Re: [PATCH 2.6.21-rt2] PowerPC: decrementer clockevent driver

From
Daniel Walker <hidden>
Date
2007-05-20 02:45:44
Also in
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Reply to
Paul Mackerras, 2007-05-19
On Sat, 2007-05-19 at 13:33 +1000, Paul Mackerras wrote: 
Daniel Walker writes:
quoted
On Fri, 2007-05-18 at 19:06 +0400, Sergei Shtylyov wrote:
quoted
    Well, the decrementer frequency may change, at least in theory (if the bus 
clock changes).
Does that happen very often?
If it did, gettimeofday would start reporting seriously wrong values,
since the timebase and the decrementer count at the same rate, and we
don't have any provision for fixing things up if that rate changed.
Fortunately there are no powerpc platforms where the rate is
variable.
In terms of clocksources, gettimeofday() would have to switch to another
clocksource if the decrementer started to act that way .. That's why it
is possible to register more than one clocksource, to allow for the
switching. The decrementer frequency doesn't change even with cpufreq?

Daniel
Thread (50 messages) 50 messages, 12 authors, last reply 2007-10-18
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