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Commit 48957155 authored by Mark Rutland's avatar Mark Rutland Committed by Will Deacon
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ARM: perf: only register a CPU PMU when present 



Currently, an "empty" struct pmu is registered as the CPU PMU,
regardless of whether there is a physical PMU. This burdens the
accessor functions with checks to see whether a PMU is actually
present.

This patch changes initialisation to register a PMU only if there is a
supported PMU present, and removes the checks that this change makes
redundant.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Reviewed-by: default avatarWill Deacon <will.deacon@arm.com>
Reviewed-by: default avatarJamie Iles <jamie@jamieiles.com>
Reviewed-by: default avatarAshwin Chaugule <ashwinc@codeaurora.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 5f12a761

arch/arm/kernel/perf_event.c

+2 −16
Original line number Diff line number Diff line
@@ -250,9 +250,6 @@ armpmu_stop(struct perf_event *event, int flags) 
{

	struct hw_perf_event *hwc = &event->hw;



	if (!armpmu)

		return;



	/*

	 * ARM pmu always has to update the counter, so ignore

	 * PERF_EF_UPDATE, see comments in armpmu_start().
@@ -270,9 +267,6 @@ armpmu_start(struct perf_event *event, int flags) 
{

	struct hw_perf_event *hwc = &event->hw;



	if (!armpmu)

		return;



	/*

	 * ARM pmu always has to reprogram the period, so ignore

	 * PERF_EF_RELOAD, see the comment below.
@@ -567,9 +561,6 @@ static int armpmu_event_init(struct perf_event *event) 
		return -ENOENT;

	}



	if (!armpmu)

		return -ENODEV;



	event->destroy = hw_perf_event_destroy;



	if (!atomic_inc_not_zero(&active_events)) {
@@ -599,9 +590,6 @@ static void armpmu_enable(struct pmu *pmu) 
	int idx, enabled = 0;

	struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);



	if (!armpmu)

		return;



	for (idx = 0; idx < armpmu->num_events; ++idx) {

		struct perf_event *event = cpuc->events[idx];
@@ -618,7 +606,6 @@ static void armpmu_enable(struct pmu *pmu) 


static void armpmu_disable(struct pmu *pmu)

{

	if (armpmu)

	armpmu->stop();

}
@@ -738,12 +725,11 @@ init_hw_perf_events(void) 
	if (armpmu) {

		pr_info("enabled with %s PMU driver, %d counters available\n",

			armpmu->name, armpmu->num_events);

		perf_pmu_register(&pmu, "cpu", PERF_TYPE_RAW);

	} else {

		pr_info("no hardware support available\n");

	}



	perf_pmu_register(&pmu, "cpu", PERF_TYPE_RAW);



	return 0;

}

early_initcall(init_hw_perf_events);