linux-kernel - Re: [PATCH v5 2/5] tick: Add freeze timer events

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Message-ID: <CAGAzgsqwOhTYz9D=XYkMYHBZsmajUH8HJoMOJOe3DfG8WVusRA@mail.gmail.com>
Date:   Tue, 18 Jul 2017 13:09:48 -0700
From:   "dbasehore ." <dbasehore@...omium.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Rajneesh Bhardwaj <rajneesh.bhardwaj@...el.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Len Brown <len.brown@...el.com>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v5 2/5] tick: Add freeze timer events

On Mon, Jul 17, 2017 at 11:40 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Mon, 17 Jul 2017, dbasehore . wrote:
>> On Mon, Jul 17, 2017 at 6:33 PM, Rafael J. Wysocki <rafael@...nel.org> wrote:
>> I could make a patch to try it out. I would probably add a flag to rtc
>> timers to indicate whether it wakes the system (default true). We
>> would have to add a sync with the rtc irq and the rtc irqwork. I would
>> probably add a rtc_timer_sync function that would flush the rtc irq
>> and flush the irqwork. I would call this after the freeze_ops sync
>> function since the sci irq needs to finish before syncing with the rtc
>> irq. Also, pm_wakeup_irq seems racy with the current implementation of
>> s2idle_loop since the RTC irq could be mistakenly set as pm_wakeup_irq
>> when something else actually triggered the full wakeup. Fortunately, I
>> don't think pm_wakeup_irq is used for anything except debugging, but
>> we might change that.
>
> There is another option which you might consider. We can reserve one of the
> HPET comparators for that purpose and have a special interrupt handler for
> it. Checking the HPET for expiry from the low level code should be trivial.
>

Does that handle setting up new timers properly or does the timer sync
code still need to be written?

> Thanks,
>
>         tglx
>
>