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

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Message-ID: <20210124154320.GA131753@roeck-us.net>
Date:   Sun, 24 Jan 2021 07:43:20 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Tomas Winkler <tomas.winkler@...el.com>
Cc:     Wim Van Sebroeck <wim@...ana.be>, linux-watchdog@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Alexander Usyskin <alexander.usyskin@...el.com>,
        stable@...r.kernel.org
Subject: Re: [watchdog v2] watchdog: mei_wdt: request stop on unregister

On Sun, Jan 24, 2021 at 01:49:38PM +0200, Tomas Winkler wrote:
> 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>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
> 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
>