +		port->iotype = UPIO_PORT;
> +		port->iobase = regs->start;
> +
> +		return 0;
> +	}
> +
> +	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (regs) {
> +		port->iotype  = UPIO_MEM;
> +		port->mapbase = regs->start;
> +		port->mapsize = resource_size(regs);
> +		port->flags   |= UPF_IOREMAP;

Remove the extra alignment, it didn't help much anyway as 1 out of 4 had 
that |.

> +
> +		port->membase = devm_ioremap(&pdev->dev, port->mapbase,
> +					     port->mapsize);
> +		if (!port->membase)
> +			return -ENOMEM;
> +
> +		return 0;
> +	}
> +
> +	dev_err(&pdev->dev, "no registers defined\n");
> +	return -EINVAL;
> +}
> +
> +static u8 ni16550_read_fifo_size(struct uart_8250_port *uart, int reg)
> +{
> +	/*
> +	 * Very old implementations don't have the TFS or RFS registers
> +	 * defined, so we may read all-0s or all-1s. For such devices,
> +	 * assume a FIFO size of 128.
> +	 */
> +	u8 value = serial_in(uart, reg);
> +
> +	if (value == 0x00 || value == 0xFF)
> +		return 128;
> +
> +	return value;
> +}
> +
> +static void ni16550_set_mctrl(struct uart_port *port, unsigned int mctrl)
> +{
> +	mctrl |= UART_MCR_CLKSEL;
> +
> +	serial8250_do_set_mctrl(port, mctrl);
> +}
> +
> +static int ni16550_probe(struct platform_device *pdev)
> +{
> +	const struct ni16550_device_info *info;
> +	struct device *dev = &pdev->dev;
> +	struct uart_8250_port uart = {};
> +	struct ni16550_data *data;
> +	const char *portmode;
> +	unsigned int prescaler;
> +	int txfifosz, rxfifosz;
> +	int rs232_property;
> +	int ret;
> +	int irq;
> +
> +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	spin_lock_init(&uart.port.lock);
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0)
> +		return irq;
> +
> +	ret = ni16550_get_regs(pdev, &uart.port);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* early setup so that serial_in()/serial_out() work */
> +	serial8250_set_defaults(&uart);
> +
> +	info = device_get_match_data(dev);
> +
> +	uart.port.dev		= dev;
> +	uart.port.irq		= irq;
> +	uart.port.irqflags	= IRQF_SHARED;
> +	uart.port.flags		= UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
> +					| UPF_FIXED_PORT | UPF_FIXED_TYPE;
> +	uart.port.startup	= ni16550_port_startup;
> +	uart.port.shutdown	= ni16550_port_shutdown;
> +
> +	/*
> +	 * Hardware instantiation of FIFO sizes are held in registers.
> +	 */
> +	txfifosz = ni16550_read_fifo_size(&uart, NI16550_TFS_OFFSET);
> +	rxfifosz = ni16550_read_fifo_size(&uart, NI16550_RFS_OFFSET);
> +
> +	dev_dbg(dev, "NI 16550 has TX FIFO size %d, RX FIFO size %d\n",
> +		txfifosz, rxfifosz);
> +
> +	uart.port.type		= PORT_16550A;
> +	uart.port.fifosize	= txfifosz;
> +	uart.tx_loadsz		= txfifosz;
> +	uart.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10;
> +	uart.capabilities	= UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR;
> +
> +	/*
> +	 * Declaration of the base clock frequency can come from one of:
> +	 * - static declaration in this driver (for older ACPI IDs)
> +	 * - a "clock-frquency" ACPI or OF device property
> +	 * - an associated OF clock definition
> +	 */
> +	if (info->uartclk)
> +		uart.port.uartclk = info->uartclk;
> +	if (device_property_read_u32(dev, "clock-frequency",
> +				     &uart.port.uartclk)) {
> +		data->clk = devm_clk_get_optional_enabled(dev, "baudclk");
> +		if (data->clk)
> +			uart.port.uartclk = clk_get_rate(data->clk);
> +	}
> +
> +	if (!uart.port.uartclk) {
> +		dev_err(dev, "unable to determine clock frequency!\n");
> +		ret = -ENODEV;
> +		goto err;
> +	}
> +
> +	if (info->prescaler)
> +		prescaler = info->prescaler;
> +	device_property_read_u32(dev, "clock-prescaler", &prescaler);
> +
> +	if (prescaler != 0) {
> +		uart.port.set_mctrl = ni16550_set_mctrl;
> +		ni16550_config_prescaler(&uart, (u8)prescaler);
> +	}
> +
> +	/*
> +	 * The determination of whether or not this is an RS-485 or RS-232 port
> +	 * can come from a device property (if present), or it can come from
> +	 * the PMR (if present), and otherwise we're solely an RS-485 port.
> +	 *
> +	 * This is a device-specific property, and thus has a vendor-prefixed
> +	 * "ni,serial-port-mode" form as a devicetree binding. However, there
> +	 * are old devices in the field using "transceiver" as an ACPI device
> +	 * property, so we have to check for that as well.
> +	 */
> +	if (!device_property_read_string(dev, "ni,serial-port-mode",
> +					 &portmode) ||
> +	    !device_property_read_string(dev, "transceiver", &portmode)) {
> +		rs232_property = strncmp(portmode, "RS-232", 6) == 0;
> +
> +		dev_dbg(dev, "port is in %s mode (via device property)",
> +			(rs232_property ? "RS-232" : "RS-485"));
> +	} else if (info->flags & NI_HAS_PMR) {
> +		rs232_property = is_pmr_rs232_mode(&uart);
> +
> +		dev_dbg(dev, "port is in %s mode (via PMR)",
> +			(rs232_property ? "RS-232" : "RS-485"));
> +	} else {
> +		rs232_property = 0;
> +
> +		dev_dbg(dev, "port is fixed as RS-485");
> +	}
> +
> +	if (!rs232_property) {
> +		/*
> +		 * Neither the 'transceiver' property nor the PMR indicate
> +		 * that this is an RS-232 port, so it must be an RS-485 one.
> +		 */
> +		ni16550_rs485_setup(&uart.port);
> +	}
> +
> +	ret = serial8250_register_8250_port(&uart);
> +	if (ret < 0)
> +		goto err;
> +	data->line = ret;
> +
> +	platform_set_drvdata(pdev, data);
> +	return 0;
> +
> +err:
> +	clk_disable_unprepare(data->clk);
> +	return ret;
> +}
> +
> +static int ni16550_remove(struct platform_device *pdev)
> +{
> +	struct ni16550_data *data = platform_get_drvdata(pdev);
> +
> +	clk_disable_unprepare(data->clk);
> +	serial8250_unregister_port(data->line);
> +	return 0;
> +}
> +
> +static const struct ni16550_device_info ni16550_default = { };
> +
> +static const struct of_device_id ni16550_of_match[] = {
> +	{ .compatible = "ni,ni16550", .data = &ni16550_default },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, ni16550_of_match);
> +
> +/* NI 16550 RS-485 Interface */
> +static const struct ni16550_device_info nic7750 = {
> +	.uartclk = 33333333,
> +};
> +
> +/* NI CVS-145x RS-485 Interface */
> +static const struct ni16550_device_info nic7772 = {
> +	.uartclk = 1843200,
> +	.flags = NI_HAS_PMR,
> +};
> +
> +/* NI cRIO-904x RS-485 Interface */
> +static const struct ni16550_device_info nic792b = {
> +	/* Sets UART clock rate to 22.222 MHz with 1.125 prescale */
> +	.uartclk = 25000000,
> +	.prescaler = 0x09,
> +};
> +
> +/* NI sbRIO 96x8 RS-232/485 Interfaces */
> +static const struct ni16550_device_info nic7a69 = {
> +	/* Set UART clock rate to 29.629 MHz with 1.125 prescale */
> +	.uartclk = 29629629,
> +	.prescaler = 0x09,

To me these two comments don't seemingly agree, one states 22.222MHz and 
defines 25M clk, whereas the other states 29.629MHz and defines 29.629M 
clk. I guess one of them comes from prescaled and the other from 
postscaled frequency?

> +};
> +
> +#ifdef CONFIG_ACPI
> +static const struct acpi_device_id ni16550_acpi_match[] = {
> +	{ "NIC7750",	(kernel_ulong_t)&nic7750 },
> +	{ "NIC7772",	(kernel_ulong_t)&nic7772 },
> +	{ "NIC792B",	(kernel_ulong_t)&nic792b },
> +	{ "NIC7A69",	(kernel_ulong_t)&nic7a69 },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(acpi, ni16550_acpi_match);
> +#endif
> +
> +static struct platform_driver ni16550_driver = {
> +	.driver = {
> +		.name = "ni16550",
> +		.of_match_table = ni16550_of_match,
> +		.acpi_match_table = ACPI_PTR(ni16550_acpi_match),
> +	},
> +	.probe = ni16550_probe,
> +	.remove = ni16550_remove,
> +};
> +
> +module_platform_driver(ni16550_driver);
> +
> +MODULE_AUTHOR("Jaeden Amero <jaeden.amero@ni.com>");
> +MODULE_AUTHOR("Karthik Manamcheri <karthik.manamcheri@ni.com>");
> +MODULE_DESCRIPTION("NI 16550 Driver");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
> index 5313aa31930f..c650566fc71d 100644
> --- a/drivers/tty/serial/8250/Kconfig
> +++ b/drivers/tty/serial/8250/Kconfig
> @@ -565,6 +565,19 @@ config SERIAL_8250_BCM7271
>  	  including DMA support and high accuracy BAUD rates, say
>  	  Y to this option. If unsure, say N.
>  
> +config SERIAL_8250_NI
> +	tristate "NI 16550 based serial port"
> +	depends on SERIAL_8250
> +	depends on (X86 && ACPI) || (ARCH_ZYNQ && OF) || COMPILE_TEST
> +	help
> +	  This driver supports the integrated serial ports on National
> +          Instruments (NI) controller hardware. This is required for all NI
> +          controller models with onboard RS-485 or dual-mode RS-485/RS-232
> +          ports.

Check that the indent is same for all these lines (tab + 2 spaces).

> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called 8250_ni.
> +
>  config SERIAL_OF_PLATFORM
>  	tristate "Devicetree based probing for 8250 ports"
>  	depends on SERIAL_8250 && OF
> diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
> index 4fc2fc1f41b6..58dc1b5ff054 100644
> --- a/drivers/tty/serial/8250/Makefile
> +++ b/drivers/tty/serial/8250/Makefile
> @@ -45,6 +45,7 @@ obj-$(CONFIG_SERIAL_8250_PERICOM)	+= 8250_pericom.o
>  obj-$(CONFIG_SERIAL_8250_PXA)		+= 8250_pxa.o
>  obj-$(CONFIG_SERIAL_8250_TEGRA)		+= 8250_tegra.o
>  obj-$(CONFIG_SERIAL_8250_BCM7271)	+= 8250_bcm7271.o
> +obj-$(CONFIG_SERIAL_8250_NI)		+= 8250_ni.o
>  obj-$(CONFIG_SERIAL_OF_PLATFORM)	+= 8250_of.o
>  
>  CFLAGS_8250_ingenic.o += -I$(srctree)/scripts/dtc/libfdt
> 

-- 
 i.

Re: [PATCH v3 tty-next 2/2] serial: 8250: add driver for NI UARTs

[Brenda Streiff]

On 4/19/23 06:43, Ilpo Järvinen wrote:
> 
>> +	pcr = serial_in(up, NI16550_PCR_OFFSET);
>> +	pcr &= ~NI16550_PCR_WIRE_MODE_MASK;
>> +
>> +	if (rs485->flags & SER_RS485_ENABLED) {
>> +		/* RS-485 */
>> +		dev_dbg(port->dev, "2-wire Auto\n");
>> +		pcr |= NI16550_PCR_AUTO_RS485;
>> +		up->acr |= NI16550_ACR_AUTO_DTR_EN;
>> +	} else {
>> +		/* RS-422 */
>> +		dev_dbg(port->dev, "4-wire\n");
>> +		pcr |= NI16550_PCR_RS422;
>> +		up->acr &= ~NI16550_ACR_AUTO_DTR_EN;
>> +	}
> 
> Does this difference also mean the UART's RS485 could support
> SER_RS485_RX_DURING_TX? (half-duplex vs full-duplex RS-485)

Maybe. At least on some devices it appears that it might be possible to
support this with a combination of the NI16550_PCR_ECHO_RS485 mode (this
is "2-Wire DTR Controlled With Echo" in NI parlance [1]) along with the
AUTO_DTR mode set in ACR (which asserts DTR if there's data in the TX
FIFO).

We've never tried using it in that way (neither in prior versions of this
driver nor our driver for this hardware on Windows), so I'm not sure that
works that way on all revisions of the hardware, so I'm hesitant to
include that in this patchset for now.

[1] https://www.ni.com/en-us/support/documentation/supplemental/18/transceiver-modes-on-ni-rs-485-serial-cards.html

>> +
>> +static const struct serial_rs485 ni16550_rs485_supported = {
>> +	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND,
> 
> The driver does not seem to change anything based on the value of
> SER_RS485_RTS_ON_SEND, was this an oversight or is RTS on/off on/after
> send not supported?

Not so much "not supported" as "doesn't matter"?

SER_RS485_RTS_(ON/AFTER)_SEND (which would be a misnomer anyway, as we use
DTR and not RTS) appear to let userspace indicate whether or not the
transmitter is active-high or active-low, under the assumption that the
UART driver doesn't know anything itself about its attached transceiver.
This driver does, so it doesn't need either flag to do the right thing.

However, there is existing userspace software does try to configure the
SER_RS485_RTS_(ON/AFTER)_SEND flags; for instance, pyserial's RS485Settings
sets rts_level_for_tx=True [2] and this maps directly to RTS_ON_SEND. Our
own proprietary Linux software also sets these flags. So the behavior we
want is to we effectively treat them as don't-cares here.

I can add comments on that further though, because I can see how that looks
a bit confusing.

[2] https://github.com/pyserial/pyserial/blob/31fa4807d73ed4eb9891a88a15817b439c4eea2d/serial/rs485.py#L22

>> +
>> +/* NI cRIO-904x RS-485 Interface */
>> +static const struct ni16550_device_info nic792b = {
>> +	/* Sets UART clock rate to 22.222 MHz with 1.125 prescale */
>> +	.uartclk = 25000000,
>> +	.prescaler = 0x09,
>> +};
>> +
>> +/* NI sbRIO 96x8 RS-232/485 Interfaces */
>> +static const struct ni16550_device_info nic7a69 = {
>> +	/* Set UART clock rate to 29.629 MHz with 1.125 prescale */
>> +	.uartclk = 29629629,
>> +	.prescaler = 0x09,
> 
> To me these two comments don't seemingly agree, one states 22.222MHz and
> defines 25M clk, whereas the other states 29.629MHz and defines 29.629M
> clk. I guess one of them comes from prescaled and the other from
> postscaled frequency?

This was an error-- the comment is correct, I had the uartclk value wrong
(should be 22222222).