Re: [PATCH v6 4/8] watchdog: rzv2h: Propagate WDTDCR access errors

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] watchdog: rzv2h: unconfigured hardware reset on stop error path
--

commit b536187da1b8888ce4af583c2cf2a8479cfaaa53
Author: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>

watchdog: rzv2h: Propagate WDTDCR access errors

This commit updates the watchdog start and stop paths to handle WDTDCR
register access errors. It propagates failures back to the caller and
unwinds acquired resources, attempting to restore the reset state.

> diff --git a/drivers/watchdog/rzv2h_wdt.c b/drivers/watchdog/rzv2h_wdt.c
> --- a/drivers/watchdog/rzv2h_wdt.c
> +++ b/drivers/watchdog/rzv2h_wdt.c

[ ... ]

> @@ -169,8 +179,13 @@ static int rzv2h_wdt_stop(struct watchdog_device *wdev)
>  	if (ret)
>  		return ret;
>  
> -	if (priv->of_data->wdtdcr)
> -		rzt2h_wdt_wdtdcr_count_stop(priv);
> +	if (priv->of_data->wdtdcr) {
> +		ret = rzt2h_wdt_wdtdcr_count_stop(priv);
> +		if (ret) {
> +			reset_control_deassert(priv->rstc);
> +			return ret;
> +		}
> +	}

[Severity: High]
Does this error path unwind leave the hardware in an unconfigured state?

Earlier in rzv2h_wdt_stop(), reset_control_assert() places the watchdog IP
into reset, which clears its configuration registers to default values. If
rzt2h_wdt_wdtdcr_count_stop() fails, this path deasserts the reset line but
does not restore the previous running configuration, missing the required
udelay(3) and rzv2h_wdt_setup() initialization.

Since rzv2h_wdt_stop() returns an error, won't the watchdog core assume the
device is still active and continue to issue keepalive pings?

If the core pings the newly-deasserted but unconfigured watchdog, it seems
this would start the down-counter with default reset register values,
triggering an immediate unintended hardware reset.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260923104054.3324830-1-prabhakar.mahadev-lad.rj@bp.renesas.com?part=4