1. 根目录:
2. drivers
3. thermal
4. cpu_cooling.c

/*
 *  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;
	struct list_head node;
};
static DEFINE_IDR(cpufreq_idr);
static DEFINE_MUTEX(cooling_cpufreq_lock);

static unsigned int cpufreq_dev_count;

static LIST_HEAD(cpufreq_dev_list);

/**
 * 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;
	unsigned long max_level = 0, level = 0;
	unsigned int freq = CPUFREQ_ENTRY_INVALID;
	int descend = -1;
	struct cpufreq_frequency_table *pos, *table =
					cpufreq_frequency_get_table(cpu);

	if (!output)
		return -EINVAL;

	if (!table)
		return -EINVAL;

	cpufreq_for_each_valid_entry(pos, table) {
		/* ignore duplicate entry */
		if (freq == pos->frequency)
			continue;

		/* get the frequency order */
		if (freq != CPUFREQ_ENTRY_INVALID && descend == -1)
			descend = freq > pos->frequency;

		freq = pos->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);

	i = 0;
	cpufreq_for_each_valid_entry(pos, table) {
		/* ignore duplicate entry */
		if (freq == pos->frequency)
			continue;

		/* now we have a valid frequency entry */
		freq = pos->frequency;

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

	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;

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

	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 hijack 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;
	struct cpufreq_cooling_device *cpufreq_dev;

	if (event != CPUFREQ_ADJUST)
		return 0;

	mutex_lock(&cooling_cpufreq_lock);
	list_for_each_entry(cpufreq_dev, &cpufreq_dev_list, node) {
		if (!cpumask_test_cpu(policy->cpu,
					&cpufreq_dev->allowed_cpus))
			continue;

		if (!cpufreq_dev->cpufreq_val)
			cpufreq_dev->cpufreq_val = get_cpu_frequency(
					cpumask_any(&cpufreq_dev->allowed_cpus),
					cpufreq_dev->cpufreq_state);

		max_freq = cpufreq_dev->cpufreq_val;

		if (policy->max != max_freq)
			cpufreq_verify_within_limits(policy, 0, max_freq);
	}
	mutex_unlock(&cooling_cpufreq_lock);

	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++;
	list_add(&cpufreq_dev->node, &cpufreq_dev_list);

	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);
	list_del(&cpufreq_dev->node);
	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);