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From:   Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>
To:     wim@linux-watchdog.org, linux@roeck-us.net, shawnguo@kernel.org
Cc:     linux-watchdog@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        grzegorz.jaszczyk@linaro.org
Subject: [PATCH 1/2] watchdog: introduce watchdog_dev_suspend/resume
Date:   Tue, 15 Jun 2021 14:39:03 +0200
Message-Id: <20210615123904.2568052-2-grzegorz.jaszczyk@linaro.org>
In-Reply-To: <20210615123904.2568052-1-grzegorz.jaszczyk@linaro.org>
References: <20210615123904.2568052-1-grzegorz.jaszczyk@linaro.org>
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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 introduce
watchdog_dev_suspend/resume which can be used by any wdog driver and
actually cancel ping worker during suspend and restore it back, if
needed, during resume.

Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>
---
 drivers/watchdog/watchdog_dev.c | 49 +++++++++++++++++++++++++++++++++
 include/linux/watchdog.h        |  2 ++
 2 files changed, 51 insertions(+)

diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 2946f3a63110..3feca1567281 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -1219,6 +1219,55 @@ void __exit watchdog_dev_exit(void)
 	kthread_destroy_worker(watchdog_kworker);
 }
 
+int watchdog_dev_suspend(struct watchdog_device *wdd)
+{
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+	int ret;
+
+	if (!wdd->wd_data)
+		return -ENODEV;
+
+	/* ping for the last time before suspend */
+	mutex_lock(&wd_data->lock);
+	if (watchdog_worker_should_ping(wd_data))
+		ret = __watchdog_ping(wd_data->wdd);
+	mutex_unlock(&wd_data->lock);
+
+	if (ret)
+		return ret;
+
+	/*
+	 * make sure that watchdog worker will not kick in when the wdog is
+	 * suspended
+	 */
+	hrtimer_cancel(&wd_data->timer);
+	kthread_cancel_work_sync(&wd_data->work);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(watchdog_dev_suspend);
+
+int watchdog_dev_resume(struct watchdog_device *wdd)
+{
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+	int ret;
+
+	if (!wdd->wd_data)
+		return -ENODEV;
+
+	/*
+	 * __watchdog_ping will also retrigger hrtimer and therefore restore the
+	 * ping worker if needed.
+	 */
+	mutex_lock(&wd_data->lock);
+	if (watchdog_worker_should_ping(wd_data))
+		ret = __watchdog_ping(wd_data->wdd);
+	mutex_unlock(&wd_data->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(watchdog_dev_resume);
+
 module_param(handle_boot_enabled, bool, 0444);
 MODULE_PARM_DESC(handle_boot_enabled,
 	"Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
index 9b19e6bb68b5..febfde3b1ff6 100644
--- a/include/linux/watchdog.h
+++ b/include/linux/watchdog.h
@@ -209,6 +209,8 @@ extern int watchdog_init_timeout(struct watchdog_device *wdd,
 				  unsigned int timeout_parm, struct device *dev);
 extern int watchdog_register_device(struct watchdog_device *);
 extern void watchdog_unregister_device(struct watchdog_device *);
+int watchdog_dev_suspend(struct watchdog_device *wdd);
+int watchdog_dev_resume(struct watchdog_device *wdd);
 
 int watchdog_set_last_hw_keepalive(struct watchdog_device *, unsigned int);
 
-- 
2.29.0