[PATCH v3 0/2] serial: add KEBA UART driver

[PATCH v3 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 modes 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.

v3:
- add info to commit why device tree / ACPI is not possible (Lukas Wunner)
- separate if and comment for change in uart_get_rs485_mode() (Lukas Wunner)

v2:
- use BIT() for flag definition (Jiri Slaby)
- use enum for UART mode definition (Jiri Slaby)
- use BIT() for capability flag definition (Jiri Slaby)
- use GENMASK() for capability mask (Jiri Slaby)
- use unsigned int for serial line number (Jiri Slaby)
- use unsigned int for flags (Jiri Slaby)

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 | 281 ++++++++++++++++++++++++++++
 drivers/tty/serial/8250/Kconfig     |  13 ++
 drivers/tty/serial/8250/Makefile    |   1 +
 drivers/tty/serial/serial_core.c    |   8 +
 4 files changed, 303 insertions(+)
 create mode 100644 drivers/tty/serial/8250/8250_keba.c

-- 
2.39.5

[PATCH v3 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 within uart_get_rs485_mode(). 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.

The default rs485 mode can also be set by firmware nodes. But for some
devices a firmware node does not exist. E.g., for a PCIe based serial
interface on x86 no device tree is available and the ACPI information of
the BIOS often cannot by modified. In this case it shall be possible,
that a driver works out of the box by setting a reasonable default rs485
mode.

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, 8 insertions(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 4757293ece8c..9c476d9667a3 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -3536,6 +3536,14 @@ int uart_get_rs485_mode(struct uart_port *port)
 	if (!(port->rs485_supported.flags & SER_RS485_ENABLED))
 		return 0;
 
+	/*
+	 * Retrieve properties only 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 (!dev_fwnode(dev))
+		return 0;
+
 	ret = device_property_read_u32_array(dev, "rs485-rts-delay",
 					     rs485_delay, 2);
 	if (!ret) {
-- 
2.39.5

[PATCH v3 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 | 281 ++++++++++++++++++++++++++++
 drivers/tty/serial/8250/Kconfig     |  13 ++
 drivers/tty/serial/8250/Makefile    |   1 +
 3 files changed, 295 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..b923556139ee
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_keba.c
@@ -0,0 +1,281 @@
+// 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		BIT(0)
+#define KUART_USE_CAPABILITY	BIT(1)
+
+/* 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 */
+enum kuart_mode {
+	KUART_MODE_NONE = 0,
+	KUART_MODE_RS485,
+	KUART_MODE_RS422,
+	KUART_MODE_RS232
+};
+
+/* capability flags */
+#define KUART_CAPABILITY_NONE	BIT(KUART_MODE_NONE)
+#define KUART_CAPABILITY_RS485	BIT(KUART_MODE_RS485)
+#define KUART_CAPABILITY_RS422	BIT(KUART_MODE_RS422)
+#define KUART_CAPABILITY_RS232	BIT(KUART_MODE_RS232)
+#define KUART_CAPABILITY_MASK	GENMASK(3, 0)
+
+/* 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;
+	unsigned int line;
+
+	unsigned int flags;
+	u8 capability;
+	enum kuart_mode mode;
+};
+
+static void kuart_set_phy_mode(struct kuart *kuart, enum kuart_mode 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;
+	enum kuart_mode 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 v3 2/2] serial: 8250: add driver for KEBA UART

[Lukas Wunner]

On Mon, Oct 20, 2025 at 09:06:58PM +0200, Gerhard Engleder wrote:
> +++ b/drivers/tty/serial/8250/8250_keba.c
> @@ -0,0 +1,281 @@
> +// 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>

Duplicate inclusion of <linux/module.h>.

Usually these are sorted alphabetically.

Thanks,

Lukas

Re: [PATCH v3 1/2] serial: Keep rs485 settings for devices without firmware node

[Lukas Wunner]

On Mon, Oct 20, 2025 at 09:06:57PM +0200, Gerhard Engleder wrote:
> +++ b/drivers/tty/serial/serial_core.c
> @@ -3536,6 +3536,14 @@ int uart_get_rs485_mode(struct uart_port *port)
>  	if (!(port->rs485_supported.flags & SER_RS485_ENABLED))
>  		return 0;
>  
> +	/*
> +	 * Retrieve properties only if a firmware node exist. If no firmware
> +	 * node exist, then don't touch rs485 config and keep initial rs485

s/exist/exists/

Thanks,

Lukas

Re: [PATCH v3 1/2] serial: Keep rs485 settings for devices without firmware node

[Gerhard Engleder]

On 23.10.25 12:17, Lukas Wunner wrote:
> On Mon, Oct 20, 2025 at 09:06:57PM +0200, Gerhard Engleder wrote:
>> +++ b/drivers/tty/serial/serial_core.c
>> @@ -3536,6 +3536,14 @@ int uart_get_rs485_mode(struct uart_port *port)
>>   	if (!(port->rs485_supported.flags & SER_RS485_ENABLED))
>>   		return 0;
>>   
>> +	/*
>> +	 * Retrieve properties only if a firmware node exist. If no firmware
>> +	 * node exist, then don't touch rs485 config and keep initial rs485
> 
> s/exist/exists/

Will be fixed. Thanks!

Gerhard

Re: [PATCH v3 2/2] serial: 8250: add driver for KEBA UART

[Gerhard Engleder]

On 23.10.25 03:56, Lukas Wunner wrote:
> On Mon, Oct 20, 2025 at 09:06:58PM +0200, Gerhard Engleder wrote:
>> +++ b/drivers/tty/serial/8250/8250_keba.c
>> @@ -0,0 +1,281 @@
>> +// 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>
> 
> Duplicate inclusion of <linux/module.h>.
> 
> Usually these are sorted alphabetically.

Cleaned up and ordered. Thanks!

Gerhard