[PATCH v4 4/4] perf/marvell: cn10k DDR perf event core ownership

[Bharat Bhushan]

As DDR perf event counters are not per core, so they should be accessed
only by one core at a time. Select new core when previously owning core
is going offline.

Signed-off-by: Bharat Bhushan <bbhushan2@xxxxxxxxxxx>
---
v1->v2->v3->v4:
 - No change

 drivers/perf/marvell_cn10k_ddr_pmu.c | 50 ++++++++++++++++++++++++++--
 include/linux/cpuhotplug.h           |  1 +
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/drivers/perf/marvell_cn10k_ddr_pmu.c b/drivers/perf/marvell_cn10k_ddr_pmu.c
index 21fccb9090c5..bef0cee3a46a 100644
--- a/drivers/perf/marvell_cn10k_ddr_pmu.c
+++ b/drivers/perf/marvell_cn10k_ddr_pmu.c
@@ -129,6 +129,7 @@ struct cn10k_ddr_pmu {
 	int active_events;
 	struct perf_event *events[DDRC_PERF_NUM_COUNTERS];
 	struct hrtimer hrtimer;
+	struct hlist_node node;
 };
 
 #define to_cn10k_ddr_pmu(p)	container_of(p, struct cn10k_ddr_pmu, pmu)
@@ -610,6 +611,24 @@ static enum hrtimer_restart cn10k_ddr_pmu_timer_handler(struct hrtimer *hrtimer)
 	return HRTIMER_RESTART;
 }
 
+static int cn10k_ddr_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
+{
+	struct cn10k_ddr_pmu *pmu = hlist_entry_safe(node, struct cn10k_ddr_pmu,
+						     node);
+	unsigned int target;
+
+	if (cpu != pmu->cpu)
+		return 0;
+
+	target = cpumask_any_but(cpu_online_mask, cpu);
+	if (target >= nr_cpu_ids)
+		return 0;
+
+	perf_pmu_migrate_context(&pmu->pmu, cpu, target);
+	pmu->cpu = target;
+	return 0;
+}
+
 static int cn10k_ddr_perf_probe(struct platform_device *pdev)
 {
 	struct cn10k_ddr_pmu *ddr_pmu;
@@ -661,18 +680,31 @@ static int cn10k_ddr_perf_probe(struct platform_device *pdev)
 	hrtimer_init(&ddr_pmu->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	ddr_pmu->hrtimer.function = cn10k_ddr_pmu_timer_handler;
 
+	cpuhp_state_add_instance_nocalls(
+				CPUHP_AP_PERF_ARM_MARVELL_CN10K_DDR_ONLINE,
+				&ddr_pmu->node);
+
 	ret = perf_pmu_register(&ddr_pmu->pmu, name, -1);
 	if (ret)
-		return ret;
+		goto error;
 
 	pr_info("CN10K DDR PMU Driver for ddrc@%llx\n", res->start);
 	return 0;
+error:
+	cpuhp_state_remove_instance_nocalls(
+				CPUHP_AP_PERF_ARM_MARVELL_CN10K_DDR_ONLINE,
+				&ddr_pmu->node);
+	return ret;
 }
 
 static int cn10k_ddr_perf_remove(struct platform_device *pdev)
 {
 	struct cn10k_ddr_pmu *ddr_pmu = platform_get_drvdata(pdev);
 
+	cpuhp_state_remove_instance_nocalls(
+				CPUHP_AP_PERF_ARM_MARVELL_CN10K_DDR_ONLINE,
+				&ddr_pmu->node);
+
 	perf_pmu_unregister(&ddr_pmu->pmu);
 	return 0;
 }
@@ -695,12 +727,26 @@ static struct platform_driver cn10k_ddr_pmu_driver = {
 
 static int __init cn10k_ddr_pmu_init(void)
 {
-	return platform_driver_register(&cn10k_ddr_pmu_driver);
+	int ret;
+
+	ret = cpuhp_setup_state_multi(
+				CPUHP_AP_PERF_ARM_MARVELL_CN10K_DDR_ONLINE,
+				"perf/marvell/cn10k/ddr:online", NULL,
+				cn10k_ddr_pmu_offline_cpu);
+	if (ret)
+		return ret;
+
+	ret = platform_driver_register(&cn10k_ddr_pmu_driver);
+	if (ret)
+		cpuhp_remove_multi_state(
+				CPUHP_AP_PERF_ARM_MARVELL_CN10K_DDR_ONLINE);
+	return ret;
 }
 
 static void __exit cn10k_ddr_pmu_exit(void)
 {
 	platform_driver_unregister(&cn10k_ddr_pmu_driver);
+	cpuhp_remove_multi_state(CPUHP_AP_PERF_ARM_MARVELL_CN10K_DDR_ONLINE);
 }
 
 module_init(cn10k_ddr_pmu_init);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 832d8a74fa59..a4b521f12b58 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -227,6 +227,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_ARM_QCOM_L3_ONLINE,
 	CPUHP_AP_PERF_ARM_APM_XGENE_ONLINE,
 	CPUHP_AP_PERF_ARM_CAVIUM_TX2_UNCORE_ONLINE,
+	CPUHP_AP_PERF_ARM_MARVELL_CN10K_DDR_ONLINE,
 	CPUHP_AP_PERF_POWERPC_NEST_IMC_ONLINE,
 	CPUHP_AP_PERF_POWERPC_CORE_IMC_ONLINE,
 	CPUHP_AP_PERF_POWERPC_THREAD_IMC_ONLINE,
-- 
2.17.1