Commit a0feb6db authored by Lorenzo Pieralisi's avatar Lorenzo Pieralisi Committed by Russell King

ARM: 7358/1: perf: add PMU hotplug notifier

When a CPU is taken out of reset, either cold booted or hotplugged in,
some of its PMU registers can contain UNKNOWN values.

This patch adds a hotplug notifier to ARM core perf code so that upon
CPU restart the PMU unit is reset and becomes ready to use again.
Signed-off-by: default avatarLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 3f31ae12
...@@ -679,6 +679,28 @@ static void __init cpu_pmu_init(struct arm_pmu *armpmu) ...@@ -679,6 +679,28 @@ static void __init cpu_pmu_init(struct arm_pmu *armpmu)
armpmu->type = ARM_PMU_DEVICE_CPU; armpmu->type = ARM_PMU_DEVICE_CPU;
} }
/*
* PMU hardware loses all context when a CPU goes offline.
* When a CPU is hotplugged back in, since some hardware registers are
* UNKNOWN at reset, the PMU must be explicitly reset to avoid reading
* junk values out of them.
*/
static int __cpuinit pmu_cpu_notify(struct notifier_block *b,
unsigned long action, void *hcpu)
{
if ((action & ~CPU_TASKS_FROZEN) != CPU_STARTING)
return NOTIFY_DONE;
if (cpu_pmu && cpu_pmu->reset)
cpu_pmu->reset(NULL);
return NOTIFY_OK;
}
static struct notifier_block __cpuinitdata pmu_cpu_notifier = {
.notifier_call = pmu_cpu_notify,
};
/* /*
* CPU PMU identification and registration. * CPU PMU identification and registration.
*/ */
...@@ -730,6 +752,7 @@ init_hw_perf_events(void) ...@@ -730,6 +752,7 @@ init_hw_perf_events(void)
pr_info("enabled with %s PMU driver, %d counters available\n", pr_info("enabled with %s PMU driver, %d counters available\n",
cpu_pmu->name, cpu_pmu->num_events); cpu_pmu->name, cpu_pmu->num_events);
cpu_pmu_init(cpu_pmu); cpu_pmu_init(cpu_pmu);
register_cpu_notifier(&pmu_cpu_notifier);
armpmu_register(cpu_pmu, "cpu", PERF_TYPE_RAW); armpmu_register(cpu_pmu, "cpu", PERF_TYPE_RAW);
} else { } else {
pr_info("no hardware support available\n"); pr_info("no hardware support available\n");
......
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