Hi,

On 11/29/2016 04:52 AM, Will Deacon wrote:

On Wed, Nov 09, 2016 at 05:39:51PM -0600, Jeremy Linton wrote:

quoted

On systems with multiple PMU types the PMU to CPU affinity
needs to be detected and set. The CPU to interrupt affinity
should also be set.

(trimming)

quoted

+static int probe_plat_pmu(struct arm_pmu *pmu,
+			     const struct pmu_probe_info *info,
+			     unsigned int pmuid)
 {
-	int cpu = get_cpu();
-	unsigned int cpuid = read_cpuid_id();
 	int ret = -ENODEV;
+	int cpu;
+	int aff_ctr = 0;
+	static int duplicate_pmus;
+	struct platform_device *pdev = pmu->plat_device;
+	int irq = platform_get_irq(pdev, 0);

-	pr_info("probing PMU on CPU %d\n", cpu);
+	if (irq >= 0 && !irq_is_percpu(irq)) {
+		pmu->irq_affinity = kcalloc(pdev->num_resources, sizeof(int),
+					    GFP_KERNEL);
+		if (!pmu->irq_affinity)
+			return -ENOMEM;
+	}

+	for_each_possible_cpu(cpu) {
+		unsigned int cpuid = read_specific_cpuid(cpu);
+
+		if (cpuid == pmuid) {
+			cpumask_set_cpu(cpu, &pmu->supported_cpus);
+			if (pmu->irq_affinity) {
+				pmu->irq_affinity[aff_ctr] = cpu;
+				aff_ctr++;
+			}
+		}
+	}
+
+	/* find the type of PMU given the CPU */
 	for (; info->init != NULL; info++) {
-		if ((cpuid & info->mask) != info->cpuid)
+		if ((pmuid & info->mask) != info->cpuid)
 			continue;
 		ret = info->init(pmu);
+		/*
+		 * if this pmu declaration is unspecified and we have
+		 * previously found a PMU on this platform then append
+		 * a PMU number to the pmu name. This avoids changing
+		 * the names of PMUs that are specific to a class of CPUs.
+		 * The assumption is that if we match a specific PMU in the
+		 * provided pmu_probe_info then it's unique, and another PMU
+		 * in the system will match a different entry rather than
+		 * needing the _number to assure its unique.
+		 */
+		if ((!info->cpuid) && (duplicate_pmus)) {

This is a bit grim: if you had a PMU with a non-zero info->cpuid, then you
later found a PMU with a zeroed info->cpuid, the latter would get a
redundant suffix. This doesn't happen in reality, because the ACPI case
always has info->cpuid == 0, but if somebody extends armv8_pmu_probe_table
then we'd get this and probably not realise.

Hoisting the duplicate_pmus inside the !info->cpuid fixes that...

I think the duplicate_pmus counter needs to be tied explicitly to the
"default type" (i.e. when info->cpuid == 0, but see my next comment).

quoted

+			pmu->name = kasprintf(GFP_KERNEL, "%s_%d",
+					    pmu->name, duplicate_pmus);
+			if (!pmu->name) {
+				kfree(pmu->irq_affinity);
+				ret = -ENOMEM;
+			}
+		}

This code doesn't run for the device-tree probing case, but I think it would
be useful to do the same numbering trick for e.g. systems with multiple PMUs
that all end up matching on armv8_pmuv3.

Ok, its pretty straightforward to move the check into 
arm_pmu_device_probe() itself and do a string compare against 
DEFAULT_V8_PMU define rather than !cpuid.

Ok, I will do that and post v11 as soon as I hear from Russell about 
what he wants to do with read_specific_cpuid().