linux-kernel - Re: [PATCH v4] watchdog: qcom_wdt: set WDOG_HW

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Date:   Sat, 31 Oct 2020 07:08:44 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Robert Marko <robert.marko@...tura.hr>, agross@...nel.org,
        bjorn.andersson@...aro.org, wim@...ux-watchdog.org,
        linux-arm-msm@...r.kernel.org, linux-watchdog@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Luka Perkov <luka.perkov@...tura.hr>
Subject: Re: [PATCH v4] watchdog: qcom_wdt: set WDOG_HW_RUNNING bit when
 appropriate

On 10/31/20 5:11 AM, Robert Marko wrote:
> If the watchdog hardware is enabled/running during boot, e.g.
> due to a boot loader configuring it, we must tell the
> watchdog framework about this fact so that it can ping the
> watchdog until userspace opens the device and takes over
> control.
> 
> Do so using the WDOG_HW_RUNNING flag that exists for exactly
> that use-case.
> 
> Signed-off-by: Robert Marko <robert.marko@...tura.hr>

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

> Cc: Luka Perkov <luka.perkov@...tura.hr>
> ---
> Changes in v4:
> * Use QCOM_WDT_ENABLE macro
> 
> Changes in v3:
> * Drop call to stop as start already does it
> * Update commit message
> 
> Changes in v2:
> * Correct authorship
> 
>  drivers/watchdog/qcom-wdt.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
> index ab7465d186fd..07d399c4edc4 100644
> --- a/drivers/watchdog/qcom-wdt.c
> +++ b/drivers/watchdog/qcom-wdt.c
> @@ -152,6 +152,13 @@ static int qcom_wdt_restart(struct watchdog_device *wdd, unsigned long action,
>  	return 0;
>  }
>  
> +static int qcom_wdt_is_running(struct watchdog_device *wdd)
> +{
> +	struct qcom_wdt *wdt = to_qcom_wdt(wdd);
> +
> +	return (readl(wdt_addr(wdt, WDT_EN)) & QCOM_WDT_ENABLE);
> +}
> +
>  static const struct watchdog_ops qcom_wdt_ops = {
>  	.start		= qcom_wdt_start,
>  	.stop		= qcom_wdt_stop,
> @@ -294,6 +301,17 @@ static int qcom_wdt_probe(struct platform_device *pdev)
>  	wdt->wdd.timeout = min(wdt->wdd.max_timeout, 30U);
>  	watchdog_init_timeout(&wdt->wdd, 0, dev);
>  
> +	/*
> +	 * If WDT is already running, call WDT start which
> +	 * will stop the WDT, set timeouts as bootloader
> +	 * might use different ones and set running bit
> +	 * to inform the WDT subsystem to ping the WDT
> +	 */
> +	if (qcom_wdt_is_running(&wdt->wdd)) {
> +		qcom_wdt_start(&wdt->wdd);
> +		set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
> +	}
> +
>  	ret = devm_watchdog_register_device(dev, &wdt->wdd);
>  	if (ret)
>  		return ret;
>