From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Punit Agrawal <punit.agrawal@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Suzuki K. Poulose <suzuki.poulose@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
---
 drivers/bus/arm-cci.c      |   53 +++++++++++++++++++--------------------------
 include/linux/cpuhotplug.h |    1 
 2 files changed, 24 insertions(+), 30 deletions(-)

--- a/drivers/bus/arm-cci.c
+++ b/drivers/bus/arm-cci.c
@@ -144,12 +144,15 @@ struct cci_pmu {
 	int num_cntrs;
 	atomic_t active_events;
 	struct mutex reserve_mutex;
-	struct notifier_block cpu_nb;
+	struct list_head entry;
 	cpumask_t cpus;
 };
 
 #define to_cci_pmu(c)	(container_of(c, struct cci_pmu, pmu))
 
+static DEFINE_MUTEX(cci_pmu_mutex);
+static LIST_HEAD(cci_pmu_list);
+
 enum cci_models {
 #ifdef CONFIG_ARM_CCI400_PMU
 	CCI400_R0,
@@ -1503,31 +1506,26 @@ static int cci_pmu_init(struct cci_pmu *
 	return perf_pmu_register(&cci_pmu->pmu, name, -1);
 }
 
-static int cci_pmu_cpu_notifier(struct notifier_block *self,
-				unsigned long action, void *hcpu)
+static int cci_pmu_offline_cpu(unsigned int cpu)
 {
-	struct cci_pmu *cci_pmu = container_of(self,
-					struct cci_pmu, cpu_nb);
-	unsigned int cpu = (long)hcpu;
+	struct cci_pmu *cci_pmu;
 	unsigned int target;
 
-	switch (action & ~CPU_TASKS_FROZEN) {
-	case CPU_DOWN_PREPARE:
+	mutex_lock(&cci_pmu_mutex);
+	list_for_each_entry(cci_pmu, &cci_pmu_list, entry) {
 		if (!cpumask_test_and_clear_cpu(cpu, &cci_pmu->cpus))
-			break;
+			continue;
 		target = cpumask_any_but(cpu_online_mask, cpu);
-		if (target >= nr_cpu_ids) // UP, last CPU
-			break;
+		if (target >= nr_cpu_ids)
+			continue;
 		/*
 		 * TODO: migrate context once core races on event->ctx have
 		 * been fixed.
 		 */
 		cpumask_set_cpu(target, &cci_pmu->cpus);
-	default:
-		break;
 	}
-
-	return NOTIFY_OK;
+	mutex_unlock(&cci_pmu_mutex);
+	return 0;
 }
 
 static struct cci_pmu_model cci_pmu_models[] = {
@@ -1766,24 +1764,13 @@ static int cci_pmu_probe(struct platform
 	atomic_set(&cci_pmu->active_events, 0);
 	cpumask_set_cpu(smp_processor_id(), &cci_pmu->cpus);
 
-	cci_pmu->cpu_nb = (struct notifier_block) {
-		.notifier_call	= cci_pmu_cpu_notifier,
-		/*
-		 * to migrate uncore events, our notifier should be executed
-		 * before perf core's notifier.
-		 */
-		.priority	= CPU_PRI_PERF + 1,
-	};
-
-	ret = register_cpu_notifier(&cci_pmu->cpu_nb);
+	ret = cci_pmu_init(cci_pmu, pdev);
 	if (ret)
 		return ret;
 
-	ret = cci_pmu_init(cci_pmu, pdev);
-	if (ret) {
-		unregister_cpu_notifier(&cci_pmu->cpu_nb);
-		return ret;
-	}
+	mutex_lock(&cci_pmu_mutex);
+	list_add(&cci_pmu->entry, &cci_pmu_list);
+	mutex_unlock(&cci_pmu_mutex);
 
 	pr_info("ARM %s PMU driver probed", cci_pmu->model->name);
 	return 0;
@@ -1817,6 +1804,12 @@ static int __init cci_platform_init(void
 {
 	int ret;
 
+	ret = cpuhp_setup_state_nocalls(CPUHP_AP_PERF_ARM_CCI_ONLINE,
+					"AP_PERF_ARM_CCI_ONLINE", NULL,
+					cci_pmu_offline_cpu);
+	if (ret)
+		return ret;
+
 	ret = platform_driver_register(&cci_pmu_driver);
 	if (ret)
 		return ret;
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -45,6 +45,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_X86_CSTATE_ONLINE,
 	CPUHP_AP_PERF_S390_CF_ONLINE,
 	CPUHP_AP_PERF_S390_SF_ONLINE,
+	CPUHP_AP_PERF_ARM_CCI_ONLINE,
 	CPUHP_AP_NOTIFY_ONLINE,
 	CPUHP_AP_ONLINE_DYN,
 	CPUHP_AP_ONLINE_DYN_END		= CPUHP_AP_ONLINE_DYN + 30,