sh_wdt_probe() calls watchdog_register_device() -- exposing
/dev/watchdogN -- before timer_setup() and pm_runtime_enable() run. A
start command landing in that window calls mod_timer() on an
uninitialized timer (NULL ->function) and resumes via
pm_runtime_get_sync() before PM is enabled.

Move timer_setup() and pm_runtime_enable() before the register call,
matching the order already used by rzg2l_wdt.c/rzv2h_wdt.c. Add
pm_runtime_disable() on the now-possible post-enable register-failure
path.

Fixes: 8f5585ec3d17 ("watchdog: shwdt: driver model conversion.")
Assisted-by: Claude:claude-opus-4
Signed-off-by: Cong Nguyen <congnt264@gmail.com>
---
 drivers/watchdog/shwdt.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/watchdog/shwdt.c b/drivers/watchdog/shwdt.c
index 719f100aae60..c22b8e760476 100644
--- a/drivers/watchdog/shwdt.c
+++ b/drivers/watchdog/shwdt.c
@@ -263,19 +263,20 @@ static int sh_wdt_probe(struct platform_device *pdev)
 	dev_info(&pdev->dev, "configured with heartbeat=%d sec (nowayout=%d)\n",
 		 sh_wdt_dev.timeout, nowayout);
 
+	timer_setup(&wdt->timer, sh_wdt_ping, 0);
+	wdt->timer.expires	= next_ping_period(clock_division_ratio);
+
+	pm_runtime_enable(&pdev->dev);
+
 	rc = watchdog_register_device(&sh_wdt_dev);
 	if (unlikely(rc)) {
 		dev_err(&pdev->dev, "Can't register watchdog (err=%d)\n", rc);
+		pm_runtime_disable(&pdev->dev);
 		return rc;
 	}
 
-	timer_setup(&wdt->timer, sh_wdt_ping, 0);
-	wdt->timer.expires	= next_ping_period(clock_division_ratio);
-
 	dev_info(&pdev->dev, "initialized.\n");
 
-	pm_runtime_enable(&pdev->dev);
-
 	return 0;
 }
 
-- 
2.25.1

On Mon, Sep 14, 2026 at 07:36:09PM +0700, Cong Nguyen wrote:
> sh_wdt_probe() calls watchdog_register_device() -- exposing
> /dev/watchdogN -- before timer_setup() and pm_runtime_enable() run. A
> start command landing in that window calls mod_timer() on an
> uninitialized timer (NULL ->function) and resumes via
> pm_runtime_get_sync() before PM is enabled.
> 
> Move timer_setup() and pm_runtime_enable() before the register call,
> matching the order already used by rzg2l_wdt.c/rzv2h_wdt.c. Add
> pm_runtime_disable() on the now-possible post-enable register-failure
> path.
> 
> Fixes: 8f5585ec3d17 ("watchdog: shwdt: driver model conversion.")
> Assisted-by: Claude:claude-opus-4
> Signed-off-by: Cong Nguyen <congnt264@gmail.com>

The other problems in this driver make me wonder if this change
is worth the trouble. Is this an actually observed problem ?
Because if not it would be better to leave the driver alone.
If this _is_ an actually observed problem, the code should be
rearranged to depend on the watchdog core for timer handling.

Thanks,
Guenter

> ---
>  drivers/watchdog/shwdt.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/watchdog/shwdt.c b/drivers/watchdog/shwdt.c
> index 719f100aae60..c22b8e760476 100644
> --- a/drivers/watchdog/shwdt.c
> +++ b/drivers/watchdog/shwdt.c
> @@ -263,19 +263,20 @@ static int sh_wdt_probe(struct platform_device *pdev)
>  	dev_info(&pdev->dev, "configured with heartbeat=%d sec (nowayout=%d)\n",
>  		 sh_wdt_dev.timeout, nowayout);
>  
> +	timer_setup(&wdt->timer, sh_wdt_ping, 0);
> +	wdt->timer.expires	= next_ping_period(clock_division_ratio);
> +
> +	pm_runtime_enable(&pdev->dev);
> +
>  	rc = watchdog_register_device(&sh_wdt_dev);
>  	if (unlikely(rc)) {
>  		dev_err(&pdev->dev, "Can't register watchdog (err=%d)\n", rc);
> +		pm_runtime_disable(&pdev->dev);
>  		return rc;
>  	}
>  
> -	timer_setup(&wdt->timer, sh_wdt_ping, 0);
> -	wdt->timer.expires	= next_ping_period(clock_division_ratio);
> -
>  	dev_info(&pdev->dev, "initialized.\n");
>  
> -	pm_runtime_enable(&pdev->dev);
> -
>  	return 0;
>  }
>