platform: cznic: turris-omnia-mcu: Add support for MCU watchdog

Add support for the watchdog mechanism provided by the MCU.

Signed-off-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Link: https://lore.kernel.org/r/20240701113010.16447-6-kabel@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/platform/cznic/Kconfig

@@ -19,6 +19,7 @@ config TURRIS_OMNIA_MCU
 	select GPIOLIB
 	select GPIOLIB_IRQCHIP
 	select RTC_CLASS
+	select WATCHDOG_CORE
 	help
 	  Say Y here to add support for the features implemented by the
 	  microcontroller on the CZ.NIC's Turris Omnia SOHO router.
@@ -26,6 +27,7 @@ config TURRIS_OMNIA_MCU
 	  - board poweroff into true low power mode (with voltage regulators
 	    disabled) and the ability to configure wake up from this mode (via
 	    rtcwake)
+	  - MCU watchdog
 	  - GPIO pins
 	    - to get front button press events (the front button can be
 	      configured either to generate press events to the CPU or to change

drivers/platform/cznic/Makefile

@@ -4,3 +4,4 @@ obj-$(CONFIG_TURRIS_OMNIA_MCU)	+= turris-omnia-mcu.o
 turris-omnia-mcu-y		:= turris-omnia-mcu-base.o
 turris-omnia-mcu-y		+= turris-omnia-mcu-gpio.o
 turris-omnia-mcu-y		+= turris-omnia-mcu-sys-off-wakeup.o
+turris-omnia-mcu-y		+= turris-omnia-mcu-watchdog.o

drivers/platform/cznic/turris-omnia-mcu-base.c

@@ -377,6 +377,10 @@ static int omnia_mcu_probe(struct i2c_client *client)
 	if (err)
 		return err;
 
+	err = omnia_mcu_register_watchdog(mcu);
+	if (err)
+		return err;
+
 	return omnia_mcu_register_gpiochip(mcu);
 }
 

drivers/platform/cznic/turris-omnia-mcu-watchdog.c

@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * CZ.NIC's Turris Omnia MCU watchdog driver
+ *
+ * 2024 by Marek Behún <kabel@kernel.org>
+ */
+
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/moduleparam.h>
+#include <linux/types.h>
+#include <linux/units.h>
+#include <linux/watchdog.h>
+
+#include <linux/turris-omnia-mcu-interface.h>
+#include "turris-omnia-mcu.h"
+
+#define WATCHDOG_TIMEOUT		120
+
+static unsigned int timeout;
+module_param(timeout, int, 0);
+MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds");
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+module_param(nowayout, bool, 0);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
+			   __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+static int omnia_wdt_start(struct watchdog_device *wdt)
+{
+	struct omnia_mcu *mcu = watchdog_get_drvdata(wdt);
+
+	return omnia_cmd_write_u8(mcu->client, OMNIA_CMD_SET_WATCHDOG_STATE, 1);
+}
+
+static int omnia_wdt_stop(struct watchdog_device *wdt)
+{
+	struct omnia_mcu *mcu = watchdog_get_drvdata(wdt);
+
+	return omnia_cmd_write_u8(mcu->client, OMNIA_CMD_SET_WATCHDOG_STATE, 0);
+}
+
+static int omnia_wdt_ping(struct watchdog_device *wdt)
+{
+	struct omnia_mcu *mcu = watchdog_get_drvdata(wdt);
+
+	return omnia_cmd_write_u8(mcu->client, OMNIA_CMD_SET_WATCHDOG_STATE, 1);
+}
+
+static int omnia_wdt_set_timeout(struct watchdog_device *wdt,
+				 unsigned int timeout)
+{
+	struct omnia_mcu *mcu = watchdog_get_drvdata(wdt);
+
+	return omnia_cmd_write_u16(mcu->client, OMNIA_CMD_SET_WDT_TIMEOUT,
+				   timeout * DECI);
+}
+
+static unsigned int omnia_wdt_get_timeleft(struct watchdog_device *wdt)
+{
+	struct omnia_mcu *mcu = watchdog_get_drvdata(wdt);
+	u16 timeleft;
+	int err;
+
+	err = omnia_cmd_read_u16(mcu->client, OMNIA_CMD_GET_WDT_TIMELEFT,
+				 &timeleft);
+	if (err) {
+		dev_err(&mcu->client->dev, "Cannot get watchdog timeleft: %d\n",
+			err);
+		return 0;
+	}
+
+	return timeleft / DECI;
+}
+
+static const struct watchdog_info omnia_wdt_info = {
+	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
+	.identity = "Turris Omnia MCU Watchdog",
+};
+
+static const struct watchdog_ops omnia_wdt_ops = {
+	.owner		= THIS_MODULE,
+	.start		= omnia_wdt_start,
+	.stop		= omnia_wdt_stop,
+	.ping		= omnia_wdt_ping,
+	.set_timeout	= omnia_wdt_set_timeout,
+	.get_timeleft	= omnia_wdt_get_timeleft,
+};
+
+int omnia_mcu_register_watchdog(struct omnia_mcu *mcu)
+{
+	struct device *dev = &mcu->client->dev;
+	u8 state;
+	int err;
+
+	if (!(mcu->features & OMNIA_FEAT_WDT_PING))
+		return 0;
+
+	mcu->wdt.info = &omnia_wdt_info;
+	mcu->wdt.ops = &omnia_wdt_ops;
+	mcu->wdt.parent = dev;
+	mcu->wdt.min_timeout = 1;
+	mcu->wdt.max_timeout = 65535 / DECI;
+
+	mcu->wdt.timeout = WATCHDOG_TIMEOUT;
+	watchdog_init_timeout(&mcu->wdt, timeout, dev);
+
+	watchdog_set_drvdata(&mcu->wdt, mcu);
+
+	omnia_wdt_set_timeout(&mcu->wdt, mcu->wdt.timeout);
+
+	err = omnia_cmd_read_u8(mcu->client, OMNIA_CMD_GET_WATCHDOG_STATE,
+				&state);
+	if (err)
+		return dev_err_probe(dev, err,
+				     "Cannot get MCU watchdog state\n");
+
+	if (state)
+		set_bit(WDOG_HW_RUNNING, &mcu->wdt.status);
+
+	watchdog_set_nowayout(&mcu->wdt, nowayout);
+	watchdog_stop_on_reboot(&mcu->wdt);
+	err = devm_watchdog_register_device(dev, &mcu->wdt);
+	if (err)
+		return dev_err_probe(dev, err,
+				     "Cannot register MCU watchdog\n");
+
+	return 0;
+}

drivers/platform/cznic/turris-omnia-mcu.h

@@ -13,6 +13,7 @@
 #include <linux/if_ether.h>
 #include <linux/mutex.h>
 #include <linux/types.h>
+#include <linux/watchdog.h>
 #include <linux/workqueue.h>
 #include <asm/byteorder.h>
 #include <asm/unaligned.h>
@@ -43,6 +44,9 @@ struct omnia_mcu {
 	struct rtc_device *rtcdev;
 	u32 rtc_alarm;
 	bool front_button_poweron;
+
+	/* MCU watchdog */
+	struct watchdog_device wdt;
 };
 
 int omnia_cmd_write_read(const struct i2c_client *client,
@@ -55,6 +59,25 @@ static inline int omnia_cmd_write(const struct i2c_client *client, void *cmd,
 	return omnia_cmd_write_read(client, cmd, len, NULL, 0);
 }
 
+static inline int omnia_cmd_write_u8(const struct i2c_client *client, u8 cmd,
+				     u8 val)
+{
+	u8 buf[2] = { cmd, val };
+
+	return omnia_cmd_write(client, buf, sizeof(buf));
+}
+
+static inline int omnia_cmd_write_u16(const struct i2c_client *client, u8 cmd,
+				      u16 val)
+{
+	u8 buf[3];
+
+	buf[0] = cmd;
+	put_unaligned_le16(val, &buf[1]);
+
+	return omnia_cmd_write(client, buf, sizeof(buf));
+}
+
 static inline int omnia_cmd_write_u32(const struct i2c_client *client, u8 cmd,
 				      u32 val)
 {
@@ -158,5 +181,6 @@ extern const struct attribute_group omnia_mcu_poweroff_group;
 
 int omnia_mcu_register_gpiochip(struct omnia_mcu *mcu);
 int omnia_mcu_register_sys_off_and_wakeup(struct omnia_mcu *mcu);
+int omnia_mcu_register_watchdog(struct omnia_mcu *mcu);
 
 #endif /* __TURRIS_OMNIA_MCU_H */