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metag: perf: add missing prev_count updates

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The prev_count needs setting when changing the counter value, otherwise
the calculated delta will be wrong, which for frequency sampling
(dynamic period sampling) results in sampling at too high a frequency.

For non-interrupting performance counters it should also be cleared when
enabling the counter since the write to the PERF_COUNT register will
clear the perf counter.

This also includes a minor change to remove the u64 cast from the
metag_pmu->write() call as metag_pmu->write() takes a u32 anyway, and in
any case GCC is smart enough to optimise away the cast.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
This commit is contained in:
James Hogan 2013-02-27 16:16:38 +00:00
parent db59932f62
commit c6ac1e6eda
1 changed files with 10 additions and 2 deletions
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12
arch/metag/kernel/perf/perf_event.c
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@ -240,8 +240,10 @@ int metag_pmu_event_set_period(struct perf_event *event,
if (left > (s64)metag_pmu->max_period)
left = metag_pmu->max_period;
if (metag_pmu->write)
metag_pmu->write(idx, (u64)(-left) & MAX_PERIOD);
if (metag_pmu->write) {
local64_set(&hwc->prev_count, -(s32)left);
metag_pmu->write(idx, -left & MAX_PERIOD);
}
perf_event_update_userpage(event);
@ -651,6 +653,12 @@ static void metag_pmu_enable_counter(struct hw_perf_event *event, int idx)
* set to a specific value that needs preserving.
*/
tmp |= metag_in32(PERF_COUNT(idx)) & 0x00ffffff;
else
/*
* Older cores reset the counter on write, so prev_count needs
* resetting too so we can calculate a correct delta.
*/
local64_set(&event->prev_count, 0);
metag_out32(tmp, PERF_COUNT(idx));
unlock: