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: Alexander Shiyan <shc_work@mail.ru>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

3 files changed, 263 insertions, 0 deletions

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index af8f7c75e03c..7a2fedab0fb5 100644
--- a/drivers/watchdog/Kconfig
+++ b/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
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index af2251682214..985a66cda76f 100644
--- a/drivers/watchdog/Makefile
+++ b/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
diff --git a/drivers/watchdog/gpio_wdt.c b/drivers/watchdog/gpio_wdt.c
new file mode 100644
index 000000000000..220a9e07cfd5
--- /dev/null
+++ b/drivers/watchdog/gpio_wdt.c
@@ -0,0 +1,254 @@
+/*
+ * 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");