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ARM: 6835/1: perf: ensure overflows aren't missed due to IRQ latency
If a counter overflows during a perf stat profiling run it may overtake the last known value of the counter: 0 prev new 0xffffffff |----------|-------|----------------------| In this case, the number of events that have occurred is (0xffffffff - prev) + new. Unfortunately, the event update code will not realise an overflow has occurred and will instead report the event delta as (new - prev) which may be considerably smaller than the real count. This patch adds an extra argument to armpmu_event_update which indicates whether or not an overflow has occurred. If an overflow has occurred then we use the maximum period of the counter to calculate the elapsed events. Acked-by: Jamie Iles <jamie@jamieiles.com> Reported-by: Ashwin Chaugule <ashwinc@codeaurora.org> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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