ACPI: intel_idle : break dependency between modules

When the system is booted with some cpus offline, the idle
driver is not initialized. When a cpu is set online, the
acpi code call the intel idle init function. Unfortunately
this code introduce a dependency between intel_idle and acpi.

This patch is intended to remove this dependency by using the
notifier of intel_idle. This patch has the benefit of
encapsulating the intel_idle driver and remove some exported
functions.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

drivers/acpi/processor_driver.c

@@ -427,18 +427,11 @@ static int acpi_cpu_soft_notify(struct notifier_block *nfb,
 		 * Initialize missing things
 		 */
 		if (pr->flags.need_hotplug_init) {
-			struct cpuidle_driver *idle_driver =
-				cpuidle_get_driver();
-
 			printk(KERN_INFO "Will online and init hotplugged "
 			       "CPU: %d\n", pr->id);
 			WARN(acpi_processor_start(pr), "Failed to start CPU:"
 				" %d\n", pr->id);
 			pr->flags.need_hotplug_init = 0;
-			if (idle_driver && !strcmp(idle_driver->name,
-						   "intel_idle")) {
-				intel_idle_cpu_init(pr->id);
-			}
 		/* Normal CPU soft online event */
 		} else {
 			acpi_processor_ppc_has_changed(pr, 0);

drivers/idle/intel_idle.c

@@ -96,6 +96,7 @@ static const struct idle_cpu *icpu;
 static struct cpuidle_device __percpu *intel_idle_cpuidle_devices;
 static int intel_idle(struct cpuidle_device *dev,
 			struct cpuidle_driver *drv, int index);
+static int intel_idle_cpu_init(int cpu);
 
 static struct cpuidle_state *cpuidle_state_table;
 
@@ -302,22 +303,35 @@ static void __setup_broadcast_timer(void *arg)
 	clockevents_notify(reason, &cpu);
 }
 
-static int setup_broadcast_cpuhp_notify(struct notifier_block *n,
-		unsigned long action, void *hcpu)
+static int cpu_hotplug_notify(struct notifier_block *n,
+			      unsigned long action, void *hcpu)
 {
 	int hotcpu = (unsigned long)hcpu;
+	struct cpuidle_device *dev;
 
 	switch (action & 0xf) {
 	case CPU_ONLINE:
-		smp_call_function_single(hotcpu, __setup_broadcast_timer,
-			(void *)true, 1);
+
+		if (lapic_timer_reliable_states != LAPIC_TIMER_ALWAYS_RELIABLE)
+			smp_call_function_single(hotcpu, __setup_broadcast_timer,
+						 (void *)true, 1);
+
+		/*
+		 * Some systems can hotplug a cpu at runtime after
+		 * the kernel has booted, we have to initialize the
+		 * driver in this case
+		 */
+		dev = per_cpu_ptr(intel_idle_cpuidle_devices, hotcpu);
+		if (!dev->registered)
+			intel_idle_cpu_init(hotcpu);
+
 		break;
 	}
 	return NOTIFY_OK;
 }
 
-static struct notifier_block setup_broadcast_notifier = {
-	.notifier_call = setup_broadcast_cpuhp_notify,
+static struct notifier_block cpu_hotplug_notifier = {
+	.notifier_call = cpu_hotplug_notify,
 };
 
 static void auto_demotion_disable(void *dummy)
@@ -405,10 +419,10 @@ static int intel_idle_probe(void)
 
 	if (boot_cpu_has(X86_FEATURE_ARAT))	/* Always Reliable APIC Timer */
 		lapic_timer_reliable_states = LAPIC_TIMER_ALWAYS_RELIABLE;
-	else {
+	else
 		on_each_cpu(__setup_broadcast_timer, (void *)true, 1);
-		register_cpu_notifier(&setup_broadcast_notifier);
-	}
+
+	register_cpu_notifier(&cpu_hotplug_notifier);
 
 	pr_debug(PREFIX "v" INTEL_IDLE_VERSION
 		" model 0x%X\n", boot_cpu_data.x86_model);
@@ -494,7 +508,7 @@ static int intel_idle_cpuidle_driver_init(void)
  * allocate, initialize, register cpuidle_devices
  * @cpu: cpu/core to initialize
  */
-int intel_idle_cpu_init(int cpu)
+static int intel_idle_cpu_init(int cpu)
 {
 	int cstate;
 	struct cpuidle_device *dev;
@@ -539,7 +553,6 @@ int intel_idle_cpu_init(int cpu)
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(intel_idle_cpu_init);
 
 static int __init intel_idle_init(void)
 {
@@ -581,10 +594,10 @@ static void __exit intel_idle_exit(void)
 	intel_idle_cpuidle_devices_uninit();
 	cpuidle_unregister_driver(&intel_idle_driver);
 
-	if (lapic_timer_reliable_states != LAPIC_TIMER_ALWAYS_RELIABLE) {
+
+	if (lapic_timer_reliable_states != LAPIC_TIMER_ALWAYS_RELIABLE)
 		on_each_cpu(__setup_broadcast_timer, (void *)false, 1);
-		unregister_cpu_notifier(&setup_broadcast_notifier);
-	}
+	unregister_cpu_notifier(&cpu_hotplug_notifier);
 
 	return;
 }

include/linux/cpuidle.h

@@ -206,14 +206,7 @@ struct cpuidle_governor {
 extern int cpuidle_register_governor(struct cpuidle_governor *gov);
 extern void cpuidle_unregister_governor(struct cpuidle_governor *gov);
 
-#ifdef CONFIG_INTEL_IDLE
-extern int intel_idle_cpu_init(int cpu);
 #else
-static inline int intel_idle_cpu_init(int cpu) { return -1; }
-#endif
-
-#else
-static inline int intel_idle_cpu_init(int cpu) { return -1; }
 
 static inline int cpuidle_register_governor(struct cpuidle_governor *gov)
 {return 0;}