Re: [PATCH v4] fix it87_wdt early reboot by reporting running timer

[Guenter Roeck <linux@roeck-us.net>]

On 11/17/25 04:11, René Rebe wrote:
> Some products, such as the Ugreen DXP4800 Plus NAS, ship with the it87
> wdt enabled by the firmware and a broken BIOS option that does not
> allow to change the time or turn it off. As this makes installing
> Linux rather difficult, change the it87_wdt to report it running to
> the watchdog core.
> 
> Signed-off-by: René Rebe <rene@exactco.de>

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

> ---
> v1:
> - just clear hw timer register
> v2:
> - detect running hw timer and report to watchdog core
> v3:
> - multiply TOV1 in _wdt_get_timeout
> - don't wrongly and superfluously set .max_hw_heartbeat_ms
> - don't call set_timeout manually
> v4:
> - simplify to wdt_running
> - move code up to not move superio_exit
> 
> diff --git a/drivers/watchdog/it87_wdt.c b/drivers/watchdog/it87_wdt.c
> index 3b8488c86a2f..8ba7e03857ca 100644
> --- a/drivers/watchdog/it87_wdt.c
> +++ b/drivers/watchdog/it87_wdt.c
> @@ -188,6 +188,12 @@ static void _wdt_update_timeout(unsigned int t)
>   		superio_outb(t >> 8, WDTVALMSB);
>   }
>   
> +/* Internal function, should be called after superio_select(GPIO) */
> +static bool _wdt_running(void)
> +{
> +	return superio_inb(WDTVALLSB) || (max_units > 255 && superio_inb(WDTVALMSB));
> +}
> +
>   static int wdt_update_timeout(unsigned int t)
>   {
>   	int ret;
> @@ -374,6 +381,12 @@ static int __init it87_wdt_init(void)
>   		}
>   	}
>   
> +	/* wdt already left running by firmware? */
> +	if (_wdt_running()) {
> +		pr_info("Left running by firmware.\n");
> +		set_bit(WDOG_HW_RUNNING, &wdt_dev.status);
> +	}
> +
>   	superio_exit();
>   
>   	if (timeout < 1 || timeout > max_units * 60) {
>