linux-kernel - Re: [PATCH] watchdog: da9062: do not ping the hw during stop()

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Date:   Sat, 25 Jan 2020 15:11:26 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Marco Felsch <m.felsch@...gutronix.de>
Cc:     support.opensource@...semi.com, stwiss.opensource@...semi.com,
        Adam.Thomson.Opensource@...semi.com,
        linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...gutronix.de
Subject: Re: [PATCH] watchdog: da9062: do not ping the hw during stop()

On Mon, Jan 20, 2020 at 10:17:29AM +0100, Marco Felsch wrote:
> The da9062 hw has a minimum ping cool down phase of at least 200ms. The
> driver takes that into account by setting the min_hw_heartbeat_ms to
> 300ms and the core guarantees that the hw limit is observed for the
> ping() calls. But the core can't guarantees the required minimum ping

guarantee

> cool down phase if a stop() command is send immediately after the ping()
> command. So it is not allowed to ping the watchdog within the stop()
> command as the driver do. Remove the ping can be done without doubts

does

> because the watchdog gets disabled anyway and a (re)start reset the

resets

> watchdog counter too.
> 
> Signed-off-by: Marco Felsch <m.felsch@...gutronix.de>

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

> ---
>  drivers/watchdog/da9062_wdt.c | 7 -------
>  1 file changed, 7 deletions(-)
> 
> diff --git a/drivers/watchdog/da9062_wdt.c b/drivers/watchdog/da9062_wdt.c
> index 77b6b5336067..0ad15d55071c 100644
> --- a/drivers/watchdog/da9062_wdt.c
> +++ b/drivers/watchdog/da9062_wdt.c
> @@ -97,13 +97,6 @@ static int da9062_wdt_stop(struct watchdog_device *wdd)
>  	struct da9062_watchdog *wdt = watchdog_get_drvdata(wdd);
>  	int ret;
>  
> -	ret = da9062_reset_watchdog_timer(wdt);
> -	if (ret) {
> -		dev_err(wdt->hw->dev, "Failed to ping the watchdog (err = %d)\n",
> -			ret);
> -		return ret;
> -	}
> -
>  	ret = regmap_update_bits(wdt->hw->regmap,
>  				 DA9062AA_CONTROL_D,
>  				 DA9062AA_TWDSCALE_MASK,