From: Christian Riesch <christian@riesch.at>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Christoph Lameter <cl@linux.com>,
john stultz <johnstul@us.ibm.com>,
Richard Cochran <richardcochran@gmail.com>,
linux-kernel@vger.kernel.org,
devicetree-discuss@lists.ozlabs.org, linux-api@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org,
Arnd Bergmann <arnd@arndb.de>, David Miller <davem@davemloft.net>,
Krzysztof Halasa <khc@pm.waw.pl>,
Peter Zijlstra <peterz@infradead.org>,
Rodolfo Giometti <giometti@linux.it>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v6 0/8] ptp: IEEE 1588 hardware clock support
Date: Thu, 23 Sep 2010 23:34:06 +0200 [thread overview]
Message-ID: <4C9BC7CE.8020400@riesch.at> (raw)
In-Reply-To: <20100923223417.4ed62e5b@lxorguk.ukuu.org.uk>
Alan Cox wrote:
>> It implies clock tuning in userspace for a potential sub microsecond
>> accurate clock. The clock accuracy will be limited by user space
>> latencies and noise. You wont be able to discipline the system clock
>> accurately.
>
> Noise matters, latency doesn't.
Well put! That's why we need hardware support for PTP timestamping to
reduce the noise, but get along well with the clock servo that is
steering the PHC in user space.
Christian
next prev parent reply other threads:[~2010-09-23 21:34 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-23 17:30 [PATCH v6 0/8] ptp: IEEE 1588 hardware clock support Richard Cochran
2010-09-23 17:31 ` [PATCH 1/8] posix clocks: introduce a syscall for clock tuning Richard Cochran
[not found] ` <b94ef1cd9c04ef3ad5964408bd0af7251add78de.1285261534.git.richard.cochran-3mrvs1K0uXizZXS1Dc/lvw@public.gmane.org>
2010-09-23 19:48 ` john stultz
[not found] ` <1285271331.2587.56.camel-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2010-09-24 7:29 ` Richard Cochran
[not found] ` <20100924072946.GA5043-7KxsofuKt4IfAd9E5cN8NEzG7cXyKsk/@public.gmane.org>
2010-09-24 17:55 ` john stultz
2010-09-23 22:03 ` Benjamin Herrenschmidt
2010-09-23 22:12 ` Thomas Gleixner
[not found] ` <alpine.LFD.2.00.1009240008390.2416-bi+AKbBUZKagILUCTcTcHdKyNwTtLsGr@public.gmane.org>
2010-09-24 1:20 ` Benjamin Herrenschmidt
2010-09-24 7:55 ` Richard Cochran
[not found] ` <20100924075534.GB5043-7KxsofuKt4IfAd9E5cN8NEzG7cXyKsk/@public.gmane.org>
2010-09-24 22:12 ` Benjamin Herrenschmidt
2010-09-23 17:31 ` [PATCH 2/8] posix clocks: dynamic clock ids Richard Cochran
2010-09-23 17:31 ` [PATCH 3/8] posix clocks: introduce a sysfs presence Richard Cochran
[not found] ` <cover.1285261533.git.richard.cochran-3mrvs1K0uXizZXS1Dc/lvw@public.gmane.org>
2010-09-23 17:32 ` [PATCH 4/8] ptp: Added a brand new class driver for ptp clocks Richard Cochran
2010-09-23 17:32 ` [PATCH 5/8] ptp: Added a simulated PTP hardware clock Richard Cochran
2010-09-23 17:33 ` [PATCH 6/8] ptp: Added a clock that uses the eTSEC found on the MPC85xx Richard Cochran
[not found] ` <57b64051c816dc9cb856bbb9f38fc901c9d3d651.1285261535.git.richard.cochran-3mrvs1K0uXizZXS1Dc/lvw@public.gmane.org>
2010-09-23 19:17 ` Christoph Lameter
[not found] ` <alpine.DEB.2.00.1009231348150.2962-sBS69tsa9Uj/9pzu0YdTqQ@public.gmane.org>
2010-09-23 20:43 ` Alan Cox
[not found] ` <20100923214359.3f287b11-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org>
2010-09-23 20:32 ` Christoph Lameter
2010-09-23 21:26 ` Christian Riesch
2010-09-24 11:52 ` Alan Cox
2010-09-24 8:49 ` Richard Cochran
2010-09-23 17:33 ` [PATCH 7/8] ptp: Added a clock driver for the IXP46x Richard Cochran
2010-09-23 17:34 ` [PATCH 8/8] ptp: Added a clock driver for the National Semiconductor PHYTER Richard Cochran
2010-09-23 17:53 ` [PATCH v6 0/8] ptp: IEEE 1588 hardware clock support Christoph Lameter
2010-09-23 18:21 ` Jacob Keller
2010-09-23 18:36 ` Christoph Lameter
[not found] ` <alpine.DEB.2.00.1009231238170.2962-sBS69tsa9Uj/9pzu0YdTqQ@public.gmane.org>
2010-09-23 18:59 ` john stultz
[not found] ` <1285268380.2587.11.camel-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2010-09-23 19:15 ` Christoph Lameter
2010-09-23 20:28 ` john stultz
2010-09-23 20:49 ` Christoph Lameter
[not found] ` <alpine.DEB.2.00.1009231533040.7522-sBS69tsa9Uj/9pzu0YdTqQ@public.gmane.org>
2010-09-23 21:34 ` Alan Cox
2010-09-23 21:34 ` Christian Riesch [this message]
[not found] ` <4C9BC7CE.8020400-U4+xqT1Vg0VeoWH0uzbU5w@public.gmane.org>
2010-09-27 15:37 ` Christoph Lameter
2010-09-30 3:50 ` Christian Riesch
2010-10-02 1:44 ` M. Warner Losh
2010-09-23 21:42 ` john stultz
[not found] ` <1285278136.2587.154.camel-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2010-09-27 15:52 ` Christoph Lameter
2010-09-27 16:14 ` M. Warner Losh
[not found] ` <20100927.101423.702773873740300798.imp-uzTCJ5RojNnQT0dZR+AlfA@public.gmane.org>
2010-09-28 6:34 ` Richard Cochran
2010-09-24 8:33 ` Richard Cochran
2010-09-23 19:38 ` john stultz
[not found] ` <1285270733.2587.46.camel-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2010-09-24 13:50 ` Richard Cochran
[not found] ` <20100924135001.GB3113-7KxsofuKt4IfAd9E5cN8NEzG7cXyKsk/@public.gmane.org>
2010-09-24 14:57 ` Alan Cox
2010-09-23 20:36 ` Alan Cox
2010-09-23 20:49 ` john stultz
[not found] ` <1285274952.2587.113.camel-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2010-09-23 21:30 ` Alan Cox
2010-09-23 22:03 ` john stultz
[not found] ` <20100923213654.0c64b047-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org>
2010-09-24 13:14 ` Richard Cochran
[not found] ` <20100924131407.GA3113-7KxsofuKt4IfAd9E5cN8NEzG7cXyKsk/@public.gmane.org>
2010-09-24 14:02 ` Alan Cox
2010-09-24 14:07 ` Alan Cox
2010-09-27 15:56 ` Christoph Lameter
2010-09-27 17:05 ` Alan Cox
2010-09-28 6:47 ` Richard Cochran
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