Re: [RFC/PATCH 1/2] Basic generic time/clocksource code for PowerPC

Gabriel Paubert writes:

On Fri, Sep 07, 2007 at 12:41:38AM +1000, Paul Mackerras wrote:

quoted

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
synchronization.

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.

Paul.