drivers/cpuidle/cpuidle.c - kernel/msm-4.19 - Gitiles

 /*
  * 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/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_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;
 }

 #if defined(CONFIG_ARCH_HAS_CPU_IDLE_WAIT)
 static void cpuidle_kick_cpus(void)
 {
 	cpu_idle_wait();
 }
 #elif defined(CONFIG_SMP)
 # error "Arch needs cpu_idle_wait() equivalent here"
 #else /* !CONFIG_ARCH_HAS_CPU_IDLE_WAIT && !CONFIG_SMP */
 static void cpuidle_kick_cpus(void) {}
 #endif

 static int __cpuidle_register_device(struct cpuidle_device *dev);

 static inline int cpuidle_enter(struct cpuidle_device *dev,
 				struct cpuidle_driver *drv, int index)
 {
 	struct cpuidle_state *target_state = &drv->states[index];
 	return target_state->enter(dev, drv, index);
 }

 static inline int cpuidle_enter_tk(struct cpuidle_device *dev,
 			       struct cpuidle_driver *drv, int index)
 {
 	return cpuidle_wrap_enter(dev, drv, index, cpuidle_enter);
 }

 typedef int (*cpuidle_enter_t)(struct cpuidle_device *dev,
 			       struct cpuidle_driver *drv, int index);

 static cpuidle_enter_t cpuidle_enter_ops;

 /**
  * 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 = cpuidle_get_driver();
 	int next_state, entered_state;

 	if (off)
 		return -ENODEV;

 	if (!initialized)
 		return -ENODEV;

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

 #if 0
 	/* shows regressions, re-enable for 2.6.29 */
 	/*
 	 * run any timers that can be run now, at this point
 	 * before calculating the idle duration etc.
 	 */
 	hrtimer_peek_ahead_timers();
 #endif

 	/* ask the governor for the next state */
 	next_state = cpuidle_curr_governor->select(drv, dev);
 	if (need_resched()) {
 		local_irq_enable();
 		return 0;
 	}

 	trace_power_start(POWER_CSTATE, next_state, dev->cpu);
 	trace_cpu_idle(next_state, dev->cpu);

 	entered_state = cpuidle_enter_ops(dev, drv, next_state);

 	trace_power_end(dev->cpu);
 	trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu);

 	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 +=
 				(unsigned long long)dev->last_residency;
 		dev->states_usage[entered_state].usage++;
 	} else {
 		dev->last_residency = 0;
 	}

 	/* 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;
 		cpuidle_kick_cpus();
 	}
 }

 /**
  * 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);

 /**
  * cpuidle_wrap_enter - performs timekeeping and irqen around enter function
  * @dev: pointer to a valid cpuidle_device object
  * @drv: pointer to a valid cpuidle_driver object
  * @index: index of the target cpuidle state.
  */
 int cpuidle_wrap_enter(struct cpuidle_device *dev,
 				struct cpuidle_driver *drv, int index,
 				int (*enter)(struct cpuidle_device *dev,
 					struct cpuidle_driver *drv, int index))
 {
 	ktime_t time_start, time_end;
 	s64 diff;

 	time_start = ktime_get();

 	index = 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;

 	return index;
 }

 #ifdef CONFIG_ARCH_HAS_CPU_RELAX
 static int poll_idle(struct cpuidle_device *dev,
 		struct cpuidle_driver *drv, int index)
 {
 	ktime_t	t1, t2;
 	s64 diff;

 	t1 = ktime_get();
 	local_irq_enable();
 	while (!need_resched())
 		cpu_relax();

 	t2 = ktime_get();
 	diff = ktime_to_us(ktime_sub(t2, t1));
 	if (diff > INT_MAX)
 		diff = INT_MAX;

 	dev->last_residency = (int) diff;

 	return index;
 }

 static void poll_idle_init(struct cpuidle_driver *drv)
 {
 	struct cpuidle_state *state = &drv->states[0];

 	snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
 	snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
 	state->exit_latency = 0;
 	state->target_residency = 0;
 	state->power_usage = -1;
 	state->flags = 0;
 	state->enter = poll_idle;
 	state->disable = 0;
 }
 #else
 static void poll_idle_init(struct cpuidle_driver *drv) {}
 #endif /* CONFIG_ARCH_HAS_CPU_RELAX */

 /**
  * 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, i;
 	struct cpuidle_driver *drv = cpuidle_get_driver();

 	if (dev->enabled)
 		return 0;
 	if (!drv || !cpuidle_curr_governor)
 		return -EIO;
 	if (!dev->state_count)
 		return -EINVAL;

 	if (dev->registered == 0) {
 		ret = __cpuidle_register_device(dev);
 		if (ret)
 			return ret;
 	}

 	cpuidle_enter_ops = drv->en_core_tk_irqen ?
 		cpuidle_enter_tk : cpuidle_enter;

 	poll_idle_init(drv);

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

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

 	for (i = 0; i < dev->state_count; i++) {
 		dev->states_usage[i].usage = 0;
 		dev->states_usage[i].time = 0;
 	}
 	dev->last_residency = 0;

 	smp_wmb();

 	dev->enabled = 1;

 	enabled_devices++;
 	return 0;

 fail_sysfs:
 	cpuidle_remove_state_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)
 {
 	if (!dev->enabled)
 		return;
 	if (!cpuidle_get_driver() || !cpuidle_curr_governor)
 		return;

 	dev->enabled = 0;

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

 	cpuidle_remove_state_sysfs(dev);
 	enabled_devices--;
 }

 EXPORT_SYMBOL_GPL(cpuidle_disable_device);

 /**
  * __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 device *cpu_dev = get_cpu_device((unsigned long)dev->cpu);
 	struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();

 	if (!dev)
 		return -EINVAL;
 	if (!try_module_get(cpuidle_driver->owner))
 		return -EINVAL;

 	init_completion(&dev->kobj_unregister);

 	per_cpu(cpuidle_devices, dev->cpu) = dev;
 	list_add(&dev->device_list, &cpuidle_detected_devices);
 	if ((ret = cpuidle_add_sysfs(cpu_dev))) {
 		module_put(cpuidle_driver->owner);
 		return ret;
 	}

 	dev->registered = 1;
 	return 0;
 }

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

 	mutex_lock(&cpuidle_lock);

 	if ((ret = __cpuidle_register_device(dev))) {
 		mutex_unlock(&cpuidle_lock);
 		return ret;
 	}

 	cpuidle_enable_device(dev);
 	cpuidle_install_idle_handler();

 	mutex_unlock(&cpuidle_lock);

 	return 0;

 }

 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)
 {
 	struct device *cpu_dev = get_cpu_device((unsigned long)dev->cpu);
 	struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();

 	if (dev->registered == 0)
 		return;

 	cpuidle_pause_and_lock();

 	cpuidle_disable_device(dev);

 	cpuidle_remove_sysfs(cpu_dev);
 	list_del(&dev->device_list);
 	wait_for_completion(&dev->kobj_unregister);
 	per_cpu(cpuidle_devices, dev->cpu) = NULL;

 	cpuidle_resume_and_unlock();

 	module_put(cpuidle_driver->owner);
 }

 EXPORT_SYMBOL_GPL(cpuidle_unregister_device);

 #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/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_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;
	}

	#if defined(CONFIG_ARCH_HAS_CPU_IDLE_WAIT)
	static void cpuidle_kick_cpus(void)
	{
	cpu_idle_wait();
	}
	#elif defined(CONFIG_SMP)
	# error "Arch needs cpu_idle_wait() equivalent here"
	#else /* !CONFIG_ARCH_HAS_CPU_IDLE_WAIT && !CONFIG_SMP */
	static void cpuidle_kick_cpus(void) {}
	#endif

	static int __cpuidle_register_device(struct cpuidle_device *dev);

	static inline int cpuidle_enter(struct cpuidle_device *dev,
	struct cpuidle_driver *drv, int index)
	{
	struct cpuidle_state *target_state = &drv->states[index];
	return target_state->enter(dev, drv, index);
	}

	static inline int cpuidle_enter_tk(struct cpuidle_device *dev,
	struct cpuidle_driver *drv, int index)
	{
	return cpuidle_wrap_enter(dev, drv, index, cpuidle_enter);
	}

	typedef int (cpuidle_enter_t)(struct cpuidle_device dev,
	struct cpuidle_driver *drv, int index);

	static cpuidle_enter_t cpuidle_enter_ops;

	/**
	* 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 = cpuidle_get_driver();
	int next_state, entered_state;

	if (off)
	return -ENODEV;

	if (!initialized)
	return -ENODEV;

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

	#if 0
	/* shows regressions, re-enable for 2.6.29 */
	/*
	* run any timers that can be run now, at this point
	* before calculating the idle duration etc.
	*/
	hrtimer_peek_ahead_timers();
	#endif

	/* ask the governor for the next state */
	next_state = cpuidle_curr_governor->select(drv, dev);
	if (need_resched()) {
	local_irq_enable();
	return 0;
	}

	trace_power_start(POWER_CSTATE, next_state, dev->cpu);
	trace_cpu_idle(next_state, dev->cpu);

	entered_state = cpuidle_enter_ops(dev, drv, next_state);

	trace_power_end(dev->cpu);
	trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu);

	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 +=
	(unsigned long long)dev->last_residency;
	dev->states_usage[entered_state].usage++;
	} else {
	dev->last_residency = 0;
	}

	/* 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;
	cpuidle_kick_cpus();
	}
	}

	/**
	* 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);

	/**
	* cpuidle_wrap_enter - performs timekeeping and irqen around enter function
	* @dev: pointer to a valid cpuidle_device object
	* @drv: pointer to a valid cpuidle_driver object
	* @index: index of the target cpuidle state.
	*/
	int cpuidle_wrap_enter(struct cpuidle_device *dev,
	struct cpuidle_driver *drv, int index,
	int (enter)(struct cpuidle_device dev,
	struct cpuidle_driver *drv, int index))
	{
	ktime_t time_start, time_end;
	s64 diff;

	time_start = ktime_get();

	index = 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;

	return index;
	}

	#ifdef CONFIG_ARCH_HAS_CPU_RELAX
	static int poll_idle(struct cpuidle_device *dev,
	struct cpuidle_driver *drv, int index)
	{
	ktime_t t1, t2;
	s64 diff;

	t1 = ktime_get();
	local_irq_enable();
	while (!need_resched())
	cpu_relax();

	t2 = ktime_get();
	diff = ktime_to_us(ktime_sub(t2, t1));
	if (diff > INT_MAX)
	diff = INT_MAX;

	dev->last_residency = (int) diff;

	return index;
	}

	static void poll_idle_init(struct cpuidle_driver *drv)
	{
	struct cpuidle_state *state = &drv->states[0];

	snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
	snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
	state->exit_latency = 0;
	state->target_residency = 0;
	state->power_usage = -1;
	state->flags = 0;
	state->enter = poll_idle;
	state->disable = 0;
	}
	#else
	static void poll_idle_init(struct cpuidle_driver *drv) {}
	#endif /* CONFIG_ARCH_HAS_CPU_RELAX */

	/**
	* 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, i;
	struct cpuidle_driver *drv = cpuidle_get_driver();

	if (dev->enabled)
	return 0;
	if (!drv \|\| !cpuidle_curr_governor)
	return -EIO;
	if (!dev->state_count)
	return -EINVAL;

	if (dev->registered == 0) {
	ret = __cpuidle_register_device(dev);
	if (ret)
	return ret;
	}

	cpuidle_enter_ops = drv->en_core_tk_irqen ?
	cpuidle_enter_tk : cpuidle_enter;

	poll_idle_init(drv);

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

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

	for (i = 0; i < dev->state_count; i++) {
	dev->states_usage[i].usage = 0;
	dev->states_usage[i].time = 0;
	}
	dev->last_residency = 0;

	smp_wmb();

	dev->enabled = 1;

	enabled_devices++;
	return 0;

	fail_sysfs:
	cpuidle_remove_state_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)
	{
	if (!dev->enabled)
	return;
	if (!cpuidle_get_driver() \|\| !cpuidle_curr_governor)
	return;

	dev->enabled = 0;

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

	cpuidle_remove_state_sysfs(dev);
	enabled_devices--;
	}

	EXPORT_SYMBOL_GPL(cpuidle_disable_device);

	/**
	* __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 device *cpu_dev = get_cpu_device((unsigned long)dev->cpu);
	struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();

	if (!dev)
	return -EINVAL;
	if (!try_module_get(cpuidle_driver->owner))
	return -EINVAL;

	init_completion(&dev->kobj_unregister);

	per_cpu(cpuidle_devices, dev->cpu) = dev;
	list_add(&dev->device_list, &cpuidle_detected_devices);
	if ((ret = cpuidle_add_sysfs(cpu_dev))) {
	module_put(cpuidle_driver->owner);
	return ret;
	}

	dev->registered = 1;
	return 0;
	}

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

	mutex_lock(&cpuidle_lock);

	if ((ret = __cpuidle_register_device(dev))) {
	mutex_unlock(&cpuidle_lock);
	return ret;
	}

	cpuidle_enable_device(dev);
	cpuidle_install_idle_handler();

	mutex_unlock(&cpuidle_lock);

	return 0;

	}

	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)
	{
	struct device *cpu_dev = get_cpu_device((unsigned long)dev->cpu);
	struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();

	if (dev->registered == 0)
	return;

	cpuidle_pause_and_lock();

	cpuidle_disable_device(dev);

	cpuidle_remove_sysfs(cpu_dev);
	list_del(&dev->device_list);
	wait_for_completion(&dev->kobj_unregister);
	per_cpu(cpuidle_devices, dev->cpu) = NULL;

	cpuidle_resume_and_unlock();

	module_put(cpuidle_driver->owner);
	}

	EXPORT_SYMBOL_GPL(cpuidle_unregister_device);

	#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);