clocksource/arm_arch_timer: Convert to hotplug state machine

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

Signed-off-by: Richard Cochran <rcochran@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153336.048259040@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

drivers/clocksource/arm_arch_timer.c

@@ -370,8 +370,10 @@ static bool arch_timer_has_nonsecure_ppi(void)
 		arch_timer_ppi[PHYS_NONSECURE_PPI]);
 }
 
-static int arch_timer_setup(struct clock_event_device *clk)
+static int arch_timer_starting_cpu(unsigned int cpu)
 {
+	struct clock_event_device *clk = this_cpu_ptr(arch_timer_evt);
+
 	__arch_timer_setup(ARCH_CP15_TIMER, clk);
 
 	enable_percpu_irq(arch_timer_ppi[arch_timer_uses_ppi], 0);
@@ -527,29 +529,14 @@ static void arch_timer_stop(struct clock_event_device *clk)
 	clk->set_state_shutdown(clk);
 }
 
-static int arch_timer_cpu_notify(struct notifier_block *self,
-					   unsigned long action, void *hcpu)
+static int arch_timer_dying_cpu(unsigned int cpu)
 {
-	/*
-	 * Grab cpu pointer in each case to avoid spurious
-	 * preemptible warnings
-	 */
-	switch (action & ~CPU_TASKS_FROZEN) {
-	case CPU_STARTING:
-		arch_timer_setup(this_cpu_ptr(arch_timer_evt));
-		break;
-	case CPU_DYING:
-		arch_timer_stop(this_cpu_ptr(arch_timer_evt));
-		break;
-	}
+	struct clock_event_device *clk = this_cpu_ptr(arch_timer_evt);
 
-	return NOTIFY_OK;
+	arch_timer_stop(clk);
+	return 0;
 }
 
-static struct notifier_block arch_timer_cpu_nb = {
-	.notifier_call = arch_timer_cpu_notify,
-};
-
 #ifdef CONFIG_CPU_PM
 static unsigned int saved_cntkctl;
 static int arch_timer_cpu_pm_notify(struct notifier_block *self,
@@ -570,11 +557,21 @@ static int __init arch_timer_cpu_pm_init(void)
 {
 	return cpu_pm_register_notifier(&arch_timer_cpu_pm_notifier);
 }
+
+static void __init arch_timer_cpu_pm_deinit(void)
+{
+	WARN_ON(cpu_pm_unregister_notifier(&arch_timer_cpu_pm_notifier));
+}
+
 #else
 static int __init arch_timer_cpu_pm_init(void)
 {
 	return 0;
 }
+
+static void __init arch_timer_cpu_pm_deinit(void)
+{
+}
 #endif
 
 static int __init arch_timer_register(void)
@@ -621,22 +618,23 @@ static int __init arch_timer_register(void)
 		goto out_free;
 	}
 
-	err = register_cpu_notifier(&arch_timer_cpu_nb);
-	if (err)
-		goto out_free_irq;
-
 	err = arch_timer_cpu_pm_init();
 	if (err)
 		goto out_unreg_notify;
 
-	/* Immediately configure the timer on the boot CPU */
-	arch_timer_setup(this_cpu_ptr(arch_timer_evt));
 
+	/* Register and immediately configure the timer on the boot CPU */
+	err = cpuhp_setup_state(CPUHP_AP_ARM_ARCH_TIMER_STARTING,
+				"AP_ARM_ARCH_TIMER_STARTING",
+				arch_timer_starting_cpu, arch_timer_dying_cpu);
+	if (err)
+		goto out_unreg_cpupm;
 	return 0;
 
+out_unreg_cpupm:
+	arch_timer_cpu_pm_deinit();
+
 out_unreg_notify:
-	unregister_cpu_notifier(&arch_timer_cpu_nb);
-out_free_irq:
 	free_percpu_irq(arch_timer_ppi[arch_timer_uses_ppi], arch_timer_evt);
 	if (arch_timer_has_nonsecure_ppi())
 		free_percpu_irq(arch_timer_ppi[PHYS_NONSECURE_PPI],

include/linux/cpuhotplug.h

@@ -36,6 +36,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_XTENSA_STARTING,
 	CPUHP_AP_ARM_VFP_STARTING,
 	CPUHP_AP_PERF_ARM_STARTING,
+	CPUHP_AP_ARM_ARCH_TIMER_STARTING,
 	CPUHP_AP_KVM_STARTING,
 	CPUHP_AP_NOTIFY_STARTING,
 	CPUHP_AP_ONLINE,