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RE: [PATCH v3 1/4] Add correlated clocksource deriving system time from an auxiliary clocksource

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> -----Original Message-----
> From: Peter Zijlstra [mailto:peterz@infradead.org]
> Sent: Friday, September 04, 2015 7:28 AM
> To: Richard Cochran
> Cc: Hall, Christopher S; Thomas Gleixner; Kirsher, Jeffrey T;
> hpa@zytor.com; mingo@redhat.com; john.stultz@linaro.org; x86@kernel.org;
> linux-kernel@vger.kernel.org; netdev@vger.kernel.org; intel-wired-
> lan@lists.osuosl.org
> Subject: Re: [PATCH v3 1/4] Add correlated clocksource deriving system time
> from an auxiliary clocksource
> 
> > > (several milliseconds) and the result will be out of date by some
> fraction of that
> > > amount.
> >
> > Why does it take milliseconds to read one audio time stamp?
> 
> So what I suspect, but please correct me if I'm wrong Chris, is that a
> DSP will buffer and process audio signals, and only later wake up the
> main CPU.
> 
> So by the time the CPU is made aware of the data, it's 'old'.

That's about right.  The DSP runs on a 1 ms cadence.  Any access to registers controlled by the DSP will take 1-2 DSP ticks to access.
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[PATCH v3 1/4] Add correlated clocksource deriving system time from an auxiliary clocksource "Christopher S. Hall" <christopher.s.hall@intel.com> - 2015-08-22 04:00 +0200
  Re: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource Thomas Gleixner <tglx@linutronix.de> - 2015-08-22 22:20 +0200
    RE: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource "Hall, Christopher S" <christopher.s.hall@intel.com> - 2015-09-04 01:30 +0200
      Re: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource Richard Cochran <richardcochran@gmail.com> - 2015-09-04 10:20 +0200
        Re: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource Peter Zijlstra <peterz@infradead.org> - 2015-09-04 16:30 +0200
          RE: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource "Hall, Christopher S" <christopher.s.hall@intel.com> - 2015-09-04 23:20 +0200
      RE: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource Thomas Gleixner <tglx@linutronix.de> - 2015-09-04 15:10 +0200
        Re: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource Peter Zijlstra <peterz@infradead.org> - 2015-09-04 17:20 +0200
          Re: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource Richard Cochran <richardcochran@gmail.com> - 2015-09-04 17:20 +0200
            Re: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource Peter Zijlstra <peterz@infradead.org> - 2015-09-04 17:50 +0200
              Re: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource Thomas Gleixner <tglx@linutronix.de> - 2015-09-04 18:40 +0200
                RE: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource "Hall, Christopher S" <christopher.s.hall@intel.com> - 2015-09-04 23:10 +0200
                RE: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource Thomas Gleixner <tglx@linutronix.de> - 2015-09-05 10:50 +0200
                Re: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource Ingo Molnar <mingo@kernel.org> - 2015-09-05 12:10 +0200
        Re: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource Richard Cochran <richardcochran@gmail.com> - 2015-09-04 17:40 +0200
      Re: [PATCH v3 1/4] Add correlated clocksource deriving system time  from an auxiliary clocksource John Stultz <john.stultz@linaro.org> - 2015-09-05 00:00 +0200

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