From: Thomas Gleixner <tglx@linutronix.de>
To: Richard Cochran <richardcochran@gmail.com>
Cc: "Christopher S. Hall" <christopher.s.hall@intel.com>,
jeffrey.t.kirsher@intel.com, hpa@zytor.com, mingo@redhat.com,
john.stultz@linaro.org, peterz@infradead.org, x86@kernel.org,
intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, kevin.b.stanton@intel.com
Subject: Re: [PATCH v4 1/4] Produce system time from correlated clocksource
Date: Tue, 13 Oct 2015 21:15:51 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.11.1510132113470.25029@nanos> (raw)
In-Reply-To: <20151013083113.GA1931@localhost.localdomain>
On Tue, 13 Oct 2015, Richard Cochran wrote:
> On Tue, Oct 13, 2015 at 09:51:02AM +0200, Thomas Gleixner wrote:
> >
> > You are restricting the problem space to this particular use
> > case. There are other use cases where PTP is not available or not the
> > relevant reference, but you still want to correlate time domains to
> > ART.
>
> They may well be other use cases, but they have not been identified
> here. The PTP to media clock problem has a very simple solution. You
> do not need a history of system time stamps to solve it.
Well, these use cases are not in the focus of Christopher, but I have
a few in my head. Think industrial fieldbusses.
> Even if you wanted to correlate the system time's UTC with the media
> clock, still you don't need any shadow history for that. Just feed
> (ART, UTC) pairs into the DSP at a regular rate, and let the DSP do
> the math. This does not need to be part of the central time keeping
> code at all.
That's not working. The firmware is not going to change, no matter
what.
Thanks,
tglx
next prev parent reply other threads:[~2015-10-13 19:15 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-12 18:45 [PATCH v4 0/4] Patchset enabling hardware based cross-timestamps for next gen Intel platforms Christopher S. Hall
2015-10-12 18:45 ` [PATCH v4 1/4] Produce system time from correlated clocksource Christopher S. Hall
2015-10-13 4:58 ` Richard Cochran
2015-10-13 7:51 ` Thomas Gleixner
2015-10-13 8:31 ` Richard Cochran
2015-10-13 19:15 ` Thomas Gleixner [this message]
2015-10-13 21:12 ` Richard Cochran
2015-10-14 7:21 ` Thomas Gleixner
2015-10-14 9:29 ` Richard Cochran
2015-10-14 14:22 ` Thomas Gleixner
2015-10-14 16:18 ` Richard Cochran
2015-10-15 2:34 ` Christopher Hall
2015-10-15 5:41 ` Richard Cochran
2015-10-15 8:13 ` Thomas Gleixner
2015-10-13 5:26 ` Richard Cochran
2015-10-13 13:50 ` Richard Cochran
2015-10-13 19:42 ` Thomas Gleixner
2015-10-15 1:57 ` Christopher Hall
2015-10-15 5:57 ` Richard Cochran
2015-10-15 8:15 ` Thomas Gleixner
2015-10-20 0:18 ` Christopher Hall
2015-10-20 0:36 ` John Stultz
2015-10-20 8:54 ` Richard Cochran
2015-10-20 10:48 ` Thomas Gleixner
2015-10-20 11:51 ` Richard Cochran
2015-10-20 14:55 ` Richard Cochran
2015-10-20 19:11 ` Thomas Gleixner
2015-10-20 19:36 ` Richard Cochran
2015-10-20 20:16 ` John Stultz
2015-10-21 7:44 ` Thomas Gleixner
2015-11-03 19:18 ` Stanton, Kevin B
2015-11-09 21:17 ` John Stultz
2015-10-12 18:45 ` [PATCH v4 2/4] Always running timer " Christopher S. Hall
2015-10-13 2:03 ` kbuild test robot
2015-11-18 23:53 ` Jacob Pan
2015-10-12 18:45 ` [PATCH v4 3/4] Add PTP_SYS_OFFSET_PRECISE for driver crosstimestamping Christopher S. Hall
2015-10-13 13:59 ` Richard Cochran
2015-10-15 2:47 ` Christopher Hall
2015-11-07 2:15 ` Christopher Hall
2015-10-12 18:45 ` [PATCH v4 4/4] Adds hardware supported cross timestamp Christopher S. Hall
2015-10-13 2:10 ` kbuild test robot
2015-10-13 2:11 ` kbuild test robot
2015-10-13 2:31 ` David Miller
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