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 15:30:43 +0000
From:   Ken Sloat <KSloat@...pglobal.com>
To:     Guenter Roeck <linux@...ck-us.net>,
        "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>,
        Ken Sloat <KSloat@...pglobal.com>
Subject: RE: [PATCH v1 1/1] watchdog: atmel: atmel-sama5d4-wdt: Disable
 watchdog on system suspend

Hi Guenter,

> -----Original Message-----
> From: Guenter Roeck <groeck7@...il.com> On Behalf Of Guenter Roeck
> Sent: Wednesday, June 12, 2019 11:24 AM
> To: Ken Sloat <KSloat@...pglobal.com>; nicolas.ferre@...rochip.com
> Cc: alexandre.belloni@...tlin.com; ludovic.desroches@...rochip.com;
> wim@...ux-watchdog.org; linux-arm-kernel@...ts.infradead.org; linux-
> watchdog@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v1 1/1] watchdog: atmel: atmel-sama5d4-wdt: Disable
> watchdog on system suspend
> 
> [This is an EXTERNAL EMAIL]
> ________________________________
> 
> 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().

Yes I was wondering about that but wanted feedback on the subject first.
I can simply consolidate the statements, the sama5d4_wdt_init statement
present now should probably be called first anyways, so something like this
within resume_early:

struct sama5d4_wdt = dev_get_drvdata(dev); 

sama5d4_wdt_init(wdt);

if (watchdog_active(&wdt->wdd))
        sama5d4_wdt_start(&wdt->wdd);

return 0;

If that sounds good I will resubmit.

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

Thanks,
Ken Sloat