watchdog: GPIO-controlled watchdog

This patch adds a watchdog driver for devices controlled through GPIO,
(Analog Devices ADM706, Maxim MAX823, National NE555 etc).
Signed-off-by: NAlexander Shiyan <shc_work@mail.ru>
Reviewed-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NWim Van Sebroeck <wim@iguana.be>

Documentation/devicetree/bindings/watchdog/gpio-wdt.txt

+* GPIO-controlled Watchdog
+
+Required Properties:
+- compatible: Should contain "linux,wdt-gpio".
+- gpios: From common gpio binding; gpio connection to WDT reset pin.
+- hw_algo: The algorithm used by the driver. Should be one of the
+  following values:
+  - toggle: Either a high-to-low or a low-to-high transition clears
+    the WDT counter. The watchdog timer is disabled when GPIO is
+    left floating or connected to a three-state buffer.
+  - level: Low or high level starts counting WDT timeout,
+    the opposite level disables the WDT. Active level is determined
+    by the GPIO flags.
+- hw_margin_ms: Maximum time to reset watchdog circuit (milliseconds).
+
+Example:
+	watchdog: watchdog {
+		/* ADM706 */
+		compatible = "linux,wdt-gpio";
+		gpios = <&gpio3 9 GPIO_ACTIVE_LOW>;
+		hw_algo = "toggle";
+		hw_margin_ms = <1600>;
+	};

drivers/watchdog/Kconfig

@@ -87,6 +87,14 @@ config DA9055_WATCHDOG
 	  This driver can also be built as a module.  If so, the module
 	  will be called da9055_wdt.
 
+config GPIO_WATCHDOG
+	tristate "Watchdog device controlled through GPIO-line"
+	depends on OF_GPIO
+	select WATCHDOG_CORE
+	help
+	  If you say yes here you get support for watchdog device
+	  controlled through GPIO-line.
+
 config WM831X_WATCHDOG
 	tristate "WM831x watchdog"
 	depends on MFD_WM831X

drivers/watchdog/Makefile

@@ -172,6 +172,7 @@ obj-$(CONFIG_XEN_WDT) += xen_wdt.o
 # Architecture Independent
 obj-$(CONFIG_DA9052_WATCHDOG) += da9052_wdt.o
 obj-$(CONFIG_DA9055_WATCHDOG) += da9055_wdt.o
+obj-$(CONFIG_GPIO_WATCHDOG)	+= gpio_wdt.o
 obj-$(CONFIG_WM831X_WATCHDOG) += wm831x_wdt.o
 obj-$(CONFIG_WM8350_WATCHDOG) += wm8350_wdt.o
 obj-$(CONFIG_MAX63XX_WATCHDOG) += max63xx_wdt.o

drivers/watchdog/gpio_wdt.c

+/*
+ * Driver for watchdog device controlled through GPIO-line
+ *
+ * Author: 2013, Alexander Shiyan <shc_work@mail.ru>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/err.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+#include <linux/of_gpio.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+#include <linux/watchdog.h>
+
+#define SOFT_TIMEOUT_MIN	1
+#define SOFT_TIMEOUT_DEF	60
+#define SOFT_TIMEOUT_MAX	0xffff
+
+enum {
+	HW_ALGO_TOGGLE,
+	HW_ALGO_LEVEL,
+};
+
+struct gpio_wdt_priv {
+	int			gpio;
+	bool			active_low;
+	bool			state;
+	unsigned int		hw_algo;
+	unsigned int		hw_margin;
+	unsigned long		last_jiffies;
+	struct notifier_block	notifier;
+	struct timer_list	timer;
+	struct watchdog_device	wdd;
+};
+
+static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
+{
+	gpio_set_value_cansleep(priv->gpio, !priv->active_low);
+
+	/* Put GPIO back to tristate */
+	if (priv->hw_algo == HW_ALGO_TOGGLE)
+		gpio_direction_input(priv->gpio);
+}
+
+static int gpio_wdt_start(struct watchdog_device *wdd)
+{
+	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
+
+	priv->state = priv->active_low;
+	gpio_direction_output(priv->gpio, priv->state);
+	priv->last_jiffies = jiffies;
+	mod_timer(&priv->timer, priv->last_jiffies + priv->hw_margin);
+
+	return 0;
+}
+
+static int gpio_wdt_stop(struct watchdog_device *wdd)
+{
+	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
+
+	mod_timer(&priv->timer, 0);
+	gpio_wdt_disable(priv);
+
+	return 0;
+}
+
+static int gpio_wdt_ping(struct watchdog_device *wdd)
+{
+	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
+
+	priv->last_jiffies = jiffies;
+
+	return 0;
+}
+
+static int gpio_wdt_set_timeout(struct watchdog_device *wdd, unsigned int t)
+{
+	wdd->timeout = t;
+
+	return gpio_wdt_ping(wdd);
+}
+
+static void gpio_wdt_hwping(unsigned long data)
+{
+	struct watchdog_device *wdd = (struct watchdog_device *)data;
+	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
+
+	if (time_after(jiffies, priv->last_jiffies +
+		       msecs_to_jiffies(wdd->timeout * 1000))) {
+		dev_crit(wdd->dev, "Timer expired. System will reboot soon!\n");
+		return;
+	}
+
+	/* Restart timer */
+	mod_timer(&priv->timer, jiffies + priv->hw_margin);
+
+	switch (priv->hw_algo) {
+	case HW_ALGO_TOGGLE:
+		/* Toggle output pin */
+		priv->state = !priv->state;
+		gpio_set_value_cansleep(priv->gpio, priv->state);
+		break;
+	case HW_ALGO_LEVEL:
+		/* Pulse */
+		gpio_set_value_cansleep(priv->gpio, !priv->active_low);
+		udelay(1);
+		gpio_set_value_cansleep(priv->gpio, priv->active_low);
+		break;
+	}
+}
+
+static int gpio_wdt_notify_sys(struct notifier_block *nb, unsigned long code,
+			       void *unused)
+{
+	struct gpio_wdt_priv *priv = container_of(nb, struct gpio_wdt_priv,
+						  notifier);
+
+	mod_timer(&priv->timer, 0);
+
+	switch (code) {
+	case SYS_HALT:
+	case SYS_POWER_OFF:
+		gpio_wdt_disable(priv);
+		break;
+	default:
+		break;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static const struct watchdog_info gpio_wdt_ident = {
+	.options	= WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
+			  WDIOF_SETTIMEOUT,
+	.identity	= "GPIO Watchdog",
+};
+
+static const struct watchdog_ops gpio_wdt_ops = {
+	.owner		= THIS_MODULE,
+	.start		= gpio_wdt_start,
+	.stop		= gpio_wdt_stop,
+	.ping		= gpio_wdt_ping,
+	.set_timeout	= gpio_wdt_set_timeout,
+};
+
+static int gpio_wdt_probe(struct platform_device *pdev)
+{
+	struct gpio_wdt_priv *priv;
+	enum of_gpio_flags flags;
+	unsigned int hw_margin;
+	unsigned long f = 0;
+	const char *algo;
+	int ret;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->gpio = of_get_gpio_flags(pdev->dev.of_node, 0, &flags);
+	if (!gpio_is_valid(priv->gpio))
+		return priv->gpio;
+
+	priv->active_low = flags & OF_GPIO_ACTIVE_LOW;
+
+	ret = of_property_read_string(pdev->dev.of_node, "hw_algo", &algo);
+	if (ret)
+		return ret;
+	if (!strncmp(algo, "toggle", 6)) {
+		priv->hw_algo = HW_ALGO_TOGGLE;
+		f = GPIOF_IN;
+	} else if (!strncmp(algo, "level", 5)) {
+		priv->hw_algo = HW_ALGO_LEVEL;
+		f = priv->active_low ? GPIOF_OUT_INIT_HIGH : GPIOF_OUT_INIT_LOW;
+	} else {
+		return -EINVAL;
+	}
+
+	ret = devm_gpio_request_one(&pdev->dev, priv->gpio, f,
+				    dev_name(&pdev->dev));
+	if (ret)
+		return ret;
+
+	ret = of_property_read_u32(pdev->dev.of_node,
+				   "hw_margin_ms", &hw_margin);
+	if (ret)
+		return ret;
+	/* Disallow values lower than 2 and higher than 65535 ms */
+	if (hw_margin < 2 || hw_margin > 65535)
+		return -EINVAL;
+
+	/* Use safe value (1/2 of real timeout) */
+	priv->hw_margin = msecs_to_jiffies(hw_margin / 2);
+
+	watchdog_set_drvdata(&priv->wdd, priv);
+
+	priv->wdd.info		= &gpio_wdt_ident;
+	priv->wdd.ops		= &gpio_wdt_ops;
+	priv->wdd.min_timeout	= SOFT_TIMEOUT_MIN;
+	priv->wdd.max_timeout	= SOFT_TIMEOUT_MAX;
+
+	if (watchdog_init_timeout(&priv->wdd, 0, &pdev->dev) < 0)
+		priv->wdd.timeout = SOFT_TIMEOUT_DEF;
+
+	setup_timer(&priv->timer, gpio_wdt_hwping, (unsigned long)&priv->wdd);
+
+	ret = watchdog_register_device(&priv->wdd);
+	if (ret)
+		return ret;
+
+	priv->notifier.notifier_call = gpio_wdt_notify_sys;
+	ret = register_reboot_notifier(&priv->notifier);
+	if (ret)
+		watchdog_unregister_device(&priv->wdd);
+
+	return ret;
+}
+
+static int gpio_wdt_remove(struct platform_device *pdev)
+{
+	struct gpio_wdt_priv *priv = platform_get_drvdata(pdev);
+
+	del_timer_sync(&priv->timer);
+	unregister_reboot_notifier(&priv->notifier);
+	watchdog_unregister_device(&priv->wdd);
+
+	return 0;
+}
+
+static const struct of_device_id gpio_wdt_dt_ids[] = {
+	{ .compatible = "linux,wdt-gpio", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
+
+static struct platform_driver gpio_wdt_driver = {
+	.driver	= {
+		.name		= "gpio-wdt",
+		.owner		= THIS_MODULE,
+		.of_match_table	= gpio_wdt_dt_ids,
+	},
+	.probe	= gpio_wdt_probe,
+	.remove	= gpio_wdt_remove,
+};
+module_platform_driver(gpio_wdt_driver);
+
+MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
+MODULE_DESCRIPTION("GPIO Watchdog");
+MODULE_LICENSE("GPL");