blackfin/perf: Convert hotplug notifier to state machine

Install the callback via the state machine and let the core invoke
the callbacks on the already online CPUs.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Miao <realmz6@gmail.com>
Cc: adi-buildroot-devel@lists.sourceforge.net
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153334.265797537@linutronix.deSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/blackfin/kernel/perf_event.c

@@ -453,29 +453,13 @@ static struct pmu pmu = {
 	.read        = bfin_pmu_read,
 };
 
-static void bfin_pmu_setup(int cpu)
+static int bfin_pmu_prepare_cpu(unsigned int cpu)
 {
 	struct cpu_hw_events *cpuhw = &per_cpu(cpu_hw_events, cpu);
 
+	bfin_write_PFCTL(0);
 	memset(cpuhw, 0, sizeof(struct cpu_hw_events));
-}
-
-static int
-bfin_pmu_notifier(struct notifier_block *self, unsigned long action, void *hcpu)
-{
-	unsigned int cpu = (long)hcpu;
-
-	switch (action & ~CPU_TASKS_FROZEN) {
-	case CPU_UP_PREPARE:
-		bfin_write_PFCTL(0);
-		bfin_pmu_setup(cpu);
-		break;
-
-	default:
-		break;
-	}
-
-	return NOTIFY_OK;
+	return 0;
 }
 
 static int __init bfin_pmu_init(void)
@@ -491,8 +475,8 @@ static int __init bfin_pmu_init(void)
 
 	ret = perf_pmu_register(&pmu, "cpu", PERF_TYPE_RAW);
 	if (!ret)
-		perf_cpu_notifier(bfin_pmu_notifier);
-
+		cpuhp_setup_state(CPUHP_PERF_BFIN, "PERF_BFIN",
+				  bfin_pmu_prepare_cpu, NULL);
 	return ret;
 }
 early_initcall(bfin_pmu_init);

include/linux/cpuhotplug.h

@@ -9,6 +9,7 @@ enum cpuhp_state {
 	CPUHP_PERF_X86_UNCORE_PREP,
 	CPUHP_PERF_X86_AMD_UNCORE_PREP,
 	CPUHP_PERF_X86_RAPL_PREP,
+	CPUHP_PERF_BFIN,
 	CPUHP_NOTIFY_PREPARE,
 	CPUHP_BRINGUP_CPU,
 	CPUHP_AP_IDLE_DEAD,