drivers/cpuidle/cpuidle.c - arm/linux-arm-legacy - Git at Google

 /*
  * cpuidle.c - core cpuidle infrastructure
  *
  * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
  *               Shaohua Li <shaohua.li@intel.com>
  *               Adam Belay <abelay@novell.com>
  *
  * This code is licenced under the GPL.
  */

 #include <linux/clockchips.h>
 #include <linux/kernel.h>
 #include <linux/mutex.h>
 #include <linux/sched.h>
 #include <linux/notifier.h>
 #include <linux/pm_qos.h>
 #include <linux/cpu.h>
 #include <linux/cpuidle.h>
 #include <linux/ktime.h>
 #include <linux/hrtimer.h>
 #include <linux/module.h>
 #include <trace/events/power.h>

 #include "cpuidle.h"

 DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
 DEFINE_PER_CPU(struct cpuidle_device, cpuidle_dev);

 DEFINE_MUTEX(cpuidle_lock);
 LIST_HEAD(cpuidle_detected_devices);

 static int enabled_devices;
 static int off __read_mostly;
 static int initialized __read_mostly;

 int cpuidle_disabled(void)
 {
 	return off;
 }
 void disable_cpuidle(void)
 {
 	off = 1;
 }

 /**
  * cpuidle_play_dead - cpu off-lining
  *
  * Returns in case of an error or no driver
  */
 int cpuidle_play_dead(void)
 {
 	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
 	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
 	int i;

 	if (!drv)
 		return -ENODEV;

 	/* Find lowest-power state that supports long-term idle */
 	for (i = drv->state_count - 1; i >= CPUIDLE_DRIVER_STATE_START; i--)
 		if (drv->states[i].enter_dead)
 			return drv->states[i].enter_dead(dev, i);

 	return -ENODEV;
 }

 /**
  * cpuidle_enter_state - enter the state and update stats
  * @dev: cpuidle device for this cpu
  * @drv: cpuidle driver for this cpu
  * @next_state: index into drv->states of the state to enter
  */
 int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
 			int index)
 {
 	int entered_state;

 	struct cpuidle_state *target_state = &drv->states[index];
 	ktime_t time_start, time_end;
 	s64 diff;

 	time_start = ktime_get();

 	entered_state = target_state->enter(dev, drv, index);

 	time_end = ktime_get();

 	local_irq_enable();

 	diff = ktime_to_us(ktime_sub(time_end, time_start));
 	if (diff > INT_MAX)
 		diff = INT_MAX;

 	dev->last_residency = (int) diff;

 	if (entered_state >= 0) {
 		/* Update cpuidle counters */
 		/* This can be moved to within driver enter routine
 		 * but that results in multiple copies of same code.
 		 */
 		dev->states_usage[entered_state].time += dev->last_residency;
 		dev->states_usage[entered_state].usage++;
 	} else {
 		dev->last_residency = 0;
 	}

 	return entered_state;
 }

 /**
  * cpuidle_idle_call - the main idle loop
  *
  * NOTE: no locks or semaphores should be used here
  * return non-zero on failure
  */
 int cpuidle_idle_call(void)
 {
 	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
 	struct cpuidle_driver *drv;
 	int next_state, entered_state;
 	bool broadcast;

 	if (off || !initialized)
 		return -ENODEV;

 	/* check if the device is ready */
 	if (!dev || !dev->enabled)
 		return -EBUSY;

 	drv = cpuidle_get_cpu_driver(dev);

 	/* ask the governor for the next state */
 	next_state = cpuidle_curr_governor->select(drv, dev);
 	if (need_resched()) {
 		dev->last_residency = 0;
 		/* give the governor an opportunity to reflect on the outcome */
 		if (cpuidle_curr_governor->reflect)
 			cpuidle_curr_governor->reflect(dev, next_state);
 		local_irq_enable();
 		return 0;
 	}

 	trace_cpu_idle_rcuidle(next_state, dev->cpu);

 	broadcast = !!(drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP);

 	if (broadcast)
 		clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu);

 	if (cpuidle_state_is_coupled(dev, drv, next_state))
 		entered_state = cpuidle_enter_state_coupled(dev, drv,
 							    next_state);
 	else
 		entered_state = cpuidle_enter_state(dev, drv, next_state);

 	if (broadcast)
 		clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu);

 	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);

 	/* give the governor an opportunity to reflect on the outcome */
 	if (cpuidle_curr_governor->reflect)
 		cpuidle_curr_governor->reflect(dev, entered_state);

 	return 0;
 }

 /**
  * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
  */
 void cpuidle_install_idle_handler(void)
 {
 	if (enabled_devices) {
 		/* Make sure all changes finished before we switch to new idle */
 		smp_wmb();
 		initialized = 1;
 	}
 }

 /**
  * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
  */
 void cpuidle_uninstall_idle_handler(void)
 {
 	if (enabled_devices) {
 		initialized = 0;
 		kick_all_cpus_sync();
 	}
 }

 /**
  * cpuidle_pause_and_lock - temporarily disables CPUIDLE
  */
 void cpuidle_pause_and_lock(void)
 {
 	mutex_lock(&cpuidle_lock);
 	cpuidle_uninstall_idle_handler();
 }

 EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);

 /**
  * cpuidle_resume_and_unlock - resumes CPUIDLE operation
  */
 void cpuidle_resume_and_unlock(void)
 {
 	cpuidle_install_idle_handler();
 	mutex_unlock(&cpuidle_lock);
 }

 EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);

 /* Currently used in suspend/resume path to suspend cpuidle */
 void cpuidle_pause(void)
 {
 	mutex_lock(&cpuidle_lock);
 	cpuidle_uninstall_idle_handler();
 	mutex_unlock(&cpuidle_lock);
 }

 /* Currently used in suspend/resume path to resume cpuidle */
 void cpuidle_resume(void)
 {
 	mutex_lock(&cpuidle_lock);
 	cpuidle_install_idle_handler();
 	mutex_unlock(&cpuidle_lock);
 }

 /**
  * cpuidle_enable_device - enables idle PM for a CPU
  * @dev: the CPU
  *
  * This function must be called between cpuidle_pause_and_lock and
  * cpuidle_resume_and_unlock when used externally.
  */
 int cpuidle_enable_device(struct cpuidle_device *dev)
 {
 	int ret;
 	struct cpuidle_driver *drv;

 	if (!dev)
 		return -EINVAL;

 	if (dev->enabled)
 		return 0;

 	drv = cpuidle_get_cpu_driver(dev);

 	if (!drv || !cpuidle_curr_governor)
 		return -EIO;

 	if (!dev->registered)
 		return -EINVAL;

 	if (!dev->state_count)
 		dev->state_count = drv->state_count;

 	ret = cpuidle_add_device_sysfs(dev);
 	if (ret)
 		return ret;

 	if (cpuidle_curr_governor->enable &&
 	    (ret = cpuidle_curr_governor->enable(drv, dev)))
 		goto fail_sysfs;

 	smp_wmb();

 	dev->enabled = 1;

 	enabled_devices++;
 	return 0;

 fail_sysfs:
 	cpuidle_remove_device_sysfs(dev);

 	return ret;
 }

 EXPORT_SYMBOL_GPL(cpuidle_enable_device);

 /**
  * cpuidle_disable_device - disables idle PM for a CPU
  * @dev: the CPU
  *
  * This function must be called between cpuidle_pause_and_lock and
  * cpuidle_resume_and_unlock when used externally.
  */
 void cpuidle_disable_device(struct cpuidle_device *dev)
 {
 	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);

 	if (!dev || !dev->enabled)
 		return;

 	if (!drv || !cpuidle_curr_governor)
 		return;

 	dev->enabled = 0;

 	if (cpuidle_curr_governor->disable)
 		cpuidle_curr_governor->disable(drv, dev);

 	cpuidle_remove_device_sysfs(dev);
 	enabled_devices--;
 }

 EXPORT_SYMBOL_GPL(cpuidle_disable_device);

 static void __cpuidle_unregister_device(struct cpuidle_device *dev)
 {
 	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);

 	list_del(&dev->device_list);
 	per_cpu(cpuidle_devices, dev->cpu) = NULL;
 	module_put(drv->owner);
 }

 static void __cpuidle_device_init(struct cpuidle_device *dev)
 {
 	memset(dev->states_usage, 0, sizeof(dev->states_usage));
 	dev->last_residency = 0;
 }

 /**
  * __cpuidle_register_device - internal register function called before register
  * and enable routines
  * @dev: the cpu
  *
  * cpuidle_lock mutex must be held before this is called
  */
 static int __cpuidle_register_device(struct cpuidle_device *dev)
 {
 	int ret;
 	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);

 	if (!try_module_get(drv->owner))
 		return -EINVAL;

 	per_cpu(cpuidle_devices, dev->cpu) = dev;
 	list_add(&dev->device_list, &cpuidle_detected_devices);

 	ret = cpuidle_coupled_register_device(dev);
 	if (ret)
 		__cpuidle_unregister_device(dev);
 	else
 		dev->registered = 1;

 	return ret;
 }

 /**
  * cpuidle_register_device - registers a CPU's idle PM feature
  * @dev: the cpu
  */
 int cpuidle_register_device(struct cpuidle_device *dev)
 {
 	int ret = -EBUSY;

 	if (!dev)
 		return -EINVAL;

 	mutex_lock(&cpuidle_lock);

 	if (dev->registered)
 		goto out_unlock;

 	__cpuidle_device_init(dev);

 	ret = __cpuidle_register_device(dev);
 	if (ret)
 		goto out_unlock;

 	ret = cpuidle_add_sysfs(dev);
 	if (ret)
 		goto out_unregister;

 	ret = cpuidle_enable_device(dev);
 	if (ret)
 		goto out_sysfs;

 	cpuidle_install_idle_handler();

 out_unlock:
 	mutex_unlock(&cpuidle_lock);

 	return ret;

 out_sysfs:
 	cpuidle_remove_sysfs(dev);
 out_unregister:
 	__cpuidle_unregister_device(dev);
 	goto out_unlock;
 }

 EXPORT_SYMBOL_GPL(cpuidle_register_device);

 /**
  * cpuidle_unregister_device - unregisters a CPU's idle PM feature
  * @dev: the cpu
  */
 void cpuidle_unregister_device(struct cpuidle_device *dev)
 {
 	if (!dev || dev->registered == 0)
 		return;

 	cpuidle_pause_and_lock();

 	cpuidle_disable_device(dev);

 	cpuidle_remove_sysfs(dev);

 	__cpuidle_unregister_device(dev);

 	cpuidle_coupled_unregister_device(dev);

 	cpuidle_resume_and_unlock();
 }

 EXPORT_SYMBOL_GPL(cpuidle_unregister_device);

 /**
  * cpuidle_unregister: unregister a driver and the devices. This function
  * can be used only if the driver has been previously registered through
  * the cpuidle_register function.
  *
  * @drv: a valid pointer to a struct cpuidle_driver
  */
 void cpuidle_unregister(struct cpuidle_driver *drv)
 {
 	int cpu;
 	struct cpuidle_device *device;

 	for_each_cpu(cpu, drv->cpumask) {
 		device = &per_cpu(cpuidle_dev, cpu);
 		cpuidle_unregister_device(device);
 	}

 	cpuidle_unregister_driver(drv);
 }
 EXPORT_SYMBOL_GPL(cpuidle_unregister);

 /**
  * cpuidle_register: registers the driver and the cpu devices with the
  * coupled_cpus passed as parameter. This function is used for all common
  * initialization pattern there are in the arch specific drivers. The
  * devices is globally defined in this file.
  *
  * @drv         : a valid pointer to a struct cpuidle_driver
  * @coupled_cpus: a cpumask for the coupled states
  *
  * Returns 0 on success, < 0 otherwise
  */
 int cpuidle_register(struct cpuidle_driver *drv,
 		     const struct cpumask *const coupled_cpus)
 {
 	int ret, cpu;
 	struct cpuidle_device *device;

 	ret = cpuidle_register_driver(drv);
 	if (ret) {
 		pr_err("failed to register cpuidle driver\n");
 		return ret;
 	}

 	for_each_cpu(cpu, drv->cpumask) {
 		device = &per_cpu(cpuidle_dev, cpu);
 		device->cpu = cpu;

 #ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
 		/*
 		 * On multiplatform for ARM, the coupled idle states could be
 		 * enabled in the kernel even if the cpuidle driver does not
 		 * use it. Note, coupled_cpus is a struct copy.
 		 */
 		if (coupled_cpus)
 			device->coupled_cpus = *coupled_cpus;
 #endif
 		ret = cpuidle_register_device(device);
 		if (!ret)
 			continue;

 		pr_err("Failed to register cpuidle device for cpu%d\n", cpu);

 		cpuidle_unregister(drv);
 		break;
 	}

 	return ret;
 }
 EXPORT_SYMBOL_GPL(cpuidle_register);

 #ifdef CONFIG_SMP

 static void smp_callback(void *v)
 {
 	/* we already woke the CPU up, nothing more to do */
 }

 /*
  * This function gets called when a part of the kernel has a new latency
  * requirement.  This means we need to get all processors out of their C-state,
  * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
  * wakes them all right up.
  */
 static int cpuidle_latency_notify(struct notifier_block *b,
 		unsigned long l, void *v)
 {
 	smp_call_function(smp_callback, NULL, 1);
 	return NOTIFY_OK;
 }

 static struct notifier_block cpuidle_latency_notifier = {
 	.notifier_call = cpuidle_latency_notify,
 };

 static inline void latency_notifier_init(struct notifier_block *n)
 {
 	pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
 }

 #else /* CONFIG_SMP */

 #define latency_notifier_init(x) do { } while (0)

 #endif /* CONFIG_SMP */

 /**
  * cpuidle_init - core initializer
  */
 static int __init cpuidle_init(void)
 {
 	int ret;

 	if (cpuidle_disabled())
 		return -ENODEV;

 	ret = cpuidle_add_interface(cpu_subsys.dev_root);
 	if (ret)
 		return ret;

 	latency_notifier_init(&cpuidle_latency_notifier);

 	return 0;
 }

 module_param(off, int, 0444);
 core_initcall(cpuidle_init);
	/*
	* cpuidle.c - core cpuidle infrastructure
	*
	* (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
	* Shaohua Li <shaohua.li@intel.com>
	* Adam Belay <abelay@novell.com>
	*
	* This code is licenced under the GPL.
	*/

	#include <linux/clockchips.h>
	#include <linux/kernel.h>
	#include <linux/mutex.h>
	#include <linux/sched.h>
	#include <linux/notifier.h>
	#include <linux/pm_qos.h>
	#include <linux/cpu.h>
	#include <linux/cpuidle.h>
	#include <linux/ktime.h>
	#include <linux/hrtimer.h>
	#include <linux/module.h>
	#include <trace/events/power.h>

	#include "cpuidle.h"

	DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
	DEFINE_PER_CPU(struct cpuidle_device, cpuidle_dev);

	DEFINE_MUTEX(cpuidle_lock);
	LIST_HEAD(cpuidle_detected_devices);

	static int enabled_devices;
	static int off __read_mostly;
	static int initialized __read_mostly;

	int cpuidle_disabled(void)
	{
	return off;
	}
	void disable_cpuidle(void)
	{
	off = 1;
	}

	/**
	* cpuidle_play_dead - cpu off-lining
	*
	* Returns in case of an error or no driver
	*/
	int cpuidle_play_dead(void)
	{
	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
	int i;

	if (!drv)
	return -ENODEV;

	/* Find lowest-power state that supports long-term idle */
	for (i = drv->state_count - 1; i >= CPUIDLE_DRIVER_STATE_START; i--)
	if (drv->states[i].enter_dead)
	return drv->states[i].enter_dead(dev, i);

	return -ENODEV;
	}

	/**
	* cpuidle_enter_state - enter the state and update stats
	* @dev: cpuidle device for this cpu
	* @drv: cpuidle driver for this cpu
	* @next_state: index into drv->states of the state to enter
	*/
	int cpuidle_enter_state(struct cpuidle_device dev, struct cpuidle_driver drv,
	int index)
	{
	int entered_state;

	struct cpuidle_state *target_state = &drv->states[index];
	ktime_t time_start, time_end;
	s64 diff;

	time_start = ktime_get();

	entered_state = target_state->enter(dev, drv, index);

	time_end = ktime_get();

	local_irq_enable();

	diff = ktime_to_us(ktime_sub(time_end, time_start));
	if (diff > INT_MAX)
	diff = INT_MAX;

	dev->last_residency = (int) diff;

	if (entered_state >= 0) {
	/* Update cpuidle counters */
	/* This can be moved to within driver enter routine
	* but that results in multiple copies of same code.
	*/
	dev->states_usage[entered_state].time += dev->last_residency;
	dev->states_usage[entered_state].usage++;
	} else {
	dev->last_residency = 0;
	}

	return entered_state;
	}

	/**
	* cpuidle_idle_call - the main idle loop
	*
	* NOTE: no locks or semaphores should be used here
	* return non-zero on failure
	*/
	int cpuidle_idle_call(void)
	{
	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
	struct cpuidle_driver *drv;
	int next_state, entered_state;
	bool broadcast;

	if (off \|\| !initialized)
	return -ENODEV;

	/* check if the device is ready */
	if (!dev \|\| !dev->enabled)
	return -EBUSY;

	drv = cpuidle_get_cpu_driver(dev);

	/* ask the governor for the next state */
	next_state = cpuidle_curr_governor->select(drv, dev);
	if (need_resched()) {
	dev->last_residency = 0;
	/* give the governor an opportunity to reflect on the outcome */
	if (cpuidle_curr_governor->reflect)
	cpuidle_curr_governor->reflect(dev, next_state);
	local_irq_enable();
	return 0;
	}

	trace_cpu_idle_rcuidle(next_state, dev->cpu);

	broadcast = !!(drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP);

	if (broadcast)
	clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu);

	if (cpuidle_state_is_coupled(dev, drv, next_state))
	entered_state = cpuidle_enter_state_coupled(dev, drv,
	next_state);
	else
	entered_state = cpuidle_enter_state(dev, drv, next_state);

	if (broadcast)
	clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu);

	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);

	/* give the governor an opportunity to reflect on the outcome */
	if (cpuidle_curr_governor->reflect)
	cpuidle_curr_governor->reflect(dev, entered_state);

	return 0;
	}

	/**
	* cpuidle_install_idle_handler - installs the cpuidle idle loop handler
	*/
	void cpuidle_install_idle_handler(void)
	{
	if (enabled_devices) {
	/* Make sure all changes finished before we switch to new idle */
	smp_wmb();
	initialized = 1;
	}
	}

	/**
	* cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
	*/
	void cpuidle_uninstall_idle_handler(void)
	{
	if (enabled_devices) {
	initialized = 0;
	kick_all_cpus_sync();
	}
	}

	/**
	* cpuidle_pause_and_lock - temporarily disables CPUIDLE
	*/
	void cpuidle_pause_and_lock(void)
	{
	mutex_lock(&cpuidle_lock);
	cpuidle_uninstall_idle_handler();
	}

	EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);

	/**
	* cpuidle_resume_and_unlock - resumes CPUIDLE operation
	*/
	void cpuidle_resume_and_unlock(void)
	{
	cpuidle_install_idle_handler();
	mutex_unlock(&cpuidle_lock);
	}

	EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);

	/* Currently used in suspend/resume path to suspend cpuidle */
	void cpuidle_pause(void)
	{
	mutex_lock(&cpuidle_lock);
	cpuidle_uninstall_idle_handler();
	mutex_unlock(&cpuidle_lock);
	}

	/* Currently used in suspend/resume path to resume cpuidle */
	void cpuidle_resume(void)
	{
	mutex_lock(&cpuidle_lock);
	cpuidle_install_idle_handler();
	mutex_unlock(&cpuidle_lock);
	}

	/**
	* cpuidle_enable_device - enables idle PM for a CPU
	* @dev: the CPU
	*
	* This function must be called between cpuidle_pause_and_lock and
	* cpuidle_resume_and_unlock when used externally.
	*/
	int cpuidle_enable_device(struct cpuidle_device *dev)
	{
	int ret;
	struct cpuidle_driver *drv;

	if (!dev)
	return -EINVAL;

	if (dev->enabled)
	return 0;

	drv = cpuidle_get_cpu_driver(dev);

	if (!drv \|\| !cpuidle_curr_governor)
	return -EIO;

	if (!dev->registered)
	return -EINVAL;

	if (!dev->state_count)
	dev->state_count = drv->state_count;

	ret = cpuidle_add_device_sysfs(dev);
	if (ret)
	return ret;

	if (cpuidle_curr_governor->enable &&
	(ret = cpuidle_curr_governor->enable(drv, dev)))
	goto fail_sysfs;

	smp_wmb();

	dev->enabled = 1;

	enabled_devices++;
	return 0;

	fail_sysfs:
	cpuidle_remove_device_sysfs(dev);

	return ret;
	}

	EXPORT_SYMBOL_GPL(cpuidle_enable_device);

	/**
	* cpuidle_disable_device - disables idle PM for a CPU
	* @dev: the CPU
	*
	* This function must be called between cpuidle_pause_and_lock and
	* cpuidle_resume_and_unlock when used externally.
	*/
	void cpuidle_disable_device(struct cpuidle_device *dev)
	{
	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);

	if (!dev \|\| !dev->enabled)
	return;

	if (!drv \|\| !cpuidle_curr_governor)
	return;

	dev->enabled = 0;

	if (cpuidle_curr_governor->disable)
	cpuidle_curr_governor->disable(drv, dev);

	cpuidle_remove_device_sysfs(dev);
	enabled_devices--;
	}

	EXPORT_SYMBOL_GPL(cpuidle_disable_device);

	static void __cpuidle_unregister_device(struct cpuidle_device *dev)
	{
	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);

	list_del(&dev->device_list);
	per_cpu(cpuidle_devices, dev->cpu) = NULL;
	module_put(drv->owner);
	}

	static void __cpuidle_device_init(struct cpuidle_device *dev)
	{
	memset(dev->states_usage, 0, sizeof(dev->states_usage));
	dev->last_residency = 0;
	}

	/**
	* __cpuidle_register_device - internal register function called before register
	* and enable routines
	* @dev: the cpu
	*
	* cpuidle_lock mutex must be held before this is called
	*/
	static int __cpuidle_register_device(struct cpuidle_device *dev)
	{
	int ret;
	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);

	if (!try_module_get(drv->owner))
	return -EINVAL;

	per_cpu(cpuidle_devices, dev->cpu) = dev;
	list_add(&dev->device_list, &cpuidle_detected_devices);

	ret = cpuidle_coupled_register_device(dev);
	if (ret)
	__cpuidle_unregister_device(dev);
	else
	dev->registered = 1;

	return ret;
	}

	/**
	* cpuidle_register_device - registers a CPU's idle PM feature
	* @dev: the cpu
	*/
	int cpuidle_register_device(struct cpuidle_device *dev)
	{
	int ret = -EBUSY;

	if (!dev)
	return -EINVAL;

	mutex_lock(&cpuidle_lock);

	if (dev->registered)
	goto out_unlock;

	__cpuidle_device_init(dev);

	ret = __cpuidle_register_device(dev);
	if (ret)
	goto out_unlock;

	ret = cpuidle_add_sysfs(dev);
	if (ret)
	goto out_unregister;

	ret = cpuidle_enable_device(dev);
	if (ret)
	goto out_sysfs;

	cpuidle_install_idle_handler();

	out_unlock:
	mutex_unlock(&cpuidle_lock);

	return ret;

	out_sysfs:
	cpuidle_remove_sysfs(dev);
	out_unregister:
	__cpuidle_unregister_device(dev);
	goto out_unlock;
	}

	EXPORT_SYMBOL_GPL(cpuidle_register_device);

	/**
	* cpuidle_unregister_device - unregisters a CPU's idle PM feature
	* @dev: the cpu
	*/
	void cpuidle_unregister_device(struct cpuidle_device *dev)
	{
	if (!dev \|\| dev->registered == 0)
	return;

	cpuidle_pause_and_lock();

	cpuidle_disable_device(dev);

	cpuidle_remove_sysfs(dev);

	__cpuidle_unregister_device(dev);

	cpuidle_coupled_unregister_device(dev);

	cpuidle_resume_and_unlock();
	}

	EXPORT_SYMBOL_GPL(cpuidle_unregister_device);

	/**
	* cpuidle_unregister: unregister a driver and the devices. This function
	* can be used only if the driver has been previously registered through
	* the cpuidle_register function.
	*
	* @drv: a valid pointer to a struct cpuidle_driver
	*/
	void cpuidle_unregister(struct cpuidle_driver *drv)
	{
	int cpu;
	struct cpuidle_device *device;

	for_each_cpu(cpu, drv->cpumask) {
	device = &per_cpu(cpuidle_dev, cpu);
	cpuidle_unregister_device(device);
	}

	cpuidle_unregister_driver(drv);
	}
	EXPORT_SYMBOL_GPL(cpuidle_unregister);

	/**
	* cpuidle_register: registers the driver and the cpu devices with the
	* coupled_cpus passed as parameter. This function is used for all common
	* initialization pattern there are in the arch specific drivers. The
	* devices is globally defined in this file.
	*
	* @drv : a valid pointer to a struct cpuidle_driver
	* @coupled_cpus: a cpumask for the coupled states
	*
	* Returns 0 on success, < 0 otherwise
	*/
	int cpuidle_register(struct cpuidle_driver *drv,
	const struct cpumask *const coupled_cpus)
	{
	int ret, cpu;
	struct cpuidle_device *device;

	ret = cpuidle_register_driver(drv);
	if (ret) {
	pr_err("failed to register cpuidle driver\n");
	return ret;
	}

	for_each_cpu(cpu, drv->cpumask) {
	device = &per_cpu(cpuidle_dev, cpu);
	device->cpu = cpu;

	#ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
	/*
	* On multiplatform for ARM, the coupled idle states could be
	* enabled in the kernel even if the cpuidle driver does not
	* use it. Note, coupled_cpus is a struct copy.
	*/
	if (coupled_cpus)
	device->coupled_cpus = *coupled_cpus;
	#endif
	ret = cpuidle_register_device(device);
	if (!ret)
	continue;

	pr_err("Failed to register cpuidle device for cpu%d\n", cpu);

	cpuidle_unregister(drv);
	break;
	}

	return ret;
	}
	EXPORT_SYMBOL_GPL(cpuidle_register);

	#ifdef CONFIG_SMP

	static void smp_callback(void *v)
	{
	/* we already woke the CPU up, nothing more to do */
	}

	/*
	* This function gets called when a part of the kernel has a new latency
	* requirement. This means we need to get all processors out of their C-state,
	* and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
	* wakes them all right up.
	*/
	static int cpuidle_latency_notify(struct notifier_block *b,
	unsigned long l, void *v)
	{
	smp_call_function(smp_callback, NULL, 1);
	return NOTIFY_OK;
	}

	static struct notifier_block cpuidle_latency_notifier = {
	.notifier_call = cpuidle_latency_notify,
	};

	static inline void latency_notifier_init(struct notifier_block *n)
	{
	pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
	}

	#else /* CONFIG_SMP */

	#define latency_notifier_init(x) do { } while (0)

	#endif /* CONFIG_SMP */

	/**
	* cpuidle_init - core initializer
	*/
	static int __init cpuidle_init(void)
	{
	int ret;

	if (cpuidle_disabled())
	return -ENODEV;

	ret = cpuidle_add_interface(cpu_subsys.dev_root);
	if (ret)
	return ret;

	latency_notifier_init(&cpuidle_latency_notifier);

	return 0;
	}

	module_param(off, int, 0444);
	core_initcall(cpuidle_init);