drivers/thermal/cpu_cooling.c - kernel/lockdown - Git at Google

 /*
  *  linux/drivers/thermal/cpu_cooling.c
  *
  *  Copyright (C) 2012	Samsung Electronics Co., Ltd(http://www.samsung.com)
  *  Copyright (C) 2012  Amit Daniel <amit.kachhap@linaro.org>
  *
  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
  *  the Free Software Foundation; version 2 of the License.
  *
  *  This program is distributed in the hope that it will be useful, but
  *  WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  *  General Public License for more details.
  *
  *  You should have received a copy of the GNU General Public License along
  *  with this program; if not, write to the Free Software Foundation, Inc.,
  *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
  *
  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  */
 #include <linux/module.h>
 #include <linux/thermal.h>
 #include <linux/cpufreq.h>
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/cpu.h>
 #include <linux/cpu_cooling.h>

 /**
  * struct cpufreq_cooling_device - data for cooling device with cpufreq
  * @id: unique integer value corresponding to each cpufreq_cooling_device
  *	registered.
  * @cool_dev: thermal_cooling_device pointer to keep track of the
  *	registered cooling device.
  * @cpufreq_state: integer value representing the current state of cpufreq
  *	cooling	devices.
  * @cpufreq_val: integer value representing the absolute value of the clipped
  *	frequency.
  * @allowed_cpus: all the cpus involved for this cpufreq_cooling_device.
  *
  * This structure is required for keeping information of each
  * cpufreq_cooling_device registered. In order to prevent corruption of this a
  * mutex lock cooling_cpufreq_lock is used.
  */
 struct cpufreq_cooling_device {
 	int id;
 	struct thermal_cooling_device *cool_dev;
 	unsigned int cpufreq_state;
 	unsigned int cpufreq_val;
 	struct cpumask allowed_cpus;
 };
 static DEFINE_IDR(cpufreq_idr);
 static DEFINE_MUTEX(cooling_cpufreq_lock);

 static unsigned int cpufreq_dev_count;

 /* notify_table passes value to the CPUFREQ_ADJUST callback function. */
 #define NOTIFY_INVALID NULL
 static struct cpufreq_cooling_device *notify_device;

 /**
  * get_idr - function to get a unique id.
  * @idr: struct idr * handle used to create a id.
  * @id: int * value generated by this function.
  *
  * This function will populate @id with an unique
  * id, using the idr API.
  *
  * Return: 0 on success, an error code on failure.
  */
 static int get_idr(struct idr *idr, int *id)
 {
 	int ret;

 	mutex_lock(&cooling_cpufreq_lock);
 	ret = idr_alloc(idr, NULL, 0, 0, GFP_KERNEL);
 	mutex_unlock(&cooling_cpufreq_lock);
 	if (unlikely(ret < 0))
 		return ret;
 	*id = ret;

 	return 0;
 }

 /**
  * release_idr - function to free the unique id.
  * @idr: struct idr * handle used for creating the id.
  * @id: int value representing the unique id.
  */
 static void release_idr(struct idr *idr, int id)
 {
 	mutex_lock(&cooling_cpufreq_lock);
 	idr_remove(idr, id);
 	mutex_unlock(&cooling_cpufreq_lock);
 }

 /* Below code defines functions to be used for cpufreq as cooling device */

 /**
  * is_cpufreq_valid - function to check frequency transitioning capability.
  * @cpu: cpu for which check is needed.
  *
  * This function will check the current state of the system if
  * it is capable of changing the frequency for a given @cpu.
  *
  * Return: 0 if the system is not currently capable of changing
  * the frequency of given cpu. !0 in case the frequency is changeable.
  */
 static int is_cpufreq_valid(int cpu)
 {
 	struct cpufreq_policy policy;

 	return !cpufreq_get_policy(&policy, cpu);
 }

 enum cpufreq_cooling_property {
 	GET_LEVEL,
 	GET_FREQ,
 	GET_MAXL,
 };

 /**
  * get_property - fetch a property of interest for a give cpu.
  * @cpu: cpu for which the property is required
  * @input: query parameter
  * @output: query return
  * @property: type of query (frequency, level, max level)
  *
  * This is the common function to
  * 1. get maximum cpu cooling states
  * 2. translate frequency to cooling state
  * 3. translate cooling state to frequency
  * Note that the code may be not in good shape
  * but it is written in this way in order to:
  * a) reduce duplicate code as most of the code can be shared.
  * b) make sure the logic is consistent when translating between
  *    cooling states and frequencies.
  *
  * Return: 0 on success, -EINVAL when invalid parameters are passed.
  */
 static int get_property(unsigned int cpu, unsigned long input,
 			unsigned int *output,
 			enum cpufreq_cooling_property property)
 {
 	int i, j;
 	unsigned long max_level = 0, level = 0;
 	unsigned int freq = CPUFREQ_ENTRY_INVALID;
 	int descend = -1;
 	struct cpufreq_frequency_table *table =
 					cpufreq_frequency_get_table(cpu);

 	if (!output)
 		return -EINVAL;

 	if (!table)
 		return -EINVAL;

 	for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
 		/* ignore invalid entries */
 		if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
 			continue;

 		/* ignore duplicate entry */
 		if (freq == table[i].frequency)
 			continue;

 		/* get the frequency order */
 		if (freq != CPUFREQ_ENTRY_INVALID && descend == -1)
 			descend = !!(freq > table[i].frequency);

 		freq = table[i].frequency;
 		max_level++;
 	}

 	/* No valid cpu frequency entry */
 	if (max_level == 0)
 		return -EINVAL;

 	/* max_level is an index, not a counter */
 	max_level--;

 	/* get max level */
 	if (property == GET_MAXL) {
 		*output = (unsigned int)max_level;
 		return 0;
 	}

 	if (property == GET_FREQ)
 		level = descend ? input : (max_level - input);

 	for (i = 0, j = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
 		/* ignore invalid entry */
 		if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
 			continue;

 		/* ignore duplicate entry */
 		if (freq == table[i].frequency)
 			continue;

 		/* now we have a valid frequency entry */
 		freq = table[i].frequency;

 		if (property == GET_LEVEL && (unsigned int)input == freq) {
 			/* get level by frequency */
 			*output = descend ? j : (max_level - j);
 			return 0;
 		}
 		if (property == GET_FREQ && level == j) {
 			/* get frequency by level */
 			*output = freq;
 			return 0;
 		}
 		j++;
 	}

 	return -EINVAL;
 }

 /**
  * cpufreq_cooling_get_level - for a give cpu, return the cooling level.
  * @cpu: cpu for which the level is required
  * @freq: the frequency of interest
  *
  * This function will match the cooling level corresponding to the
  * requested @freq and return it.
  *
  * Return: The matched cooling level on success or THERMAL_CSTATE_INVALID
  * otherwise.
  */
 unsigned long cpufreq_cooling_get_level(unsigned int cpu, unsigned int freq)
 {
 	unsigned int val;

 	if (get_property(cpu, (unsigned long)freq, &val, GET_LEVEL))
 		return THERMAL_CSTATE_INVALID;

 	return (unsigned long)val;
 }
 EXPORT_SYMBOL_GPL(cpufreq_cooling_get_level);

 /**
  * get_cpu_frequency - get the absolute value of frequency from level.
  * @cpu: cpu for which frequency is fetched.
  * @level: cooling level
  *
  * This function matches cooling level with frequency. Based on a cooling level
  * of frequency, equals cooling state of cpu cooling device, it will return
  * the corresponding frequency.
  *	e.g level=0 --> 1st MAX FREQ, level=1 ---> 2nd MAX FREQ, .... etc
  *
  * Return: 0 on error, the corresponding frequency otherwise.
  */
 static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
 {
 	int ret = 0;
 	unsigned int freq;

 	ret = get_property(cpu, level, &freq, GET_FREQ);
 	if (ret)
 		return 0;

 	return freq;
 }

 /**
  * cpufreq_apply_cooling - function to apply frequency clipping.
  * @cpufreq_device: cpufreq_cooling_device pointer containing frequency
  *	clipping data.
  * @cooling_state: value of the cooling state.
  *
  * Function used to make sure the cpufreq layer is aware of current thermal
  * limits. The limits are applied by updating the cpufreq policy.
  *
  * Return: 0 on success, an error code otherwise (-EINVAL in case wrong
  * cooling state).
  */
 static int cpufreq_apply_cooling(struct cpufreq_cooling_device *cpufreq_device,
 				 unsigned long cooling_state)
 {
 	unsigned int cpuid, clip_freq;
 	struct cpumask *mask = &cpufreq_device->allowed_cpus;
 	unsigned int cpu = cpumask_any(mask);


 	/* Check if the old cooling action is same as new cooling action */
 	if (cpufreq_device->cpufreq_state == cooling_state)
 		return 0;

 	clip_freq = get_cpu_frequency(cpu, cooling_state);
 	if (!clip_freq)
 		return -EINVAL;

 	cpufreq_device->cpufreq_state = cooling_state;
 	cpufreq_device->cpufreq_val = clip_freq;
 	notify_device = cpufreq_device;

 	for_each_cpu(cpuid, mask) {
 		if (is_cpufreq_valid(cpuid))
 			cpufreq_update_policy(cpuid);
 	}

 	notify_device = NOTIFY_INVALID;

 	return 0;
 }

 /**
  * cpufreq_thermal_notifier - notifier callback for cpufreq policy change.
  * @nb:	struct notifier_block * with callback info.
  * @event: value showing cpufreq event for which this function invoked.
  * @data: callback-specific data
  *
  * Callback to highjack the notification on cpufreq policy transition.
  * Every time there is a change in policy, we will intercept and
  * update the cpufreq policy with thermal constraints.
  *
  * Return: 0 (success)
  */
 static int cpufreq_thermal_notifier(struct notifier_block *nb,
 				    unsigned long event, void *data)
 {
 	struct cpufreq_policy *policy = data;
 	unsigned long max_freq = 0;

 	if (event != CPUFREQ_ADJUST || notify_device == NOTIFY_INVALID)
 		return 0;

 	if (cpumask_test_cpu(policy->cpu, &notify_device->allowed_cpus))
 		max_freq = notify_device->cpufreq_val;
 	else
 		return 0;

 	/* Never exceed user_policy.max */
 	if (max_freq > policy->user_policy.max)
 		max_freq = policy->user_policy.max;

 	if (policy->max != max_freq)
 		cpufreq_verify_within_limits(policy, 0, max_freq);

 	return 0;
 }

 /* cpufreq cooling device callback functions are defined below */

 /**
  * cpufreq_get_max_state - callback function to get the max cooling state.
  * @cdev: thermal cooling device pointer.
  * @state: fill this variable with the max cooling state.
  *
  * Callback for the thermal cooling device to return the cpufreq
  * max cooling state.
  *
  * Return: 0 on success, an error code otherwise.
  */
 static int cpufreq_get_max_state(struct thermal_cooling_device *cdev,
 				 unsigned long *state)
 {
 	struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;
 	struct cpumask *mask = &cpufreq_device->allowed_cpus;
 	unsigned int cpu;
 	unsigned int count = 0;
 	int ret;

 	cpu = cpumask_any(mask);

 	ret = get_property(cpu, 0, &count, GET_MAXL);

 	if (count > 0)
 		*state = count;

 	return ret;
 }

 /**
  * cpufreq_get_cur_state - callback function to get the current cooling state.
  * @cdev: thermal cooling device pointer.
  * @state: fill this variable with the current cooling state.
  *
  * Callback for the thermal cooling device to return the cpufreq
  * current cooling state.
  *
  * Return: 0 on success, an error code otherwise.
  */
 static int cpufreq_get_cur_state(struct thermal_cooling_device *cdev,
 				 unsigned long *state)
 {
 	struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;

 	*state = cpufreq_device->cpufreq_state;

 	return 0;
 }

 /**
  * cpufreq_set_cur_state - callback function to set the current cooling state.
  * @cdev: thermal cooling device pointer.
  * @state: set this variable to the current cooling state.
  *
  * Callback for the thermal cooling device to change the cpufreq
  * current cooling state.
  *
  * Return: 0 on success, an error code otherwise.
  */
 static int cpufreq_set_cur_state(struct thermal_cooling_device *cdev,
 				 unsigned long state)
 {
 	struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;

 	return cpufreq_apply_cooling(cpufreq_device, state);
 }

 /* Bind cpufreq callbacks to thermal cooling device ops */
 static struct thermal_cooling_device_ops const cpufreq_cooling_ops = {
 	.get_max_state = cpufreq_get_max_state,
 	.get_cur_state = cpufreq_get_cur_state,
 	.set_cur_state = cpufreq_set_cur_state,
 };

 /* Notifier for cpufreq policy change */
 static struct notifier_block thermal_cpufreq_notifier_block = {
 	.notifier_call = cpufreq_thermal_notifier,
 };

 /**
  * __cpufreq_cooling_register - helper function to create cpufreq cooling device
  * @np: a valid struct device_node to the cooling device device tree node
  * @clip_cpus: cpumask of cpus where the frequency constraints will happen.
  *
  * This interface function registers the cpufreq cooling device with the name
  * "thermal-cpufreq-%x". This api can support multiple instances of cpufreq
  * cooling devices. It also gives the opportunity to link the cooling device
  * with a device tree node, in order to bind it via the thermal DT code.
  *
  * Return: a valid struct thermal_cooling_device pointer on success,
  * on failure, it returns a corresponding ERR_PTR().
  */
 static struct thermal_cooling_device *
 __cpufreq_cooling_register(struct device_node *np,
 			   const struct cpumask *clip_cpus)
 {
 	struct thermal_cooling_device *cool_dev;
 	struct cpufreq_cooling_device *cpufreq_dev = NULL;
 	unsigned int min = 0, max = 0;
 	char dev_name[THERMAL_NAME_LENGTH];
 	int ret = 0, i;
 	struct cpufreq_policy policy;

 	/* Verify that all the clip cpus have same freq_min, freq_max limit */
 	for_each_cpu(i, clip_cpus) {
 		/* continue if cpufreq policy not found and not return error */
 		if (!cpufreq_get_policy(&policy, i))
 			continue;
 		if (min == 0 && max == 0) {
 			min = policy.cpuinfo.min_freq;
 			max = policy.cpuinfo.max_freq;
 		} else {
 			if (min != policy.cpuinfo.min_freq ||
 			    max != policy.cpuinfo.max_freq)
 				return ERR_PTR(-EINVAL);
 		}
 	}
 	cpufreq_dev = kzalloc(sizeof(struct cpufreq_cooling_device),
 			      GFP_KERNEL);
 	if (!cpufreq_dev)
 		return ERR_PTR(-ENOMEM);

 	cpumask_copy(&cpufreq_dev->allowed_cpus, clip_cpus);

 	ret = get_idr(&cpufreq_idr, &cpufreq_dev->id);
 	if (ret) {
 		kfree(cpufreq_dev);
 		return ERR_PTR(-EINVAL);
 	}

 	snprintf(dev_name, sizeof(dev_name), "thermal-cpufreq-%d",
 		 cpufreq_dev->id);

 	cool_dev = thermal_of_cooling_device_register(np, dev_name, cpufreq_dev,
 						      &cpufreq_cooling_ops);
 	if (IS_ERR(cool_dev)) {
 		release_idr(&cpufreq_idr, cpufreq_dev->id);
 		kfree(cpufreq_dev);
 		return cool_dev;
 	}
 	cpufreq_dev->cool_dev = cool_dev;
 	cpufreq_dev->cpufreq_state = 0;
 	mutex_lock(&cooling_cpufreq_lock);

 	/* Register the notifier for first cpufreq cooling device */
 	if (cpufreq_dev_count == 0)
 		cpufreq_register_notifier(&thermal_cpufreq_notifier_block,
 					  CPUFREQ_POLICY_NOTIFIER);
 	cpufreq_dev_count++;

 	mutex_unlock(&cooling_cpufreq_lock);

 	return cool_dev;
 }

 /**
  * cpufreq_cooling_register - function to create cpufreq cooling device.
  * @clip_cpus: cpumask of cpus where the frequency constraints will happen.
  *
  * This interface function registers the cpufreq cooling device with the name
  * "thermal-cpufreq-%x". This api can support multiple instances of cpufreq
  * cooling devices.
  *
  * Return: a valid struct thermal_cooling_device pointer on success,
  * on failure, it returns a corresponding ERR_PTR().
  */
 struct thermal_cooling_device *
 cpufreq_cooling_register(const struct cpumask *clip_cpus)
 {
 	return __cpufreq_cooling_register(NULL, clip_cpus);
 }
 EXPORT_SYMBOL_GPL(cpufreq_cooling_register);

 /**
  * of_cpufreq_cooling_register - function to create cpufreq cooling device.
  * @np: a valid struct device_node to the cooling device device tree node
  * @clip_cpus: cpumask of cpus where the frequency constraints will happen.
  *
  * This interface function registers the cpufreq cooling device with the name
  * "thermal-cpufreq-%x". This api can support multiple instances of cpufreq
  * cooling devices. Using this API, the cpufreq cooling device will be
  * linked to the device tree node provided.
  *
  * Return: a valid struct thermal_cooling_device pointer on success,
  * on failure, it returns a corresponding ERR_PTR().
  */
 struct thermal_cooling_device *
 of_cpufreq_cooling_register(struct device_node *np,
 			    const struct cpumask *clip_cpus)
 {
 	if (!np)
 		return ERR_PTR(-EINVAL);

 	return __cpufreq_cooling_register(np, clip_cpus);
 }
 EXPORT_SYMBOL_GPL(of_cpufreq_cooling_register);

 /**
  * cpufreq_cooling_unregister - function to remove cpufreq cooling device.
  * @cdev: thermal cooling device pointer.
  *
  * This interface function unregisters the "thermal-cpufreq-%x" cooling device.
  */
 void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
 {
 	struct cpufreq_cooling_device *cpufreq_dev;

 	if (!cdev)
 		return;

 	cpufreq_dev = cdev->devdata;
 	mutex_lock(&cooling_cpufreq_lock);
 	cpufreq_dev_count--;

 	/* Unregister the notifier for the last cpufreq cooling device */
 	if (cpufreq_dev_count == 0)
 		cpufreq_unregister_notifier(&thermal_cpufreq_notifier_block,
 					    CPUFREQ_POLICY_NOTIFIER);
 	mutex_unlock(&cooling_cpufreq_lock);

 	thermal_cooling_device_unregister(cpufreq_dev->cool_dev);
 	release_idr(&cpufreq_idr, cpufreq_dev->id);
 	kfree(cpufreq_dev);
 }
 EXPORT_SYMBOL_GPL(cpufreq_cooling_unregister);
	/*
	* linux/drivers/thermal/cpu_cooling.c
	*
	* Copyright (C) 2012 Samsung Electronics Co., Ltd(http://www.samsung.com)
	* Copyright (C) 2012 Amit Daniel <amit.kachhap@linaro.org>
	*
	* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; version 2 of the License.
	*
	* This program is distributed in the hope that it will be useful, but
	* WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License along
	* with this program; if not, write to the Free Software Foundation, Inc.,
	* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
	*
	* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	*/
	#include <linux/module.h>
	#include <linux/thermal.h>
	#include <linux/cpufreq.h>
	#include <linux/err.h>
	#include <linux/slab.h>
	#include <linux/cpu.h>
	#include <linux/cpu_cooling.h>

	/**
	* struct cpufreq_cooling_device - data for cooling device with cpufreq
	* @id: unique integer value corresponding to each cpufreq_cooling_device
	* registered.
	* @cool_dev: thermal_cooling_device pointer to keep track of the
	* registered cooling device.
	* @cpufreq_state: integer value representing the current state of cpufreq
	* cooling devices.
	* @cpufreq_val: integer value representing the absolute value of the clipped
	* frequency.
	* @allowed_cpus: all the cpus involved for this cpufreq_cooling_device.
	*
	* This structure is required for keeping information of each
	* cpufreq_cooling_device registered. In order to prevent corruption of this a
	* mutex lock cooling_cpufreq_lock is used.
	*/
	struct cpufreq_cooling_device {
	int id;
	struct thermal_cooling_device *cool_dev;
	unsigned int cpufreq_state;
	unsigned int cpufreq_val;
	struct cpumask allowed_cpus;
	};
	static DEFINE_IDR(cpufreq_idr);
	static DEFINE_MUTEX(cooling_cpufreq_lock);

	static unsigned int cpufreq_dev_count;

	/* notify_table passes value to the CPUFREQ_ADJUST callback function. */
	#define NOTIFY_INVALID NULL
	static struct cpufreq_cooling_device *notify_device;

	/**
	* get_idr - function to get a unique id.
	* @idr: struct idr * handle used to create a id.
	* @id: int * value generated by this function.
	*
	* This function will populate @id with an unique
	* id, using the idr API.
	*
	* Return: 0 on success, an error code on failure.
	*/
	static int get_idr(struct idr idr, int id)
	{
	int ret;

	mutex_lock(&cooling_cpufreq_lock);
	ret = idr_alloc(idr, NULL, 0, 0, GFP_KERNEL);
	mutex_unlock(&cooling_cpufreq_lock);
	if (unlikely(ret < 0))
	return ret;
	*id = ret;

	return 0;
	}

	/**
	* release_idr - function to free the unique id.
	* @idr: struct idr * handle used for creating the id.
	* @id: int value representing the unique id.
	*/
	static void release_idr(struct idr *idr, int id)
	{
	mutex_lock(&cooling_cpufreq_lock);
	idr_remove(idr, id);
	mutex_unlock(&cooling_cpufreq_lock);
	}

	/* Below code defines functions to be used for cpufreq as cooling device */

	/**
	* is_cpufreq_valid - function to check frequency transitioning capability.
	* @cpu: cpu for which check is needed.
	*
	* This function will check the current state of the system if
	* it is capable of changing the frequency for a given @cpu.
	*
	* Return: 0 if the system is not currently capable of changing
	* the frequency of given cpu. !0 in case the frequency is changeable.
	*/
	static int is_cpufreq_valid(int cpu)
	{
	struct cpufreq_policy policy;

	return !cpufreq_get_policy(&policy, cpu);
	}

	enum cpufreq_cooling_property {
	GET_LEVEL,
	GET_FREQ,
	GET_MAXL,
	};

	/**
	* get_property - fetch a property of interest for a give cpu.
	* @cpu: cpu for which the property is required
	* @input: query parameter
	* @output: query return
	* @property: type of query (frequency, level, max level)
	*
	* This is the common function to
	* 1. get maximum cpu cooling states
	* 2. translate frequency to cooling state
	* 3. translate cooling state to frequency
	* Note that the code may be not in good shape
	* but it is written in this way in order to:
	* a) reduce duplicate code as most of the code can be shared.
	* b) make sure the logic is consistent when translating between
	* cooling states and frequencies.
	*
	* Return: 0 on success, -EINVAL when invalid parameters are passed.
	*/
	static int get_property(unsigned int cpu, unsigned long input,
	unsigned int *output,
	enum cpufreq_cooling_property property)
	{
	int i, j;
	unsigned long max_level = 0, level = 0;
	unsigned int freq = CPUFREQ_ENTRY_INVALID;
	int descend = -1;
	struct cpufreq_frequency_table *table =
	cpufreq_frequency_get_table(cpu);

	if (!output)
	return -EINVAL;

	if (!table)
	return -EINVAL;

	for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
	/* ignore invalid entries */
	if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
	continue;

	/* ignore duplicate entry */
	if (freq == table[i].frequency)
	continue;

	/* get the frequency order */
	if (freq != CPUFREQ_ENTRY_INVALID && descend == -1)
	descend = !!(freq > table[i].frequency);

	freq = table[i].frequency;
	max_level++;
	}

	/* No valid cpu frequency entry */
	if (max_level == 0)
	return -EINVAL;

	/* max_level is an index, not a counter */
	max_level--;

	/* get max level */
	if (property == GET_MAXL) {
	*output = (unsigned int)max_level;
	return 0;
	}

	if (property == GET_FREQ)
	level = descend ? input : (max_level - input);

	for (i = 0, j = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
	/* ignore invalid entry */
	if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
	continue;

	/* ignore duplicate entry */
	if (freq == table[i].frequency)
	continue;

	/* now we have a valid frequency entry */
	freq = table[i].frequency;

	if (property == GET_LEVEL && (unsigned int)input == freq) {
	/* get level by frequency */
	*output = descend ? j : (max_level - j);
	return 0;
	}
	if (property == GET_FREQ && level == j) {
	/* get frequency by level */
	*output = freq;
	return 0;
	}
	j++;
	}

	return -EINVAL;
	}

	/**
	* cpufreq_cooling_get_level - for a give cpu, return the cooling level.
	* @cpu: cpu for which the level is required
	* @freq: the frequency of interest
	*
	* This function will match the cooling level corresponding to the
	* requested @freq and return it.
	*
	* Return: The matched cooling level on success or THERMAL_CSTATE_INVALID
	* otherwise.
	*/
	unsigned long cpufreq_cooling_get_level(unsigned int cpu, unsigned int freq)
	{
	unsigned int val;

	if (get_property(cpu, (unsigned long)freq, &val, GET_LEVEL))
	return THERMAL_CSTATE_INVALID;

	return (unsigned long)val;
	}
	EXPORT_SYMBOL_GPL(cpufreq_cooling_get_level);

	/**
	* get_cpu_frequency - get the absolute value of frequency from level.
	* @cpu: cpu for which frequency is fetched.
	* @level: cooling level
	*
	* This function matches cooling level with frequency. Based on a cooling level
	* of frequency, equals cooling state of cpu cooling device, it will return
	* the corresponding frequency.
	* e.g level=0 --> 1st MAX FREQ, level=1 ---> 2nd MAX FREQ, .... etc
	*
	* Return: 0 on error, the corresponding frequency otherwise.
	*/
	static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
	{
	int ret = 0;
	unsigned int freq;

	ret = get_property(cpu, level, &freq, GET_FREQ);
	if (ret)
	return 0;

	return freq;
	}

	/**
	* cpufreq_apply_cooling - function to apply frequency clipping.
	* @cpufreq_device: cpufreq_cooling_device pointer containing frequency
	* clipping data.
	* @cooling_state: value of the cooling state.
	*
	* Function used to make sure the cpufreq layer is aware of current thermal
	* limits. The limits are applied by updating the cpufreq policy.
	*
	* Return: 0 on success, an error code otherwise (-EINVAL in case wrong
	* cooling state).
	*/
	static int cpufreq_apply_cooling(struct cpufreq_cooling_device *cpufreq_device,
	unsigned long cooling_state)
	{
	unsigned int cpuid, clip_freq;
	struct cpumask *mask = &cpufreq_device->allowed_cpus;
	unsigned int cpu = cpumask_any(mask);


	/* Check if the old cooling action is same as new cooling action */
	if (cpufreq_device->cpufreq_state == cooling_state)
	return 0;

	clip_freq = get_cpu_frequency(cpu, cooling_state);
	if (!clip_freq)
	return -EINVAL;

	cpufreq_device->cpufreq_state = cooling_state;
	cpufreq_device->cpufreq_val = clip_freq;
	notify_device = cpufreq_device;

	for_each_cpu(cpuid, mask) {
	if (is_cpufreq_valid(cpuid))
	cpufreq_update_policy(cpuid);
	}

	notify_device = NOTIFY_INVALID;

	return 0;
	}

	/**
	* cpufreq_thermal_notifier - notifier callback for cpufreq policy change.
	* @nb: struct notifier_block * with callback info.
	* @event: value showing cpufreq event for which this function invoked.
	* @data: callback-specific data
	*
	* Callback to highjack the notification on cpufreq policy transition.
	* Every time there is a change in policy, we will intercept and
	* update the cpufreq policy with thermal constraints.
	*
	* Return: 0 (success)
	*/
	static int cpufreq_thermal_notifier(struct notifier_block *nb,
	unsigned long event, void *data)
	{
	struct cpufreq_policy *policy = data;
	unsigned long max_freq = 0;

	if (event != CPUFREQ_ADJUST \|\| notify_device == NOTIFY_INVALID)
	return 0;

	if (cpumask_test_cpu(policy->cpu, &notify_device->allowed_cpus))
	max_freq = notify_device->cpufreq_val;
	else
	return 0;

	/* Never exceed user_policy.max */
	if (max_freq > policy->user_policy.max)
	max_freq = policy->user_policy.max;

	if (policy->max != max_freq)
	cpufreq_verify_within_limits(policy, 0, max_freq);

	return 0;
	}

	/* cpufreq cooling device callback functions are defined below */

	/**
	* cpufreq_get_max_state - callback function to get the max cooling state.
	* @cdev: thermal cooling device pointer.
	* @state: fill this variable with the max cooling state.
	*
	* Callback for the thermal cooling device to return the cpufreq
	* max cooling state.
	*
	* Return: 0 on success, an error code otherwise.
	*/
	static int cpufreq_get_max_state(struct thermal_cooling_device *cdev,
	unsigned long *state)
	{
	struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;
	struct cpumask *mask = &cpufreq_device->allowed_cpus;
	unsigned int cpu;
	unsigned int count = 0;
	int ret;

	cpu = cpumask_any(mask);

	ret = get_property(cpu, 0, &count, GET_MAXL);

	if (count > 0)
	*state = count;

	return ret;
	}

	/**
	* cpufreq_get_cur_state - callback function to get the current cooling state.
	* @cdev: thermal cooling device pointer.
	* @state: fill this variable with the current cooling state.
	*
	* Callback for the thermal cooling device to return the cpufreq
	* current cooling state.
	*
	* Return: 0 on success, an error code otherwise.
	*/
	static int cpufreq_get_cur_state(struct thermal_cooling_device *cdev,
	unsigned long *state)
	{
	struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;

	*state = cpufreq_device->cpufreq_state;

	return 0;
	}

	/**
	* cpufreq_set_cur_state - callback function to set the current cooling state.
	* @cdev: thermal cooling device pointer.
	* @state: set this variable to the current cooling state.
	*
	* Callback for the thermal cooling device to change the cpufreq
	* current cooling state.
	*
	* Return: 0 on success, an error code otherwise.
	*/
	static int cpufreq_set_cur_state(struct thermal_cooling_device *cdev,
	unsigned long state)
	{
	struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;

	return cpufreq_apply_cooling(cpufreq_device, state);
	}

	/* Bind cpufreq callbacks to thermal cooling device ops */
	static struct thermal_cooling_device_ops const cpufreq_cooling_ops = {
	.get_max_state = cpufreq_get_max_state,
	.get_cur_state = cpufreq_get_cur_state,
	.set_cur_state = cpufreq_set_cur_state,
	};

	/* Notifier for cpufreq policy change */
	static struct notifier_block thermal_cpufreq_notifier_block = {
	.notifier_call = cpufreq_thermal_notifier,
	};

	/**
	* __cpufreq_cooling_register - helper function to create cpufreq cooling device
	* @np: a valid struct device_node to the cooling device device tree node
	* @clip_cpus: cpumask of cpus where the frequency constraints will happen.
	*
	* This interface function registers the cpufreq cooling device with the name
	* "thermal-cpufreq-%x". This api can support multiple instances of cpufreq
	* cooling devices. It also gives the opportunity to link the cooling device
	* with a device tree node, in order to bind it via the thermal DT code.
	*
	* Return: a valid struct thermal_cooling_device pointer on success,
	* on failure, it returns a corresponding ERR_PTR().
	*/
	static struct thermal_cooling_device *
	__cpufreq_cooling_register(struct device_node *np,
	const struct cpumask *clip_cpus)
	{
	struct thermal_cooling_device *cool_dev;
	struct cpufreq_cooling_device *cpufreq_dev = NULL;
	unsigned int min = 0, max = 0;
	char dev_name[THERMAL_NAME_LENGTH];
	int ret = 0, i;
	struct cpufreq_policy policy;

	/* Verify that all the clip cpus have same freq_min, freq_max limit */
	for_each_cpu(i, clip_cpus) {
	/* continue if cpufreq policy not found and not return error */
	if (!cpufreq_get_policy(&policy, i))
	continue;
	if (min == 0 && max == 0) {
	min = policy.cpuinfo.min_freq;
	max = policy.cpuinfo.max_freq;
	} else {
	if (min != policy.cpuinfo.min_freq \|\|
	max != policy.cpuinfo.max_freq)
	return ERR_PTR(-EINVAL);
	}
	}
	cpufreq_dev = kzalloc(sizeof(struct cpufreq_cooling_device),
	GFP_KERNEL);
	if (!cpufreq_dev)
	return ERR_PTR(-ENOMEM);

	cpumask_copy(&cpufreq_dev->allowed_cpus, clip_cpus);

	ret = get_idr(&cpufreq_idr, &cpufreq_dev->id);
	if (ret) {
	kfree(cpufreq_dev);
	return ERR_PTR(-EINVAL);
	}

	snprintf(dev_name, sizeof(dev_name), "thermal-cpufreq-%d",
	cpufreq_dev->id);

	cool_dev = thermal_of_cooling_device_register(np, dev_name, cpufreq_dev,
	&cpufreq_cooling_ops);
	if (IS_ERR(cool_dev)) {
	release_idr(&cpufreq_idr, cpufreq_dev->id);
	kfree(cpufreq_dev);
	return cool_dev;
	}
	cpufreq_dev->cool_dev = cool_dev;
	cpufreq_dev->cpufreq_state = 0;
	mutex_lock(&cooling_cpufreq_lock);

	/* Register the notifier for first cpufreq cooling device */
	if (cpufreq_dev_count == 0)
	cpufreq_register_notifier(&thermal_cpufreq_notifier_block,
	CPUFREQ_POLICY_NOTIFIER);
	cpufreq_dev_count++;

	mutex_unlock(&cooling_cpufreq_lock);

	return cool_dev;
	}

	/**
	* cpufreq_cooling_register - function to create cpufreq cooling device.
	* @clip_cpus: cpumask of cpus where the frequency constraints will happen.
	*
	* This interface function registers the cpufreq cooling device with the name
	* "thermal-cpufreq-%x". This api can support multiple instances of cpufreq
	* cooling devices.
	*
	* Return: a valid struct thermal_cooling_device pointer on success,
	* on failure, it returns a corresponding ERR_PTR().
	*/
	struct thermal_cooling_device *
	cpufreq_cooling_register(const struct cpumask *clip_cpus)
	{
	return __cpufreq_cooling_register(NULL, clip_cpus);
	}
	EXPORT_SYMBOL_GPL(cpufreq_cooling_register);

	/**
	* of_cpufreq_cooling_register - function to create cpufreq cooling device.
	* @np: a valid struct device_node to the cooling device device tree node
	* @clip_cpus: cpumask of cpus where the frequency constraints will happen.
	*
	* This interface function registers the cpufreq cooling device with the name
	* "thermal-cpufreq-%x". This api can support multiple instances of cpufreq
	* cooling devices. Using this API, the cpufreq cooling device will be
	* linked to the device tree node provided.
	*
	* Return: a valid struct thermal_cooling_device pointer on success,
	* on failure, it returns a corresponding ERR_PTR().
	*/
	struct thermal_cooling_device *
	of_cpufreq_cooling_register(struct device_node *np,
	const struct cpumask *clip_cpus)
	{
	if (!np)
	return ERR_PTR(-EINVAL);

	return __cpufreq_cooling_register(np, clip_cpus);
	}
	EXPORT_SYMBOL_GPL(of_cpufreq_cooling_register);

	/**
	* cpufreq_cooling_unregister - function to remove cpufreq cooling device.
	* @cdev: thermal cooling device pointer.
	*
	* This interface function unregisters the "thermal-cpufreq-%x" cooling device.
	*/
	void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
	{
	struct cpufreq_cooling_device *cpufreq_dev;

	if (!cdev)
	return;

	cpufreq_dev = cdev->devdata;
	mutex_lock(&cooling_cpufreq_lock);
	cpufreq_dev_count--;

	/* Unregister the notifier for the last cpufreq cooling device */
	if (cpufreq_dev_count == 0)
	cpufreq_unregister_notifier(&thermal_cpufreq_notifier_block,
	CPUFREQ_POLICY_NOTIFIER);
	mutex_unlock(&cooling_cpufreq_lock);

	thermal_cooling_device_unregister(cpufreq_dev->cool_dev);
	release_idr(&cpufreq_idr, cpufreq_dev->id);
	kfree(cpufreq_dev);
	}
	EXPORT_SYMBOL_GPL(cpufreq_cooling_unregister);