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author | Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> | 2016-02-23 21:22:39 +0300 |
---|---|---|
committer | Will Deacon <will.deacon@arm.com> | 2016-02-26 17:37:06 +0300 |
commit | da4e4f18afe0f3729d68f3785c5802f786d36e34 (patch) | |
tree | 79bea24abaddb8f5c7ed32b763dbb182a5e072bb /drivers | |
parent | 94085fe570e7b87597d4695e6fa77d4256efd29e (diff) | |
download | linux-da4e4f18afe0f3729d68f3785c5802f786d36e34.tar.xz |
drivers/perf: arm_pmu: implement CPU_PM notifier
When a CPU is suspended (either through suspend-to-RAM or CPUidle),
its PMU registers content can be lost, which means that counters
registers values that were initialized on power down entry have to be
reprogrammed on power-up to make sure the counters set-up is preserved
(ie on power-up registers take the reset values on Cold or Warm reset,
which can be architecturally UNKNOWN).
To guarantee seamless profiling conditions across a core power down
this patch adds a CPU PM notifier to ARM pmus, that upon CPU PM
entry/exit from low-power states saves/restores the pmu registers
set-up (by using the ARM perf API), so that the power-down/up cycle does
not affect the perf behaviour (apart from a black-out period between
power-up/down CPU PM notifications that is unavoidable).
Cc: Will Deacon <will.deacon@arm.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Acked-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Acked-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/perf/arm_pmu.c | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c index ca63a452393a..11bacc7220a1 100644 --- a/drivers/perf/arm_pmu.c +++ b/drivers/perf/arm_pmu.c @@ -13,6 +13,7 @@ #include <linux/bitmap.h> #include <linux/cpumask.h> +#include <linux/cpu_pm.h> #include <linux/export.h> #include <linux/kernel.h> #include <linux/of_device.h> @@ -710,6 +711,93 @@ static int cpu_pmu_notify(struct notifier_block *b, unsigned long action, return NOTIFY_OK; } +#ifdef CONFIG_CPU_PM +static void cpu_pm_pmu_setup(struct arm_pmu *armpmu, unsigned long cmd) +{ + struct pmu_hw_events *hw_events = this_cpu_ptr(armpmu->hw_events); + struct perf_event *event; + int idx; + + for (idx = 0; idx < armpmu->num_events; idx++) { + /* + * If the counter is not used skip it, there is no + * need of stopping/restarting it. + */ + if (!test_bit(idx, hw_events->used_mask)) + continue; + + event = hw_events->events[idx]; + + switch (cmd) { + case CPU_PM_ENTER: + /* + * Stop and update the counter + */ + armpmu_stop(event, PERF_EF_UPDATE); + break; + case CPU_PM_EXIT: + case CPU_PM_ENTER_FAILED: + /* Restore and enable the counter */ + armpmu_start(event, PERF_EF_RELOAD); + break; + default: + break; + } + } +} + +static int cpu_pm_pmu_notify(struct notifier_block *b, unsigned long cmd, + void *v) +{ + struct arm_pmu *armpmu = container_of(b, struct arm_pmu, cpu_pm_nb); + struct pmu_hw_events *hw_events = this_cpu_ptr(armpmu->hw_events); + int enabled = bitmap_weight(hw_events->used_mask, armpmu->num_events); + + if (!cpumask_test_cpu(smp_processor_id(), &armpmu->supported_cpus)) + return NOTIFY_DONE; + + /* + * Always reset the PMU registers on power-up even if + * there are no events running. + */ + if (cmd == CPU_PM_EXIT && armpmu->reset) + armpmu->reset(armpmu); + + if (!enabled) + return NOTIFY_OK; + + switch (cmd) { + case CPU_PM_ENTER: + armpmu->stop(armpmu); + cpu_pm_pmu_setup(armpmu, cmd); + break; + case CPU_PM_EXIT: + cpu_pm_pmu_setup(armpmu, cmd); + case CPU_PM_ENTER_FAILED: + armpmu->start(armpmu); + break; + default: + return NOTIFY_DONE; + } + + return NOTIFY_OK; +} + +static int cpu_pm_pmu_register(struct arm_pmu *cpu_pmu) +{ + cpu_pmu->cpu_pm_nb.notifier_call = cpu_pm_pmu_notify; + return cpu_pm_register_notifier(&cpu_pmu->cpu_pm_nb); +} + +static void cpu_pm_pmu_unregister(struct arm_pmu *cpu_pmu) +{ + cpu_pm_unregister_notifier(&cpu_pmu->cpu_pm_nb); +} +#else +static inline int cpu_pm_pmu_register(struct arm_pmu *cpu_pmu) { return 0; } +static inline void cpu_pm_pmu_unregister(struct arm_pmu *cpu_pmu) { } +#endif + static int cpu_pmu_init(struct arm_pmu *cpu_pmu) { int err; @@ -725,6 +813,10 @@ static int cpu_pmu_init(struct arm_pmu *cpu_pmu) if (err) goto out_hw_events; + err = cpu_pm_pmu_register(cpu_pmu); + if (err) + goto out_unregister; + for_each_possible_cpu(cpu) { struct pmu_hw_events *events = per_cpu_ptr(cpu_hw_events, cpu); raw_spin_lock_init(&events->pmu_lock); @@ -746,6 +838,8 @@ static int cpu_pmu_init(struct arm_pmu *cpu_pmu) return 0; +out_unregister: + unregister_cpu_notifier(&cpu_pmu->hotplug_nb); out_hw_events: free_percpu(cpu_hw_events); return err; @@ -753,6 +847,7 @@ out_hw_events: static void cpu_pmu_destroy(struct arm_pmu *cpu_pmu) { + cpu_pm_pmu_unregister(cpu_pmu); unregister_cpu_notifier(&cpu_pmu->hotplug_nb); free_percpu(cpu_pmu->hw_events); } |