watchdog: introduce watchdog_dev_suspend/resume

The watchdog drivers often disable wdog clock during suspend and then
enable it again during resume. Nevertheless the ping worker is still
running and can issue low-level ping while the wdog clock is disabled
causing the system hang. To prevent such condition register pm notifier
in the watchdog core which will call watchdog_dev_suspend/resume and
actually cancel ping worker during suspend and restore it back, if
needed, during resume.

Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20210618195033.3209598-2-grzegorz.jaszczyk@linaro.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

1 files changed, 37 insertions, 0 deletions

diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
index 5df0a22e2cb4..3fe8a7edc252 100644
--- a/drivers/watchdog/watchdog_core.c
+++ b/drivers/watchdog/watchdog_core.c
@@ -34,6 +34,7 @@
 #include <linux/idr.h>		/* For ida_* macros */
 #include <linux/err.h>		/* For IS_ERR macros */
 #include <linux/of.h>		/* For of_get_timeout_sec */
+#include <linux/suspend.h>
 
 #include "watchdog_core.h"	/* For watchdog_dev_register/... */
 
@@ -185,6 +186,33 @@ static int watchdog_restart_notifier(struct notifier_block *nb,
 	return NOTIFY_DONE;
 }
 
+static int watchdog_pm_notifier(struct notifier_block *nb, unsigned long mode,
+				void *data)
+{
+	struct watchdog_device *wdd;
+	int ret = 0;
+
+	wdd = container_of(nb, struct watchdog_device, pm_nb);
+
+	switch (mode) {
+	case PM_HIBERNATION_PREPARE:
+	case PM_RESTORE_PREPARE:
+	case PM_SUSPEND_PREPARE:
+		ret = watchdog_dev_suspend(wdd);
+		break;
+	case PM_POST_HIBERNATION:
+	case PM_POST_RESTORE:
+	case PM_POST_SUSPEND:
+		ret = watchdog_dev_resume(wdd);
+		break;
+	}
+
+	if (ret)
+		return NOTIFY_BAD;
+
+	return NOTIFY_DONE;
+}
+
 /**
  * watchdog_set_restart_priority - Change priority of restart handler
  * @wdd: watchdog device
@@ -292,6 +320,15 @@ static int __watchdog_register_device(struct watchdog_device *wdd)
 				wdd->id, ret);
 	}
 
+	if (test_bit(WDOG_NO_PING_ON_SUSPEND, &wdd->status)) {
+		wdd->pm_nb.notifier_call = watchdog_pm_notifier;
+
+		ret = register_pm_notifier(&wdd->pm_nb);
+		if (ret)
+			pr_warn("watchdog%d: Cannot register pm handler (%d)\n",
+				wdd->id, ret);
+	}
+
 	return 0;
 }