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author | Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com> | 2012-03-06 17:37:45 +0100 |
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committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2012-03-07 09:40:50 +0000 |
commit | a0feb6db0fe03326d7d2c7a4615ce3289615c023 (patch) | |
tree | 5252086b8224c588148af6a48618030aa6e4827a /arch/arm | |
parent | 3f31ae121348afd9ed39700ea2a63c17cd7eeed1 (diff) | |
download | blackbird-op-linux-a0feb6db0fe03326d7d2c7a4615ce3289615c023.tar.gz blackbird-op-linux-a0feb6db0fe03326d7d2c7a4615ce3289615c023.zip |
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: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm')
-rw-r--r-- | arch/arm/kernel/perf_event.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c index 56173ae16448..b2abfa18f137 100644 --- a/arch/arm/kernel/perf_event.c +++ b/arch/arm/kernel/perf_event.c @@ -680,6 +680,28 @@ static void __init cpu_pmu_init(struct arm_pmu *armpmu) } /* + * 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. */ static int __init @@ -730,6 +752,7 @@ init_hw_perf_events(void) pr_info("enabled with %s PMU driver, %d counters available\n", cpu_pmu->name, cpu_pmu->num_events); cpu_pmu_init(cpu_pmu); + register_cpu_notifier(&pmu_cpu_notifier); armpmu_register(cpu_pmu, "cpu", PERF_TYPE_RAW); } else { pr_info("no hardware support available\n"); |