[RFC/PATCH 1/2] Basic generic time/clocksource code for PowerPC
paulus at samba.org
Fri Sep 7 04:20:12 EST 2007
Gabriel Paubert writes:
> On Fri, Sep 07, 2007 at 12:41:38AM +1000, Paul Mackerras wrote:
> > This changes PowerPC to use the generic time infrastructure for
> > gettimeofday et al. We register a clocksource which uses the timebase
> > register, or the RTC on the 601.
> > It also gets rid of the RTC update stuff. IIRC we discussed removing
> > this some time ago but never actually did it.
> So who will be in charge of updating the RTC now? The update
> every 11 min is there to stay on x86(-64) it seems.
I had an impression that ntpd would do it, but that seems to be wrong.
I also have been unable to find where in the kernel source there is
code for x86[-64] to do the RTC updates. Do you know where it is?
Doing the updates from timer_interrupt will no longer really be
suitable since it is not called at regular intervals any more. The
best thing would be for the ntp code to set up a timer when it reaches
> Removing this will have strange side effects: as an example,
> your laptop clock will be good if it synchronized on NTP,
> then you put it to sleep, disconnect the network and RTC read
> on wake up returns a wrong value, giving wrong timestamps.
No, the suspend/resume code reads the RTC on both suspend and resume,
and advances xtime by the difference between the two readings. So the
time might be out by up to a second after resume, but it shouldn't be
way off, assuming that your RTC is advancing at the right speed.
> As someone who has a network of tens of machines using
> NTP for synchornisation I think it is a very bad idea
> unless we have a replacement.
OK, but I think that doing it in timer_interrupt is the wrong place.
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