Re: [PATCH 1/3] watchdog: digicolor: Avoid division by zero

[Baruch Siach]

Hi Tzung-Bi Shih,

On Sun, Sep 13 2026, Tzung-Bi Shih wrote:
> clk_get_rate() could return 0.  Avoid a division by zero panic.
>
> Since get_timeleft() cannot propagate errors, check the clock rate early
> in probe() and cache the rate in the driver data as it is unlikely to
> change at runtime.
>
> Fixes: 336694a01dae ("watchdog: digicolor: driver for Conexant Digicolor CX92755 SoC")
> Signed-off-by: Tzung-Bi Shih <tzungbi@xxxxxxxxxx>

Acked-by: Baruch Siach <baruch@xxxxxxxxxx>

Thanks,
baruch

> ---
>  drivers/watchdog/digicolor_wdt.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/watchdog/digicolor_wdt.c b/drivers/watchdog/digicolor_wdt.c
> index 073d37867f47..de1a3267a972 100644
> --- a/drivers/watchdog/digicolor_wdt.c
> +++ b/drivers/watchdog/digicolor_wdt.c
> @@ -25,6 +25,7 @@ struct dc_wdt {
>  	void __iomem		*base;
>  	struct clk		*clk;
>  	spinlock_t		lock;
> +	unsigned long		rate;
>  };
>  
>  static unsigned timeout;
> @@ -61,7 +62,7 @@ static int dc_wdt_start(struct watchdog_device *wdog)
>  {
>  	struct dc_wdt *wdt = watchdog_get_drvdata(wdog);
>  
> -	dc_wdt_set(wdt, wdog->timeout * clk_get_rate(wdt->clk));
> +	dc_wdt_set(wdt, wdog->timeout * wdt->rate);
>  
>  	return 0;
>  }
> @@ -79,7 +80,7 @@ static int dc_wdt_set_timeout(struct watchdog_device *wdog, unsigned int t)
>  {
>  	struct dc_wdt *wdt = watchdog_get_drvdata(wdog);
>  
> -	dc_wdt_set(wdt, t * clk_get_rate(wdt->clk));
> +	dc_wdt_set(wdt, t * wdt->rate);
>  	wdog->timeout = t;
>  
>  	return 0;
> @@ -90,7 +91,7 @@ static unsigned int dc_wdt_get_timeleft(struct watchdog_device *wdog)
>  	struct dc_wdt *wdt = watchdog_get_drvdata(wdog);
>  	uint32_t count = readl_relaxed(wdt->base + TIMER_A_COUNT);
>  
> -	return count / clk_get_rate(wdt->clk);
> +	return count / wdt->rate;
>  }
>  
>  static const struct watchdog_ops dc_wdt_ops = {
> @@ -130,7 +131,11 @@ static int dc_wdt_probe(struct platform_device *pdev)
>  	wdt->clk = devm_clk_get(dev, NULL);
>  	if (IS_ERR(wdt->clk))
>  		return PTR_ERR(wdt->clk);
> -	dc_wdt_wdd.max_timeout = U32_MAX / clk_get_rate(wdt->clk);
> +
> +	wdt->rate = clk_get_rate(wdt->clk);
> +	if (!wdt->rate)
> +		return -EINVAL;
> +	dc_wdt_wdd.max_timeout = U32_MAX / wdt->rate;
>  	dc_wdt_wdd.timeout = dc_wdt_wdd.max_timeout;
>  	dc_wdt_wdd.parent = dev;

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