xref: /device/soc/rockchip/common/sdk_linux/drivers/devfreq/devfreq.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * devfreq: Generic Dynamic Voltage and Frequency Scaling (DVFS) Framework
 *        for Non-CPU Devices.
 *
 * Copyright (C) 2011 Samsung Electronics
 *    MyungJoo Ham <myungjoo.ham@samsung.com>
 */

#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/sched.h>
#include <linux/debugfs.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/pm_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 <linux/of.h>
#include <linux/pm_qos.h>
#include "governor.h"

#define CREATE_TRACE_POINTS
#include <trace/events/devfreq.h>

#define HZ_PER_KHZ 1000

static struct class *devfreq_class;
static struct dentry *devfreq_debugfs;

/*
 * devfreq core provides delayed work based load monitoring helper
 * functions. Governors can use these or can implement their own
 * monitoring mechanism.
 */
static struct workqueue_struct *devfreq_wq;

/* The list of all device-devfreq governors */
static LIST_HEAD(devfreq_governor_list);
/* The list of all device-devfreq */
static LIST_HEAD(devfreq_list);
static DEFINE_MUTEX(devfreq_list_lock);

static const char timer_name[][DEVFREQ_NAME_LEN] = {
    [DEVFREQ_TIMER_DEFERRABLE] = {"deferrable"},
    [DEVFREQ_TIMER_DELAYED] = {"delayed"},
};

/**
 * find_device_devfreq() - find devfreq struct using device pointer
 * @dev:    device pointer used to lookup device devfreq.
 *
 * Search the list of device devfreqs and return the matched device's
 * devfreq info. devfreq_list_lock should be held by the caller.
 */
static struct devfreq *find_device_devfreq(struct device *dev)
{
    struct devfreq *tmp_devfreq;

    lockdep_assert_held(&devfreq_list_lock);

    if (IS_ERR_OR_NULL(dev)) {
        pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
        return ERR_PTR(-EINVAL);
    }

    list_for_each_entry(tmp_devfreq, &devfreq_list, node)
    {
        if (tmp_devfreq->dev.parent == dev) {
            return tmp_devfreq;
        }
    }

    return ERR_PTR(-ENODEV);
}

static unsigned long find_available_min_freq(struct devfreq *devfreq)
{
    struct dev_pm_opp *opp;
    unsigned long min_freq = 0;

    opp = dev_pm_opp_find_freq_ceil(devfreq->dev.parent, &min_freq);
    if (IS_ERR(opp)) {
        min_freq = 0;
    } else {
        dev_pm_opp_put(opp);
    }

    return min_freq;
}

static unsigned long find_available_max_freq(struct devfreq *devfreq)
{
    struct dev_pm_opp *opp;
    unsigned long max_freq = ULONG_MAX;

    opp = dev_pm_opp_find_freq_floor(devfreq->dev.parent, &max_freq);
    if (IS_ERR(opp)) {
        max_freq = 0;
    } else {
        dev_pm_opp_put(opp);
    }

    return max_freq;
}

/**
 * get_freq_range() - Get the current freq range
 * @devfreq:    the devfreq instance
 * @min_freq:    the min frequency
 * @max_freq:    the max frequency
 *
 * This takes into consideration all constraints.
 */
static void get_freq_range(struct devfreq *devfreq, unsigned long *min_freq, unsigned long *max_freq)
{
    unsigned long *freq_table = devfreq->profile->freq_table;
    s32 qos_min_freq, qos_max_freq;

    lockdep_assert_held(&devfreq->lock);

    /*
     * Initialize minimum/maximum frequency from freq table.
     * The devfreq drivers can initialize this in either ascending or
     * descending order and devfreq core supports both.
     */
    if (freq_table[0] < freq_table[devfreq->profile->max_state - 1]) {
        *min_freq = freq_table[0];
        *max_freq = freq_table[devfreq->profile->max_state - 1];
    } else {
        *min_freq = freq_table[devfreq->profile->max_state - 1];
        *max_freq = freq_table[0];
    }

    /* Apply constraints from PM QoS */
    qos_min_freq = dev_pm_qos_read_value(devfreq->dev.parent, DEV_PM_QOS_MIN_FREQUENCY);
    qos_max_freq = dev_pm_qos_read_value(devfreq->dev.parent, DEV_PM_QOS_MAX_FREQUENCY);
    *min_freq = max(*min_freq, (unsigned long)HZ_PER_KHZ * qos_min_freq);
    if (qos_max_freq != PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE) {
        *max_freq = min(*max_freq, (unsigned long)HZ_PER_KHZ * qos_max_freq);
    }

    /* Apply constraints from OPP interface */
    *min_freq = max(*min_freq, devfreq->scaling_min_freq);
    *max_freq = min(*max_freq, devfreq->scaling_max_freq);

    if (*min_freq > *max_freq) {
        *min_freq = *max_freq;
    }
}

/**
 * devfreq_get_freq_level() - Lookup freq_table for the frequency
 * @devfreq:    the devfreq instance
 * @freq:    the target frequency
 */
static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
{
    int lev;

    for (lev = 0; lev < devfreq->profile->max_state; lev++) {
        if (freq == devfreq->profile->freq_table[lev]) {
            return lev;
        }
    }

    return -EINVAL;
}

static int set_freq_table(struct devfreq *devfreq)
{
    struct devfreq_dev_profile *profile = devfreq->profile;
    struct dev_pm_opp *opp;
    unsigned long freq;
    int i, count;

    /* Initialize the freq_table from OPP table */
    count = dev_pm_opp_get_opp_count(devfreq->dev.parent);
    if (count <= 0) {
        return -EINVAL;
    }

    profile->max_state = count;
    profile->freq_table =
        devm_kcalloc(devfreq->dev.parent, profile->max_state, sizeof(*profile->freq_table), GFP_KERNEL);
    if (!profile->freq_table) {
        profile->max_state = 0;
        return -ENOMEM;
    }

    for (i = 0, freq = 0; i < profile->max_state; i++, freq++) {
        opp = dev_pm_opp_find_freq_ceil(devfreq->dev.parent, &freq);
        if (IS_ERR(opp)) {
            devm_kfree(devfreq->dev.parent, profile->freq_table);
            profile->max_state = 0;
            return PTR_ERR(opp);
        }
        dev_pm_opp_put(opp);
        profile->freq_table[i] = freq;
    }

    return 0;
}

/**
 * devfreq_update_status() - Update statistics of devfreq behavior
 * @devfreq:    the devfreq instance
 * @freq:    the update target frequency
 */
int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
{
    int lev, prev_lev, ret = 0;
    u64 cur_time;

    lockdep_assert_held(&devfreq->lock);
    cur_time = get_jiffies_64();

    /* Immediately exit if previous_freq is not initialized yet. */
    if (!devfreq->previous_freq) {
        goto out;
    }

    prev_lev = devfreq_get_freq_level(devfreq, devfreq->previous_freq);
    if (prev_lev < 0) {
        ret = prev_lev;
        goto out;
    }

    devfreq->stats.time_in_state[prev_lev] += cur_time - devfreq->stats.last_update;

    lev = devfreq_get_freq_level(devfreq, freq);
    if (lev < 0) {
        ret = lev;
        goto out;
    }

    if (lev != prev_lev) {
        devfreq->stats.trans_table[(prev_lev * devfreq->profile->max_state) + lev]++;
        devfreq->stats.total_trans++;
    }

out:
    devfreq->stats.last_update = cur_time;
    return ret;
}
EXPORT_SYMBOL(devfreq_update_status);

/**
 * find_devfreq_governor() - find devfreq governor from name
 * @name:    name of the governor
 *
 * Search the list of devfreq governors and return the matched
 * governor's pointer. devfreq_list_lock should be held by the caller.
 */
static struct devfreq_governor *find_devfreq_governor(const char *name)
{
    struct devfreq_governor *tmp_governor;

    lockdep_assert_held(&devfreq_list_lock);

    if (IS_ERR_OR_NULL(name)) {
        pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
        return ERR_PTR(-EINVAL);
    }

    list_for_each_entry(tmp_governor, &devfreq_governor_list, node)
    {
        if (!strncmp(tmp_governor->name, name, DEVFREQ_NAME_LEN)) {
            return tmp_governor;
        }
    }

    return ERR_PTR(-ENODEV);
}

/**
 * try_then_request_governor() - Try to find the governor and request the
 *                               module if is not found.
 * @name:    name of the governor
 *
 * Search the list of devfreq governors and request the module and try again
 * if is not found. This can happen when both drivers (the governor driver
 * and the driver that call devfreq_add_device) are built as modules.
 * devfreq_list_lock should be held by the caller. Returns the matched
 * governor's pointer or an error pointer.
 */
static struct devfreq_governor *try_then_request_governor(const char *name)
{
    struct devfreq_governor *governor;
    int err = 0;

    lockdep_assert_held(&devfreq_list_lock);

    if (IS_ERR_OR_NULL(name)) {
        pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
        return ERR_PTR(-EINVAL);
    }

    governor = find_devfreq_governor(name);
    if (IS_ERR(governor)) {
        mutex_unlock(&devfreq_list_lock);

        if (!strncmp(name, DEVFREQ_GOV_SIMPLE_ONDEMAND, DEVFREQ_NAME_LEN)) {
            err = request_module("governor_%s", "simpleondemand");
        } else {
            err = request_module("governor_%s", name);
        }
        /* Restore previous state before return */
        mutex_lock(&devfreq_list_lock);
        if (err) {
            return (err < 0) ? ERR_PTR(err) : ERR_PTR(-EINVAL);
        }

        governor = find_devfreq_governor(name);
    }

    return governor;
}

static int devfreq_notify_transition(struct devfreq *devfreq, struct devfreq_freqs *freqs, unsigned int state)
{
    if (!devfreq) {
        return -EINVAL;
    }

    switch (state) {
        case DEVFREQ_PRECHANGE:
            srcu_notifier_call_chain(&devfreq->transition_notifier_list, DEVFREQ_PRECHANGE, freqs);
            break;

        case DEVFREQ_POSTCHANGE:
            srcu_notifier_call_chain(&devfreq->transition_notifier_list, DEVFREQ_POSTCHANGE, freqs);
            break;
        default:
            return -EINVAL;
    }

    return 0;
}

static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq, u32 flags)
{
    struct devfreq_freqs freqs;
    unsigned long cur_freq;
    int err = 0;

    if (devfreq->profile->get_cur_freq) {
        devfreq->profile->get_cur_freq(devfreq->dev.parent, &cur_freq);
    } else {
        cur_freq = devfreq->previous_freq;
    }

    freqs.old = cur_freq;
    freqs.new = new_freq;
    devfreq_notify_transition(devfreq, &freqs, DEVFREQ_PRECHANGE);

    err = devfreq->profile->target(devfreq->dev.parent, &new_freq, flags);
    if (err) {
        freqs.new = cur_freq;
        devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
        return err;
    }

    freqs.new = new_freq;
    devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);

    if (devfreq_update_status(devfreq, new_freq)) {
        dev_err(&devfreq->dev, "Couldn't update frequency transition information.\n");
    }

    devfreq->previous_freq = new_freq;

    if (devfreq->suspend_freq) {
        devfreq->resume_freq = new_freq;
    }

    return err;
}

/* Load monitoring helper functions for governors use */

/**
 * update_devfreq() - Reevaluate the device and configure frequency.
 * @devfreq:    the devfreq instance.
 *
 * Note: Lock devfreq->lock before calling update_devfreq
 *     This function is exported for governors.
 */
int update_devfreq(struct devfreq *devfreq)
{
    unsigned long freq, min_freq, max_freq;
    int err = 0;
    u32 flags = 0;

    lockdep_assert_held(&devfreq->lock);

    if (!devfreq->governor) {
        return -EINVAL;
    }

    /* Reevaluate the proper frequency */
    err = devfreq->governor->get_target_freq(devfreq, &freq);
    if (err) {
        return err;
    }
    get_freq_range(devfreq, &min_freq, &max_freq);

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

    return devfreq_set_target(devfreq, freq, flags);
}
EXPORT_SYMBOL(update_devfreq);

/**
 * devfreq_monitor() - Periodically poll devfreq objects.
 * @work:    the work struct used to run devfreq_monitor periodically.
 *
 */
static void devfreq_monitor(struct work_struct *work)
{
    int err;
    struct devfreq *devfreq = container_of(work, struct devfreq, work.work);

    mutex_lock(&devfreq->lock);
    err = update_devfreq(devfreq);
    if (err) {
        dev_err(&devfreq->dev, "dvfs failed with (%d) error\n", err);
    }

    queue_delayed_work(devfreq_wq, &devfreq->work, msecs_to_jiffies(devfreq->profile->polling_ms));
    mutex_unlock(&devfreq->lock);

    trace_devfreq_monitor(devfreq);
}

/**
 * devfreq_monitor_start() - Start load monitoring of devfreq instance
 * @devfreq:    the devfreq instance.
 *
 * Helper function for starting devfreq device load monitoring. By
 * default delayed work based monitoring is supported. Function
 * to be called from governor in response to DEVFREQ_GOV_START
 * event when device is added to devfreq framework.
 */
void devfreq_monitor_start(struct devfreq *devfreq)
{
    if (devfreq->governor->interrupt_driven) {
        return;
    }

    switch (devfreq->profile->timer) {
        case DEVFREQ_TIMER_DEFERRABLE:
            INIT_DEFERRABLE_WORK(&devfreq->work, devfreq_monitor);
            break;
        case DEVFREQ_TIMER_DELAYED:
            INIT_DELAYED_WORK(&devfreq->work, devfreq_monitor);
            break;
        default:
            return;
    }

    if (devfreq->profile->polling_ms) {
        queue_delayed_work(devfreq_wq, &devfreq->work, msecs_to_jiffies(devfreq->profile->polling_ms));
    }
}
EXPORT_SYMBOL(devfreq_monitor_start);

/**
 * devfreq_monitor_stop() - Stop load monitoring of a devfreq instance
 * @devfreq:    the devfreq instance.
 *
 * Helper function to stop devfreq device load monitoring. Function
 * to be called from governor in response to DEVFREQ_GOV_STOP
 * event when device is removed from devfreq framework.
 */
void devfreq_monitor_stop(struct devfreq *devfreq)
{
    if (devfreq->governor->interrupt_driven) {
        return;
    }

    cancel_delayed_work_sync(&devfreq->work);
}
EXPORT_SYMBOL(devfreq_monitor_stop);

/**
 * devfreq_monitor_suspend() - Suspend load monitoring of a devfreq instance
 * @devfreq:    the devfreq instance.
 *
 * Helper function to suspend devfreq device load monitoring. Function
 * to be called from governor in response to DEVFREQ_GOV_SUSPEND
 * event or when polling interval is set to zero.
 *
 * Note: Though this function is same as devfreq_monitor_stop(),
 * intentionally kept separate to provide hooks for collecting
 * transition statistics.
 */
void devfreq_monitor_suspend(struct devfreq *devfreq)
{
    mutex_lock(&devfreq->lock);
    if (devfreq->stop_polling) {
        mutex_unlock(&devfreq->lock);
        return;
    }

    devfreq_update_status(devfreq, devfreq->previous_freq);
    devfreq->stop_polling = true;
    mutex_unlock(&devfreq->lock);

    if (devfreq->governor->interrupt_driven) {
        return;
    }

    cancel_delayed_work_sync(&devfreq->work);
}
EXPORT_SYMBOL(devfreq_monitor_suspend);

/**
 * devfreq_monitor_resume() - Resume load monitoring of a devfreq instance
 * @devfreq:    the devfreq instance.
 *
 * Helper function to resume devfreq device load monitoring. Function
 * to be called from governor in response to DEVFREQ_GOV_RESUME
 * event or when polling interval is set to non-zero.
 */
void devfreq_monitor_resume(struct devfreq *devfreq)
{
    unsigned long freq;

    mutex_lock(&devfreq->lock);
    if (!devfreq->stop_polling) {
        goto out;
    }

    if (devfreq->governor->interrupt_driven) {
        goto out_update;
    }

    if (!delayed_work_pending(&devfreq->work) && devfreq->profile->polling_ms) {
        queue_delayed_work(devfreq_wq, &devfreq->work, msecs_to_jiffies(devfreq->profile->polling_ms));
    }

out_update:
    devfreq->stats.last_update = get_jiffies_64();
    devfreq->stop_polling = false;

    if (devfreq->profile->get_cur_freq && !devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq)) {
        devfreq->previous_freq = freq;
    }

out:
    mutex_unlock(&devfreq->lock);
}
EXPORT_SYMBOL(devfreq_monitor_resume);

/**
 * devfreq_update_interval() - Update device devfreq monitoring interval
 * @devfreq:    the devfreq instance.
 * @delay:      new polling interval to be set.
 *
 * Helper function to set new load monitoring polling interval. Function
 * to be called from governor in response to DEVFREQ_GOV_UPDATE_INTERVAL event.
 */
void devfreq_update_interval(struct devfreq *devfreq, unsigned int *delay)
{
    unsigned int cur_delay = devfreq->profile->polling_ms;
    unsigned int new_delay = *delay;

    mutex_lock(&devfreq->lock);
    devfreq->profile->polling_ms = new_delay;

    if (devfreq->stop_polling) {
        goto out;
    }

    if (devfreq->governor->interrupt_driven) {
        goto out;
    }

    /* if new delay is zero, stop polling */
    if (!new_delay) {
        mutex_unlock(&devfreq->lock);
        cancel_delayed_work_sync(&devfreq->work);
        return;
    }

    /* if current delay is zero, start polling with new delay */
    if (!cur_delay) {
        queue_delayed_work(devfreq_wq, &devfreq->work, msecs_to_jiffies(devfreq->profile->polling_ms));
        goto out;
    }

    /* if current delay is greater than new delay, restart polling */
    if (cur_delay > new_delay) {
        mutex_unlock(&devfreq->lock);
        cancel_delayed_work_sync(&devfreq->work);
        mutex_lock(&devfreq->lock);
        if (!devfreq->stop_polling) {
            queue_delayed_work(devfreq_wq, &devfreq->work, msecs_to_jiffies(devfreq->profile->polling_ms));
        }
    }
out:
    mutex_unlock(&devfreq->lock);
}
EXPORT_SYMBOL(devfreq_update_interval);

/**
 * devfreq_notifier_call() - Notify that the device frequency requirements
 *                 has been changed out of devfreq framework.
 * @nb:        the notifier_block (supposed to be devfreq->nb)
 * @type:    not used
 * @devp:    not used
 *
 * Called by a notifier that uses devfreq->nb.
 */
static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type, void *devp)
{
    struct devfreq *devfreq = container_of(nb, struct devfreq, nb);
    int err = -EINVAL;

    mutex_lock(&devfreq->lock);

    devfreq->scaling_min_freq = find_available_min_freq(devfreq);
    if (!devfreq->scaling_min_freq) {
        goto out;
    }

    devfreq->scaling_max_freq = find_available_max_freq(devfreq);
    if (!devfreq->scaling_max_freq) {
        devfreq->scaling_max_freq = ULONG_MAX;
        goto out;
    }

    err = update_devfreq(devfreq);

out:
    mutex_unlock(&devfreq->lock);
    if (err) {
        dev_err(devfreq->dev.parent, "failed to update frequency from OPP notifier (%d)\n", err);
    }

    return NOTIFY_OK;
}

/**
 * qos_notifier_call() - Common handler for QoS constraints.
 * @devfreq:    the devfreq instance.
 */
static int qos_notifier_call(struct devfreq *devfreq)
{
    int err;

    mutex_lock(&devfreq->lock);
    err = update_devfreq(devfreq);
    mutex_unlock(&devfreq->lock);
    if (err) {
        dev_err(devfreq->dev.parent, "failed to update frequency from PM QoS (%d)\n", err);
    }

    return NOTIFY_OK;
}

/**
 * qos_min_notifier_call() - Callback for QoS min_freq changes.
 * @nb:        Should be devfreq->nb_min
 */
static int qos_min_notifier_call(struct notifier_block *nb, unsigned long val, void *ptr)
{
    return qos_notifier_call(container_of(nb, struct devfreq, nb_min));
}

/**
 * qos_max_notifier_call() - Callback for QoS max_freq changes.
 * @nb:        Should be devfreq->nb_max
 */
static int qos_max_notifier_call(struct notifier_block *nb, unsigned long val, void *ptr)
{
    return qos_notifier_call(container_of(nb, struct devfreq, nb_max));
}

/**
 * devfreq_dev_release() - Callback for struct device to release the device.
 * @dev:    the devfreq device
 *
 * Remove devfreq from the list and release its resources.
 */
static void devfreq_dev_release(struct device *dev)
{
    struct devfreq *devfreq = to_devfreq(dev);
    int err;

    mutex_lock(&devfreq_list_lock);
    list_del(&devfreq->node);
    mutex_unlock(&devfreq_list_lock);

    err = dev_pm_qos_remove_notifier(devfreq->dev.parent, &devfreq->nb_max, DEV_PM_QOS_MAX_FREQUENCY);
    if (err && err != -ENOENT) {
        dev_warn(dev->parent, "Failed to remove max_freq notifier: %d\n", err);
    }
    err = dev_pm_qos_remove_notifier(devfreq->dev.parent, &devfreq->nb_min, DEV_PM_QOS_MIN_FREQUENCY);
    if (err && err != -ENOENT) {
        dev_warn(dev->parent, "Failed to remove min_freq notifier: %d\n", err);
    }

    if (dev_pm_qos_request_active(&devfreq->user_max_freq_req)) {
        err = dev_pm_qos_remove_request(&devfreq->user_max_freq_req);
        if (err < 0) {
            dev_warn(dev->parent, "Failed to remove max_freq request: %d\n", err);
        }
    }
    if (dev_pm_qos_request_active(&devfreq->user_min_freq_req)) {
        err = dev_pm_qos_remove_request(&devfreq->user_min_freq_req);
        if (err < 0) {
            dev_warn(dev->parent, "Failed to remove min_freq request: %d\n", err);
        }
    }

    if (devfreq->profile->exit) {
        devfreq->profile->exit(devfreq->dev.parent);
    }

    mutex_destroy(&devfreq->lock);
    kfree(devfreq);
}

/**
 * devfreq_remove_device() - Remove devfreq feature from a device.
 * @devfreq:    the devfreq instance to be removed
 *
 * The opposite of devfreq_add_device().
 */
int devfreq_remove_device(struct devfreq *devfreq)
{
    if (!devfreq) {
        return -EINVAL;
    }

    if (devfreq->governor) {
        devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_STOP, NULL);
    }
    device_unregister(&devfreq->dev);

    return 0;
}
EXPORT_SYMBOL(devfreq_remove_device);

/**
 * devfreq_add_device() - Add devfreq feature to the device
 * @dev:    the device to add devfreq feature.
 * @profile:    device-specific profile to run devfreq.
 * @governor_name:    name of the policy to choose frequency.
 * @data:    private data for the governor. The devfreq framework does not
 *        touch this value.
 */
struct devfreq *devfreq_add_device(struct device *dev, struct devfreq_dev_profile *profile, const char *governor_name,
                                   void *data)
{
    struct devfreq *devfreq;
    struct devfreq_governor *governor;
    int err = 0;

    if (!dev || !profile || !governor_name) {
        dev_err(dev, "%s: Invalid parameters.\n", __func__);
        return ERR_PTR(-EINVAL);
    }

    mutex_lock(&devfreq_list_lock);
    devfreq = find_device_devfreq(dev);
    mutex_unlock(&devfreq_list_lock);
    if (!IS_ERR(devfreq)) {
        dev_err(dev, "%s: devfreq device already exists!\n", __func__);
        err = -EINVAL;
        goto err_out;
    }

    devfreq = kzalloc(sizeof(struct devfreq), GFP_KERNEL);
    if (!devfreq) {
        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;
    INIT_LIST_HEAD(&devfreq->node);
    devfreq->profile = profile;
    strscpy(devfreq->governor_name, governor_name, DEVFREQ_NAME_LEN);
    devfreq->previous_freq = profile->initial_freq;
    devfreq->last_status.current_frequency = profile->initial_freq;
    devfreq->data = data;
    devfreq->nb.notifier_call = devfreq_notifier_call;

    if (devfreq->profile->timer < 0 || devfreq->profile->timer >= DEVFREQ_TIMER_NUM) {
        mutex_unlock(&devfreq->lock);
        err = -EINVAL;
        goto err_dev;
    }

    if (!devfreq->profile->max_state && !devfreq->profile->freq_table) {
        mutex_unlock(&devfreq->lock);
        err = set_freq_table(devfreq);
        if (err < 0) {
            goto err_dev;
        }
        mutex_lock(&devfreq->lock);
    }

    devfreq->scaling_min_freq = find_available_min_freq(devfreq);
    if (!devfreq->scaling_min_freq) {
        mutex_unlock(&devfreq->lock);
        err = -EINVAL;
        goto err_dev;
    }

    devfreq->scaling_max_freq = find_available_max_freq(devfreq);
    if (!devfreq->scaling_max_freq) {
        mutex_unlock(&devfreq->lock);
        err = -EINVAL;
        goto err_dev;
    }

    devfreq->suspend_freq = dev_pm_opp_get_suspend_opp_freq(dev);
    atomic_set(&devfreq->suspend_count, 0);

    dev_set_name(&devfreq->dev, "%s", dev_name(dev));
    err = device_register(&devfreq->dev);
    if (err) {
        mutex_unlock(&devfreq->lock);
        put_device(&devfreq->dev);
        goto err_out;
    }

    devfreq->stats.trans_table = devm_kzalloc(
        &devfreq->dev, array3_size(sizeof(unsigned int), devfreq->profile->max_state, devfreq->profile->max_state),
        GFP_KERNEL);
    if (!devfreq->stats.trans_table) {
        mutex_unlock(&devfreq->lock);
        err = -ENOMEM;
        goto err_devfreq;
    }

    devfreq->stats.time_in_state =
        devm_kcalloc(&devfreq->dev, devfreq->profile->max_state, sizeof(*devfreq->stats.time_in_state), GFP_KERNEL);
    if (!devfreq->stats.time_in_state) {
        mutex_unlock(&devfreq->lock);
        err = -ENOMEM;
        goto err_devfreq;
    }

    devfreq->stats.total_trans = 0;
    devfreq->stats.last_update = get_jiffies_64();

    srcu_init_notifier_head(&devfreq->transition_notifier_list);

    mutex_unlock(&devfreq->lock);

    err = dev_pm_qos_add_request(dev, &devfreq->user_min_freq_req, DEV_PM_QOS_MIN_FREQUENCY, 0);
    if (err < 0) {
        goto err_devfreq;
    }
    err = dev_pm_qos_add_request(dev, &devfreq->user_max_freq_req, DEV_PM_QOS_MAX_FREQUENCY,
                                 PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE);
    if (err < 0) {
        goto err_devfreq;
    }

    devfreq->nb_min.notifier_call = qos_min_notifier_call;
    err = dev_pm_qos_add_notifier(devfreq->dev.parent, &devfreq->nb_min, DEV_PM_QOS_MIN_FREQUENCY);
    if (err) {
        goto err_devfreq;
    }

    devfreq->nb_max.notifier_call = qos_max_notifier_call;
    err = dev_pm_qos_add_notifier(devfreq->dev.parent, &devfreq->nb_max, DEV_PM_QOS_MAX_FREQUENCY);
    if (err) {
        goto err_devfreq;
    }

    mutex_lock(&devfreq_list_lock);

    governor = try_then_request_governor(devfreq->governor_name);
    if (IS_ERR(governor)) {
        dev_err(dev, "%s: Unable to find governor for the device\n", __func__);
        err = PTR_ERR(governor);
        goto err_init;
    }

    devfreq->governor = governor;
    err = devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_START, NULL);
    if (err) {
        dev_err(dev, "%s: Unable to start governor for the device\n", __func__);
        goto err_init;
    }

    list_add(&devfreq->node, &devfreq_list);

    mutex_unlock(&devfreq_list_lock);

    return devfreq;

err_init:
    mutex_unlock(&devfreq_list_lock);
err_devfreq:
    devfreq_remove_device(devfreq);
    devfreq = NULL;
err_dev:
    kfree(devfreq);
err_out:
    return ERR_PTR(err);
}
EXPORT_SYMBOL(devfreq_add_device);

static int devm_devfreq_dev_match(struct device *dev, void *res, void *data)
{
    struct devfreq **r = res;

    if (WARN_ON(!r || !*r)) {
        return 0;
    }

    return *r == data;
}

static void devm_devfreq_dev_release(struct device *dev, void *res)
{
    devfreq_remove_device(*(struct devfreq **)res);
}

/**
 * devm_devfreq_add_device() - Resource-managed devfreq_add_device()
 * @dev:    the device to add devfreq feature.
 * @profile:    device-specific profile to run devfreq.
 * @governor_name:    name of the policy to choose frequency.
 * @data:    private data for the governor. The devfreq framework does not
 *        touch this value.
 *
 * This function manages automatically the memory of devfreq device using device
 * resource management and simplify the free operation for memory of devfreq
 * device.
 */
struct devfreq *devm_devfreq_add_device(struct device *dev, struct devfreq_dev_profile *profile,
                                        const char *governor_name, void *data)
{
    struct devfreq **ptr, *devfreq;

    ptr = devres_alloc(devm_devfreq_dev_release, sizeof(*ptr), GFP_KERNEL);
    if (!ptr) {
        return ERR_PTR(-ENOMEM);
    }

    devfreq = devfreq_add_device(dev, profile, governor_name, data);
    if (IS_ERR(devfreq)) {
        devres_free(ptr);
        return devfreq;
    }

    *ptr = devfreq;
    devres_add(dev, ptr);

    return devfreq;
}
EXPORT_SYMBOL(devm_devfreq_add_device);

#ifdef CONFIG_OF
/*
 * devfreq_get_devfreq_by_node - Get the devfreq device from devicetree
 * @node - pointer to device_node
 *
 * return the instance of devfreq device
 */
struct devfreq *devfreq_get_devfreq_by_node(struct device_node *node)
{
    struct devfreq *devfreq;

    if (!node) {
        return ERR_PTR(-EINVAL);
    }

    mutex_lock(&devfreq_list_lock);
    list_for_each_entry(devfreq, &devfreq_list, node)
    {
        if (devfreq->dev.parent && devfreq->dev.parent->of_node == node) {
            mutex_unlock(&devfreq_list_lock);
            return devfreq;
        }
    }
    mutex_unlock(&devfreq_list_lock);

    return ERR_PTR(-ENODEV);
}

/*
 * devfreq_get_devfreq_by_phandle - Get the devfreq device from devicetree
 * @dev - instance to the given device
 * @phandle_name - name of property holding a phandle value
 * @index - index into list of devfreq
 *
 * return the instance of devfreq device
 */
struct devfreq *devfreq_get_devfreq_by_phandle(struct device *dev, const char *phandle_name, int index)
{
    struct device_node *node;
    struct devfreq *devfreq;

    if (!dev || !phandle_name) {
        return ERR_PTR(-EINVAL);
    }

    if (!dev->of_node) {
        return ERR_PTR(-EINVAL);
    }

    node = of_parse_phandle(dev->of_node, phandle_name, index);
    if (!node) {
        return ERR_PTR(-ENODEV);
    }

    devfreq = devfreq_get_devfreq_by_node(node);
    of_node_put(node);

    return devfreq;
}

#else
struct devfreq *devfreq_get_devfreq_by_node(struct device_node *node)
{
    return ERR_PTR(-ENODEV);
}

struct devfreq *devfreq_get_devfreq_by_phandle(struct device *dev, const char *phandle_name, int index)
{
    return ERR_PTR(-ENODEV);
}
#endif /* CONFIG_OF */
EXPORT_SYMBOL_GPL(devfreq_get_devfreq_by_node);
EXPORT_SYMBOL_GPL(devfreq_get_devfreq_by_phandle);

/**
 * devm_devfreq_remove_device() - Resource-managed devfreq_remove_device()
 * @dev:    the device from which to remove devfreq feature.
 * @devfreq:    the devfreq instance to be removed
 */
void devm_devfreq_remove_device(struct device *dev, struct devfreq *devfreq)
{
    WARN_ON(devres_release(dev, devm_devfreq_dev_release, devm_devfreq_dev_match, devfreq));
}
EXPORT_SYMBOL(devm_devfreq_remove_device);

/**
 * devfreq_suspend_device() - Suspend devfreq of a device.
 * @devfreq: the devfreq instance to be suspended
 *
 * This function is intended to be called by the pm callbacks
 * (e.g., runtime_suspend, suspend) of the device driver that
 * holds the devfreq.
 */
int devfreq_suspend_device(struct devfreq *devfreq)
{
    int ret;

    if (!devfreq) {
        return -EINVAL;
    }

    if (atomic_inc_return(&devfreq->suspend_count) > 1) {
        return 0;
    }

    if (devfreq->governor) {
        ret = devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_SUSPEND, NULL);
        if (ret) {
            return ret;
        }
    }

    if (devfreq->suspend_freq) {
        mutex_lock(&devfreq->lock);
        ret = devfreq_set_target(devfreq, devfreq->suspend_freq, 0);
        mutex_unlock(&devfreq->lock);
        if (ret) {
            return ret;
        }
    }

    return 0;
}
EXPORT_SYMBOL(devfreq_suspend_device);

/**
 * devfreq_resume_device() - Resume devfreq of a device.
 * @devfreq: the devfreq instance to be resumed
 *
 * This function is intended to be called by the pm callbacks
 * (e.g., runtime_resume, resume) of the device driver that
 * holds the devfreq.
 */
int devfreq_resume_device(struct devfreq *devfreq)
{
    int ret;

    if (!devfreq) {
        return -EINVAL;
    }

    if (atomic_dec_return(&devfreq->suspend_count) >= 1) {
        return 0;
    }

    if (devfreq->resume_freq) {
        mutex_lock(&devfreq->lock);
        ret = devfreq_set_target(devfreq, devfreq->resume_freq, 0);
        mutex_unlock(&devfreq->lock);
        if (ret) {
            return ret;
        }
    }

    if (devfreq->governor) {
        ret = devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_RESUME, NULL);
        if (ret) {
            return ret;
        }
    }

    return 0;
}
EXPORT_SYMBOL(devfreq_resume_device);

/**
 * devfreq_suspend() - Suspend devfreq governors and devices
 *
 * Called during system wide Suspend/Hibernate cycles for suspending governors
 * and devices preserving the state for resume. On some platforms the devfreq
 * device must have precise state (frequency) after resume in order to provide
 * fully operating setup.
 */
void devfreq_suspend(void)
{
    struct devfreq *devfreq;
    int ret;

    mutex_lock(&devfreq_list_lock);
    list_for_each_entry(devfreq, &devfreq_list, node)
    {
        ret = devfreq_suspend_device(devfreq);
        if (ret) {
            dev_err(&devfreq->dev, "failed to suspend devfreq device\n");
        }
    }
    mutex_unlock(&devfreq_list_lock);
}

/**
 * devfreq_resume() - Resume devfreq governors and devices
 *
 * Called during system wide Suspend/Hibernate cycle for resuming governors and
 * devices that are suspended with devfreq_suspend().
 */
void devfreq_resume(void)
{
    struct devfreq *devfreq;
    int ret;

    mutex_lock(&devfreq_list_lock);
    list_for_each_entry(devfreq, &devfreq_list, node)
    {
        ret = devfreq_resume_device(devfreq);
        if (ret) {
            dev_warn(&devfreq->dev, "failed to resume devfreq device\n");
        }
    }
    mutex_unlock(&devfreq_list_lock);
}

/**
 * devfreq_add_governor() - Add devfreq governor
 * @governor:    the devfreq governor to be added
 */
int devfreq_add_governor(struct devfreq_governor *governor)
{
    struct devfreq_governor *g;
    struct devfreq *devfreq;
    int err = 0;

    if (!governor) {
        pr_err("%s: Invalid parameters.\n", __func__);
        return -EINVAL;
    }

    mutex_lock(&devfreq_list_lock);
    g = find_devfreq_governor(governor->name);
    if (!IS_ERR(g)) {
        pr_err("%s: governor %s already registered\n", __func__, g->name);
        err = -EINVAL;
        goto err_out;
    }

    list_add(&governor->node, &devfreq_governor_list);

    list_for_each_entry(devfreq, &devfreq_list, node)
    {
        int ret = 0;
        struct device *dev = devfreq->dev.parent;

        if (!strncmp(devfreq->governor_name, governor->name, DEVFREQ_NAME_LEN)) {
            /* The following should never occur */
            if (devfreq->governor) {
                dev_warn(dev, "%s: Governor %s already present\n", __func__, devfreq->governor->name);
                ret = devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_STOP, NULL);
                if (ret) {
                    dev_warn(dev, "%s: Governor %s stop = %d\n", __func__, devfreq->governor->name, ret);
                }
                /* Fall through */
            }
            devfreq->governor = governor;
            ret = devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_START, NULL);
            if (ret) {
                dev_warn(dev, "%s: Governor %s start=%d\n", __func__, devfreq->governor->name, ret);
            }
        }
    }

err_out:
    mutex_unlock(&devfreq_list_lock);

    return err;
}
EXPORT_SYMBOL(devfreq_add_governor);

/**
 * devfreq_remove_governor() - Remove devfreq feature from a device.
 * @governor:    the devfreq governor to be removed
 */
int devfreq_remove_governor(struct devfreq_governor *governor)
{
    struct devfreq_governor *g;
    struct devfreq *devfreq;
    int err = 0;

    if (!governor) {
        pr_err("%s: Invalid parameters.\n", __func__);
        return -EINVAL;
    }

    mutex_lock(&devfreq_list_lock);
    g = find_devfreq_governor(governor->name);
    if (IS_ERR(g)) {
        pr_err("%s: governor %s not registered\n", __func__, governor->name);
        err = PTR_ERR(g);
        goto err_out;
    }
    list_for_each_entry(devfreq, &devfreq_list, node)
    {
        int ret;
        struct device *dev = devfreq->dev.parent;

        if (!strncmp(devfreq->governor_name, governor->name, DEVFREQ_NAME_LEN)) {
            /* we should have a devfreq governor! */
            if (!devfreq->governor) {
                dev_warn(dev, "%s: Governor %s NOT present\n", __func__, governor->name);
                continue;
                /* Fall through */
            }
            ret = devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_STOP, NULL);
            if (ret) {
                dev_warn(dev, "%s: Governor %s stop=%d\n", __func__, devfreq->governor->name, ret);
            }
            devfreq->governor = NULL;
        }
    }

    list_del(&governor->node);
err_out:
    mutex_unlock(&devfreq_list_lock);

    return err;
}
EXPORT_SYMBOL(devfreq_remove_governor);

static ssize_t name_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    struct devfreq *df = to_devfreq(dev);
    return sprintf(buf, "%s\n", dev_name(df->dev.parent));
}
static DEVICE_ATTR_RO(name);

static ssize_t governor_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    struct devfreq *df = to_devfreq(dev);

    if (!df->governor) {
        return -EINVAL;
    }

    return sprintf(buf, "%s\n", df->governor->name);
}

static ssize_t governor_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
    struct devfreq *df = to_devfreq(dev);
    int ret;
    char str_governor[DEVFREQ_NAME_LEN + 1];
    const struct devfreq_governor *governor, *prev_governor;

    if (!df->governor) {
        return -EINVAL;
    }

    ret = sscanf(buf, "%" __stringify(DEVFREQ_NAME_LEN) "s", str_governor);
    if (ret != 1) {
        return -EINVAL;
    }

    mutex_lock(&devfreq_list_lock);
    governor = try_then_request_governor(str_governor);
    if (IS_ERR(governor)) {
        ret = PTR_ERR(governor);
        goto out;
    }
    if (df->governor == governor) {
        ret = 0;
        goto out;
    } else if (df->governor->immutable || governor->immutable) {
        ret = -EINVAL;
        goto out;
    }

    ret = df->governor->event_handler(df, DEVFREQ_GOV_STOP, NULL);
    if (ret) {
        dev_warn(dev, "%s: Governor %s not stopped(%d)\n", __func__, df->governor->name, ret);
        goto out;
    }

    prev_governor = df->governor;
    df->governor = governor;
    strncpy(df->governor_name, governor->name, DEVFREQ_NAME_LEN);
    ret = df->governor->event_handler(df, DEVFREQ_GOV_START, NULL);
    if (ret) {
        dev_warn(dev, "%s: Governor %s not started(%d)\n", __func__, df->governor->name, ret);
        df->governor = prev_governor;
        strncpy(df->governor_name, prev_governor->name, DEVFREQ_NAME_LEN);
        ret = df->governor->event_handler(df, DEVFREQ_GOV_START, NULL);
        if (ret) {
            dev_err(dev, "%s: reverting to Governor %s failed (%d)\n", __func__, df->governor_name, ret);
            df->governor = NULL;
        }
    }
out:
    mutex_unlock(&devfreq_list_lock);

    if (!ret) {
        ret = count;
    }
    return ret;
}
static DEVICE_ATTR_RW(governor);

static ssize_t available_governors_show(struct device *d, struct device_attribute *attr, char *buf)
{
    struct devfreq *df = to_devfreq(d);
    ssize_t count = 0;

    if (!df->governor) {
        return -EINVAL;
    }

    mutex_lock(&devfreq_list_lock);

    /*
     * The devfreq with immutable governor (e.g., passive) shows
     * only own governor.
     */
    if (df->governor->immutable) {
        count = scnprintf(&buf[count], DEVFREQ_NAME_LEN, "%s ", df->governor_name);
        /*
         * The devfreq device shows the registered governor except for
         * immutable governors such as passive governor .
         */
    } else {
        struct devfreq_governor *governor;

        list_for_each_entry(governor, &devfreq_governor_list, node)
        {
            if (governor->immutable) {
                continue;
            }
            count += scnprintf(&buf[count], (PAGE_SIZE - count - 0x2), "%s ", governor->name);
        }
    }

    mutex_unlock(&devfreq_list_lock);

    /* Truncate the trailing space */
    if (count) {
        count--;
    }

    count += sprintf(&buf[count], "\n");

    return count;
}
static DEVICE_ATTR_RO(available_governors);

static ssize_t cur_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    unsigned long freq;
    struct devfreq *df = to_devfreq(dev);

    if (!df->profile) {
        return -EINVAL;
    }

    if (df->profile->get_cur_freq && !df->profile->get_cur_freq(df->dev.parent, &freq)) {
        return sprintf(buf, "%lu\n", freq);
    }

    return sprintf(buf, "%lu\n", df->previous_freq);
}
static DEVICE_ATTR_RO(cur_freq);

static ssize_t target_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    struct devfreq *df = to_devfreq(dev);

    return sprintf(buf, "%lu\n", df->previous_freq);
}
static DEVICE_ATTR_RO(target_freq);

static ssize_t polling_interval_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    struct devfreq *df = to_devfreq(dev);

    if (!df->profile) {
        return -EINVAL;
    }

    return sprintf(buf, "%d\n", df->profile->polling_ms);
}

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

    if (!df->governor) {
        return -EINVAL;
    }

    ret = sscanf(buf, "%u", &value);
    if (ret != 1) {
        return -EINVAL;
    }

    df->governor->event_handler(df, DEVFREQ_GOV_UPDATE_INTERVAL, &value);
    ret = count;

    return ret;
}
static DEVICE_ATTR_RW(polling_interval);

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

    /*
     * Protect against theoretical sysfs writes between
     * device_add and dev_pm_qos_add_request
     */
    if (!dev_pm_qos_request_active(&df->user_min_freq_req)) {
        return -EAGAIN;
    }

    ret = sscanf(buf, "%lu", &value);
    if (ret != 1) {
        return -EINVAL;
    }

    /* Round down to kHz for PM QoS */
    ret = dev_pm_qos_update_request(&df->user_min_freq_req, value / HZ_PER_KHZ);
    if (ret < 0) {
        return ret;
    }

    return count;
}

static ssize_t min_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    struct devfreq *df = to_devfreq(dev);
    unsigned long min_freq, max_freq;

    mutex_lock(&df->lock);
    get_freq_range(df, &min_freq, &max_freq);
    mutex_unlock(&df->lock);

    return sprintf(buf, "%lu\n", min_freq);
}
static DEVICE_ATTR_RW(min_freq);

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

    /*
     * Protect against theoretical sysfs writes between
     * device_add and dev_pm_qos_add_request
     */
    if (!dev_pm_qos_request_active(&df->user_max_freq_req)) {
        return -EINVAL;
    }

    ret = sscanf(buf, "%lu", &value);
    if (ret != 1) {
        return -EINVAL;
    }

    /*
     * PM QoS frequencies are in kHz so we need to convert. Convert by
     * rounding upwards so that the acceptable interval never shrinks.
     *
     * For example if the user writes "666666666" to sysfs this value will
     * be converted to 666667 kHz and back to 666667000 Hz before an OPP
     * lookup, this ensures that an OPP of 666666666Hz is still accepted.
     *
     * A value of zero means "no limit".
     */
    if (value) {
        value = DIV_ROUND_UP(value, HZ_PER_KHZ);
    } else {
        value = PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE;
    }

    ret = dev_pm_qos_update_request(&df->user_max_freq_req, value);
    if (ret < 0) {
        return ret;
    }

    return count;
}

static ssize_t max_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    struct devfreq *df = to_devfreq(dev);
    unsigned long min_freq, max_freq;

    mutex_lock(&df->lock);
    get_freq_range(df, &min_freq, &max_freq);
    mutex_unlock(&df->lock);

    return sprintf(buf, "%lu\n", max_freq);
}
static DEVICE_ATTR_RW(max_freq);

static ssize_t available_frequencies_show(struct device *d, struct device_attribute *attr, char *buf)
{
    struct devfreq *df = to_devfreq(d);
    ssize_t count = 0;
    int i;

    if (!df->profile) {
        return -EINVAL;
    }

    mutex_lock(&df->lock);

    for (i = 0; i < df->profile->max_state; i++) {
        count += scnprintf(&buf[count], (PAGE_SIZE - count - 0x2), "%lu ", df->profile->freq_table[i]);
    }

    mutex_unlock(&df->lock);
    /* Truncate the trailing space */
    if (count) {
        count--;
    }

    count += sprintf(&buf[count], "\n");

    return count;
}
static DEVICE_ATTR_RO(available_frequencies);

static ssize_t trans_stat_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    struct devfreq *df = to_devfreq(dev);
    ssize_t len;
    int i, j;
    unsigned int max_state;

    if (!df->profile) {
        return -EINVAL;
    }
    max_state = df->profile->max_state;

    if (max_state == 0) {
        return sprintf(buf, "Not Supported.\n");
    }

    mutex_lock(&df->lock);
    if (!df->stop_polling && devfreq_update_status(df, df->previous_freq)) {
        mutex_unlock(&df->lock);
        return 0;
    }
    mutex_unlock(&df->lock);

    len = sprintf(buf, "     From  :   To\n");
    len += sprintf(buf + len, "           :");
    for (i = 0; i < max_state; i++) {
        len += sprintf(buf + len, "%10lu", df->profile->freq_table[i]);
    }

    len += sprintf(buf + len, "   time(ms)\n");

    for (i = 0; i < max_state; i++) {
        if (df->profile->freq_table[i] == df->previous_freq) {
            len += sprintf(buf + len, "*");
        } else {
            len += sprintf(buf + len, " ");
        }
        len += sprintf(buf + len, "%10lu:", df->profile->freq_table[i]);
        for (j = 0; j < max_state; j++) {
            len += sprintf(buf + len, "%10u", df->stats.trans_table[(i * max_state) + j]);
        }

        len += sprintf(buf + len, "%10llu\n", (u64)jiffies64_to_msecs(df->stats.time_in_state[i]));
    }

    len += sprintf(buf + len, "Total transition : %u\n", df->stats.total_trans);
    return len;
}

static ssize_t trans_stat_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
    struct devfreq *df = to_devfreq(dev);
    int err, value;

    if (!df->profile) {
        return -EINVAL;
    }

    if (df->profile->max_state == 0) {
        return count;
    }

    err = kstrtoint(buf, 0xa, &value);
    if (err || value != 0) {
        return -EINVAL;
    }

    mutex_lock(&df->lock);
    memset(df->stats.time_in_state, 0, (df->profile->max_state * sizeof(*df->stats.time_in_state)));
    memset(df->stats.trans_table, 0, array3_size(sizeof(unsigned int), df->profile->max_state, df->profile->max_state));
    df->stats.total_trans = 0;
    df->stats.last_update = get_jiffies_64();
    mutex_unlock(&df->lock);

    return count;
}
static DEVICE_ATTR_RW(trans_stat);

static ssize_t timer_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    struct devfreq *df = to_devfreq(dev);

    if (!df->profile) {
        return -EINVAL;
    }

    return sprintf(buf, "%s\n", timer_name[df->profile->timer]);
}

static ssize_t timer_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
    struct devfreq *df = to_devfreq(dev);
    char str_timer[DEVFREQ_NAME_LEN + 1];
    int timer = -1;
    int ret = 0, i;

    if (!df->governor || !df->profile) {
        return -EINVAL;
    }

    ret = sscanf(buf, "%16s", str_timer);
    if (ret != 1) {
        return -EINVAL;
    }

    for (i = 0; i < DEVFREQ_TIMER_NUM; i++) {
        if (!strncmp(timer_name[i], str_timer, DEVFREQ_NAME_LEN)) {
            timer = i;
            break;
        }
    }

    if (timer < 0) {
        ret = -EINVAL;
        goto out;
    }

    if (df->profile->timer == timer) {
        ret = 0;
        goto out;
    }

    mutex_lock(&df->lock);
    df->profile->timer = timer;
    mutex_unlock(&df->lock);

    ret = df->governor->event_handler(df, DEVFREQ_GOV_STOP, NULL);
    if (ret) {
        dev_warn(dev, "%s: Governor %s not stopped(%d)\n", __func__, df->governor->name, ret);
        goto out;
    }

    ret = df->governor->event_handler(df, DEVFREQ_GOV_START, NULL);
    if (ret) {
        dev_warn(dev, "%s: Governor %s not started(%d)\n", __func__, df->governor->name, ret);
    }
out:
    return ret ? ret : count;
}
static DEVICE_ATTR_RW(timer);

static ssize_t load_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    int err;
    struct devfreq *devfreq = to_devfreq(dev);
    struct devfreq_dev_status stat = devfreq->last_status;
    unsigned long freq;
    ssize_t len;

    err = devfreq_update_stats(devfreq);
    if (err) {
        return err;
    }

    if (stat.total_time < stat.busy_time) {
        err = devfreq_update_stats(devfreq);
        if (err) {
            return err;
        }
    };

    if (!stat.total_time) {
        return 0;
    }

    len = sprintf(buf, "%lu", stat.busy_time * 0x64 / stat.total_time);

    if (devfreq->profile->get_cur_freq && !devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq)) {
        len += sprintf(buf + len, "@%luHz\n", freq);
    } else {
        len += sprintf(buf + len, "@%luHz\n", devfreq->previous_freq);
    }

    return len;
}
static DEVICE_ATTR_RO(load);

static struct attribute *devfreq_attrs[] = {
    &dev_attr_name.attr,
    &dev_attr_governor.attr,
    &dev_attr_available_governors.attr,
    &dev_attr_cur_freq.attr,
    &dev_attr_available_frequencies.attr,
    &dev_attr_target_freq.attr,
    &dev_attr_polling_interval.attr,
    &dev_attr_min_freq.attr,
    &dev_attr_max_freq.attr,
    &dev_attr_trans_stat.attr,
    &dev_attr_timer.attr,
    &dev_attr_load.attr,
    NULL,
};
ATTRIBUTE_GROUPS(devfreq);

/**
 * devfreq_summary_show() - Show the summary of the devfreq devices
 * @s:        seq_file instance to show the summary of devfreq devices
 * @data:    not used
 *
 * Show the summary of the devfreq devices via 'devfreq_summary' debugfs file.
 * It helps that user can know the detailed information of the devfreq devices.
 *
 * Return 0 always because it shows the information without any data change.
 */
static int devfreq_summary_show(struct seq_file *s, void *data)
{
    struct devfreq *devfreq;
    struct devfreq *p_devfreq = NULL;
    unsigned long cur_freq, min_freq, max_freq;
    unsigned int polling_ms;
    unsigned int timer;

    seq_printf(s, "%-30s %-30s %-15s %-10s %10s %12s %12s %12s\n", "dev", "parent_dev", "governor", "timer",
               "polling_ms", "cur_freq_Hz", "min_freq_Hz", "max_freq_Hz");
    seq_printf(s, "%30s %30s %15s %10s %10s %12s %12s %12s\n", "------------------------------",
               "------------------------------", "---------------", "----------", "----------", "------------",
               "------------", "------------");

    mutex_lock(&devfreq_list_lock);

    list_for_each_entry_reverse(devfreq, &devfreq_list, node)
    {
#if IS_ENABLED(CONFIG_DEVFREQ_GOV_PASSIVE)
        if (!strncmp(devfreq->governor_name, DEVFREQ_GOV_PASSIVE, DEVFREQ_NAME_LEN)) {
            struct devfreq_passive_data *data = devfreq->data;

            if (data) {
                p_devfreq = data->parent;
            }
        } else {
            p_devfreq = NULL;
        }
#endif

        mutex_lock(&devfreq->lock);
        cur_freq = devfreq->previous_freq;
        get_freq_range(devfreq, &min_freq, &max_freq);
        polling_ms = devfreq->profile->polling_ms;
        timer = devfreq->profile->timer;
        mutex_unlock(&devfreq->lock);

        seq_printf(s, "%-30s %-30s %-15s %-10s %10d %12ld %12ld %12ld\n", dev_name(&devfreq->dev),
                   p_devfreq ? dev_name(&p_devfreq->dev) : "null", devfreq->governor_name,
                   polling_ms ? timer_name[timer] : "null", polling_ms, cur_freq, min_freq, max_freq);
    }

    mutex_unlock(&devfreq_list_lock);

    return 0;
}
DEFINE_SHOW_ATTRIBUTE(devfreq_summary);

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_wq = create_freezable_workqueue("devfreq_wq");
    if (!devfreq_wq) {
        class_destroy(devfreq_class);
        pr_err("%s: couldn't create workqueue\n", __FILE__);
        return -ENOMEM;
    }
    devfreq_class->dev_groups = devfreq_groups;

    devfreq_debugfs = debugfs_create_dir("devfreq", NULL);
    debugfs_create_file("devfreq_summary", 0444, devfreq_debugfs, NULL, &devfreq_summary_fops);

    return 0;
}
subsys_initcall(devfreq_init);

/*
 * The following are helper functions for devfreq user device drivers with
 * OPP framework.
 */

/**
 * devfreq_recommended_opp() - Helper function to get proper OPP for the
 *                 freq value given to target callback.
 * @dev:    The devfreq user device. (parent of devfreq)
 * @freq:    The frequency given to target function
 * @flags:    Flags handed from devfreq framework.
 *
 * The callers are required to call dev_pm_opp_put() for the returned OPP after
 * use.
 */
struct dev_pm_opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq, u32 flags)
{
    struct dev_pm_opp *opp;

    if (flags & DEVFREQ_FLAG_LEAST_UPPER_BOUND) {
        /* The freq is an upper bound. opp should be lower */
        opp = dev_pm_opp_find_freq_floor(dev, freq);
        /* If not available, use the closest opp */
        if (opp == ERR_PTR(-ERANGE)) {
            opp = dev_pm_opp_find_freq_ceil(dev, freq);
        }
    } else {
        /* The freq is an lower bound. opp should be higher */
        opp = dev_pm_opp_find_freq_ceil(dev, freq);
        /* If not available, use the closest opp */
        if (opp == ERR_PTR(-ERANGE)) {
            opp = dev_pm_opp_find_freq_floor(dev, freq);
        }
    }

    return opp;
}
EXPORT_SYMBOL(devfreq_recommended_opp);

/**
 * devfreq_register_opp_notifier() - Helper function to get devfreq notified
 *                     for any changes in the OPP availability
 *                     changes
 * @dev:    The devfreq user device. (parent of devfreq)
 * @devfreq:    The devfreq object.
 */
int devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq)
{
    return dev_pm_opp_register_notifier(dev, &devfreq->nb);
}
EXPORT_SYMBOL(devfreq_register_opp_notifier);

/**
 * devfreq_unregister_opp_notifier() - Helper function to stop getting devfreq
 *                       notified for any changes in the OPP
 *                       availability changes anymore.
 * @dev:    The devfreq user device. (parent of devfreq)
 * @devfreq:    The devfreq object.
 *
 * At exit() callback of devfreq_dev_profile, this must be included if
 * devfreq_recommended_opp is used.
 */
int devfreq_unregister_opp_notifier(struct device *dev, struct devfreq *devfreq)
{
    return dev_pm_opp_unregister_notifier(dev, &devfreq->nb);
}
EXPORT_SYMBOL(devfreq_unregister_opp_notifier);

static void devm_devfreq_opp_release(struct device *dev, void *res)
{
    devfreq_unregister_opp_notifier(dev, *(struct devfreq **)res);
}

/**
 * devm_devfreq_register_opp_notifier() - Resource-managed
 *                      devfreq_register_opp_notifier()
 * @dev:    The devfreq user device. (parent of devfreq)
 * @devfreq:    The devfreq object.
 */
int devm_devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq)
{
    struct devfreq **ptr;
    int ret;

    ptr = devres_alloc(devm_devfreq_opp_release, sizeof(*ptr), GFP_KERNEL);
    if (!ptr) {
        return -ENOMEM;
    }

    ret = devfreq_register_opp_notifier(dev, devfreq);
    if (ret) {
        devres_free(ptr);
        return ret;
    }

    *ptr = devfreq;
    devres_add(dev, ptr);

    return 0;
}
EXPORT_SYMBOL(devm_devfreq_register_opp_notifier);

/**
 * devm_devfreq_unregister_opp_notifier() - Resource-managed
 *                        devfreq_unregister_opp_notifier()
 * @dev:    The devfreq user device. (parent of devfreq)
 * @devfreq:    The devfreq object.
 */
void devm_devfreq_unregister_opp_notifier(struct device *dev, struct devfreq *devfreq)
{
    WARN_ON(devres_release(dev, devm_devfreq_opp_release, devm_devfreq_dev_match, devfreq));
}
EXPORT_SYMBOL(devm_devfreq_unregister_opp_notifier);

/**
 * devfreq_register_notifier() - Register a driver with devfreq
 * @devfreq:    The devfreq object.
 * @nb:        The notifier block to register.
 * @list:    DEVFREQ_TRANSITION_NOTIFIER.
 */
int devfreq_register_notifier(struct devfreq *devfreq, struct notifier_block *nb, unsigned int list)
{
    int ret = 0;

    if (!devfreq) {
        return -EINVAL;
    }

    switch (list) {
        case DEVFREQ_TRANSITION_NOTIFIER:
            ret = srcu_notifier_chain_register(&devfreq->transition_notifier_list, nb);
            break;
        default:
            ret = -EINVAL;
    }

    return ret;
}
EXPORT_SYMBOL(devfreq_register_notifier);

/*
 * devfreq_unregister_notifier() - Unregister a driver with devfreq
 * @devfreq:    The devfreq object.
 * @nb:        The notifier block to be unregistered.
 * @list:    DEVFREQ_TRANSITION_NOTIFIER.
 */
int devfreq_unregister_notifier(struct devfreq *devfreq, struct notifier_block *nb, unsigned int list)
{
    int ret = 0;

    if (!devfreq) {
        return -EINVAL;
    }

    switch (list) {
        case DEVFREQ_TRANSITION_NOTIFIER:
            ret = srcu_notifier_chain_unregister(&devfreq->transition_notifier_list, nb);
            break;
        default:
            ret = -EINVAL;
    }

    return ret;
}
EXPORT_SYMBOL(devfreq_unregister_notifier);

struct devfreq_notifier_devres {
    struct devfreq *devfreq;
    struct notifier_block *nb;
    unsigned int list;
};

static void devm_devfreq_notifier_release(struct device *dev, void *res)
{
    struct devfreq_notifier_devres *this = res;

    devfreq_unregister_notifier(this->devfreq, this->nb, this->list);
}

/**
 * devm_devfreq_register_notifier()
 *    - Resource-managed devfreq_register_notifier()
 * @dev:    The devfreq user device. (parent of devfreq)
 * @devfreq:    The devfreq object.
 * @nb:        The notifier block to be unregistered.
 * @list:    DEVFREQ_TRANSITION_NOTIFIER.
 */
int devm_devfreq_register_notifier(struct device *dev, struct devfreq *devfreq, struct notifier_block *nb,
                                   unsigned int list)
{
    struct devfreq_notifier_devres *ptr;
    int ret;

    ptr = devres_alloc(devm_devfreq_notifier_release, sizeof(*ptr), GFP_KERNEL);
    if (!ptr) {
        return -ENOMEM;
    }

    ret = devfreq_register_notifier(devfreq, nb, list);
    if (ret) {
        devres_free(ptr);
        return ret;
    }

    ptr->devfreq = devfreq;
    ptr->nb = nb;
    ptr->list = list;
    devres_add(dev, ptr);

    return 0;
}
EXPORT_SYMBOL(devm_devfreq_register_notifier);

/**
 * devm_devfreq_unregister_notifier()
 *    - Resource-managed devfreq_unregister_notifier()
 * @dev:    The devfreq user device. (parent of devfreq)
 * @devfreq:    The devfreq object.
 * @nb:        The notifier block to be unregistered.
 * @list:    DEVFREQ_TRANSITION_NOTIFIER.
 */
void devm_devfreq_unregister_notifier(struct device *dev, struct devfreq *devfreq, struct notifier_block *nb,
                                      unsigned int list)
{
    WARN_ON(devres_release(dev, devm_devfreq_notifier_release, devm_devfreq_dev_match, devfreq));
}
EXPORT_SYMBOL(devm_devfreq_unregister_notifier);