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SubjectRe: [RFC V1 05/11] arm64/perf: Detect support for BRBE
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On 1/26/22 10:48 PM, Rob Herring wrote:
> On Mon, Jan 24, 2022 at 10:00:47AM +0530, Anshuman Khandual wrote:
>> CPU specific BRBE entries, cycle count, format support gets detected during
>> PMU init. This information gets saved in per-cpu struct pmu_hw_events which
>> later helps in operating BRBE during a perf event context.
>
> Another NOP commit. The subject says 'arm64' and that we detect BRBE
> support. This patch neither touches arm64 code nor detects anything.

Right, this is a NOP at this point but it will have functionality when the
driver gets added later on. I will correct the arm64 part and also update
the message saying - it just adds the infrastructure for BRBE detection not
the actual function.

>
>>
>> Cc: Will Deacon <will@kernel.org>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: linux-arm-kernel@lists.infradead.org
>> Cc: linux-kernel@vger.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>> ---
>> drivers/perf/arm_pmu_platform.c | 34 +++++++++++++++++++++++++++++++++
>> 1 file changed, 34 insertions(+)
>>
>> diff --git a/drivers/perf/arm_pmu_platform.c b/drivers/perf/arm_pmu_platform.c
>> index 513de1f54e2d..800e4a6e8bc3 100644
>> --- a/drivers/perf/arm_pmu_platform.c
>> +++ b/drivers/perf/arm_pmu_platform.c
>> @@ -172,6 +172,36 @@ static int armpmu_request_irqs(struct arm_pmu *armpmu)
>> return err;
>> }
>>
>> +static void arm_brbe_probe_cpu(void *info)
>> +{
>> + struct pmu_hw_events *hw_events;
>> + struct arm_pmu *armpmu = info;
>> +
>> + /*
>> + * Return from here, if BRBE driver has not been
>> + * implemented for this PMU. This helps prevent
>> + * kernel crash later when brbe_probe() will be
>> + * called on the PMU.
>> + */
>> + if (!armpmu->brbe_probe)
>> + return;
>> +
>> + hw_events = per_cpu_ptr(armpmu->hw_events, smp_processor_id());
>> + armpmu->brbe_probe(hw_events);
>> +}
>> +
>> +static int armpmu_request_brbe(struct arm_pmu *armpmu)
>> +{
>> + int cpu, err = 0;
>> +
>> + for_each_cpu(cpu, &armpmu->supported_cpus) {
>> + err = smp_call_function_single(cpu, arm_brbe_probe_cpu, armpmu, 1);
>> + if (err)
>> + return err;
>> + }
>> + return err;
>> +}
>> +
>> static void armpmu_free_irqs(struct arm_pmu *armpmu)
>> {
>> int cpu;
>> @@ -229,6 +259,10 @@ int arm_pmu_device_probe(struct platform_device *pdev,
>> if (ret)
>> goto out_free_irqs;
>>
>> + ret = armpmu_request_brbe(pmu);
>> + if (ret)
>> + goto out_free_irqs;
>> +
>> ret = armpmu_register(pmu);
>> if (ret) {
>> dev_err(dev, "failed to register PMU devices!\n");
>> --
>> 2.25.1
>>
>>

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