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

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Message-ID: <20151020193639.GA15095@localhost.localdomain>
Date:	Tue, 20 Oct 2015 21:36:39 +0200
From:	Richard Cochran <richardcochran@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	John Stultz <john.stultz@...aro.org>,
	Christopher Hall <christopher.s.hall@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"x86@...nel.org" <x86@...nel.org>,
	intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>, kevin.b.stanton@...el.com
Subject: Re: [PATCH v4 1/4] Produce system time from correlated clocksource

On Tue, Oct 20, 2015 at 09:11:21PM +0200, Thomas Gleixner wrote:
> Darn, we don't want to have that kind of sampling in every driver
> which has this kind of problem even if it looks like the simpler
> choice for this particular use case. This is going to be something
> which next generation chips will have on more than just the audio
> interface and we realy want to have a generic solution for this.

Right, having multiple drivers sampling is bad.

Just thinking out loud: how about a service layer that can handle
multiple drivers?  The layer samples at the maximum requested rate,
and buffers the history for the maximum requested backlog.  The
non-max rate users simply get a higher resolution than they need.

A generic solution would handle any history length for old time
stamps, within reason.  I think hard coding 4 ms (or 8 ms or 800 ms)
is clunky.

Thanks,
Richard
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