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perf: arm_pmuv3: Factor out PMCCNTR_EL0 use conditions

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PMCCNTR_EL0 is preferred for counting CPU_CYCLES under certain
conditions. Factor out the condition check to a separate function
for further extension. Add documents for better understanding.
No functional changes intended.

Reviewed-by: James Clark <james.clark@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Yicong Yang
2025-08-20 16:45:33 +08:00
committed by Will Deacon
parent 00d7a1af5a
commit f8f89e8cf3
1 changed files with 27 additions and 2 deletions
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29
drivers/perf/arm_pmuv3.c
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@@ -978,6 +978,32 @@ static int armv8pmu_get_chain_idx(struct pmu_hw_events *cpuc,
return -EAGAIN;
}
static bool armv8pmu_can_use_pmccntr(struct pmu_hw_events *cpuc,
struct perf_event *event)
{
struct hw_perf_event *hwc = &event->hw;
unsigned long evtype = hwc->config_base & ARMV8_PMU_EVTYPE_EVENT;
if (evtype != ARMV8_PMUV3_PERFCTR_CPU_CYCLES)
return false;
/*
* A CPU_CYCLES event with threshold counting cannot use PMCCNTR_EL0
* since it lacks threshold support.
*/
if (armv8pmu_event_get_threshold(&event->attr))
return false;
/*
* PMCCNTR_EL0 is not affected by BRBE controls like BRBCR_ELx.FZP.
* So don't use it for branch events.
*/
if (has_branch_stack(event))
return false;
return true;
}
static int armv8pmu_get_event_idx(struct pmu_hw_events *cpuc,
struct perf_event *event)
{
@@ -986,8 +1012,7 @@ static int armv8pmu_get_event_idx(struct pmu_hw_events *cpuc,
unsigned long evtype = hwc->config_base & ARMV8_PMU_EVTYPE_EVENT;
/* Always prefer to place a cycle counter into the cycle counter. */
if ((evtype == ARMV8_PMUV3_PERFCTR_CPU_CYCLES) &&
!armv8pmu_event_get_threshold(&event->attr) && !has_branch_stack(event)) {
if (armv8pmu_can_use_pmccntr(cpuc, event)) {
if (!test_and_set_bit(ARMV8_PMU_CYCLE_IDX, cpuc->used_mask))
return ARMV8_PMU_CYCLE_IDX;
else if (armv8pmu_event_is_64bit(event) &&