watchdog: core: add reboot notifier support

Many watchdog drivers register a reboot notifier in order to stop the
watchdog on system reboot. Thus we can factorize this code in the
watchdog core.

For that purpose, a new notifier block is added in watchdog_device for
internal use only, as well as a new watchdog_stop_on_reboot helper
function.

If this helper is called, watchdog core registers the related notifier
block and will stop the watchdog when SYS_HALT or SYS_DOWN is received.

Since this operation can be critical on some platforms, abort the device
registration if the reboot notifier registration fails.

Suggested-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: Damien Riegel <damien.riegel@savoirfairelinux.com>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

1 files changed, 37 insertions, 0 deletions

diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
index 88a34efac400..0bb32a487f46 100644
--- a/drivers/watchdog/watchdog_core.c
+++ b/drivers/watchdog/watchdog_core.c
@@ -138,6 +138,25 @@ int watchdog_init_timeout(struct watchdog_device *wdd,
 }
 EXPORT_SYMBOL_GPL(watchdog_init_timeout);
 
+static int watchdog_reboot_notifier(struct notifier_block *nb,
+				    unsigned long code, void *data)
+{
+	struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
+						   reboot_nb);
+
+	if (code == SYS_DOWN || code == SYS_HALT) {
+		if (watchdog_active(wdd)) {
+			int ret;
+
+			ret = wdd->ops->stop(wdd);
+			if (ret)
+				return NOTIFY_BAD;
+		}
+	}
+
+	return NOTIFY_DONE;
+}
+
 static int watchdog_restart_notifier(struct notifier_block *nb,
 				     unsigned long action, void *data)
 {
@@ -238,6 +257,21 @@ static int __watchdog_register_device(struct watchdog_device *wdd)
 		return ret;
 	}
 
+	if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
+		wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
+
+		ret = register_reboot_notifier(&wdd->reboot_nb);
+		if (ret) {
+			dev_err(wdd->dev, "Cannot register reboot notifier (%d)\n",
+				ret);
+			watchdog_dev_unregister(wdd);
+			device_destroy(watchdog_class, devno);
+			ida_simple_remove(&watchdog_ida, wdd->id);
+			wdd->dev = NULL;
+			return ret;
+		}
+	}
+
 	if (wdd->ops->restart) {
 		wdd->restart_nb.notifier_call = watchdog_restart_notifier;
 
@@ -286,6 +320,9 @@ static void __watchdog_unregister_device(struct watchdog_device *wdd)
 	if (wdd->ops->restart)
 		unregister_restart_handler(&wdd->restart_nb);
 
+	if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
+		unregister_reboot_notifier(&wdd->reboot_nb);
+
 	devno = wdd->cdev.dev;
 	ret = watchdog_dev_unregister(wdd);
 	if (ret)