[PATCH 0/2] serial: add KEBA UART driver

[PATCH 0/2] serial: add KEBA UART driver

[Gerhard Engleder]

First the serial subsystem is prepared to keep rs485 settings from the
driver if no firmware node exists. This enables drivers to configure a
default rs485 mode, which is set by the serial subsystem.

Second the driver for the KEBA UART is added. This driver supports
multiple rs485 mode and selects RS485 as default mode. This UART is
found in KEBA PLC devices. The auxiliary devices for this driver are
created by the cp500 driver.

Gerhard Engleder (2):
  serial: Keep rs485 settings for devices without firmware node
  serial: 8250: add driver for KEBA UART

 drivers/tty/serial/8250/8250_keba.c | 279 ++++++++++++++++++++++++++++
 drivers/tty/serial/8250/Kconfig     |  13 ++
 drivers/tty/serial/8250/Makefile    |   1 +
 drivers/tty/serial/serial_core.c    |   8 +-
 4 files changed, 300 insertions(+), 1 deletion(-)
 create mode 100644 drivers/tty/serial/8250/8250_keba.c

-- 
2.39.5

[PATCH 1/2] serial: Keep rs485 settings for devices without firmware node

[Gerhard Engleder]

From: Gerhard Engleder <eg@keba.com>

Commit fe7f0fa43cef ("serial: 8250: Support rs485 devicetree properties")
retrieves rs485 properties for 8250 drivers. These properties are read
from the firmware node of the device. If the firmware node does not
exist, then the rs485 flags are still reset. Thus, 8250 driver cannot
set rs485 flags to enable a defined rs485 mode during driver loading.
This is no problem so far, as no 8250 driver sets the rs485 flags.

If no firmware node exist, then it should be possible for the driver to
set a reasonable default rs485 mode. Therefore, reset rs485 flags only
if a firmware node exists.

Signed-off-by: Gerhard Engleder <eg@keba.com>
Cc: Lukas Wunner <lukas@wunner.de>
---
 drivers/tty/serial/serial_core.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 4757293ece8c..366101f85048 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -3533,7 +3533,13 @@ int uart_get_rs485_mode(struct uart_port *port)
 	u32 rs485_delay[2];
 	int ret;
 
-	if (!(port->rs485_supported.flags & SER_RS485_ENABLED))
+	/*
+	 * Retrieve properties only if rs485 is supported and if a firmware node
+	 * exist. If no firmware node exist, then don't touch rs485 config and
+	 * keep initial rs485 properties set by driver.
+	 */
+	if (!(port->rs485_supported.flags & SER_RS485_ENABLED) ||
+	    !dev_fwnode(dev))
 		return 0;
 
 	ret = device_property_read_u32_array(dev, "rs485-rts-delay",
-- 
2.39.5

[PATCH 2/2] serial: 8250: add driver for KEBA UART

[Gerhard Engleder]

From: Gerhard Engleder <eg@keba.com>

The KEBA UART is found in the system FPGA of KEBA PLC devices. It is
mostly 8250 compatible with extension for some UART modes.

3 different variants exist. The simpliest variant supports only RS-232
and is used for debug interfaces. The next variant supports only RS-485
and is used mostly for communication with KEBA panel devices. The third
variant is able to support RS-232, RS-485 and RS-422. For this variant
not only the mode of the UART is configured, also the physics and
transceivers are switched according to the mode.

Signed-off-by: Gerhard Engleder <eg@keba.com>
Tested-by: Daniel Gierlinger <gida@keba.com>
---
 drivers/tty/serial/8250/8250_keba.c | 279 ++++++++++++++++++++++++++++
 drivers/tty/serial/8250/Kconfig     |  13 ++
 drivers/tty/serial/8250/Makefile    |   1 +
 3 files changed, 293 insertions(+)
 create mode 100644 drivers/tty/serial/8250/8250_keba.c

diff --git a/drivers/tty/serial/8250/8250_keba.c b/drivers/tty/serial/8250/8250_keba.c
new file mode 100644
index 000000000000..e1dccc0e1026
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_keba.c
@@ -0,0 +1,279 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2025 KEBA Industrial Automation GmbH
+ *
+ * Driver for KEBA UART FPGA IP core
+ */
+
+#include <linux/module.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/auxiliary_bus.h>
+#include <linux/misc/keba.h>
+
+#include "8250.h"
+
+#define KUART "kuart"
+
+/* flags */
+#define KUART_RS485		0x00000001
+#define KUART_USE_CAPABILITY	0x00000002
+
+/* registers */
+#define KUART_VERSION		0x0000
+#define KUART_REVISION		0x0001
+#define KUART_CAPABILITY	0x0002
+#define KUART_CONTROL		0x0004
+#define KUART_BASE		0x000C
+#define KUART_REGSHIFT		2
+#define KUART_CLK		1843200
+
+/* mode flags */
+#define KUART_MODE_NONE		0
+#define KUART_MODE_RS485	1
+#define KUART_MODE_RS422	2
+#define KUART_MODE_RS232	3
+
+/* capability flags */
+#define KUART_CAPABILITY_NONE	(1<<KUART_MODE_NONE)
+#define KUART_CAPABILITY_RS485	(1<<KUART_MODE_RS485)
+#define KUART_CAPABILITY_RS422	(1<<KUART_MODE_RS422)
+#define KUART_CAPABILITY_RS232	(1<<KUART_MODE_RS232)
+#define KUART_CAPABILITY_MASK	0x0000000f
+
+/* Additional Control Register DTR line configuration */
+#define UART_ACR_DTRLC_MASK		0x18
+#define UART_ACR_DTRLC_COMPAT		0x00
+#define UART_ACR_DTRLC_ENABLE_LOW	0x10
+
+struct kuart {
+	struct keba_uart_auxdev *auxdev;
+	void __iomem *base;
+	int line;
+
+	unsigned long flags;
+	u8 capability;
+	int mode;
+};
+
+static void kuart_set_phy_mode(struct kuart *kuart, int mode)
+{
+	iowrite8(mode, kuart->base + KUART_CONTROL);
+}
+
+static void kuart_enhanced_mode(struct uart_8250_port *up, bool enable)
+{
+	u8 lcr, efr;
+
+	/* backup LCR register */
+	lcr = serial_in(up, UART_LCR);
+
+	/* enable 650 compatible register set (EFR, ...) */
+	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
+
+	/* enable/disable enhanced mode with indexed control registers */
+	efr = serial_in(up, UART_EFR);
+	if (enable)
+		efr |= UART_EFR_ECB;
+	else
+		efr &= ~UART_EFR_ECB;
+	serial_out(up, UART_EFR, efr);
+
+	/* disable 650 compatible register set, restore LCR */
+	serial_out(up, UART_LCR, lcr);
+}
+
+static void kuart_dtr_line_config(struct uart_8250_port *up, u8 dtrlc)
+{
+	u8 acr;
+
+	/* set index register to 0 to access ACR register */
+	serial_out(up, UART_SCR, UART_ACR);
+
+	/* set value register to 0x10 writing DTR mode (1,0) */
+	acr = serial_in(up, UART_LSR);
+	acr &= ~UART_ACR_DTRLC_MASK;
+	acr |= dtrlc;
+	serial_out(up, UART_LSR, acr);
+}
+
+static int kuart_rs485_config(struct uart_port *port, struct ktermios *termios,
+			      struct serial_rs485 *rs485)
+{
+	struct uart_8250_port *up = up_to_u8250p(port);
+	struct kuart *kuart = port->private_data;
+	int mode;
+	u8 dtrlc;
+
+	if (rs485->flags & SER_RS485_ENABLED) {
+		if (rs485->flags & SER_RS485_MODE_RS422)
+			mode = KUART_MODE_RS422;
+		else
+			mode = KUART_MODE_RS485;
+	} else {
+		mode = KUART_MODE_RS232;
+	}
+
+	if (mode == kuart->mode)
+		return 0;
+
+	if (kuart->flags & KUART_USE_CAPABILITY) {
+		/* deactivate physical interface, break before make */
+		kuart_set_phy_mode(kuart, KUART_MODE_NONE);
+	}
+
+	if (mode == KUART_MODE_RS485) {
+		/*
+		 * Set DTR line configuration of 95x UART to DTR mode (1,0).
+		 * In this mode the DTR pin drives the active-low enable pin of
+		 * an external RS485 buffer. The DTR pin will be forced low
+		 * whenever the transmitter is not empty, otherwise DTR pin is
+		 * high.
+		 */
+		dtrlc = UART_ACR_DTRLC_ENABLE_LOW;
+	} else {
+		/*
+		 * Set DTR line configuration of 95x UART to DTR mode (0,0).
+		 * In this mode the DTR pin is compatible with 16C450, 16C550,
+		 * 16C650 and 16c670 (i.e. normal).
+		 */
+		dtrlc = UART_ACR_DTRLC_COMPAT;
+	}
+
+	kuart_enhanced_mode(up, true);
+	kuart_dtr_line_config(up, dtrlc);
+	kuart_enhanced_mode(up, false);
+
+	if (kuart->flags & KUART_USE_CAPABILITY) {
+		/* activate selected physical interface */
+		kuart_set_phy_mode(kuart, mode);
+	}
+
+	kuart->mode = mode;
+
+	return 0;
+}
+
+static int kuart_probe(struct auxiliary_device *auxdev,
+		       const struct auxiliary_device_id *id)
+{
+	struct device *dev = &auxdev->dev;
+	struct uart_8250_port uart = {};
+	struct resource res;
+	struct kuart *kuart;
+	int retval;
+
+	kuart = devm_kzalloc(dev, sizeof(*kuart), GFP_KERNEL);
+	if (!kuart)
+		return -ENOMEM;
+	kuart->auxdev = container_of(auxdev, struct keba_uart_auxdev, auxdev);
+	kuart->flags = id->driver_data;
+	auxiliary_set_drvdata(auxdev, kuart);
+
+	/*
+	 * map only memory in front of UART registers, UART registers will be
+	 * mapped by serial port
+	 */
+	res = kuart->auxdev->io;
+	res.end = res.start + KUART_BASE - 1;
+	kuart->base = devm_ioremap_resource(dev, &res);
+	if (IS_ERR(kuart->base))
+		return PTR_ERR(kuart->base);
+
+	if (kuart->flags & KUART_USE_CAPABILITY) {
+		/*
+		 * supported modes are read from capability register, at least
+		 * one mode other than none must be supported
+		 */
+		kuart->capability = ioread8(kuart->base + KUART_CAPABILITY) &
+				    KUART_CAPABILITY_MASK;
+		if ((kuart->capability & ~KUART_CAPABILITY_NONE) == 0)
+			return -EIO;
+	}
+
+	spin_lock_init(&uart.port.lock);
+	uart.port.dev = dev;
+	uart.port.mapbase = kuart->auxdev->io.start + KUART_BASE;
+	uart.port.irq = kuart->auxdev->irq;
+	uart.port.uartclk = KUART_CLK;
+	uart.port.private_data = kuart;
+
+	/* 8 bit registers are 32 bit aligned => shift register offset */
+	uart.port.iotype = UPIO_MEM32;
+	uart.port.regshift = KUART_REGSHIFT;
+
+	/*
+	 * UART mixes 16550, 16750 and 16C950 (for RS485) standard => auto
+	 * configuration works best
+	 */
+	uart.port.flags = UPF_SKIP_TEST | UPF_BOOT_AUTOCONF | UPF_IOREMAP;
+
+	/*
+	 * UART supports RS485, RS422 and RS232 with switching of physical
+	 * interface
+	 */
+	uart.port.rs485_config = kuart_rs485_config;
+	if (kuart->flags & KUART_RS485) {
+		uart.port.rs485_supported.flags = SER_RS485_ENABLED |
+						  SER_RS485_RTS_ON_SEND;
+		uart.port.rs485.flags = SER_RS485_ENABLED |
+					SER_RS485_RTS_ON_SEND;
+	}
+	if (kuart->flags & KUART_USE_CAPABILITY) {
+		/* default mode priority is RS485 > RS422 > RS232 */
+		if (kuart->capability & KUART_CAPABILITY_RS422) {
+			uart.port.rs485_supported.flags |= SER_RS485_ENABLED |
+							   SER_RS485_RTS_ON_SEND |
+							   SER_RS485_MODE_RS422;
+			uart.port.rs485.flags = SER_RS485_ENABLED |
+						SER_RS485_RTS_ON_SEND |
+						SER_RS485_MODE_RS422;
+		}
+		if (kuart->capability & KUART_CAPABILITY_RS485) {
+			uart.port.rs485_supported.flags |= SER_RS485_ENABLED |
+							   SER_RS485_RTS_ON_SEND;
+			uart.port.rs485.flags = SER_RS485_ENABLED |
+						SER_RS485_RTS_ON_SEND;
+		}
+	}
+
+	retval = serial8250_register_8250_port(&uart);
+	if (retval < 0) {
+		dev_err(&auxdev->dev, "UART registration failed!\n");
+		return retval;
+	}
+	kuart->line = retval;
+
+	return 0;
+}
+
+static void kuart_remove(struct auxiliary_device *auxdev)
+{
+	struct kuart *kuart = auxiliary_get_drvdata(auxdev);
+
+	if (kuart->flags & KUART_USE_CAPABILITY)
+		kuart_set_phy_mode(kuart, KUART_MODE_NONE);
+
+	serial8250_unregister_port(kuart->line);
+}
+
+static const struct auxiliary_device_id kuart_devtype_aux[] = {
+	{ .name = "keba.rs485-uart", .driver_data = KUART_RS485 },
+	{ .name = "keba.rs232-uart", .driver_data = 0 },
+	{ .name = "keba.uart", .driver_data = KUART_USE_CAPABILITY },
+	{}
+};
+MODULE_DEVICE_TABLE(auxiliary, kuart_devtype_aux);
+
+static struct auxiliary_driver kuart_driver_aux = {
+	.name = KUART,
+	.id_table = kuart_devtype_aux,
+	.probe  = kuart_probe,
+	.remove = kuart_remove,
+};
+module_auxiliary_driver(kuart_driver_aux);
+
+MODULE_AUTHOR("Gerhard Engleder <eg@keba.com>");
+MODULE_DESCRIPTION("KEBA 8250 serial port driver");
+MODULE_LICENSE("GPL");
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index f64ef0819cd4..5c3e4bcb3b93 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -430,6 +430,19 @@ config SERIAL_8250_IOC3
 	  behind the IOC3 device on those systems.  Maximum baud speed is
 	  38400bps using this driver.
 
+config SERIAL_8250_KEBA
+	tristate "Support for KEBA 8250 UART"
+	depends on SERIAL_8250
+	depends on KEBA_CP500
+	help
+	  Selecting this option will add support for KEBA UARTs. These UARTs
+	  are used for the serial interfaces of KEBA PLCs.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called 8250_keba.
+
+	  If unsure, say N.
+
 config SERIAL_8250_RT288X
 	bool "Ralink RT288x/RT305x/RT3662/RT3883 serial port support"
 	depends on SERIAL_8250
diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
index 513a0941c284..f7a463c9860a 100644
--- a/drivers/tty/serial/8250/Makefile
+++ b/drivers/tty/serial/8250/Makefile
@@ -38,6 +38,7 @@ obj-$(CONFIG_SERIAL_8250_HP300)		+= 8250_hp300.o
 obj-$(CONFIG_SERIAL_8250_HUB6)		+= 8250_hub6.o
 obj-$(CONFIG_SERIAL_8250_INGENIC)	+= 8250_ingenic.o
 obj-$(CONFIG_SERIAL_8250_IOC3)		+= 8250_ioc3.o
+obj-$(CONFIG_SERIAL_8250_KEBA)		+= 8250_keba.o
 obj-$(CONFIG_SERIAL_8250_LPC18XX)	+= 8250_lpc18xx.o
 obj-$(CONFIG_SERIAL_8250_LPSS)		+= 8250_lpss.o
 obj-$(CONFIG_SERIAL_8250_MEN_MCB)	+= 8250_men_mcb.o
-- 
2.39.5

Re: [PATCH 2/2] serial: 8250: add driver for KEBA UART

[Jiri Slaby]

On 14. 10. 25, 21:15, Gerhard Engleder wrote:
> From: Gerhard Engleder <eg@keba.com>
> 
> The KEBA UART is found in the system FPGA of KEBA PLC devices. It is
> mostly 8250 compatible with extension for some UART modes.
> 
> 3 different variants exist. The simpliest variant supports only RS-232
> and is used for debug interfaces. The next variant supports only RS-485
> and is used mostly for communication with KEBA panel devices. The third
> variant is able to support RS-232, RS-485 and RS-422. For this variant
> not only the mode of the UART is configured, also the physics and
> transceivers are switched according to the mode.
> 
> Signed-off-by: Gerhard Engleder <eg@keba.com>
> Tested-by: Daniel Gierlinger <gida@keba.com>
> ---
>   drivers/tty/serial/8250/8250_keba.c | 279 ++++++++++++++++++++++++++++
>   drivers/tty/serial/8250/Kconfig     |  13 ++
>   drivers/tty/serial/8250/Makefile    |   1 +
>   3 files changed, 293 insertions(+)
>   create mode 100644 drivers/tty/serial/8250/8250_keba.c
> 
> diff --git a/drivers/tty/serial/8250/8250_keba.c b/drivers/tty/serial/8250/8250_keba.c
> new file mode 100644
> index 000000000000..e1dccc0e1026
> --- /dev/null
> +++ b/drivers/tty/serial/8250/8250_keba.c
> @@ -0,0 +1,279 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2025 KEBA Industrial Automation GmbH
> + *
> + * Driver for KEBA UART FPGA IP core
> + */
> +
> +#include <linux/module.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/device.h>
> +#include <linux/auxiliary_bus.h>
> +#include <linux/misc/keba.h>
> +
> +#include "8250.h"
> +
> +#define KUART "kuart"
> +
> +/* flags */
> +#define KUART_RS485		0x00000001
> +#define KUART_USE_CAPABILITY	0x00000002

use BIT()

> +/* registers */
> +#define KUART_VERSION		0x0000
> +#define KUART_REVISION		0x0001
> +#define KUART_CAPABILITY	0x0002
> +#define KUART_CONTROL		0x0004
> +#define KUART_BASE		0x000C
> +#define KUART_REGSHIFT		2
> +#define KUART_CLK		1843200
> +
> +/* mode flags */
> +#define KUART_MODE_NONE		0
> +#define KUART_MODE_RS485	1
> +#define KUART_MODE_RS422	2
> +#define KUART_MODE_RS232	3

Use enum.

> +/* capability flags */
> +#define KUART_CAPABILITY_NONE	(1<<KUART_MODE_NONE)
> +#define KUART_CAPABILITY_RS485	(1<<KUART_MODE_RS485)
> +#define KUART_CAPABILITY_RS422	(1<<KUART_MODE_RS422)
> +#define KUART_CAPABILITY_RS232	(1<<KUART_MODE_RS232)

use BIT()

> +#define KUART_CAPABILITY_MASK	0x0000000f

Use GENMASK().

> +/* Additional Control Register DTR line configuration */
> +#define UART_ACR_DTRLC_MASK		0x18
> +#define UART_ACR_DTRLC_COMPAT		0x00
> +#define UART_ACR_DTRLC_ENABLE_LOW	0x10
> +
> +struct kuart {
> +	struct keba_uart_auxdev *auxdev;
> +	void __iomem *base;
> +	int line;

unsigned

> +
> +	unsigned long flags;

I would say unsigned int would be enough.

> +	u8 capability;
> +	int mode;

Use the new enum as a type.

> +};
> +
> +static void kuart_set_phy_mode(struct kuart *kuart, int mode)

enum too.

> +{
> +	iowrite8(mode, kuart->base + KUART_CONTROL);
> +}
...
> +static int kuart_rs485_config(struct uart_port *port, struct ktermios *termios,
> +			      struct serial_rs485 *rs485)
> +{
> +	struct uart_8250_port *up = up_to_u8250p(port);
> +	struct kuart *kuart = port->private_data;
> +	int mode;

enum

...
> +	return 0;
> +}

Otherwise looks good.

thanks,
-- 
js
suse labs

Re: [PATCH 2/2] serial: 8250: add driver for KEBA UART

[Gerhard Engleder]

On 15.10.25 08:14, Jiri Slaby wrote:
> On 14. 10. 25, 21:15, Gerhard Engleder wrote:
>> +/* flags */
>> +#define KUART_RS485        0x00000001
>> +#define KUART_USE_CAPABILITY    0x00000002
> 
> use BIT()
> 
>> +/* registers */
>> +#define KUART_VERSION        0x0000
>> +#define KUART_REVISION        0x0001
>> +#define KUART_CAPABILITY    0x0002
>> +#define KUART_CONTROL        0x0004
>> +#define KUART_BASE        0x000C
>> +#define KUART_REGSHIFT        2
>> +#define KUART_CLK        1843200
>> +
>> +/* mode flags */
>> +#define KUART_MODE_NONE        0
>> +#define KUART_MODE_RS485    1
>> +#define KUART_MODE_RS422    2
>> +#define KUART_MODE_RS232    3
> 
> Use enum.
> 
>> +/* capability flags */
>> +#define KUART_CAPABILITY_NONE    (1<<KUART_MODE_NONE)
>> +#define KUART_CAPABILITY_RS485    (1<<KUART_MODE_RS485)
>> +#define KUART_CAPABILITY_RS422    (1<<KUART_MODE_RS422)
>> +#define KUART_CAPABILITY_RS232    (1<<KUART_MODE_RS232)
> 
> use BIT()
> 
>> +#define KUART_CAPABILITY_MASK    0x0000000f
> 
> Use GENMASK().
> 
>> +/* Additional Control Register DTR line configuration */
>> +#define UART_ACR_DTRLC_MASK        0x18
>> +#define UART_ACR_DTRLC_COMPAT        0x00
>> +#define UART_ACR_DTRLC_ENABLE_LOW    0x10
>> +
>> +struct kuart {
>> +    struct keba_uart_auxdev *auxdev;
>> +    void __iomem *base;
>> +    int line;
> 
> unsigned
> 
>> +
>> +    unsigned long flags;
> 
> I would say unsigned int would be enough.
> 
>> +    u8 capability;
>> +    int mode;
> 
> Use the new enum as a type.
> 
>> +};
>> +
>> +static void kuart_set_phy_mode(struct kuart *kuart, int mode)
> 
> enum too.
> 
>> +{
>> +    iowrite8(mode, kuart->base + KUART_CONTROL);
>> +}
> ...
>> +static int kuart_rs485_config(struct uart_port *port, struct ktermios 
>> *termios,
>> +                  struct serial_rs485 *rs485)
>> +{
>> +    struct uart_8250_port *up = up_to_u8250p(port);
>> +    struct kuart *kuart = port->private_data;
>> +    int mode;
> 
> enum
> 
> ...
>> +    return 0;
>> +}

I will improve the code as suggested.

Thank you for your review!

Gerhard