watchdog: Add ChromeOS EC-based watchdog driver

Embedded Controller (EC) present on Chromebook devices
can be used as a watchdog.
Implement a driver to support it.

Signed-off-by: Lukasz Majczak <lma@chromium.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20240126095721.782782-3-lma@chromium.org
Signed-off-by: Lee Jones <lee@kernel.org>

MAINTAINERS

@@ -4990,6 +4990,12 @@ R:	Sami Kyöstilä <skyostil@chromium.org>
 S:	Maintained
 F:	drivers/platform/chrome/cros_hps_i2c.c
 
+CHROMEOS EC WATCHDOG
+M:	Lukasz Majczak <lma@chromium.org>
+L:	chrome-platform@lists.linux.dev
+S:	Maintained
+F:	drivers/watchdog/cros_ec_wdt.c
+
 CHRONTEL CH7322 CEC DRIVER
 M:	Joe Tessler <jrt@google.com>
 L:	linux-media@vger.kernel.org

drivers/watchdog/Kconfig

@@ -181,6 +181,17 @@ config BD957XMUF_WATCHDOG
 	  watchdog. Alternatively say M to compile the driver as a module,
 	  which will be called bd9576_wdt.
 
+config CROS_EC_WATCHDOG
+	tristate "ChromeOS EC-based watchdog"
+	select WATCHDOG_CORE
+	depends on CROS_EC
+	help
+	  Watchdog driver for Chromebook devices equipped with embedded controller.
+	  Trigger event is recorded in EC and checked on the subsequent boot.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called cros_ec_wdt.
+
 config DA9052_WATCHDOG
 	tristate "Dialog DA9052 Watchdog"
 	depends on PMIC_DA9052 || COMPILE_TEST

drivers/watchdog/Makefile

@@ -217,6 +217,7 @@ obj-$(CONFIG_XEN_WDT) += xen_wdt.o
 
 # Architecture Independent
 obj-$(CONFIG_BD957XMUF_WATCHDOG) += bd9576_wdt.o
+obj-$(CONFIG_CROS_EC_WATCHDOG) += cros_ec_wdt.o
 obj-$(CONFIG_DA9052_WATCHDOG) += da9052_wdt.o
 obj-$(CONFIG_DA9055_WATCHDOG) += da9055_wdt.o
 obj-$(CONFIG_DA9062_WATCHDOG) += da9062_wdt.o

drivers/watchdog/cros_ec_wdt.c

@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2024 Google LLC.
+ * Author: Lukasz Majczak <lma@chromium.com>
+ */
+
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_data/cros_ec_commands.h>
+#include <linux/platform_data/cros_ec_proto.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+
+#define CROS_EC_WATCHDOG_DEFAULT_TIME	30 /* seconds */
+#define DRV_NAME	"cros-ec-wdt"
+
+union cros_ec_wdt_data {
+	struct ec_params_hang_detect req;
+	struct ec_response_hang_detect resp;
+} __packed;
+
+static int cros_ec_wdt_send_cmd(struct cros_ec_device *cros_ec,
+				union cros_ec_wdt_data *arg)
+{
+	int ret;
+	struct {
+		struct cros_ec_command msg;
+		union cros_ec_wdt_data data;
+	} __packed buf = {
+		.msg = {
+			.version = 0,
+			.command = EC_CMD_HANG_DETECT,
+			.insize  = (arg->req.command == EC_HANG_DETECT_CMD_GET_STATUS) ?
+				   sizeof(struct ec_response_hang_detect) :
+				   0,
+			.outsize = sizeof(struct ec_params_hang_detect),
+		},
+		.data.req = arg->req
+	};
+
+	ret = cros_ec_cmd_xfer_status(cros_ec, &buf.msg);
+	if (ret < 0)
+		return ret;
+
+	arg->resp = buf.data.resp;
+
+	return 0;
+}
+
+static int cros_ec_wdt_ping(struct watchdog_device *wdd)
+{
+	struct cros_ec_device *cros_ec = watchdog_get_drvdata(wdd);
+	union cros_ec_wdt_data arg;
+	int ret;
+
+	arg.req.command = EC_HANG_DETECT_CMD_RELOAD;
+	ret = cros_ec_wdt_send_cmd(cros_ec, &arg);
+	if (ret < 0)
+		dev_dbg(wdd->parent, "Failed to ping watchdog (%d)", ret);
+
+	return ret;
+}
+
+static int cros_ec_wdt_start(struct watchdog_device *wdd)
+{
+	struct cros_ec_device *cros_ec = watchdog_get_drvdata(wdd);
+	union cros_ec_wdt_data arg;
+	int ret;
+
+	/* Prepare watchdog on EC side */
+	arg.req.command = EC_HANG_DETECT_CMD_SET_TIMEOUT;
+	arg.req.reboot_timeout_sec = wdd->timeout;
+	ret = cros_ec_wdt_send_cmd(cros_ec, &arg);
+	if (ret < 0)
+		dev_dbg(wdd->parent, "Failed to start watchdog (%d)", ret);
+
+	return ret;
+}
+
+static int cros_ec_wdt_stop(struct watchdog_device *wdd)
+{
+	struct cros_ec_device *cros_ec = watchdog_get_drvdata(wdd);
+	union cros_ec_wdt_data arg;
+	int ret;
+
+	arg.req.command = EC_HANG_DETECT_CMD_CANCEL;
+	ret = cros_ec_wdt_send_cmd(cros_ec, &arg);
+	if (ret < 0)
+		dev_dbg(wdd->parent, "Failed to stop watchdog (%d)", ret);
+
+	return ret;
+}
+
+static int cros_ec_wdt_set_timeout(struct watchdog_device *wdd, unsigned int t)
+{
+	unsigned int old_timeout = wdd->timeout;
+	int ret;
+
+	wdd->timeout = t;
+	ret = cros_ec_wdt_start(wdd);
+	if (ret < 0)
+		wdd->timeout = old_timeout;
+
+	return ret;
+}
+
+static const struct watchdog_info cros_ec_wdt_ident = {
+	.options          = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
+	.firmware_version = 0,
+	.identity         = DRV_NAME,
+};
+
+static const struct watchdog_ops cros_ec_wdt_ops = {
+	.owner		 = THIS_MODULE,
+	.ping		 = cros_ec_wdt_ping,
+	.start		 = cros_ec_wdt_start,
+	.stop		 = cros_ec_wdt_stop,
+	.set_timeout = cros_ec_wdt_set_timeout,
+};
+
+static int cros_ec_wdt_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct cros_ec_dev *ec_dev = dev_get_drvdata(dev->parent);
+	struct cros_ec_device *cros_ec = ec_dev->ec_dev;
+	struct watchdog_device *wdd;
+	union cros_ec_wdt_data arg;
+	int ret = 0;
+
+	wdd = devm_kzalloc(&pdev->dev, sizeof(*wdd), GFP_KERNEL);
+	if (!wdd)
+		return -ENOMEM;
+
+	arg.req.command = EC_HANG_DETECT_CMD_GET_STATUS;
+	ret = cros_ec_wdt_send_cmd(cros_ec, &arg);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to get watchdog bootstatus");
+
+	wdd->parent = &pdev->dev;
+	wdd->info = &cros_ec_wdt_ident;
+	wdd->ops = &cros_ec_wdt_ops;
+	wdd->timeout = CROS_EC_WATCHDOG_DEFAULT_TIME;
+	wdd->min_timeout = EC_HANG_DETECT_MIN_TIMEOUT;
+	wdd->max_timeout = EC_HANG_DETECT_MAX_TIMEOUT;
+	if (arg.resp.status == EC_HANG_DETECT_AP_BOOT_EC_WDT)
+		wdd->bootstatus = WDIOF_CARDRESET;
+
+	arg.req.command = EC_HANG_DETECT_CMD_CLEAR_STATUS;
+	ret = cros_ec_wdt_send_cmd(cros_ec, &arg);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to clear watchdog bootstatus");
+
+	watchdog_stop_on_reboot(wdd);
+	watchdog_stop_on_unregister(wdd);
+	watchdog_set_drvdata(wdd, cros_ec);
+	platform_set_drvdata(pdev, wdd);
+
+	return devm_watchdog_register_device(dev, wdd);
+}
+
+static int __maybe_unused cros_ec_wdt_suspend(struct platform_device *pdev, pm_message_t state)
+{
+	struct watchdog_device *wdd = platform_get_drvdata(pdev);
+	int ret = 0;
+
+	if (watchdog_active(wdd))
+		ret = cros_ec_wdt_stop(wdd);
+
+	return ret;
+}
+
+static int __maybe_unused cros_ec_wdt_resume(struct platform_device *pdev)
+{
+	struct watchdog_device *wdd = platform_get_drvdata(pdev);
+	int ret = 0;
+
+	if (watchdog_active(wdd))
+		ret = cros_ec_wdt_start(wdd);
+
+	return ret;
+}
+
+static const struct platform_device_id cros_ec_wdt_id[] = {
+	{ DRV_NAME, 0 },
+	{}
+};
+
+static struct platform_driver cros_ec_wdt_driver = {
+	.probe		= cros_ec_wdt_probe,
+	.suspend	= pm_ptr(cros_ec_wdt_suspend),
+	.resume		= pm_ptr(cros_ec_wdt_resume),
+	.driver		= {
+		.name	= DRV_NAME,
+	},
+	.id_table	= cros_ec_wdt_id,
+};
+
+module_platform_driver(cros_ec_wdt_driver);
+
+MODULE_DEVICE_TABLE(platform, cros_ec_wdt_id);
+MODULE_DESCRIPTION("Cros EC Watchdog Device Driver");
+MODULE_LICENSE("GPL");