linux-kernel - Re: [PATCH v1 1/1] watchdog: atmel: atmel-sama5d4-wdt: Disable watchdog on system suspend

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Date:   Wed, 12 Jun 2019 08:24:10 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Ken Sloat <KSloat@...pglobal.com>,
        "nicolas.ferre@...rochip.com" <nicolas.ferre@...rochip.com>
Cc:     "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 v1 1/1] watchdog: atmel: atmel-sama5d4-wdt: Disable
 watchdog on system suspend

On 6/12/19 8:02 AM, 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>
> ---
>   drivers/watchdog/sama5d4_wdt.c | 31 +++++++++++++++++++++++++++++--
>   1 file changed, 29 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/watchdog/sama5d4_wdt.c b/drivers/watchdog/sama5d4_wdt.c
> index 111695223aae..84eb4db23993 100644
> --- a/drivers/watchdog/sama5d4_wdt.c
> +++ b/drivers/watchdog/sama5d4_wdt.c
> @@ -280,6 +280,18 @@ 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_suspend_late(struct device *dev)
> +{
> +	struct sama5d4_wdt *wdt;
> +
> +	wdt = dev_get_drvdata(dev);
> +
> +	if (watchdog_active(&wdt->wdd))
> +		sama5d4_wdt_stop(&wdt->wdd);
> +
> +	return 0;
> +}
> +
>   static int sama5d4_wdt_resume(struct device *dev)
>   {
>   	struct sama5d4_wdt *wdt = dev_get_drvdata(dev);
> @@ -293,10 +305,25 @@ static int sama5d4_wdt_resume(struct device *dev)
>   
>   	return 0;
>   }
> +
> +static int sama5d4_wdt_resume_early(struct device *dev)
> +{
> +	struct sama5d4_wdt *wdt;
> +
> +	wdt = dev_get_drvdata(dev);
> +
> +	if (watchdog_active(&wdt->wdd))
> +		sama5d4_wdt_start(&wdt->wdd);
> +
> +	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_SYSTEM_SLEEP_PM_OPS(NULL, sama5d4_wdt_resume)
> +	SET_LATE_SYSTEM_SLEEP_PM_OPS(sama5d4_wdt_suspend_late,
> +			sama5d4_wdt_resume_early)

I don't think you need both sama5d4_wdt_resume()
and sama5d4_wdt_resume_early().

Guenter

> +};
>   
>   static struct platform_driver sama5d4_wdt_driver = {
>   	.probe		= sama5d4_wdt_probe,
>