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

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Message-ID: <alpine.DEB.2.11.1510140920200.25029@nanos>
Date:	Wed, 14 Oct 2015 09:21:42 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Richard Cochran <richardcochran@...il.com>
cc:	"Christopher S. Hall" <christopher.s.hall@...el.com>,
	jeffrey.t.kirsher@...el.com, hpa@...or.com, mingo@...hat.com,
	john.stultz@...aro.org, peterz@...radead.org, x86@...nel.org,
	intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kevin.b.stanton@...el.com
Subject: Re: [PATCH v4 1/4] Produce system time from correlated clocksource

On Tue, 13 Oct 2015, Richard Cochran wrote:
> On Tue, Oct 13, 2015 at 09:15:51PM +0200, Thomas Gleixner wrote:
> > That's not working. The firmware is not going to change, no matter
> > what.
> 
> Can we at least have a explanation of how the firmware operates?  How
> are (ART,sys) pairs are generated, and how they are supposed to get
> into the DSP?

The firmware gives you an ART/audio timestamp pair. The firmware does
neither know about system time nor about PTP time.

So we have to do correlation in software.

Thanks,

	tglx
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