linux-kernel - Re: [RFC V1 05/11] arm64/perf: Detect support for BRBE

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Date:   Wed, 26 Jan 2022 11:18:59 -0600
From:   Rob Herring <robh@...nel.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: [RFC V1 05/11] arm64/perf: Detect support for BRBE

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.

> 
> Cc: Will Deacon <will@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....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
> 
>