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

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Date:   Mon, 24 Jan 2022 10:00:47 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     Anshuman Khandual <anshuman.khandual@....com>,
        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: [RFC V1 05/11] arm64/perf: Detect support for BRBE

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.

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