linux-kernel - Re: [PATCH] watchdog: stm32_iwdg: initialize default timeout

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Date: Wed, 28 Feb 2024 10:36:31 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Ben Wolsieffer <ben.wolsieffer@...ring.com>,
 linux-kernel@...r.kernel.org, linux-watchdog@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org
Cc: Wim Van Sebroeck <wim@...ux-watchdog.org>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 Christophe Roullier <christophe.roullier@...com>
Subject: Re: [PATCH] watchdog: stm32_iwdg: initialize default timeout

On 2/28/24 10:27, Ben Wolsieffer wrote:
> The driver never sets a default timeout value, therefore it is
> initialized to zero. When CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED is
> enabled, the watchdog is started during probe. The kernel is supposed to
> automatically ping the watchdog from this point until userspace takes
> over, but this does not happen if the configured timeout is zero. A zero
> timeout causes watchdog_need_worker() to return false, so the heartbeat
> worker does not run and the system therefore resets soon after the
> driver is probed.
> 
> This patch fixes this by setting an arbitrary non-zero default timeout.
> The default could be read from the hardware instead, but I didn't see
> any reason to add this complexity.
> 
> This has been tested on an STM32F746.
> 
> Fixes: 85fdc63fe256 ("drivers: watchdog: stm32_iwdg: set WDOG_HW_RUNNING at probe")
> Signed-off-by: Ben Wolsieffer <ben.wolsieffer@...ring.com>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
>   drivers/watchdog/stm32_iwdg.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/watchdog/stm32_iwdg.c b/drivers/watchdog/stm32_iwdg.c
> index d9fd50df9802..5404e0387620 100644
> --- a/drivers/watchdog/stm32_iwdg.c
> +++ b/drivers/watchdog/stm32_iwdg.c
> @@ -20,6 +20,8 @@
>   #include <linux/platform_device.h>
>   #include <linux/watchdog.h>
>   
> +#define DEFAULT_TIMEOUT 10
> +
>   /* IWDG registers */
>   #define IWDG_KR		0x00 /* Key register */
>   #define IWDG_PR		0x04 /* Prescaler Register */
> @@ -248,6 +250,7 @@ static int stm32_iwdg_probe(struct platform_device *pdev)
>   	wdd->parent = dev;
>   	wdd->info = &stm32_iwdg_info;
>   	wdd->ops = &stm32_iwdg_ops;
> +	wdd->timeout = DEFAULT_TIMEOUT;
>   	wdd->min_timeout = DIV_ROUND_UP((RLR_MIN + 1) * PR_MIN, wdt->rate);
>   	wdd->max_hw_heartbeat_ms = ((RLR_MAX + 1) * wdt->data->max_prescaler *
>   				    1000) / wdt->rate;