Re: [PATCH 7/7] rtc: cmos: Add suspend/resume endurance testing hook

Zhang Rui
2022-05-07T07:41:23Z

On Sat, 2022-05-07 at 09:31 +0200, Alexandre Belloni wrote:
> On 07/05/2022 10:00:40+0800, Zhang Rui wrote:
> > Hi, Alexandre,
> >
> > Thanks for reviewing the patch.
> >
> > On Fri, 2022-05-06 at 23:46 +0200, Alexandre Belloni wrote:
> > > Hello,
> > >
> > > I assume I can ignore this patch as this seems to be only for
> > > testing
> >
> > The main purpose of this patch is for automate testing.
> > But this doesn't mean it cannot be part of upstream code, right?
> >
> > > I'm not even sure why this is needed as this completely breaks
> > > setting
> > > the alarm time.
> >
> > Or overrides the alarm time, :)
> >
> > People rely on the rtc alarm in the automated suspend stress test,
> > which suspend and resume the system for over 1000 iterations.
> > As I mentioned in the cover letter of this patch series, if the
> > system
> > suspend time varies from under 1 second to over 60 seconds, how to
> > alarm the RTC before suspend?
> > This feature is critical in this scenario.
> >
> > Plus, the current solution is transparent to people who don't
> > known/use
> > this "rtc_wake_override_sec" parameter. And for people who use
> > this,
> > they should know that the previous armed RTC alarm will be overrode
> > whenever a system suspend is triggered. I can add a message when
> > the
> > parameter is set, if needed.
> >
>
> It is not transparent, if I read your patch properly, this breaks
> wakeup
> for everyone...
>
> > > On 05/05/2022 09:58:14+0800, Zhang Rui wrote:
> > > > +static int cmos_pm_notify(struct notifier_block *nb, unsigned
> > > > long
> > > > mode, void *_unused)
> > > > +{
> > > > + struct cmos_rtc *cmos = container_of(nb, struct
> > > > cmos_rtc,
> > > > pm_nb);
> > > > + struct rtc_device *rtc = cmos->rtc;
> > > > + unsigned long now;
> > > > + struct rtc_wkalrm alm;
> > > > +
> > > > + if (rtc_wake_override_sec == 0)
> > > > + return NOTIFY_OK;
> > > > +
> > > > + switch (mode) {
> > > > + case PM_SUSPEND_PREPARE:
> > > > + /*
> > > > + * Cancel the timer to make sure it won't fire
> > > > + * before rtc is rearmed later.
> > > > + */
> > > > + rtc_timer_cancel(rtc, &rtc->aie_timer);
> > > > + break;
> > > > + case PM_SUSPEND_LATE:
> > > > + if (rtc_read_time(rtc, &alm.time))
> > > > + return NOTIFY_BAD;
> > > > +
> > > > + now = rtc_tm_to_time64(&alm.time);
> > > > + memset(&alm, 0, sizeof(alm));
> > > > + rtc_time64_to_tm(now + rtc_wake_override_sec,
> > > > &alm.time);
> > > > + alm.enabled = true;
> > > > + if (rtc_set_alarm(rtc, &alm))
> > > > + return NOTIFY_BAD;
>
> ... because if rtc_wake_override_sec is not set, this sets the alarm
> to
> now which is the current RTC time, ensuring the alarm will never
> trigger.

No.
As the code below
> > > >
> > > > if (rtc_wake_override_sec == 0)
> > > > + return NOTIFY_OK;

We check for rtc_wake_override_sec at the beginning of the notifier
callback. So it takes effect only if a) rtc_wake_override_sec is set,
AND b) a suspend is triggered.

thanks,
rui