Re: [PATCH v6 5/5] watchdog: aaeon: Add watchdog driver for SRG-IMX8P MCU

[Guenter Roeck]

On 6/30/26 05:51, Thomas Perrot (Schneider Electric) wrote:
> Add watchdog driver for the Aaeon SRG-IMX8P embedded controller.
> This driver provides system monitoring and recovery capabilities
> through the MCU's watchdog timer.
>
> The watchdog supports start, stop, and ping operations with a maximum
> hardware heartbeat of 25 seconds and a default timeout of 240 seconds.
> The software timeout can be changed via the WDIOC_SETTIMEOUT ioctl,
> the DT timeout-sec property, or the watchdog_timeout kernel boot
> parameter.
>
> Co-developed-by: Jérémie Dautheribes (Schneider Electric) <jeremie.dautheribes@xxxxxxxxxxx>
> Signed-off-by: Jérémie Dautheribes (Schneider Electric) <jeremie.dautheribes@xxxxxxxxxxx>
> Signed-off-by: Thomas Perrot (Schneider Electric) <thomas.perrot@xxxxxxxxxxx>
> Acked-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> ---
>   MAINTAINERS                      |   1 +
>   drivers/watchdog/Kconfig         |  10 +++
>   drivers/watchdog/Makefile        |   1 +
>   drivers/watchdog/aaeon_mcu_wdt.c | 144 +++++++++++++++++++++++++++++++++++++++
>   4 files changed, 156 insertions(+)
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 2538f8c4bc14..7b92af42c9fd 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -193,6 +193,7 @@ S:	Maintained
>   F:	Documentation/devicetree/bindings/mfd/aaeon,srg-imx8p-mcu.yaml
>   F:	drivers/gpio/gpio-aaeon-mcu.c
>   F:	drivers/mfd/aaeon-mcu.c
> +F:	drivers/watchdog/aaeon_mcu_wdt.c
>   F:	include/linux/mfd/aaeon-mcu.h
>   
>   AAEON UPBOARD FPGA MFD DRIVER
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index d3b9df7d466b..f67a0b453316 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -420,6 +420,16 @@ config SL28CPLD_WATCHDOG
>   
>   # ARM Architecture
>   
> +config AAEON_MCU_WATCHDOG
> +	tristate "Aaeon MCU Watchdog"
> +	depends on MFD_AAEON_MCU
> +	select WATCHDOG_CORE
> +	help
> +	  Select this option to enable watchdog timer support for the Aaeon
> +	  SRG-IMX8P onboard microcontroller (MCU). This driver provides
> +	  watchdog functionality through the MCU, allowing system monitoring
> +	  and automatic recovery from system hangs.
> +
>   config AIROHA_WATCHDOG
>   	tristate "Airoha EN7581 Watchdog"
>   	depends on ARCH_AIROHA || COMPILE_TEST
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index ba52099b1253..2deec425d3ea 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -37,6 +37,7 @@ obj-$(CONFIG_USBPCWATCHDOG) += pcwd_usb.o
>   # ALPHA Architecture
>   
>   # ARM Architecture
> +obj-$(CONFIG_AAEON_MCU_WATCHDOG) += aaeon_mcu_wdt.o
>   obj-$(CONFIG_ARM_SP805_WATCHDOG) += sp805_wdt.o
>   obj-$(CONFIG_ARM_SBSA_WATCHDOG) += sbsa_gwdt.o
>   obj-$(CONFIG_ARMADA_37XX_WATCHDOG) += armada_37xx_wdt.o
> diff --git a/drivers/watchdog/aaeon_mcu_wdt.c b/drivers/watchdog/aaeon_mcu_wdt.c
> new file mode 100644
> index 000000000000..347ee8269bfd
> --- /dev/null
> +++ b/drivers/watchdog/aaeon_mcu_wdt.c
> @@ -0,0 +1,144 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Aaeon MCU Watchdog driver
> + *
> + * Copyright (C) 2026 Bootlin
> + * Author: Jérémie Dautheribes <jeremie.dautheribes@xxxxxxxxxxx>
> + * Author: Thomas Perrot <thomas.perrot@xxxxxxxxxxx>
> + */
> +
> +#include <linux/mfd/aaeon-mcu.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/watchdog.h>
> +
> +#define AAEON_MCU_PING_WDT	0x73
> +
> +#define AAEON_MCU_WDT_TIMEOUT         240
> +#define AAEON_MCU_WDT_HEARTBEAT_MS    25000
> +#define AAEON_MCU_WDT_MIN_TIMEOUT     1
> +#define AAEON_MCU_WDT_MAX_TIMEOUT     3600
> +
> +static unsigned int timeout;
> +module_param(timeout, uint, 0);
> +MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds");
> +
> +struct aaeon_mcu_wdt {
> +	struct watchdog_device wdt;
> +	struct regmap *regmap;
> +};
> +
> +static int aaeon_mcu_wdt_cmd(struct aaeon_mcu_wdt *data, u8 opcode, u8 arg)
> +{
> +	return regmap_write(data->regmap, AAEON_MCU_REG(opcode, arg), 0);
> +}
> +
> +static int aaeon_mcu_wdt_start(struct watchdog_device *wdt)
> +{
> +	struct aaeon_mcu_wdt *data = watchdog_get_drvdata(wdt);
> +
> +	return aaeon_mcu_wdt_cmd(data, AAEON_MCU_CONTROL_WDT_OPCODE, 0x01);
> +}
> +
> +static int aaeon_mcu_wdt_status(struct watchdog_device *wdt, bool *enabled)
> +{
> +	struct aaeon_mcu_wdt *data = watchdog_get_drvdata(wdt);
> +	unsigned int rsp;
> +	int ret;
> +
> +	ret = regmap_read(data->regmap,
> +			  AAEON_MCU_REG(AAEON_MCU_CONTROL_WDT_OPCODE, 0x02),
> +			  &rsp);
> +	if (ret)
> +		return ret;
> +
> +	*enabled = rsp == 0x01;
> +	return 0;
> +}
> +
> +static int aaeon_mcu_wdt_stop(struct watchdog_device *wdt)
> +{
> +	struct aaeon_mcu_wdt *data = watchdog_get_drvdata(wdt);
> +
> +	return aaeon_mcu_wdt_cmd(data, AAEON_MCU_CONTROL_WDT_OPCODE, 0x00);
> +}
> +
> +static int aaeon_mcu_wdt_ping(struct watchdog_device *wdt)
> +{
> +	struct aaeon_mcu_wdt *data = watchdog_get_drvdata(wdt);
> +
> +	return aaeon_mcu_wdt_cmd(data, AAEON_MCU_PING_WDT, 0x00);
> +}
> +
> +static const struct watchdog_info aaeon_mcu_wdt_info = {
> +	.identity	= "Aaeon MCU Watchdog",
> +	.options	= WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT
> +};
> +
> +static const struct watchdog_ops aaeon_mcu_wdt_ops = {
> +	.owner		= THIS_MODULE,
> +	.start		= aaeon_mcu_wdt_start,
> +	.stop		= aaeon_mcu_wdt_stop,
> +	.ping		= aaeon_mcu_wdt_ping,
> +};
> +
> +static int aaeon_mcu_wdt_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct watchdog_device *wdt;
> +	struct aaeon_mcu_wdt *data;
> +	bool enabled;
> +	int ret;
> +
> +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	data->regmap = dev_get_regmap(dev->parent, NULL);
> +	if (!data->regmap)
> +		return -ENODEV;
> +
> +	wdt = &data->wdt;
> +	wdt->parent = dev;
> +	wdt->info = &aaeon_mcu_wdt_info;
> +	wdt->ops = &aaeon_mcu_wdt_ops;
> +	/*
> +	 * The MCU firmware has a fixed hardware timeout of 25 seconds that
> +	 * cannot be changed. The watchdog core handles automatic pinging to
> +	 * support software timeouts longer than the hardware limit. The default
> +	 * software timeout of 240 seconds can be overridden via the DT
> +	 * timeout-sec property or the watchdog_timeout kernel boot parameter.
> +	 */
> +	wdt->timeout = AAEON_MCU_WDT_TIMEOUT;
> +	wdt->min_timeout = AAEON_MCU_WDT_MIN_TIMEOUT;
> +	wdt->max_timeout = AAEON_MCU_WDT_MAX_TIMEOUT;
> +	wdt->max_hw_heartbeat_ms = AAEON_MCU_WDT_HEARTBEAT_MS;

Either max_timeout or max_hw_heartbeat_ms should be set, but not both.
From the include file:

 * @max_timeout:The watchdog devices maximum timeout value (in seconds)
 *              as configurable from user space. Only relevant if
 *              max_hw_heartbeat_ms is not provided.

In other words, max_timeout is ignored by the watchdog core.

> +	watchdog_init_timeout(wdt, timeout, dev);

As pointed out by Sashiko, this will not initialize the timeout from
devicetree. You'll need to either adjust the code or the comment above.

Thanks,
Guenter

> +
> +	watchdog_set_drvdata(wdt, data);
> +	watchdog_stop_on_reboot(wdt);
> +
> +	ret = aaeon_mcu_wdt_status(wdt, &enabled);
> +	if (ret)
> +		return ret;
> +
> +	if (enabled)
> +		set_bit(WDOG_HW_RUNNING, &wdt->status);
> +
> +	return devm_watchdog_register_device(dev, wdt);
> +}
> +
> +static struct platform_driver aaeon_mcu_wdt_driver = {
> +	.driver		= {
> +		.name	= "aaeon-mcu-wdt",
> +	},
> +	.probe		= aaeon_mcu_wdt_probe,
> +};
> +
> +module_platform_driver(aaeon_mcu_wdt_driver);
> +
> +MODULE_ALIAS("platform:aaeon-mcu-wdt");
> +MODULE_DESCRIPTION("Aaeon MCU Watchdog Driver");
> +MODULE_AUTHOR("Jérémie Dautheribes <jeremie.dautheribes@xxxxxxxxxxx>");
> +MODULE_LICENSE("GPL");