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

Alexandre Belloni
2022-05-07T07:31:35Z

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.

--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering