watchdog: gpio_wdt: Add "always_running" feature to GPIO watchdog

On some chips, like the TPS386000, the trigger cannot be disabled
and the CPU must keep toggling the line at all times. Add a switch
"always_running" to keep toggling the GPIO line regardless of the
state of the soft part of the watchdog. The "armed" member keeps
track of whether a timeout must also cause a reset.

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

diff --git a/Documentation/devicetree/bindings/watchdog/gpio-wdt.txt b/Documentation/devicetree/bindings/watchdog/gpio-wdt.txt
index 37afec1..1987949 100644 (file)
--- a/Documentation/devicetree/bindings/watchdog/gpio-wdt.txt
+++ b/Documentation/devicetree/bindings/watchdog/gpio-wdt.txt
@@ -13,6 +13,11 @@ Required Properties:
     by the GPIO flags.
 - hw_margin_ms: Maximum time to reset watchdog circuit (milliseconds).
 
+Optional Properties:
+- always-running: If the watchdog timer cannot be disabled, add this flag to
+  have the driver keep toggling the signal without a client. It will only cease
+  to toggle the signal when the device is open and the timeout elapsed.
+
 Example:
        watchdog: watchdog {
                /* ADM706 */

diff --git a/drivers/watchdog/gpio_wdt.c b/drivers/watchdog/gpio_wdt.c
index bbdb19b..cbc313d 100644 (file)
--- a/drivers/watchdog/gpio_wdt.c
+++ b/drivers/watchdog/gpio_wdt.c
@@ -31,6 +31,8 @@ struct gpio_wdt_priv {
        int                     gpio;
        bool                    active_low;
        bool                    state;
+       bool                    always_running;
+       bool                    armed;
        unsigned int            hw_algo;
        unsigned int            hw_margin;
        unsigned long           last_jiffies;
@@ -48,14 +50,20 @@ static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
                gpio_direction_input(priv->gpio);
 }
 
-static int gpio_wdt_start(struct watchdog_device *wdd)
+static void gpio_wdt_start_impl(struct gpio_wdt_priv *priv)
 {
-       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);
+}
+
+static int gpio_wdt_start(struct watchdog_device *wdd)
+{
+       struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
+
+       gpio_wdt_start_impl(priv);
+       priv->armed = true;
 
        return 0;
 }
@@ -64,8 +72,11 @@ 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);
+       priv->armed = false;
+       if (!priv->always_running) {
+               mod_timer(&priv->timer, 0);
+               gpio_wdt_disable(priv);
+       }
 
        return 0;
 }
@@ -91,8 +102,8 @@ 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))) {
+       if (priv->armed && time_after(jiffies, priv->last_jiffies +
+                                     msecs_to_jiffies(wdd->timeout * 1000))) {
                dev_crit(wdd->dev, "Timer expired. System will reboot soon!\n");
                return;
        }
@@ -197,6 +208,9 @@ static int gpio_wdt_probe(struct platform_device *pdev)
        /* Use safe value (1/2 of real timeout) */
        priv->hw_margin = msecs_to_jiffies(hw_margin / 2);
 
+       priv->always_running = of_property_read_bool(pdev->dev.of_node,
+                                                    "always-running");
+
        watchdog_set_drvdata(&priv->wdd, priv);
 
        priv->wdd.info          = &gpio_wdt_ident;
@@ -216,8 +230,15 @@ static int gpio_wdt_probe(struct platform_device *pdev)
        priv->notifier.notifier_call = gpio_wdt_notify_sys;
        ret = register_reboot_notifier(&priv->notifier);
        if (ret)
-               watchdog_unregister_device(&priv->wdd);
+               goto error_unregister;
 
+       if (priv->always_running)
+               gpio_wdt_start_impl(priv);
+
+       return 0;
+
+error_unregister:
+       watchdog_unregister_device(&priv->wdd);
        return ret;
 }