devfreq.c

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/*
 * devfreq: Generic Dynamic Voltage and Frequency Scaling (DVFS) Framework
 *      for Non-CPU Devices.
 *
 * Copyright (C) 2011 Samsung Electronics
 *  MyungJoo Ham <[email protected]>
 *
 * 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/module.h>
#include <linux/slab.h>
#include <linux/stat.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);

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);
}

int update_devfreq(struct devfreq *devfreq)
{
    unsigned long freq;
    int err = 0;
    u32 flags = 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;

    /*
     * Adjust the freuqency with user freq and QoS.
     *
     * List from the highest proiority
     * max_freq (probably called by thermal when it's too hot)
     * min_freq
     */

    if (devfreq->min_freq && freq < devfreq->min_freq) {
        freq = devfreq->min_freq;
        flags &= ~DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use GLB */
    }
    if (devfreq->max_freq && freq > devfreq->max_freq) {
        freq = devfreq->max_freq;
        flags |= DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use LUB */
    }

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

    devfreq->previous_freq = freq;
    return err;
}

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;
}

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);
}

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);
}

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;
    }
}

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 err_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 err_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);
out:
    return devfreq;

err_init:
    device_unregister(&devfreq->dev);
err_dev:
    mutex_unlock(&devfreq->lock);
    kfree(devfreq);
err_out:
    return ERR_PTR(err);
}

int devfreq_remove_device(struct devfreq *devfreq)
{
    bool central_polling;

    if (!devfreq)
        return -EINVAL;

    central_polling = !devfreq->governor->no_central_polling;

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

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

    mutex_lock(&df->lock);
    max = df->max_freq;
    if (value && max && value > max) {
        ret = -EINVAL;
        goto unlock;
    }

    df->min_freq = value;
    update_devfreq(df);
    ret = count;
unlock:
    mutex_unlock(&df->lock);
out:
    return ret;
}

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

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

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

    mutex_lock(&df->lock);
    min = df->min_freq;
    if (value && min && value < min) {
        ret = -EINVAL;
        goto unlock;
    }

    df->max_freq = value;
    update_devfreq(df);
    ret = count;
unlock:
    mutex_unlock(&df->lock);
out:
    return ret;
}

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

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),
    __ATTR(min_freq, S_IRUGO | S_IWUSR, show_min_freq, store_min_freq),
    __ATTR(max_freq, S_IRUGO | S_IWUSR, show_max_freq, store_max_freq),
    { },
};

static int __init devfreq_start_polling(void)
{
    mutex_lock(&devfreq_list_lock);
    polling = false;
    devfreq_wq = create_freezable_workqueue("devfreq_wq");
    INIT_DEFERRABLE_WORK(&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.
 */

struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq,
                    u32 flags)
{
    struct opp *opp;

    if (flags & DEVFREQ_FLAG_LEAST_UPPER_BOUND) {
        /* The freq is an upper bound. opp should be lower */
        opp = opp_find_freq_floor(dev, freq);

        /* If not available, use the closest opp */
        if (opp == ERR_PTR(-ENODEV))
            opp = opp_find_freq_ceil(dev, freq);
    } else {
        /* The freq is an lower bound. opp should be higher */
        opp = opp_find_freq_ceil(dev, freq);

        /* If not available, use the closest opp */
        if (opp == ERR_PTR(-ENODEV))
            opp = opp_find_freq_floor(dev, freq);
    }

    return opp;
}

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);
}

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 <[email protected]>");
MODULE_DESCRIPTION("devfreq class support");
MODULE_LICENSE("GPL");