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From:   Vincent Guittot <vincent.guittot@linaro.org>
Date:   Tue, 8 Jan 2019 17:42:09 +0100
Message-ID: <CAKfTPtCoOK-cYLXJ--sOfpVa9RVmzOAEN1+zB2qHMCzkJN0qaQ@mail.gmail.com>
Subject: Re: Regression in v5.0-rc1 with autosuspend hrtimers
To:     Tony Lindgren <tony@atomide.com>
Cc:     "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        "open list:THERMAL" <linux-pm@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        LAK <linux-arm-kernel@lists.infradead.org>,
        linux-omap@vger.kernel.org
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On Tue, 8 Jan 2019 at 16:53, Tony Lindgren <tony@atomide.com> wrote:
>
> * Vincent Guittot <vincent.guittot@linaro.org> [190108 08:00]:
> > Hi Tony,
> >
> > On Tue, 8 Jan 2019 at 00:38, Tony Lindgren <tony@atomide.com> wrote:
> > >
> > > Hi all,
> > >
> > > Looks like commit 8234f6734c5d ("PM-runtime: Switch autosuspend
> > > over to using hrtimers") caused a regression on at least
> > > omap5-uevm where 8250 UART rx wake no longer works. I have not
> > > noticed this happening on others so far.
> > >
> > > The devices I've tested all are using 8250 with dedicated
> > > wakeirqs configured for the rx pin. I can see the interrupt
> > > increase on omap5-uevm after some one or more keypresses,
> > > but then nothing. It seems that the uart just falls back
> > > asleep right away or something.
> > >
> > > Any ideas what might be going wrong?
> >
> > What is the autosuspend value ? Can it be that the autosuspend is set
> > to a short value but was finally greater than 10-20ms on arm32. And
> > now the autosuspend happens before and this has changed the sequence ?
>
> It's set to 3 seconds. The difference between let's say
> C-A9 pandaboard (that is working) compared to C-A15 omap5-uevm
> is that the C-A15 has arch_timer in use. Other than that things
> should behave more or less the same way.
>
> Hmm so could it be that we now rely on timers that that may
> not be capable of waking up the system from idle states with
> hrtimer?

With nohz and hrtimer enabled,  timer relies on hrtimer to generate
the tick so you should use the same interrupt.

>
> Regards,
>
> Tony
>