Re: [PATCH v4 1/4] Produce system time from correlated clocksource

From	Thomas Gleixner <tglx@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH v4 1/4] Produce system time from correlated clocksource
Date	2015-10-20 12:50 +0200
Message-ID	<qlCEq-1fd-17@gated-at.bofh.it> (permalink)
References	(3 earlier) <qjFZL-8q-7@gated-at.bofh.it> <qjLVw-DS-5@gated-at.bofh.it> <qlsOK-3LO-9@gated-at.bofh.it> <qlt85-48v-7@gated-at.bofh.it> <qlAVY-77N-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tue, 20 Oct 2015, Richard Cochran wrote:

> On Mon, Oct 19, 2015 at 05:36:56PM -0700, John Stultz wrote:
> > If we're only tracking 4ms of history, how does this solution
> > measurably improve the error over using the timestamps to generate
> > MONOTONIC_RAW clock deltas (which doesn't require keeping any history)
> > and using getnstime_raw_and_real to take an anchor point to calculate
> > the delta from?  Why is adding complexity necessary?
> 
> This idea is variant of what I suggested in another reply in this
> thread.  To my understanding, there is no need at all to keep a
> history arbitrarily 4 ms long.  Instead, the DSP driver (or whoever
> else may need such a thing) can simply sample the system time at the
> rate needed for that particular application.

That's complete nonsense. The whole point is to have a proper
correlation from ART/audio timestamps to system time. Sampling system
time does not help in any way,

Thanks,

	tglx
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Thread

Re: [PATCH v4 1/4] Produce system time from correlated clocksource "Christopher Hall" <christopher.s.hall@intel.com> - 2015-10-20 02:20 +0200
  Re: [PATCH v4 1/4] Produce system time from correlated clocksource John Stultz <john.stultz@linaro.org> - 2015-10-20 02:40 +0200
    Re: [PATCH v4 1/4] Produce system time from correlated clocksource Richard Cochran <richardcochran@gmail.com> - 2015-10-20 11:00 +0200
      Re: [PATCH v4 1/4] Produce system time from correlated clocksource Thomas Gleixner <tglx@linutronix.de> - 2015-10-20 12:50 +0200
        Re: [PATCH v4 1/4] Produce system time from correlated clocksource Richard Cochran <richardcochran@gmail.com> - 2015-10-20 14:00 +0200
          Re: [PATCH v4 1/4] Produce system time from correlated clocksource Richard Cochran <richardcochran@gmail.com> - 2015-10-20 17:00 +0200
            Re: [PATCH v4 1/4] Produce system time from correlated clocksource Thomas Gleixner <tglx@linutronix.de> - 2015-10-20 21:20 +0200
              Re: [PATCH v4 1/4] Produce system time from correlated clocksource Richard Cochran <richardcochran@gmail.com> - 2015-10-20 21:40 +0200
              Re: [PATCH v4 1/4] Produce system time from correlated clocksource John Stultz <john.stultz@linaro.org> - 2015-10-20 22:20 +0200
                Re: [PATCH v4 1/4] Produce system time from correlated clocksource Thomas Gleixner <tglx@linutronix.de> - 2015-10-21 09:50 +0200

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