Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759435Ab1CDLGM (ORCPT ); Fri, 4 Mar 2011 06:06:12 -0500 Received: from mailout-de.gmx.net ([213.165.64.22]:58291 "HELO mailout-de.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752084Ab1CDLGK (ORCPT ); Fri, 4 Mar 2011 06:06:10 -0500 X-Authenticated: #911537 X-Provags-ID: V01U2FsdGVkX19603k5/8t6s3zlk5OgDTbIWtNVie39b1qMwwOoDc Xb0xXMftPwSf05 Date: Fri, 4 Mar 2011 12:06:06 +0100 From: torbenh To: Richard Cochran Cc: john stultz , linux-kernel@vger.kernel.org, richard.cochran@omicron.at, tglx@linutronix.de Subject: Re: [PATCH 2/3] ptp: add a software clock based on clock_monotonic_raw Message-ID: <20110304110606.GB3237@siel.b> Mail-Followup-To: Richard Cochran , john stultz , linux-kernel@vger.kernel.org, richard.cochran@omicron.at, tglx@linutronix.de References: <1299173174-348-1-git-send-email-torbenh@gmx.de> <1299173174-348-3-git-send-email-torbenh@gmx.de> <1299180844.28285.111.camel@work-vm> <20110304064639.GD3824@riccoc20.at.omicron.at> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110304064639.GD3824@riccoc20.at.omicron.at> User-Agent: Mutt/1.5.20 (2009-06-14) X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2233 Lines: 52 On Fri, Mar 04, 2011 at 07:46:39AM +0100, Richard Cochran wrote: > On Thu, Mar 03, 2011 at 11:34:04AM -0800, john stultz wrote: > > On Thu, 2011-03-03 at 18:26 +0100, Torben Hohn wrote: > > > First version of a software clock. Not very useful yet, > > > as it doesnt generate events, but at least it allows > > > for testing the ptp framework without special hardware. > > > > So in the past, I pushed back on Richard for having something similar, > > as I'm not psyched about duplicating interfaces. However, your > > implementation is CLOCK_MONOTONIC_RAW instead of CLOCK_REALTIME and it > > keeps the adjustments internal, I'm not as opposed. > > (Aha! So it is okay after all ;) > > I do think a software only PHC will make it easier for people to get > started with the new interface. I have been carrying along such a > patch privately for my own testing. can you post your patch then ? if john likes somthing better in my implementation, we should merge them. i will be away for the next week, so its probably up to you. i am still trying to find out, whether 802.1AS will spec accurate ptp clocks. i have the feeling that they wont. the main concern is synchronicity of the clock inside all devices of the timing domain. that this clock i running at the same frequency as the wallclock is not important. here is a pretty confused mail about this: http://article.gmane.org/gmane.comp.audio.jackit/23606 i hope this thread will yield more useful information as it develops. i am currently acting under the assumption, that a device like this: http://www.xmos.com/products/reference-designs/avbl2 would need to be the ptp master when the computer doesnt have h/w timestamping in its NIC. i am also assuming that the clock in that device would be crappy. so we wouldnt want to servo CLOCK_REALTIME after that crappy clock. but we want an instance of that clock as accurate as possible inside the computer. so that we can bind streaming apps to this clock. -- torben Hohn -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/