Re: [PATCH v3 2/2] watchdog: w83627hf_wdt: Use WDOG_HW_RUNNING for running chip on boot

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Removing the manual hardware timeout refresh while still unconditionally switching the hardware timer base from minutes to seconds drastically truncates the remaining timeout if the BIOS originally configured it in minutes, risking unexpected system reboots.
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commit 0014048ec369e2a09098aa033aeb725449e2fd67
Author: Paul Louvel <[email protected]>

watchdog: w83627hf_wdt: Use WDOG_HW_RUNNING for running chip on boot

This patch updates the w83627hf watchdog driver to rely on the watchdog
core's WDOG_HW_RUNNING flag to keep a running watchdog alive during boot.
It replaces the previous behavior of manually issuing a single keepalive
during initialization.

> diff --git a/drivers/watchdog/w83627hf_wdt.c b/drivers/watchdog/w83627hf_wdt.c
> --- a/drivers/watchdog/w83627hf_wdt.c
> +++ b/drivers/watchdog/w83627hf_wdt.c
[ ... ]
> @@ -241,9 +241,8 @@ static int w83627hf_init(struct watchdog_device *wdog, enum chips chip)
>  			pr_warn("Stopping previously enabled watchdog until userland kicks in\n");
>  			superio_outb(cr_wdt_timeout, 0);
>  		} else {
> -			pr_info("Watchdog already running. Resetting timeout to %d sec\n",
> -				wdog->timeout);
> -			superio_outb(cr_wdt_timeout, wdog->timeout);
> +			pr_info("Watchdog already running.\n");
> +			set_bit(WDOG_HW_RUNNING, &wdog->status);
>  		}
>  	}
>  

[Severity: High]
Does removing this explicit timeout reset create a risk of unexpected reboots?

If the BIOS originally configured the watchdog with a timeout in minutes
(for example, a timeout of 5 minutes), the hardware counter cr_wdt_timeout
will hold the value 5.

Because this patch removes the explicit write of wdog->timeout (which is
typically 60) to cr_wdt_timeout, the counter retains the raw value 5.
Just after this block in w83627hf_init(), the driver unconditionally
switches the timebase to seconds:

w83627hf_init() {
    ...
    /* set second mode & disable keyboard turning off watchdog */
    t = superio_inb(cr_wdt_control) & ~0x0C;
    superio_outb(cr_wdt_control, t);
    ...
}

This immediately shrinks the remaining timeout from 5 minutes to 5 seconds.

If the watchdog core's kworker is delayed, or if the system is configured
not to ping the watchdog before user space takes over, could this unusually
short timeout cause the system to reboot unexpectedly during early boot?

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Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=2