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Message-ID: <4C7A6164.60208@riesch.at> Date: Sun, 29 Aug 2010 15:32:20 +0200 From: Christian Riesch <christian@...sch.at> To: Alan Cox <alan@...rguk.ukuu.org.uk> CC: Richard Cochran <richardcochran@...il.com>, john stultz <johnstul@...ibm.com>, Christian Riesch <christian.riesch@...cron.at>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, devicetree-discuss@...ts.ozlabs.org, linux-arm-kernel@...ts.infradead.org, Krzysztof Halasa <khc@...waw.pl>, Rodolfo Giometti <giometti@...ux.it>, Arnd Bergmann <arnd@...db.de> Subject: Re: [PATCH 1/5] ptp: Added a brand new class driver for ptp clocks. Alan Cox wrote: >> The master node in a PTP network probably takes its time from a >> precise external time source, like GPS. The GPS provides a 1 PPS >> directly to the PTP clock hardware, which latches the PTP hardware >> clock time on the PPS edge. This provides one sample as input to a >> clock servo (in the PTPd) that, in turn, regulates the PTP clock >> hardware. > > A PTP clock is TAI, Unix time is UTC. Not necessarily. AFAIK, the time distributed by IEEE1588v2 can either be based on the "PTP epoch" (timePropertiesDS.ptpTimescale=TRUE) and thus represent TAI or be based on an implementation specific arbitrary epoch (timePropertiesDS.ptpTimescale=FALSE) and represent time on some arbitrary time scale. Christian -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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