linux-kernel - Re: [PATCH 2/4] watchdog: add support for resetting keepalive timers at start

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Date:   Fri, 28 Feb 2020 09:13:14 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Tero Kristo <t-kristo@...com>
Cc:     wim@...ux-watchdog.org, linux-watchdog@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] watchdog: add support for resetting keepalive timers
 at start

On Fri, Feb 28, 2020 at 04:23:29PM +0200, Tero Kristo wrote:
> Current watchdog core pets the timer always after the initial keepalive
> time has expired from boot-up. This is incorrect for certain timers that
> don't like to be petted immediately when they are started, if they have
> not been running over the boot.
> 
> To allow drivers to reset their keepalive timers during startup, add
> a new watchdog flag to the api, WDOG_RESET_KEEPALIVE.
> 
> Signed-off-by: Tero Kristo <t-kristo@...com>
> ---
>  drivers/watchdog/watchdog_dev.c | 2 ++
>  include/linux/watchdog.h        | 1 +
>  2 files changed, 3 insertions(+)
> 
> diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
> index 8b5c742f24e8..131e40c21703 100644
> --- a/drivers/watchdog/watchdog_dev.c
> +++ b/drivers/watchdog/watchdog_dev.c
> @@ -283,6 +283,8 @@ static int watchdog_start(struct watchdog_device *wdd)
>  		set_bit(WDOG_ACTIVE, &wdd->status);
>  		wd_data->last_keepalive = started_at;
>  		watchdog_update_worker(wdd);
> +		if (test_bit(WDOG_RESET_KEEPALIVE, &wdd->status))
> +			wd_data->last_hw_keepalive = started_at;

I don't think the additional flag is needed. The code should just set
last_hw_keepalive. After all, it already sets last_keepalive, which
determines when the next internal keepalive will be sent. It makes sense
to also set last_hw_keepalive to prevent the next keepalive from being
sent too early.

Guenter