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

[Peter Zijlstra]

On Fri, Sep 04, 2015 at 10:11:22AM +0200, Richard Cochran wrote:
> On Thu, Sep 03, 2015 at 11:20:37PM +0000, Hall, Christopher S wrote:
> > In addition to the network interface, ART will be used in the audio interface as well.
> > We need to support the case where an audio co-processor will control the audio device.
> > In this case, the get_ts() function supplied by the audio driver will be very slow
> > (several milliseconds) and the result will be out of date by some fraction of that 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'.

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