drivers/devfreq/devfreq.c - kernel/msm-4.9 - Gitiles

 /*
  * devfreq: Generic Dynamic Voltage and Frequency Scaling (DVFS) Framework
  *	    for Non-CPU Devices.
  *
  * Copyright (C) 2011 Samsung Electronics
  *	MyungJoo Ham <myungjoo.ham@samsung.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */

 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/errno.h>
 #include <linux/err.h>
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/opp.h>
 #include <linux/devfreq.h>
 #include <linux/workqueue.h>
 #include <linux/platform_device.h>
 #include <linux/list.h>
 #include <linux/printk.h>
 #include <linux/hrtimer.h>
 #include "governor.h"

 struct class *devfreq_class;

 /*
  * devfreq_work periodically monitors every registered device.
  * The minimum polling interval is one jiffy. The polling interval is
  * determined by the minimum polling period among all polling devfreq
  * devices. The resolution of polling interval is one jiffy.
  */
 static bool polling;
 static struct workqueue_struct *devfreq_wq;
 static struct delayed_work devfreq_work;

 /* wait removing if this is to be removed */
 static struct devfreq *wait_remove_device;

 /* The list of all device-devfreq */
 static LIST_HEAD(devfreq_list);
 static DEFINE_MUTEX(devfreq_list_lock);

 /**
  * find_device_devfreq() - find devfreq struct using device pointer
  * @dev:	device pointer used to lookup device devfreq.
  *
  * Search the list of device devfreqs and return the matched device's
  * devfreq info. devfreq_list_lock should be held by the caller.
  */
 static struct devfreq *find_device_devfreq(struct device *dev)
 {
 	struct devfreq *tmp_devfreq;

 	if (unlikely(IS_ERR_OR_NULL(dev))) {
 		pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
 		return ERR_PTR(-EINVAL);
 	}
 	WARN(!mutex_is_locked(&devfreq_list_lock),
 	     "devfreq_list_lock must be locked.");

 	list_for_each_entry(tmp_devfreq, &devfreq_list, node) {
 		if (tmp_devfreq->dev.parent == dev)
 			return tmp_devfreq;
 	}

 	return ERR_PTR(-ENODEV);
 }

 /**
  * update_devfreq() - Reevaluate the device and configure frequency.
  * @devfreq:	the devfreq instance.
  *
  * Note: Lock devfreq->lock before calling update_devfreq
  *	 This function is exported for governors.
  */
 int update_devfreq(struct devfreq *devfreq)
 {
 	unsigned long freq;
 	int err = 0;

 	if (!mutex_is_locked(&devfreq->lock)) {
 		WARN(true, "devfreq->lock must be locked by the caller.\n");
 		return -EINVAL;
 	}

 	/* Reevaluate the proper frequency */
 	err = devfreq->governor->get_target_freq(devfreq, &freq);
 	if (err)
 		return err;

 	err = devfreq->profile->target(devfreq->dev.parent, &freq);
 	if (err)
 		return err;

 	devfreq->previous_freq = freq;
 	return err;
 }

 /**
  * devfreq_notifier_call() - Notify that the device frequency requirements
  *			   has been changed out of devfreq framework.
  * @nb		the notifier_block (supposed to be devfreq->nb)
  * @type	not used
  * @devp	not used
  *
  * Called by a notifier that uses devfreq->nb.
  */
 static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
 				 void *devp)
 {
 	struct devfreq *devfreq = container_of(nb, struct devfreq, nb);
 	int ret;

 	mutex_lock(&devfreq->lock);
 	ret = update_devfreq(devfreq);
 	mutex_unlock(&devfreq->lock);

 	return ret;
 }

 /**
  * _remove_devfreq() - Remove devfreq from the device.
  * @devfreq:	the devfreq struct
  * @skip:	skip calling device_unregister().
  *
  * Note that the caller should lock devfreq->lock before calling
  * this. _remove_devfreq() will unlock it and free devfreq
  * internally. devfreq_list_lock should be locked by the caller
  * as well (not relased at return)
  *
  * Lock usage:
  * devfreq->lock: locked before call.
  *		  unlocked at return (and freed)
  * devfreq_list_lock: locked before call.
  *		      kept locked at return.
  *		      if devfreq is centrally polled.
  *
  * Freed memory:
  * devfreq
  */
 static void _remove_devfreq(struct devfreq *devfreq, bool skip)
 {
 	if (!mutex_is_locked(&devfreq->lock)) {
 		WARN(true, "devfreq->lock must be locked by the caller.\n");
 		return;
 	}
 	if (!devfreq->governor->no_central_polling &&
 	    !mutex_is_locked(&devfreq_list_lock)) {
 		WARN(true, "devfreq_list_lock must be locked by the caller.\n");
 		return;
 	}

 	if (devfreq->being_removed)
 		return;

 	devfreq->being_removed = true;

 	if (devfreq->profile->exit)
 		devfreq->profile->exit(devfreq->dev.parent);

 	if (devfreq->governor->exit)
 		devfreq->governor->exit(devfreq);

 	if (!skip && get_device(&devfreq->dev)) {
 		device_unregister(&devfreq->dev);
 		put_device(&devfreq->dev);
 	}

 	if (!devfreq->governor->no_central_polling)
 		list_del(&devfreq->node);

 	mutex_unlock(&devfreq->lock);
 	mutex_destroy(&devfreq->lock);

 	kfree(devfreq);
 }

 /**
  * devfreq_dev_release() - Callback for struct device to release the device.
  * @dev:	the devfreq device
  *
  * This calls _remove_devfreq() if _remove_devfreq() is not called.
  * Note that devfreq_dev_release() could be called by _remove_devfreq() as
  * well as by others unregistering the device.
  */
 static void devfreq_dev_release(struct device *dev)
 {
 	struct devfreq *devfreq = to_devfreq(dev);
 	bool central_polling = !devfreq->governor->no_central_polling;

 	/*
 	 * If devfreq_dev_release() was called by device_unregister() of
 	 * _remove_devfreq(), we cannot mutex_lock(&devfreq->lock) and
 	 * being_removed is already set. This also partially checks the case
 	 * where devfreq_dev_release() is called from a thread other than
 	 * the one called _remove_devfreq(); however, this case is
 	 * dealt completely with another following being_removed check.
 	 *
 	 * Because being_removed is never being
 	 * unset, we do not need to worry about race conditions on
 	 * being_removed.
 	 */
 	if (devfreq->being_removed)
 		return;

 	if (central_polling)
 		mutex_lock(&devfreq_list_lock);

 	mutex_lock(&devfreq->lock);

 	/*
 	 * Check being_removed flag again for the case where
 	 * devfreq_dev_release() was called in a thread other than the one
 	 * possibly called _remove_devfreq().
 	 */
 	if (devfreq->being_removed) {
 		mutex_unlock(&devfreq->lock);
 		goto out;
 	}

 	/* devfreq->lock is unlocked and removed in _removed_devfreq() */
 	_remove_devfreq(devfreq, true);

 out:
 	if (central_polling)
 		mutex_unlock(&devfreq_list_lock);
 }

 /**
  * devfreq_monitor() - Periodically poll devfreq objects.
  * @work: the work struct used to run devfreq_monitor periodically.
  *
  */
 static void devfreq_monitor(struct work_struct *work)
 {
 	static unsigned long last_polled_at;
 	struct devfreq *devfreq, *tmp;
 	int error;
 	unsigned long jiffies_passed;
 	unsigned long next_jiffies = ULONG_MAX, now = jiffies;
 	struct device *dev;

 	/* Initially last_polled_at = 0, polling every device at bootup */
 	jiffies_passed = now - last_polled_at;
 	last_polled_at = now;
 	if (jiffies_passed == 0)
 		jiffies_passed = 1;

 	mutex_lock(&devfreq_list_lock);
 	list_for_each_entry_safe(devfreq, tmp, &devfreq_list, node) {
 		mutex_lock(&devfreq->lock);
 		dev = devfreq->dev.parent;

 		/* Do not remove tmp for a while */
 		wait_remove_device = tmp;

 		if (devfreq->governor->no_central_polling ||
 		    devfreq->next_polling == 0) {
 			mutex_unlock(&devfreq->lock);
 			continue;
 		}
 		mutex_unlock(&devfreq_list_lock);

 		/*
 		 * Reduce more next_polling if devfreq_wq took an extra
 		 * delay. (i.e., CPU has been idled.)
 		 */
 		if (devfreq->next_polling <= jiffies_passed) {
 			error = update_devfreq(devfreq);

 			/* Remove a devfreq with an error. */
 			if (error && error != -EAGAIN) {

 				dev_err(dev, "Due to update_devfreq error(%d), devfreq(%s) is removed from the device\n",
 					error, devfreq->governor->name);

 				/*
 				 * Unlock devfreq before locking the list
 				 * in order to avoid deadlock with
 				 * find_device_devfreq or others
 				 */
 				mutex_unlock(&devfreq->lock);
 				mutex_lock(&devfreq_list_lock);
 				/* Check if devfreq is already removed */
 				if (IS_ERR(find_device_devfreq(dev)))
 					continue;
 				mutex_lock(&devfreq->lock);
 				/* This unlocks devfreq->lock and free it */
 				_remove_devfreq(devfreq, false);
 				continue;
 			}
 			devfreq->next_polling = devfreq->polling_jiffies;
 		} else {
 			devfreq->next_polling -= jiffies_passed;
 		}

 		if (devfreq->next_polling)
 			next_jiffies = (next_jiffies > devfreq->next_polling) ?
 					devfreq->next_polling : next_jiffies;

 		mutex_unlock(&devfreq->lock);
 		mutex_lock(&devfreq_list_lock);
 	}
 	wait_remove_device = NULL;
 	mutex_unlock(&devfreq_list_lock);

 	if (next_jiffies > 0 && next_jiffies < ULONG_MAX) {
 		polling = true;
 		queue_delayed_work(devfreq_wq, &devfreq_work, next_jiffies);
 	} else {
 		polling = false;
 	}
 }

 /**
  * devfreq_add_device() - Add devfreq feature to the device
  * @dev:	the device to add devfreq feature.
  * @profile:	device-specific profile to run devfreq.
  * @governor:	the policy to choose frequency.
  * @data:	private data for the governor. The devfreq framework does not
  *		touch this value.
  */
 struct devfreq *devfreq_add_device(struct device *dev,
 				   struct devfreq_dev_profile *profile,
 				   const struct devfreq_governor *governor,
 				   void *data)
 {
 	struct devfreq *devfreq;
 	int err = 0;

 	if (!dev || !profile || !governor) {
 		dev_err(dev, "%s: Invalid parameters.\n", __func__);
 		return ERR_PTR(-EINVAL);
 	}


 	if (!governor->no_central_polling) {
 		mutex_lock(&devfreq_list_lock);
 		devfreq = find_device_devfreq(dev);
 		mutex_unlock(&devfreq_list_lock);
 		if (!IS_ERR(devfreq)) {
 			dev_err(dev, "%s: Unable to create devfreq for the device. It already has one.\n", __func__);
 			err = -EINVAL;
 			goto out;
 		}
 	}

 	devfreq = kzalloc(sizeof(struct devfreq), GFP_KERNEL);
 	if (!devfreq) {
 		dev_err(dev, "%s: Unable to create devfreq for the device\n",
 			__func__);
 		err = -ENOMEM;
 		goto out;
 	}

 	mutex_init(&devfreq->lock);
 	mutex_lock(&devfreq->lock);
 	devfreq->dev.parent = dev;
 	devfreq->dev.class = devfreq_class;
 	devfreq->dev.release = devfreq_dev_release;
 	devfreq->profile = profile;
 	devfreq->governor = governor;
 	devfreq->previous_freq = profile->initial_freq;
 	devfreq->data = data;
 	devfreq->next_polling = devfreq->polling_jiffies
 			      = msecs_to_jiffies(devfreq->profile->polling_ms);
 	devfreq->nb.notifier_call = devfreq_notifier_call;

 	dev_set_name(&devfreq->dev, dev_name(dev));
 	err = device_register(&devfreq->dev);
 	if (err) {
 		put_device(&devfreq->dev);
 		goto err_dev;
 	}

 	if (governor->init)
 		err = governor->init(devfreq);
 	if (err)
 		goto err_init;

 	mutex_unlock(&devfreq->lock);

 	if (governor->no_central_polling)
 		goto out;

 	mutex_lock(&devfreq_list_lock);

 	list_add(&devfreq->node, &devfreq_list);

 	if (devfreq_wq && devfreq->next_polling && !polling) {
 		polling = true;
 		queue_delayed_work(devfreq_wq, &devfreq_work,
 				   devfreq->next_polling);
 	}
 	mutex_unlock(&devfreq_list_lock);
 	goto out;
 err_init:
 	device_unregister(&devfreq->dev);
 err_dev:
 	mutex_unlock(&devfreq->lock);
 	kfree(devfreq);
 out:
 	if (err)
 		return ERR_PTR(err);
 	else
 		return devfreq;
 }

 /**
  * devfreq_remove_device() - Remove devfreq feature from a device.
  * @devfreq	the devfreq instance to be removed
  */
 int devfreq_remove_device(struct devfreq *devfreq)
 {
 	if (!devfreq)
 		return -EINVAL;

 	if (!devfreq->governor->no_central_polling) {
 		mutex_lock(&devfreq_list_lock);
 		while (wait_remove_device == devfreq) {
 			mutex_unlock(&devfreq_list_lock);
 			schedule();
 			mutex_lock(&devfreq_list_lock);
 		}
 	}

 	mutex_lock(&devfreq->lock);
 	_remove_devfreq(devfreq, false); /* it unlocks devfreq->lock */

 	if (!devfreq->governor->no_central_polling)
 		mutex_unlock(&devfreq_list_lock);

 	return 0;
 }

 static ssize_t show_governor(struct device *dev,
 			     struct device_attribute *attr, char *buf)
 {
 	return sprintf(buf, "%s\n", to_devfreq(dev)->governor->name);
 }

 static ssize_t show_freq(struct device *dev,
 			 struct device_attribute *attr, char *buf)
 {
 	return sprintf(buf, "%lu\n", to_devfreq(dev)->previous_freq);
 }

 static ssize_t show_polling_interval(struct device *dev,
 				     struct device_attribute *attr, char *buf)
 {
 	return sprintf(buf, "%d\n", to_devfreq(dev)->profile->polling_ms);
 }

 static ssize_t store_polling_interval(struct device *dev,
 				      struct device_attribute *attr,
 				      const char *buf, size_t count)
 {
 	struct devfreq *df = to_devfreq(dev);
 	unsigned int value;
 	int ret;

 	ret = sscanf(buf, "%u", &value);
 	if (ret != 1)
 		goto out;

 	mutex_lock(&df->lock);
 	df->profile->polling_ms = value;
 	df->next_polling = df->polling_jiffies
 			 = msecs_to_jiffies(value);
 	mutex_unlock(&df->lock);

 	ret = count;

 	if (df->governor->no_central_polling)
 		goto out;

 	mutex_lock(&devfreq_list_lock);
 	if (df->next_polling > 0 && !polling) {
 		polling = true;
 		queue_delayed_work(devfreq_wq, &devfreq_work,
 				   df->next_polling);
 	}
 	mutex_unlock(&devfreq_list_lock);
 out:
 	return ret;
 }

 static ssize_t show_central_polling(struct device *dev,
 				    struct device_attribute *attr, char *buf)
 {
 	return sprintf(buf, "%d\n",
 		       !to_devfreq(dev)->governor->no_central_polling);
 }

 static struct device_attribute devfreq_attrs[] = {
 	__ATTR(governor, S_IRUGO, show_governor, NULL),
 	__ATTR(cur_freq, S_IRUGO, show_freq, NULL),
 	__ATTR(central_polling, S_IRUGO, show_central_polling, NULL),
 	__ATTR(polling_interval, S_IRUGO | S_IWUSR, show_polling_interval,
 	       store_polling_interval),
 	{ },
 };

 /**
  * devfreq_start_polling() - Initialize data structure for devfreq framework and
  *			   start polling registered devfreq devices.
  */
 static int __init devfreq_start_polling(void)
 {
 	mutex_lock(&devfreq_list_lock);
 	polling = false;
 	devfreq_wq = create_freezable_workqueue("devfreq_wq");
 	INIT_DELAYED_WORK_DEFERRABLE(&devfreq_work, devfreq_monitor);
 	mutex_unlock(&devfreq_list_lock);

 	devfreq_monitor(&devfreq_work.work);
 	return 0;
 }
 late_initcall(devfreq_start_polling);

 static int __init devfreq_init(void)
 {
 	devfreq_class = class_create(THIS_MODULE, "devfreq");
 	if (IS_ERR(devfreq_class)) {
 		pr_err("%s: couldn't create class\n", __FILE__);
 		return PTR_ERR(devfreq_class);
 	}
 	devfreq_class->dev_attrs = devfreq_attrs;
 	return 0;
 }
 subsys_initcall(devfreq_init);

 static void __exit devfreq_exit(void)
 {
 	class_destroy(devfreq_class);
 }
 module_exit(devfreq_exit);

 /*
  * The followings are helper functions for devfreq user device drivers with
  * OPP framework.
  */

 /**
  * devfreq_recommended_opp() - Helper function to get proper OPP for the
  *			     freq value given to target callback.
  * @dev		The devfreq user device. (parent of devfreq)
  * @freq	The frequency given to target function
  *
  */
 struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq)
 {
 	struct opp *opp = opp_find_freq_ceil(dev, freq);

 	if (opp == ERR_PTR(-ENODEV))
 		opp = opp_find_freq_floor(dev, freq);
 	return opp;
 }

 /**
  * devfreq_register_opp_notifier() - Helper function to get devfreq notified
  *				   for any changes in the OPP availability
  *				   changes
  * @dev		The devfreq user device. (parent of devfreq)
  * @devfreq	The devfreq object.
  */
 int devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq)
 {
 	struct srcu_notifier_head *nh = opp_get_notifier(dev);

 	if (IS_ERR(nh))
 		return PTR_ERR(nh);
 	return srcu_notifier_chain_register(nh, &devfreq->nb);
 }

 /**
  * devfreq_unregister_opp_notifier() - Helper function to stop getting devfreq
  *				     notified for any changes in the OPP
  *				     availability changes anymore.
  * @dev		The devfreq user device. (parent of devfreq)
  * @devfreq	The devfreq object.
  *
  * At exit() callback of devfreq_dev_profile, this must be included if
  * devfreq_recommended_opp is used.
  */
 int devfreq_unregister_opp_notifier(struct device *dev, struct devfreq *devfreq)
 {
 	struct srcu_notifier_head *nh = opp_get_notifier(dev);

 	if (IS_ERR(nh))
 		return PTR_ERR(nh);
 	return srcu_notifier_chain_unregister(nh, &devfreq->nb);
 }

 MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
 MODULE_DESCRIPTION("devfreq class support");
 MODULE_LICENSE("GPL");
	/*
	* devfreq: Generic Dynamic Voltage and Frequency Scaling (DVFS) Framework
	* for Non-CPU Devices.
	*
	* Copyright (C) 2011 Samsung Electronics
	* MyungJoo Ham <myungjoo.ham@samsung.com>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/

	#include <linux/kernel.h>
	#include <linux/sched.h>
	#include <linux/errno.h>
	#include <linux/err.h>
	#include <linux/init.h>
	#include <linux/slab.h>
	#include <linux/opp.h>
	#include <linux/devfreq.h>
	#include <linux/workqueue.h>
	#include <linux/platform_device.h>
	#include <linux/list.h>
	#include <linux/printk.h>
	#include <linux/hrtimer.h>
	#include "governor.h"

	struct class *devfreq_class;

	/*
	* devfreq_work periodically monitors every registered device.
	* The minimum polling interval is one jiffy. The polling interval is
	* determined by the minimum polling period among all polling devfreq
	* devices. The resolution of polling interval is one jiffy.
	*/
	static bool polling;
	static struct workqueue_struct *devfreq_wq;
	static struct delayed_work devfreq_work;

	/* wait removing if this is to be removed */
	static struct devfreq *wait_remove_device;

	/* The list of all device-devfreq */
	static LIST_HEAD(devfreq_list);
	static DEFINE_MUTEX(devfreq_list_lock);

	/**
	* find_device_devfreq() - find devfreq struct using device pointer
	* @dev: device pointer used to lookup device devfreq.
	*
	* Search the list of device devfreqs and return the matched device's
	* devfreq info. devfreq_list_lock should be held by the caller.
	*/
	static struct devfreq find_device_devfreq(struct device dev)
	{
	struct devfreq *tmp_devfreq;

	if (unlikely(IS_ERR_OR_NULL(dev))) {
	pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
	return ERR_PTR(-EINVAL);
	}
	WARN(!mutex_is_locked(&devfreq_list_lock),
	"devfreq_list_lock must be locked.");

	list_for_each_entry(tmp_devfreq, &devfreq_list, node) {
	if (tmp_devfreq->dev.parent == dev)
	return tmp_devfreq;
	}

	return ERR_PTR(-ENODEV);
	}

	/**
	* update_devfreq() - Reevaluate the device and configure frequency.
	* @devfreq: the devfreq instance.
	*
	* Note: Lock devfreq->lock before calling update_devfreq
	* This function is exported for governors.
	*/
	int update_devfreq(struct devfreq *devfreq)
	{
	unsigned long freq;
	int err = 0;

	if (!mutex_is_locked(&devfreq->lock)) {
	WARN(true, "devfreq->lock must be locked by the caller.\n");
	return -EINVAL;
	}

	/* Reevaluate the proper frequency */
	err = devfreq->governor->get_target_freq(devfreq, &freq);
	if (err)
	return err;

	err = devfreq->profile->target(devfreq->dev.parent, &freq);
	if (err)
	return err;

	devfreq->previous_freq = freq;
	return err;
	}

	/**
	* devfreq_notifier_call() - Notify that the device frequency requirements
	* has been changed out of devfreq framework.
	* @nb the notifier_block (supposed to be devfreq->nb)
	* @type not used
	* @devp not used
	*
	* Called by a notifier that uses devfreq->nb.
	*/
	static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
	void *devp)
	{
	struct devfreq *devfreq = container_of(nb, struct devfreq, nb);
	int ret;

	mutex_lock(&devfreq->lock);
	ret = update_devfreq(devfreq);
	mutex_unlock(&devfreq->lock);

	return ret;
	}

	/**
	* _remove_devfreq() - Remove devfreq from the device.
	* @devfreq: the devfreq struct
	* @skip: skip calling device_unregister().
	*
	* Note that the caller should lock devfreq->lock before calling
	* this. _remove_devfreq() will unlock it and free devfreq
	* internally. devfreq_list_lock should be locked by the caller
	* as well (not relased at return)
	*
	* Lock usage:
	* devfreq->lock: locked before call.
	* unlocked at return (and freed)
	* devfreq_list_lock: locked before call.
	* kept locked at return.
	* if devfreq is centrally polled.
	*
	* Freed memory:
	* devfreq
	*/
	static void _remove_devfreq(struct devfreq *devfreq, bool skip)
	{
	if (!mutex_is_locked(&devfreq->lock)) {
	WARN(true, "devfreq->lock must be locked by the caller.\n");
	return;
	}
	if (!devfreq->governor->no_central_polling &&
	!mutex_is_locked(&devfreq_list_lock)) {
	WARN(true, "devfreq_list_lock must be locked by the caller.\n");
	return;
	}

	if (devfreq->being_removed)
	return;

	devfreq->being_removed = true;

	if (devfreq->profile->exit)
	devfreq->profile->exit(devfreq->dev.parent);

	if (devfreq->governor->exit)
	devfreq->governor->exit(devfreq);

	if (!skip && get_device(&devfreq->dev)) {
	device_unregister(&devfreq->dev);
	put_device(&devfreq->dev);
	}

	if (!devfreq->governor->no_central_polling)
	list_del(&devfreq->node);

	mutex_unlock(&devfreq->lock);
	mutex_destroy(&devfreq->lock);

	kfree(devfreq);
	}

	/**
	* devfreq_dev_release() - Callback for struct device to release the device.
	* @dev: the devfreq device
	*
	* This calls _remove_devfreq() if _remove_devfreq() is not called.
	* Note that devfreq_dev_release() could be called by _remove_devfreq() as
	* well as by others unregistering the device.
	*/
	static void devfreq_dev_release(struct device *dev)
	{
	struct devfreq *devfreq = to_devfreq(dev);
	bool central_polling = !devfreq->governor->no_central_polling;

	/*
	* If devfreq_dev_release() was called by device_unregister() of
	* _remove_devfreq(), we cannot mutex_lock(&devfreq->lock) and
	* being_removed is already set. This also partially checks the case
	* where devfreq_dev_release() is called from a thread other than
	* the one called _remove_devfreq(); however, this case is
	* dealt completely with another following being_removed check.
	*
	* Because being_removed is never being
	* unset, we do not need to worry about race conditions on
	* being_removed.
	*/
	if (devfreq->being_removed)
	return;

	if (central_polling)
	mutex_lock(&devfreq_list_lock);

	mutex_lock(&devfreq->lock);

	/*
	* Check being_removed flag again for the case where
	* devfreq_dev_release() was called in a thread other than the one
	* possibly called _remove_devfreq().
	*/
	if (devfreq->being_removed) {
	mutex_unlock(&devfreq->lock);
	goto out;
	}

	/* devfreq->lock is unlocked and removed in _removed_devfreq() */
	_remove_devfreq(devfreq, true);

	out:
	if (central_polling)
	mutex_unlock(&devfreq_list_lock);
	}

	/**
	* devfreq_monitor() - Periodically poll devfreq objects.
	* @work: the work struct used to run devfreq_monitor periodically.
	*
	*/
	static void devfreq_monitor(struct work_struct *work)
	{
	static unsigned long last_polled_at;
	struct devfreq devfreq, tmp;
	int error;
	unsigned long jiffies_passed;
	unsigned long next_jiffies = ULONG_MAX, now = jiffies;
	struct device *dev;

	/* Initially last_polled_at = 0, polling every device at bootup */
	jiffies_passed = now - last_polled_at;
	last_polled_at = now;
	if (jiffies_passed == 0)
	jiffies_passed = 1;

	mutex_lock(&devfreq_list_lock);
	list_for_each_entry_safe(devfreq, tmp, &devfreq_list, node) {
	mutex_lock(&devfreq->lock);
	dev = devfreq->dev.parent;

	/* Do not remove tmp for a while */
	wait_remove_device = tmp;

	if (devfreq->governor->no_central_polling \|\|
	devfreq->next_polling == 0) {
	mutex_unlock(&devfreq->lock);
	continue;
	}
	mutex_unlock(&devfreq_list_lock);

	/*
	* Reduce more next_polling if devfreq_wq took an extra
	* delay. (i.e., CPU has been idled.)
	*/
	if (devfreq->next_polling <= jiffies_passed) {
	error = update_devfreq(devfreq);

	/* Remove a devfreq with an error. */
	if (error && error != -EAGAIN) {

	dev_err(dev, "Due to update_devfreq error(%d), devfreq(%s) is removed from the device\n",
	error, devfreq->governor->name);

	/*
	* Unlock devfreq before locking the list
	* in order to avoid deadlock with
	* find_device_devfreq or others
	*/
	mutex_unlock(&devfreq->lock);
	mutex_lock(&devfreq_list_lock);
	/* Check if devfreq is already removed */
	if (IS_ERR(find_device_devfreq(dev)))
	continue;
	mutex_lock(&devfreq->lock);
	/* This unlocks devfreq->lock and free it */
	_remove_devfreq(devfreq, false);
	continue;
	}
	devfreq->next_polling = devfreq->polling_jiffies;
	} else {
	devfreq->next_polling -= jiffies_passed;
	}

	if (devfreq->next_polling)
	next_jiffies = (next_jiffies > devfreq->next_polling) ?
	devfreq->next_polling : next_jiffies;

	mutex_unlock(&devfreq->lock);
	mutex_lock(&devfreq_list_lock);
	}
	wait_remove_device = NULL;
	mutex_unlock(&devfreq_list_lock);

	if (next_jiffies > 0 && next_jiffies < ULONG_MAX) {
	polling = true;
	queue_delayed_work(devfreq_wq, &devfreq_work, next_jiffies);
	} else {
	polling = false;
	}
	}

	/**
	* devfreq_add_device() - Add devfreq feature to the device
	* @dev: the device to add devfreq feature.
	* @profile: device-specific profile to run devfreq.
	* @governor: the policy to choose frequency.
	* @data: private data for the governor. The devfreq framework does not
	* touch this value.
	*/
	struct devfreq devfreq_add_device(struct device dev,
	struct devfreq_dev_profile *profile,
	const struct devfreq_governor *governor,
	void *data)
	{
	struct devfreq *devfreq;
	int err = 0;

	if (!dev \|\| !profile \|\| !governor) {
	dev_err(dev, "%s: Invalid parameters.\n", __func__);
	return ERR_PTR(-EINVAL);
	}


	if (!governor->no_central_polling) {
	mutex_lock(&devfreq_list_lock);
	devfreq = find_device_devfreq(dev);
	mutex_unlock(&devfreq_list_lock);
	if (!IS_ERR(devfreq)) {
	dev_err(dev, "%s: Unable to create devfreq for the device. It already has one.\n", __func__);
	err = -EINVAL;
	goto out;
	}
	}

	devfreq = kzalloc(sizeof(struct devfreq), GFP_KERNEL);
	if (!devfreq) {
	dev_err(dev, "%s: Unable to create devfreq for the device\n",
	__func__);
	err = -ENOMEM;
	goto out;
	}

	mutex_init(&devfreq->lock);
	mutex_lock(&devfreq->lock);
	devfreq->dev.parent = dev;
	devfreq->dev.class = devfreq_class;
	devfreq->dev.release = devfreq_dev_release;
	devfreq->profile = profile;
	devfreq->governor = governor;
	devfreq->previous_freq = profile->initial_freq;
	devfreq->data = data;
	devfreq->next_polling = devfreq->polling_jiffies
	= msecs_to_jiffies(devfreq->profile->polling_ms);
	devfreq->nb.notifier_call = devfreq_notifier_call;

	dev_set_name(&devfreq->dev, dev_name(dev));
	err = device_register(&devfreq->dev);
	if (err) {
	put_device(&devfreq->dev);
	goto err_dev;
	}

	if (governor->init)
	err = governor->init(devfreq);
	if (err)
	goto err_init;

	mutex_unlock(&devfreq->lock);

	if (governor->no_central_polling)
	goto out;

	mutex_lock(&devfreq_list_lock);

	list_add(&devfreq->node, &devfreq_list);

	if (devfreq_wq && devfreq->next_polling && !polling) {
	polling = true;
	queue_delayed_work(devfreq_wq, &devfreq_work,
	devfreq->next_polling);
	}
	mutex_unlock(&devfreq_list_lock);
	goto out;
	err_init:
	device_unregister(&devfreq->dev);
	err_dev:
	mutex_unlock(&devfreq->lock);
	kfree(devfreq);
	out:
	if (err)
	return ERR_PTR(err);
	else
	return devfreq;
	}

	/**
	* devfreq_remove_device() - Remove devfreq feature from a device.
	* @devfreq the devfreq instance to be removed
	*/
	int devfreq_remove_device(struct devfreq *devfreq)
	{
	if (!devfreq)
	return -EINVAL;

	if (!devfreq->governor->no_central_polling) {
	mutex_lock(&devfreq_list_lock);
	while (wait_remove_device == devfreq) {
	mutex_unlock(&devfreq_list_lock);
	schedule();
	mutex_lock(&devfreq_list_lock);
	}
	}

	mutex_lock(&devfreq->lock);
	_remove_devfreq(devfreq, false); /* it unlocks devfreq->lock */

	if (!devfreq->governor->no_central_polling)
	mutex_unlock(&devfreq_list_lock);

	return 0;
	}

	static ssize_t show_governor(struct device *dev,
	struct device_attribute attr, char buf)
	{
	return sprintf(buf, "%s\n", to_devfreq(dev)->governor->name);
	}

	static ssize_t show_freq(struct device *dev,
	struct device_attribute attr, char buf)
	{
	return sprintf(buf, "%lu\n", to_devfreq(dev)->previous_freq);
	}

	static ssize_t show_polling_interval(struct device *dev,
	struct device_attribute attr, char buf)
	{
	return sprintf(buf, "%d\n", to_devfreq(dev)->profile->polling_ms);
	}

	static ssize_t store_polling_interval(struct device *dev,
	struct device_attribute *attr,
	const char *buf, size_t count)
	{
	struct devfreq *df = to_devfreq(dev);
	unsigned int value;
	int ret;

	ret = sscanf(buf, "%u", &value);
	if (ret != 1)
	goto out;

	mutex_lock(&df->lock);
	df->profile->polling_ms = value;
	df->next_polling = df->polling_jiffies
	= msecs_to_jiffies(value);
	mutex_unlock(&df->lock);

	ret = count;

	if (df->governor->no_central_polling)
	goto out;

	mutex_lock(&devfreq_list_lock);
	if (df->next_polling > 0 && !polling) {
	polling = true;
	queue_delayed_work(devfreq_wq, &devfreq_work,
	df->next_polling);
	}
	mutex_unlock(&devfreq_list_lock);
	out:
	return ret;
	}

	static ssize_t show_central_polling(struct device *dev,
	struct device_attribute attr, char buf)
	{
	return sprintf(buf, "%d\n",
	!to_devfreq(dev)->governor->no_central_polling);
	}

	static struct device_attribute devfreq_attrs[] = {
	__ATTR(governor, S_IRUGO, show_governor, NULL),
	__ATTR(cur_freq, S_IRUGO, show_freq, NULL),
	__ATTR(central_polling, S_IRUGO, show_central_polling, NULL),
	__ATTR(polling_interval, S_IRUGO \| S_IWUSR, show_polling_interval,
	store_polling_interval),
	{ },
	};

	/**
	* devfreq_start_polling() - Initialize data structure for devfreq framework and
	* start polling registered devfreq devices.
	*/
	static int __init devfreq_start_polling(void)
	{
	mutex_lock(&devfreq_list_lock);
	polling = false;
	devfreq_wq = create_freezable_workqueue("devfreq_wq");
	INIT_DELAYED_WORK_DEFERRABLE(&devfreq_work, devfreq_monitor);
	mutex_unlock(&devfreq_list_lock);

	devfreq_monitor(&devfreq_work.work);
	return 0;
	}
	late_initcall(devfreq_start_polling);

	static int __init devfreq_init(void)
	{
	devfreq_class = class_create(THIS_MODULE, "devfreq");
	if (IS_ERR(devfreq_class)) {
	pr_err("%s: couldn't create class\n", __FILE__);
	return PTR_ERR(devfreq_class);
	}
	devfreq_class->dev_attrs = devfreq_attrs;
	return 0;
	}
	subsys_initcall(devfreq_init);

	static void __exit devfreq_exit(void)
	{
	class_destroy(devfreq_class);
	}
	module_exit(devfreq_exit);

	/*
	* The followings are helper functions for devfreq user device drivers with
	* OPP framework.
	*/

	/**
	* devfreq_recommended_opp() - Helper function to get proper OPP for the
	* freq value given to target callback.
	* @dev The devfreq user device. (parent of devfreq)
	* @freq The frequency given to target function
	*
	*/
	struct opp devfreq_recommended_opp(struct device dev, unsigned long *freq)
	{
	struct opp *opp = opp_find_freq_ceil(dev, freq);

	if (opp == ERR_PTR(-ENODEV))
	opp = opp_find_freq_floor(dev, freq);
	return opp;
	}

	/**
	* devfreq_register_opp_notifier() - Helper function to get devfreq notified
	* for any changes in the OPP availability
	* changes
	* @dev The devfreq user device. (parent of devfreq)
	* @devfreq The devfreq object.
	*/
	int devfreq_register_opp_notifier(struct device dev, struct devfreq devfreq)
	{
	struct srcu_notifier_head *nh = opp_get_notifier(dev);

	if (IS_ERR(nh))
	return PTR_ERR(nh);
	return srcu_notifier_chain_register(nh, &devfreq->nb);
	}

	/**
	* devfreq_unregister_opp_notifier() - Helper function to stop getting devfreq
	* notified for any changes in the OPP
	* availability changes anymore.
	* @dev The devfreq user device. (parent of devfreq)
	* @devfreq The devfreq object.
	*
	* At exit() callback of devfreq_dev_profile, this must be included if
	* devfreq_recommended_opp is used.
	*/
	int devfreq_unregister_opp_notifier(struct device dev, struct devfreq devfreq)
	{
	struct srcu_notifier_head *nh = opp_get_notifier(dev);

	if (IS_ERR(nh))
	return PTR_ERR(nh);
	return srcu_notifier_chain_unregister(nh, &devfreq->nb);
	}

	MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
	MODULE_DESCRIPTION("devfreq class support");
	MODULE_LICENSE("GPL");