[PATCH 3/3] watchdog: honour hw_margin_ms DT property

[Stefan Roese]

On 13.03.20 17:04, Rasmus Villemoes wrote:
> Some watchdog devices, e.g. external gpio-triggered ones, must be
> reset more often than once per second, which means that the current
> rate-limiting logic in watchdog_reset() fails to keep the board alive.
> 
> gpio-wdt.txt in the linux source tree defines a "hw_margin_ms"
> property used to specifiy the maximum time allowed between resetting
> the device. Allow any watchdog device to specify such a property, and
> then use a reset period of one quarter of that. We keep the current
> default of resetting once every 1000ms.
> 
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
> ---
>   drivers/watchdog/wdt-uclass.c | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/watchdog/wdt-uclass.c b/drivers/watchdog/wdt-uclass.c
> index fb3e247c5f..436a52fd08 100644
> --- a/drivers/watchdog/wdt-uclass.c
> +++ b/drivers/watchdog/wdt-uclass.c
> @@ -15,6 +15,12 @@ DECLARE_GLOBAL_DATA_PTR;
>   
>   #define WATCHDOG_TIMEOUT_SECS	(CONFIG_WATCHDOG_TIMEOUT_MSECS / 1000)
>   
> +/*
> + * Reset every 1000ms, or however often is required as indicated by a
> + * hw_margin_ms property.
> + */
> +static ulong reset_period = 1000;
> +
>   int initr_watchdog(void)
>   {
>   	u32 timeout = WATCHDOG_TIMEOUT_SECS;
> @@ -36,6 +42,8 @@ int initr_watchdog(void)
>   	if (CONFIG_IS_ENABLED(OF_CONTROL)) {
>   		timeout = dev_read_u32_default(gd->watchdog_dev, "timeout-sec",
>   					       WATCHDOG_TIMEOUT_SECS);
> +		reset_period = dev_read_u32_default(gd->watchdog_dev, "hw_margin_ms",
> +						    4*reset_period)/4;

Nitpicking: checkpatch will most likely complain about missing spaces
here.

>   	}
>   
>   	wdt_start(gd->watchdog_dev, timeout * 1000, 0);
> @@ -117,7 +125,7 @@ void watchdog_reset(void)
>   	/* Do not reset the watchdog too often */
>   	now = get_timer(0);
>   	if (time_after(now, next_reset)) {
> -		next_reset = now + 1000;	/* reset every 1000ms */
> +		next_reset = now + reset_period;
>   		wdt_reset(gd->watchdog_dev);
>   	}
>   }
> 

Other than that:

Reviewed-by: Stefan Roese <sr at denx.de>

Thanks,
Stefan