linux-kernel - Re: [PATCH] watchdog: booke_wdt: Disable the watchdog prior to setting a new timeout value in order to avoid the following situation

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Message-ID: <20180322164710.GA31876@roeck-us.net>
Date:   Thu, 22 Mar 2018 09:47:10 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Xiaofeng Wei <xiaofeng.wei@....com>
Cc:     wim@...ana.be, linux-watchdog@...r.kernel.org,
        linux-kernel@...r.kernel.org, hongjun.chen@....com
Subject: Re: [PATCH] watchdog: booke_wdt: Disable the watchdog prior to
 setting a new timeout value in order to avoid the following situation

On Thu, Mar 22, 2018 at 11:51:46AM +0800, Xiaofeng Wei wrote:
> A watchdog timer exception also occurs if the selected time base bit transitions from 0 to 1 due
> to an mtspr that writes a 1 to the bit when its previous value was 0.
> 
Please drop "in order to ..." from the subject line. Every patch hopefully does
that.

> Signed-off-by: Xiaofeng Wei <xiaofeng.wei@....com>
> ---
>  drivers/watchdog/booke_wdt.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/watchdog/booke_wdt.c b/drivers/watchdog/booke_wdt.c
> index 3ad1e44..70e742c 100644
> --- a/drivers/watchdog/booke_wdt.c
> +++ b/drivers/watchdog/booke_wdt.c
> @@ -186,9 +186,15 @@ static int booke_wdt_stop(struct watchdog_device *wdog)
>  static int booke_wdt_set_timeout(struct watchdog_device *wdt_dev,
>  				 unsigned int timeout)
>  {
> +	if (watchdog_active(wdt_dev))
> +		on_each_cpu(__booke_wdt_disable, NULL, 0);
> +

Thios would only be necessary if the timeout actually changes. Also, does
the problem apply to _all_ chips supported by this driver or only to a
subset ?

Guenter

>  	wdt_dev->timeout = timeout;
>  	booke_wdt_set(wdt_dev);
>  
> +	if (watchdog_active(wdt_dev))
> +		on_each_cpu(__booke_wdt_enable, wdt_dev, 0);
> +
>  	return 0;
>  }
>  
> -- 
> 2.9.3
>