linux-kernel - [watchdog v2] watchdog: mei_wdt: request stop on unregister

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Date:   Sun, 24 Jan 2021 13:49:38 +0200
From:   Tomas Winkler <tomas.winkler@...el.com>
To:     Wim Van Sebroeck <wim@...ana.be>,
        Guenter Roeck <linux@...ck-us.net>
Cc:     linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alexander Usyskin <alexander.usyskin@...el.com>,
        stable@...r.kernel.org, Tomas Winkler <tomas.winkler@...el.com>
Subject: [watchdog v2] watchdog: mei_wdt: request stop on unregister

From: Alexander Usyskin <alexander.usyskin@...el.com>

The MEI bus has a special behavior on suspend it destroys
all the attached devices, this is due to the fact that also
firmware context is not persistent across power flows.

If watchdog on MEI bus is ticking before suspending the firmware
times out and reports that the OS is missing watchdog tick.
Send the stop command to the firmware on watchdog unregistered
to eliminate the false event on suspend.
This does not make the things worse from the user-space perspective
as a user-space should re-open watchdog device after
suspending before this patch.

Cc: <stable@...r.kernel.org>
Signed-off-by: Alexander Usyskin <alexander.usyskin@...el.com>
Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
---
V2: Update the commit message with better explanation

 drivers/watchdog/mei_wdt.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/watchdog/mei_wdt.c b/drivers/watchdog/mei_wdt.c
index 5391bf3e6b11..c5967d8b4256 100644
--- a/drivers/watchdog/mei_wdt.c
+++ b/drivers/watchdog/mei_wdt.c
@@ -382,6 +382,7 @@ static int mei_wdt_register(struct mei_wdt *wdt)

 	watchdog_set_drvdata(&wdt->wdd, wdt);
 	watchdog_stop_on_reboot(&wdt->wdd);
+	watchdog_stop_on_unregister(&wdt->wdd);

 	ret = watchdog_register_device(&wdt->wdd);
 	if (ret)
-- 
2.26.2