/*
 *  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++;
        }

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

        if (property == GET_FREQ)
                level = descend ? input : (max_level - input - 1);

        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 - 1);
                        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;

        /* 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 - 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)
{
        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_cooling_device_register(dev_name, cpufreq_dev,
                                                   &cpufreq_cooling_ops);
        if (!cool_dev) {
                release_idr(&cpufreq_idr, cpufreq_dev->id);
                kfree(cpufreq_dev);
                return ERR_PTR(-EINVAL);
        }
        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;
}
EXPORT_SYMBOL_GPL(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 = 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);