[v3,1/1] drivers: watchdog: stm32_iwdg: set WDOG_HW_RUNNING at probe
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Message ID 20191122132246.8473-1-christophe.roullier@st.com
State Accepted
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  • [v3,1/1] drivers: watchdog: stm32_iwdg: set WDOG_HW_RUNNING at probe
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Commit Message

Christophe ROULLIER Nov. 22, 2019, 1:22 p.m. UTC
If the watchdog hardware is already enabled during the boot process,
when the Linux watchdog driver loads, it should start/reset the watchdog
and tell the watchdog framework. As a result, ping can be generated from
the watchdog framework (if CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED is set),
until the userspace watchdog daemon takes over control

Fixes:4332d113c66a ("watchdog: Add STM32 IWDG driver")

Signed-off-by: Christophe Roullier <christophe.roullier@st.com>
---
Changes since v2:
According to Guenter
removed intermediate variable

I've tested some config and it is working as expected:
Watchdog enable in Uboot + HANDLE_BOOT_ENABLE is not set + daemon watchdog in userland ON ==> No reset IWDG2
Watchdog enable in Uboot + HANDLE_BOOT_ENABLE is not set ==> Reset IWDG2
Watchdog enable in Uboot + HANDLE_BOOT_ENABLE=y ==> No reset IWDG2
Watchdog enable in Uboot + HANDLE_BOOT_ENABLE=y + daemon watchdog in userland ON puis OFF ==> Reset IWDG2
Watchdog disable in Uboot + HANDLE_BOOT_ENABLE is not set ==> No reset IWDG2
Watchdog disable in Uboot + HANDLE_BOOT_ENABLE=y ==> No reset IWDG2
Watchdog disable in Uboot + HANDLE_BOOT_ENABLE=y + daemon watchdog in userland ON ==> No reset IWDG2
Watchdog disable in Uboot + HANDLE_BOOT_ENABLE=y + daemon watchdog in userland ON puis OFF ==> Reset IWDG2

Thanks,
Christophe

 drivers/watchdog/stm32_iwdg.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

Comments

Guenter Roeck Nov. 22, 2019, 6:15 p.m. UTC | #1
On Fri, Nov 22, 2019 at 02:22:46PM +0100, Christophe Roullier wrote:
> If the watchdog hardware is already enabled during the boot process,
> when the Linux watchdog driver loads, it should start/reset the watchdog
> and tell the watchdog framework. As a result, ping can be generated from
> the watchdog framework (if CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED is set),
> until the userspace watchdog daemon takes over control
> 
> Fixes:4332d113c66a ("watchdog: Add STM32 IWDG driver")
> 
> Signed-off-by: Christophe Roullier <christophe.roullier@st.com>

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

> ---
> Changes since v2:
> According to Guenter
> removed intermediate variable
> 
> I've tested some config and it is working as expected:
> Watchdog enable in Uboot + HANDLE_BOOT_ENABLE is not set + daemon watchdog in userland ON ==> No reset IWDG2
> Watchdog enable in Uboot + HANDLE_BOOT_ENABLE is not set ==> Reset IWDG2
> Watchdog enable in Uboot + HANDLE_BOOT_ENABLE=y ==> No reset IWDG2
> Watchdog enable in Uboot + HANDLE_BOOT_ENABLE=y + daemon watchdog in userland ON puis OFF ==> Reset IWDG2
> Watchdog disable in Uboot + HANDLE_BOOT_ENABLE is not set ==> No reset IWDG2
> Watchdog disable in Uboot + HANDLE_BOOT_ENABLE=y ==> No reset IWDG2
> Watchdog disable in Uboot + HANDLE_BOOT_ENABLE=y + daemon watchdog in userland ON ==> No reset IWDG2
> Watchdog disable in Uboot + HANDLE_BOOT_ENABLE=y + daemon watchdog in userland ON puis OFF ==> Reset IWDG2
> 
> Thanks,
> Christophe
> 
>  drivers/watchdog/stm32_iwdg.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/watchdog/stm32_iwdg.c b/drivers/watchdog/stm32_iwdg.c
> index a3a329011a06..25188d6bbe15 100644
> --- a/drivers/watchdog/stm32_iwdg.c
> +++ b/drivers/watchdog/stm32_iwdg.c
> @@ -262,6 +262,24 @@ static int stm32_iwdg_probe(struct platform_device *pdev)
>  	watchdog_set_nowayout(wdd, WATCHDOG_NOWAYOUT);
>  	watchdog_init_timeout(wdd, 0, dev);
>  
> +	/*
> +	 * In case of CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED is set
> +	 * (Means U-Boot/bootloaders leaves the watchdog running)
> +	 * When we get here we should make a decision to prevent
> +	 * any side effects before user space daemon will take care of it.
> +	 * The best option, taking into consideration that there is no
> +	 * way to read values back from hardware, is to enforce watchdog
> +	 * being run with deterministic values.
> +	 */
> +	if (IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) {
> +		ret = stm32_iwdg_start(wdd);
> +		if (ret)
> +			return ret;
> +
> +		/* Make sure the watchdog is serviced */
> +		set_bit(WDOG_HW_RUNNING, &wdd->status);
> +	}
> +
>  	ret = devm_watchdog_register_device(dev, wdd);
>  	if (ret)
>  		return ret;
> -- 
> 2.17.1
>

Patch
diff mbox series

diff --git a/drivers/watchdog/stm32_iwdg.c b/drivers/watchdog/stm32_iwdg.c
index a3a329011a06..25188d6bbe15 100644
--- a/drivers/watchdog/stm32_iwdg.c
+++ b/drivers/watchdog/stm32_iwdg.c
@@ -262,6 +262,24 @@  static int stm32_iwdg_probe(struct platform_device *pdev)
 	watchdog_set_nowayout(wdd, WATCHDOG_NOWAYOUT);
 	watchdog_init_timeout(wdd, 0, dev);
 
+	/*
+	 * In case of CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED is set
+	 * (Means U-Boot/bootloaders leaves the watchdog running)
+	 * When we get here we should make a decision to prevent
+	 * any side effects before user space daemon will take care of it.
+	 * The best option, taking into consideration that there is no
+	 * way to read values back from hardware, is to enforce watchdog
+	 * being run with deterministic values.
+	 */
+	if (IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) {
+		ret = stm32_iwdg_start(wdd);
+		if (ret)
+			return ret;
+
+		/* Make sure the watchdog is serviced */
+		set_bit(WDOG_HW_RUNNING, &wdd->status);
+	}
+
 	ret = devm_watchdog_register_device(dev, wdd);
 	if (ret)
 		return ret;