From: Tom Huynh Date: Tue, 20 Jan 2015 22:19:50 +0000 (-0600) Subject: powerpc/perf: fix fsl_emb_pmu_start to write correct pmc value X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=d2caa3cebda8b626336e100b80a0ed6f909dccab;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git powerpc/perf: fix fsl_emb_pmu_start to write correct pmc value PMCs on PowerPC increases towards 0x80000000 and triggers an overflow interrupt when the msb is set to collect a sample. Therefore, to setup for the next sample collection, pmu_start should set the pmc value to 0x80000000 - left instead of left which incorrectly delays the next overflow interrupt. Same as commit 9a45a9407c69 ("powerpc/perf: power_pmu_start restores incorrect values, breaking frequency events") for book3s. Signed-off-by: Tom Huynh Signed-off-by: Scott Wood --- diff --git a/arch/powerpc/perf/core-fsl-emb.c b/arch/powerpc/perf/core-fsl-emb.c index 4acaea01fe03..e9fe904b6538 100644 --- a/arch/powerpc/perf/core-fsl-emb.c +++ b/arch/powerpc/perf/core-fsl-emb.c @@ -389,6 +389,7 @@ static void fsl_emb_pmu_del(struct perf_event *event, int flags) static void fsl_emb_pmu_start(struct perf_event *event, int ef_flags) { unsigned long flags; + unsigned long val; s64 left; if (event->hw.idx < 0 || !event->hw.sample_period) @@ -405,7 +406,10 @@ static void fsl_emb_pmu_start(struct perf_event *event, int ef_flags) event->hw.state = 0; left = local64_read(&event->hw.period_left); - write_pmc(event->hw.idx, left); + val = 0; + if (left < 0x80000000L) + val = 0x80000000L - left; + write_pmc(event->hw.idx, val); perf_event_update_userpage(event); perf_pmu_enable(event->pmu);