[PATCH 0/3] watchdog: Avoid division by zero from clk_get_rate()

[PATCH 0/3] watchdog: Avoid division by zero from clk_get_rate()

[Tzung-Bi Shih]

The series is a follow-up of [1].

[1] https://lore.kernel.org/all/2c0b963e-6379-46a4-bae8-92ec2d76f8da@roeck-us.net

Tzung-Bi Shih (3):
  watchdog: digicolor: Avoid division by zero
  watchdog: rtd119x: Avoid division by zero
  watchdog: rzv2h: Avoid division by zero

 drivers/watchdog/digicolor_wdt.c | 13 +++++++++----
 drivers/watchdog/rtd119x_wdt.c   |  7 ++++++-
 drivers/watchdog/rzv2h_wdt.c     |  7 ++++++-
 3 files changed, 21 insertions(+), 6 deletions(-)

-- 
2.53.0

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

[Tzung-Bi Shih]

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@kernel.org>
---
 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;
 
-- 
2.53.0

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@kernel.org>

Acked-by: Baruch Siach <baruch@tkos.co.il>

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;

-- 
                                                     ~. .~   Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
   - baruch@tkos.co.il - tel: +972.52.368.4656, http://www.tkos.co.il -

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

[Guenter Roeck]

On Sun, Sep 13, 2026 at 02:48:49PM +0800, 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@kernel.org>
> Acked-by: Baruch Siach <baruch@tkos.co.il>

Applied.

Thanks,
Guenter

[PATCH 2/3] watchdog: rtd119x: Avoid division by zero

[Tzung-Bi Shih]

clk_get_rate() could return 0.  Avoid a division by zero panic.

Fixes: 2bdf6acbfead ("watchdog: Add Realtek RTD1295")
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
---
 drivers/watchdog/rtd119x_wdt.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/watchdog/rtd119x_wdt.c b/drivers/watchdog/rtd119x_wdt.c
index 984905695dde..0bfadb58917b 100644
--- a/drivers/watchdog/rtd119x_wdt.c
+++ b/drivers/watchdog/rtd119x_wdt.c
@@ -98,6 +98,7 @@ static int rtd119x_wdt_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct rtd119x_watchdog_device *data;
+	unsigned long rate;
 
 	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 	if (!data)
@@ -111,10 +112,14 @@ static int rtd119x_wdt_probe(struct platform_device *pdev)
 	if (IS_ERR(data->clk))
 		return PTR_ERR(data->clk);
 
+	rate = clk_get_rate(data->clk);
+	if (!rate)
+		return -EINVAL;
+
 	data->wdt_dev.info = &rtd119x_wdt_info;
 	data->wdt_dev.ops = &rtd119x_wdt_ops;
 	data->wdt_dev.timeout = 120;
-	data->wdt_dev.max_timeout = 0xffffffff / clk_get_rate(data->clk);
+	data->wdt_dev.max_timeout = 0xffffffff / rate;
 	data->wdt_dev.min_timeout = 1;
 	data->wdt_dev.parent = dev;
 
-- 
2.53.0

Re: [PATCH 2/3] watchdog: rtd119x: Avoid division by zero

[Guenter Roeck]

On Sun, Sep 13, 2026 at 02:48:50PM +0800, Tzung-Bi Shih wrote:
> clk_get_rate() could return 0.  Avoid a division by zero panic.
> 
> Fixes: 2bdf6acbfead ("watchdog: Add Realtek RTD1295")
> Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>

Applied.

Thanks,
Guenter

[PATCH 3/3] watchdog: rzv2h: Avoid division by zero

[Tzung-Bi Shih]

clk_get_rate() could return 0.  Avoid a division by zero panic.

Fixes: f6febd0a30b6 ("watchdog: Add Watchdog Timer driver for RZ/V2H(P)")
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
---
 drivers/watchdog/rzv2h_wdt.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/watchdog/rzv2h_wdt.c b/drivers/watchdog/rzv2h_wdt.c
index 3b6abb66a1da..83540dd9a37b 100644
--- a/drivers/watchdog/rzv2h_wdt.c
+++ b/drivers/watchdog/rzv2h_wdt.c
@@ -278,6 +278,7 @@ static int rzv2h_wdt_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct rzv2h_wdt_priv *priv;
 	struct clk *count_clk;
+	unsigned long rate;
 	int ret;
 
 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
@@ -314,8 +315,12 @@ static int rzv2h_wdt_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, -EINVAL, "Invalid count source\n");
 	}
 
+	rate = clk_get_rate(count_clk);
+	if (!rate)
+		return dev_err_probe(dev, -EINVAL, "Invalid clock rate\n");
+
 	priv->wdev.max_hw_heartbeat_ms = (MILLI * priv->of_data->timeout_cycles *
-					  priv->of_data->cks_div) / clk_get_rate(count_clk);
+					  priv->of_data->cks_div) / rate;
 	dev_dbg(dev, "max hw timeout of %dms\n", priv->wdev.max_hw_heartbeat_ms);
 
 	ret = devm_pm_runtime_enable(dev);
-- 
2.53.0

Re: [PATCH 3/3] watchdog: rzv2h: Avoid division by zero

[Guenter Roeck]

On Sun, Sep 13, 2026 at 02:48:51PM +0800, Tzung-Bi Shih wrote:
> clk_get_rate() could return 0.  Avoid a division by zero panic.
> 
> Fixes: f6febd0a30b6 ("watchdog: Add Watchdog Timer driver for RZ/V2H(P)")
> Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>

Applied.

Thanks,
Guenter