linux-kernel - Re: [PATCH v2 1/1] watchdog: atmel: atmel-sama5d4-wdt: Disable watchdog on system suspend

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Message-ID: <20190614164609.GA29814@roeck-us.net>
Date:   Fri, 14 Jun 2019 09:46:09 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Ken Sloat <KSloat@...pglobal.com>
Cc:     "nicolas.ferre@...rochip.com" <nicolas.ferre@...rochip.com>,
        "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>,
        "ludovic.desroches@...rochip.com" <ludovic.desroches@...rochip.com>,
        "wim@...ux-watchdog.org" <wim@...ux-watchdog.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/1] watchdog: atmel: atmel-sama5d4-wdt: Disable
 watchdog on system suspend

On Fri, Jun 14, 2019 at 12:53:22PM +0000, Ken Sloat wrote:
> From: Ken Sloat <ksloat@...pglobal.com>
> 
> Currently, the atmel-sama5d4-wdt continues to run after system suspend.
> Unless the system resumes within the watchdog timeout period so the
> userspace can kick it, the system will be reset. This change disables
> the watchdog on suspend if it is active and re-enables on resume. These
> actions occur during the late and early phases of suspend and resume
> respectively to minimize chances where a lock could occur while the
> watchdog is disabled.
> 
> Signed-off-by: Ken Sloat <ksloat@...pglobal.com>
> ---
>  Changes in v2:
>  -Consolidate resume and resume early statements.
> 
>  drivers/watchdog/sama5d4_wdt.c | 21 ++++++++++++++++++---
>  1 file changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/watchdog/sama5d4_wdt.c b/drivers/watchdog/sama5d4_wdt.c
> index 111695223aae..0d123f8cbcc6 100644
> --- a/drivers/watchdog/sama5d4_wdt.c
> +++ b/drivers/watchdog/sama5d4_wdt.c
> @@ -280,7 +280,17 @@ static const struct of_device_id sama5d4_wdt_of_match[] = {
>  MODULE_DEVICE_TABLE(of, sama5d4_wdt_of_match);
>  
>  #ifdef CONFIG_PM_SLEEP
> -static int sama5d4_wdt_resume(struct device *dev)
> +static int sama5d4_wdt_suspend_late(struct device *dev)
> +{
> +	struct sama5d4_wdt *wdt = dev_get_drvdata(dev);
> +
> +	if (watchdog_active(&wdt->wdd))
> +		sama5d4_wdt_stop(&wdt->wdd);
> +
> +	return 0;
> +}
> +
> +static int sama5d4_wdt_resume_early(struct device *dev)
>  {
>  	struct sama5d4_wdt *wdt = dev_get_drvdata(dev);
>  
> @@ -291,12 +301,17 @@ static int sama5d4_wdt_resume(struct device *dev)
>  	 */
>  	sama5d4_wdt_init(wdt);
>  
> +	if (watchdog_active(&wdt->wdd))
> +		sama5d4_wdt_start(&wdt->wdd);
> +

The call to sama5d4_wdt_init() above now explicitly stops the watchdog
even if we want to (re)start it. I think this would be better handled
with an else case here

	else
		sama5d4_wdt_stop(&wdt->wdd);

Guenter

>  	return 0;
>  }
>  #endif
>  
> -static SIMPLE_DEV_PM_OPS(sama5d4_wdt_pm_ops, NULL,
> -			 sama5d4_wdt_resume);
> +static const struct dev_pm_ops sama5d4_wdt_pm_ops = {
> +	SET_LATE_SYSTEM_SLEEP_PM_OPS(sama5d4_wdt_suspend_late,
> +			sama5d4_wdt_resume_early)
> +};
>  
>  static struct platform_driver sama5d4_wdt_driver = {
>  	.probe		= sama5d4_wdt_probe,
> -- 
> 2.17.1
>