/*
 *  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/kernel.h>
#include <linux/module.h>
#include <linux/thermal.h>
#include <linux/platform_device.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
 * @id: unique integer value corresponding to each cpufreq_cooling_device
 *      registered.
 * @cool_dev: thermal_cooling_device pointer to keep track of the the
 *      egistered 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.
 * @node: list_head to link all cpufreq_cooling_device together.
 *
 * This structure is required for keeping information of each
 * cpufreq_cooling_device registered as a list whose head is represented by
 * cooling_cpufreq_list. In order to prevent corruption of this list 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 LIST_HEAD(cooling_cpufreq_list);
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.
 */
static int get_idr(struct idr *idr, int *id)
{
        int err;
again:
        if (unlikely(idr_pre_get(idr, GFP_KERNEL) == 0))
                return -ENOMEM;

        mutex_lock(&cooling_cpufreq_lock);
        err = idr_get_new(idr, NULL, id);
        mutex_unlock(&cooling_cpufreq_lock);

        if (unlikely(err == -EAGAIN))
                goto again;
        else if (unlikely(err))
                return err;

        *id = *id & MAX_IDR_MASK;
        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 if a cpu has frequency transition policy.
 * @cpu: cpu for which check is needed.
 */
static int is_cpufreq_valid(int cpu)
{
        struct cpufreq_policy policy;
        return !cpufreq_get_policy(&policy, cpu);
}

/**
 * get_cpu_frequency - get the absolute value of frequency from level.
 * @cpu: cpu for which frequency is fetched.
 * @level: level of frequency of the CPU
 *      e.g level=1 --> 1st MAX FREQ, LEVEL=2 ---> 2nd MAX FREQ, .... etc
 */
static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
{
        int ret = 0, i = 0;
        unsigned long level_index;
        bool descend = false;
        struct cpufreq_frequency_table *table =
                                        cpufreq_frequency_get_table(cpu);
        if (!table)
                return ret;

        while (table[i].frequency != CPUFREQ_TABLE_END) {
                if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
                        continue;

                /*check if table in ascending or descending order*/
                if ((table[i + 1].frequency != CPUFREQ_TABLE_END) &&
                        (table[i + 1].frequency < table[i].frequency)
                        && !descend) {
                        descend = true;
                }

                /*return if level matched and table in descending order*/
                if (descend && i == level)
                        return table[i].frequency;
                i++;
        }
        i--;

        if (level > i || descend)
                return ret;
        level_index = i - level;

        /*Scan the table in reverse order and match the level*/
        while (i >= 0) {
                if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
                        continue;
                /*return if level matched*/
                if (i == level_index)
                        return table[i].frequency;
                i--;
        }
        return ret;
}

/**
 * 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.
 */
static int cpufreq_apply_cooling(struct cpufreq_cooling_device *cpufreq_device,
                                unsigned long cooling_state)
{
        unsigned int cpuid, clip_freq;
        struct cpumask *maskPtr = &cpufreq_device->allowed_cpus;
        unsigned int cpu = cpumask_any(maskPtr);


        /* 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, maskPtr) {
                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
 */
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.
 */
static int cpufreq_get_max_state(struct thermal_cooling_device *cdev,
                                 unsigned long *state)
{
        struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;
        struct cpumask *maskPtr = &cpufreq_device->allowed_cpus;
        unsigned int cpu;
        struct cpufreq_frequency_table *table;
        unsigned long count = 0;
        int i = 0;

        cpu = cpumask_any(maskPtr);
        table = cpufreq_frequency_get_table(cpu);
        if (!table) {
                *state = 0;
                return 0;
        }

        for (i = 0; (table[i].frequency != CPUFREQ_TABLE_END); i++) {
                if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
                        continue;
                count++;
        }

        if (count > 0) {
                *state = --count;
                return 0;
        }

        return -EINVAL;
}

/**
 * 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.
 */
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.
 */
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.
 */
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);
        }

        sprintf(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(cpufreq_cooling_register);

/**
 * cpufreq_cooling_unregister - function to remove cpufreq cooling device.
 * @cdev: thermal cooling device pointer.
 */
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(cpufreq_cooling_unregister);