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Re: [PATCH v2] clocksource: atmel-pit: register as a sched_clock

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2016-02-24 17:20 GMT+01:00 Sylvain Rochet <sylvain.rochet@finsecur.com>:
> Hi,
>
> On Wed, Feb 24, 2016 at 05:04:42PM +0100, Romain Izard wrote:
>> Register the counter of the Periodic Interval Timer as a possible
>> source for sched_clock. Keep the timer running even if the related
>> clockevent is disabled.
>>
>> This provides a better precision than the jiffies-based default. The
>> TCB clocksource does not work, as it is registered too late in the
>> initialization sequence.
>
> I have mixed feelings about that, but this is probably just a
> misunderstanding from my part.
>
My goal is to get a better precision on my printk and trace logs,
because the precision of jiffies is really very bad compared to
everything else I have encountered until now. But it looks like reading
a timer is quite complicated on AT91...

> The PIT timer should not be used for systems with PM_SUSPEND enabled
> and used because it takes ages to synchronize on resume, how does this
> patch affect that ?
>
> Ref: commit ac34ad27fc ("clockevents: Do not suspend/resume if
> unused")

So your advice would be to stay clear of the PIT, because it is
(globally) useless.

I'll keep it in mind.

Best regards,
-- 
Romain Izard

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Thread

[PATCH v2] clocksource: atmel-pit: register as a sched_clock Romain Izard <romain.izard.pro@gmail.com> - 2016-02-24 17:10 +0100
  Re: [PATCH v2] clocksource: atmel-pit: register as a sched_clock Alexandre Belloni <alexandre.belloni@free-electrons.com> - 2016-02-24 17:20 +0100
  Re: [PATCH v2] clocksource: atmel-pit: register as a sched_clock Romain Izard <romain.izard.pro@gmail.com> - 2016-02-24 17:50 +0100
    Re: [PATCH v2] clocksource: atmel-pit: register as a sched_clock Nicolas Ferre <nicolas.ferre@atmel.com> - 2016-02-24 18:20 +0100
  Re: [PATCH v2] clocksource: atmel-pit: register as a sched_clock Sylvain Rochet <sylvain.rochet@finsecur.com> - 2016-02-24 17:50 +0100

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