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drivers/perf: arm_pmu: implement CPU_PM notifier

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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>
This commit is contained in:
Lorenzo Pieralisi 2016-02-23 18:22:39 +00:00 committed by Will Deacon
parent 94085fe570
commit da4e4f18af
2 changed files with 96 additions and 0 deletions
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95
drivers/perf/arm_pmu.c
View file

@ -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);
}

1
include/linux/perf/arm_pmu.h
View file

@ -108,6 +108,7 @@ struct arm_pmu {
struct platform_device *plat_device;
struct pmu_hw_events __percpu *hw_events;
struct notifier_block hotplug_nb;
struct notifier_block cpu_pm_nb;
};
#define to_arm_pmu(p) (container_of(p, struct arm_pmu, pmu))