linux-kernel - Re: [PATCH v7 0/8] Patchset enabling hardware based cross-timestamps for next gen Intel platforms

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Message-ID: <op.yc8y6lni1774gr@chall-mobl2.amr.corp.intel.com>
Date:	Mon, 22 Feb 2016 10:33:47 -0800
From:	"Christopher Hall" <christopher.s.hall@...el.com>
To:	"John Stultz" <john.stultz@...aro.org>
Cc:	"Thomas Gleixner" <tglx@...utronix.de>,
	"Richard Cochran" <richardcochran@...il.com>,
	"Ingo Molnar" <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	"Jeff Kirsher" <jeffrey.t.kirsher@...el.com>,
	"x86@...nel.org" <x86@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
	"Stanton, Kevin B" <kevin.b.stanton@...el.com>,
	kevin.j.clarke@...el.com
Subject: Re: [PATCH v7 0/8] Patchset enabling hardware based cross-timestamps
 for next gen Intel platforms

On Thu, 18 Feb 2016 11:26:24 -0800, John Stultz <john.stultz@...aro.org>  
wrote:
> On Fri, Feb 12, 2016 at 12:25 PM, Christopher S. Hall
> <christopher.s.hall@...el.com> wrote:
>> Modern Intel hardware adds an Always Running Timer (ART) that allows the
>> network and audio device clocks to precisely cross timestamp the device
>> clock with the system clock. This allows a precise correlation of the
>> device time and system time.
>
> Thanks for your continued persistence here Christopher!  It is looking
> pretty good.
>
> I've queued these up for testing, and if that goes well, and don't hit
> anything else in review, I'll likely try to submit all but the last
> patch (unless there's an acked-by from the maintainer of that code)
> through Thomas for 4.6.

Hi John,

I just sent another patchset (v8). I corrected the comment problems  
pointed out by Richard Cochran. I also changed the arch/x86 code to use  
"non-stop" TSC rather than "invariant" TSC. They are *exactly* the same  
thing (i.e. read from the same bit of the CPUID leaf). The former exists  
already and should be used instead.  Patch 6/8 is the only patch that is  
changed apart from comments.

Thanks for your help reviewing this.

Chris