linux-kernel - Re: [PATCH v1 4/8] watchdog: f71808e_wdt: clear watchdog timeout occurred flag

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Date:   Tue, 30 Jun 2020 14:09:24 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Ahmad Fatoum <a.fatoum@...gutronix.de>
Cc:     Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Knud Poulsen <knpo@...e.org>, linux-watchdog@...r.kernel.org,
        kernel@...gutronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 4/8] watchdog: f71808e_wdt: clear watchdog timeout
 occurred flag

On Thu, Jun 11, 2020 at 09:17:45PM +0200, Ahmad Fatoum wrote:
> The flag indicating a watchdog timeout having occurred normally persists
> till Power-On Reset of the Fintek Super I/O chip. The user can clear it
> by writing a `1' to the bit.
> 
> The driver doesn't offer a restart method, so regular system reboot
> might not reset the Super I/O and if the watchdog isn't enabled, we
> won't touch the register containing the bit on the next boot.
> In this case all subsequent regular reboots will be wrongly flagged
> by the driver as being caused by the watchdog.
> 
> Fix this by having the flag cleared after read. This is also done by
> other drivers like those for the i6300esb and mpc8xxx_wdt.
> 
> Fixes: b97cb21a4634 ("watchdog: f71808e_wdt: Fix WDTMOUT_STS register read")
> Cc: stable@...r.kernel.org
> Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>

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

> ---
>  drivers/watchdog/f71808e_wdt.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/watchdog/f71808e_wdt.c b/drivers/watchdog/f71808e_wdt.c
> index 8e5584c54423..26bf366aebc2 100644
> --- a/drivers/watchdog/f71808e_wdt.c
> +++ b/drivers/watchdog/f71808e_wdt.c
> @@ -706,6 +706,13 @@ static int __init watchdog_init(int sioaddr)
>  	wdt_conf = superio_inb(sioaddr, F71808FG_REG_WDT_CONF);
>  	watchdog.caused_reboot = wdt_conf & BIT(F71808FG_FLAG_WDTMOUT_STS);
>  
> +	/*
> +	 * We don't want WDTMOUT_STS to stick around till regular reboot.
> +	 * Write 1 to the bit to clear it to zero.
> +	 */
> +	superio_outb(sioaddr, F71808FG_REG_WDT_CONF,
> +		     wdt_conf | BIT(F71808FG_FLAG_WDTMOUT_STS));
> +
>  	superio_exit(sioaddr);
>  
>  	err = watchdog_set_timeout(timeout);