linux-kernel - [RFC V2 5/8] driver/perf/arm_pmu_platform: Add support for BRBE attributes detection

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Date:   Tue, 12 Apr 2022 17:24:52 +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>,
        James Clark <james.clark@....com>,
        Rob Herring <robh@...nel.org>, Marc Zyngier <maz@...nel.org>,
        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 V2 5/8] driver/perf/arm_pmu_platform: Add support for BRBE attributes detection

This adds arm pmu infrastrure to probe BRBE implementation's attributes via
driver exported callbacks later. The actual BRBE feature detection will be
added by the driver itself.

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