[cascardo/linux.git] / drivers / base / power / opp / core.c

/*
 * Generic OPP Interface
 *
 * Copyright (C) 2009-2010 Texas Instruments Incorporated.
 *      Nishanth Menon
 *      Romit Dasgupta
 *      Kevin Hilman
 *
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/clk.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/device.h>
#include <linux/export.h>
#include <linux/regulator/consumer.h>

#include "opp.h"

/*
 * The root of the list of all opp-tables. All opp_table structures branch off
 * from here, with each opp_table containing the list of opps it supports in
 * various states of availability.
 */
LIST_HEAD(opp_tables);
/* Lock to allow exclusive modification to the device and opp lists */
DEFINE_MUTEX(opp_table_lock);

#define opp_rcu_lockdep_assert()                                        \
do {                                                                    \
        RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&                       \
                         !lockdep_is_held(&opp_table_lock),             \
                         "Missing rcu_read_lock() or "                  \
                         "opp_table_lock protection");                  \
} while (0)

static struct opp_device *_find_opp_dev(const struct device *dev,
                                        struct opp_table *opp_table)
{
        struct opp_device *opp_dev;

        list_for_each_entry(opp_dev, &opp_table->dev_list, node)
                if (opp_dev->dev == dev)
                        return opp_dev;

        return NULL;
}

/**
 * _find_opp_table() - find opp_table struct using device pointer
 * @dev:        device pointer used to lookup OPP table
 *
 * Search OPP table for one containing matching device. Does a RCU reader
 * operation to grab the pointer needed.
 *
 * Return: pointer to 'struct opp_table' if found, otherwise -ENODEV or
 * -EINVAL based on type of error.
 *
 * Locking: For readers, this function must be called under rcu_read_lock().
 * opp_table is a RCU protected pointer, which means that opp_table is valid
 * as long as we are under RCU lock.
 *
 * For Writers, this function must be called with opp_table_lock held.
 */
struct opp_table *_find_opp_table(struct device *dev)
{
        struct opp_table *opp_table;

        opp_rcu_lockdep_assert();

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

        list_for_each_entry_rcu(opp_table, &opp_tables, node)
                if (_find_opp_dev(dev, opp_table))
                        return opp_table;

        return ERR_PTR(-ENODEV);
}

/**
 * dev_pm_opp_get_voltage() - Gets the voltage corresponding to an opp
 * @opp:        opp for which voltage has to be returned for
 *
 * Return: voltage in micro volt corresponding to the opp, else
 * return 0
 *
 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
 * protected pointer. This means that opp which could have been fetched by
 * opp_find_freq_{exact,ceil,floor} functions is valid as long as we are
 * under RCU lock. The pointer returned by the opp_find_freq family must be
 * used in the same section as the usage of this function with the pointer
 * prior to unlocking with rcu_read_unlock() to maintain the integrity of the
 * pointer.
 */
unsigned long dev_pm_opp_get_voltage(struct dev_pm_opp *opp)
{
        struct dev_pm_opp *tmp_opp;
        unsigned long v = 0;

        opp_rcu_lockdep_assert();

        tmp_opp = rcu_dereference(opp);
        if (IS_ERR_OR_NULL(tmp_opp))
                pr_err("%s: Invalid parameters\n", __func__);
        else
                v = tmp_opp->u_volt;

        return v;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_get_voltage);

/**
 * dev_pm_opp_get_freq() - Gets the frequency corresponding to an available opp
 * @opp:        opp for which frequency has to be returned for
 *
 * Return: frequency in hertz corresponding to the opp, else
 * return 0
 *
 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
 * protected pointer. This means that opp which could have been fetched by
 * opp_find_freq_{exact,ceil,floor} functions is valid as long as we are
 * under RCU lock. The pointer returned by the opp_find_freq family must be
 * used in the same section as the usage of this function with the pointer
 * prior to unlocking with rcu_read_unlock() to maintain the integrity of the
 * pointer.
 */
unsigned long dev_pm_opp_get_freq(struct dev_pm_opp *opp)
{
        struct dev_pm_opp *tmp_opp;
        unsigned long f = 0;

        opp_rcu_lockdep_assert();

        tmp_opp = rcu_dereference(opp);
        if (IS_ERR_OR_NULL(tmp_opp) || !tmp_opp->available)
                pr_err("%s: Invalid parameters\n", __func__);
        else
                f = tmp_opp->rate;

        return f;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_get_freq);

/**
 * dev_pm_opp_is_turbo() - Returns if opp is turbo OPP or not
 * @opp: opp for which turbo mode is being verified
 *
 * Turbo OPPs are not for normal use, and can be enabled (under certain
 * conditions) for short duration of times to finish high throughput work
 * quickly. Running on them for longer times may overheat the chip.
 *
 * Return: true if opp is turbo opp, else false.
 *
 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
 * protected pointer. This means that opp which could have been fetched by
 * opp_find_freq_{exact,ceil,floor} functions is valid as long as we are
 * under RCU lock. The pointer returned by the opp_find_freq family must be
 * used in the same section as the usage of this function with the pointer
 * prior to unlocking with rcu_read_unlock() to maintain the integrity of the
 * pointer.
 */
bool dev_pm_opp_is_turbo(struct dev_pm_opp *opp)
{
        struct dev_pm_opp *tmp_opp;

        opp_rcu_lockdep_assert();

        tmp_opp = rcu_dereference(opp);
        if (IS_ERR_OR_NULL(tmp_opp) || !tmp_opp->available) {
                pr_err("%s: Invalid parameters\n", __func__);
                return false;
        }

        return tmp_opp->turbo;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_is_turbo);

/**
 * dev_pm_opp_get_max_clock_latency() - Get max clock latency in nanoseconds
 * @dev:        device for which we do this operation
 *
 * Return: This function returns the max clock latency in nanoseconds.
 *
 * Locking: This function takes rcu_read_lock().
 */
unsigned long dev_pm_opp_get_max_clock_latency(struct device *dev)
{
        struct opp_table *opp_table;
        unsigned long clock_latency_ns;

        rcu_read_lock();

        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table))
                clock_latency_ns = 0;
        else
                clock_latency_ns = opp_table->clock_latency_ns_max;

        rcu_read_unlock();
        return clock_latency_ns;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_get_max_clock_latency);

/**
 * dev_pm_opp_get_max_volt_latency() - Get max voltage latency in nanoseconds
 * @dev: device for which we do this operation
 *
 * Return: This function returns the max voltage latency in nanoseconds.
 *
 * Locking: This function takes rcu_read_lock().
 */
unsigned long dev_pm_opp_get_max_volt_latency(struct device *dev)
{
        struct opp_table *opp_table;
        struct dev_pm_opp *opp;
        struct regulator *reg;
        unsigned long latency_ns = 0;
        unsigned long min_uV = ~0, max_uV = 0;
        int ret;

        rcu_read_lock();

        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                rcu_read_unlock();
                return 0;
        }

        reg = opp_table->regulator;
        if (IS_ERR(reg)) {
                /* Regulator may not be required for device */
                rcu_read_unlock();
                return 0;
        }

        list_for_each_entry_rcu(opp, &opp_table->opp_list, node) {
                if (!opp->available)
                        continue;

                if (opp->u_volt_min < min_uV)
                        min_uV = opp->u_volt_min;
                if (opp->u_volt_max > max_uV)
                        max_uV = opp->u_volt_max;
        }

        rcu_read_unlock();

        /*
         * The caller needs to ensure that opp_table (and hence the regulator)
         * isn't freed, while we are executing this routine.
         */
        ret = regulator_set_voltage_time(reg, min_uV, max_uV);
        if (ret > 0)
                latency_ns = ret * 1000;

        return latency_ns;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_get_max_volt_latency);

/**
 * dev_pm_opp_get_max_transition_latency() - Get max transition latency in
 *                                           nanoseconds
 * @dev: device for which we do this operation
 *
 * Return: This function returns the max transition latency, in nanoseconds, to
 * switch from one OPP to other.
 *
 * Locking: This function takes rcu_read_lock().
 */
unsigned long dev_pm_opp_get_max_transition_latency(struct device *dev)
{
        return dev_pm_opp_get_max_volt_latency(dev) +
                dev_pm_opp_get_max_clock_latency(dev);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_get_max_transition_latency);

/**
 * dev_pm_opp_get_suspend_opp() - Get suspend opp
 * @dev:        device for which we do this operation
 *
 * Return: This function returns pointer to the suspend opp if it is
 * defined and available, otherwise it returns NULL.
 *
 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
 * protected pointer. The reason for the same is that the opp pointer which is
 * returned will remain valid for use with opp_get_{voltage, freq} only while
 * under the locked area. The pointer returned must be used prior to unlocking
 * with rcu_read_unlock() to maintain the integrity of the pointer.
 */
struct dev_pm_opp *dev_pm_opp_get_suspend_opp(struct device *dev)
{
        struct opp_table *opp_table;

        opp_rcu_lockdep_assert();

        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table) || !opp_table->suspend_opp ||
            !opp_table->suspend_opp->available)
                return NULL;

        return opp_table->suspend_opp;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_get_suspend_opp);

/**
 * dev_pm_opp_get_opp_count() - Get number of opps available in the opp table
 * @dev:        device for which we do this operation
 *
 * Return: This function returns the number of available opps if there are any,
 * else returns 0 if none or the corresponding error value.
 *
 * Locking: This function takes rcu_read_lock().
 */
int dev_pm_opp_get_opp_count(struct device *dev)
{
        struct opp_table *opp_table;
        struct dev_pm_opp *temp_opp;
        int count = 0;

        rcu_read_lock();

        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                count = PTR_ERR(opp_table);
                dev_err(dev, "%s: OPP table not found (%d)\n",
                        __func__, count);
                goto out_unlock;
        }

        list_for_each_entry_rcu(temp_opp, &opp_table->opp_list, node) {
                if (temp_opp->available)
                        count++;
        }

out_unlock:
        rcu_read_unlock();
        return count;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_get_opp_count);

/**
 * dev_pm_opp_find_freq_exact() - search for an exact frequency
 * @dev:                device for which we do this operation
 * @freq:               frequency to search for
 * @available:          true/false - match for available opp
 *
 * Return: Searches for exact match in the opp table and returns pointer to the
 * matching opp if found, else returns ERR_PTR in case of error and should
 * be handled using IS_ERR. Error return values can be:
 * EINVAL:      for bad pointer
 * ERANGE:      no match found for search
 * ENODEV:      if device not found in list of registered devices
 *
 * Note: available is a modifier for the search. if available=true, then the
 * match is for exact matching frequency and is available in the stored OPP
 * table. if false, the match is for exact frequency which is not available.
 *
 * This provides a mechanism to enable an opp which is not available currently
 * or the opposite as well.
 *
 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
 * protected pointer. The reason for the same is that the opp pointer which is
 * returned will remain valid for use with opp_get_{voltage, freq} only while
 * under the locked area. The pointer returned must be used prior to unlocking
 * with rcu_read_unlock() to maintain the integrity of the pointer.
 */
struct dev_pm_opp *dev_pm_opp_find_freq_exact(struct device *dev,
                                              unsigned long freq,
                                              bool available)
{
        struct opp_table *opp_table;
        struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);

        opp_rcu_lockdep_assert();

        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                int r = PTR_ERR(opp_table);

                dev_err(dev, "%s: OPP table not found (%d)\n", __func__, r);
                return ERR_PTR(r);
        }

        list_for_each_entry_rcu(temp_opp, &opp_table->opp_list, node) {
                if (temp_opp->available == available &&
                                temp_opp->rate == freq) {
                        opp = temp_opp;
                        break;
                }
        }

        return opp;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_find_freq_exact);

static noinline struct dev_pm_opp *_find_freq_ceil(struct opp_table *opp_table,
                                                   unsigned long *freq)
{
        struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);

        list_for_each_entry_rcu(temp_opp, &opp_table->opp_list, node) {
                if (temp_opp->available && temp_opp->rate >= *freq) {
                        opp = temp_opp;
                        *freq = opp->rate;
                        break;
                }
        }

        return opp;
}

/**
 * dev_pm_opp_find_freq_ceil() - Search for an rounded ceil freq
 * @dev:        device for which we do this operation
 * @freq:       Start frequency
 *
 * Search for the matching ceil *available* OPP from a starting freq
 * for a device.
 *
 * Return: matching *opp and refreshes *freq accordingly, else returns
 * ERR_PTR in case of error and should be handled using IS_ERR. Error return
 * values can be:
 * EINVAL:      for bad pointer
 * ERANGE:      no match found for search
 * ENODEV:      if device not found in list of registered devices
 *
 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
 * protected pointer. The reason for the same is that the opp pointer which is
 * returned will remain valid for use with opp_get_{voltage, freq} only while
 * under the locked area. The pointer returned must be used prior to unlocking
 * with rcu_read_unlock() to maintain the integrity of the pointer.
 */
struct dev_pm_opp *dev_pm_opp_find_freq_ceil(struct device *dev,
                                             unsigned long *freq)
{
        struct opp_table *opp_table;

        opp_rcu_lockdep_assert();

        if (!dev || !freq) {
                dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq);
                return ERR_PTR(-EINVAL);
        }

        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table))
                return ERR_CAST(opp_table);

        return _find_freq_ceil(opp_table, freq);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_find_freq_ceil);

/**
 * dev_pm_opp_find_freq_floor() - Search for a rounded floor freq
 * @dev:        device for which we do this operation
 * @freq:       Start frequency
 *
 * Search for the matching floor *available* OPP from a starting freq
 * for a device.
 *
 * Return: matching *opp and refreshes *freq accordingly, else returns
 * ERR_PTR in case of error and should be handled using IS_ERR. Error return
 * values can be:
 * EINVAL:      for bad pointer
 * ERANGE:      no match found for search
 * ENODEV:      if device not found in list of registered devices
 *
 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
 * protected pointer. The reason for the same is that the opp pointer which is
 * returned will remain valid for use with opp_get_{voltage, freq} only while
 * under the locked area. The pointer returned must be used prior to unlocking
 * with rcu_read_unlock() to maintain the integrity of the pointer.
 */
struct dev_pm_opp *dev_pm_opp_find_freq_floor(struct device *dev,
                                              unsigned long *freq)
{
        struct opp_table *opp_table;
        struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);

        opp_rcu_lockdep_assert();

        if (!dev || !freq) {
                dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq);
                return ERR_PTR(-EINVAL);
        }

        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table))
                return ERR_CAST(opp_table);

        list_for_each_entry_rcu(temp_opp, &opp_table->opp_list, node) {
                if (temp_opp->available) {
                        /* go to the next node, before choosing prev */
                        if (temp_opp->rate > *freq)
                                break;
                        else
                                opp = temp_opp;
                }
        }
        if (!IS_ERR(opp))
                *freq = opp->rate;

        return opp;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_find_freq_floor);

/*
 * The caller needs to ensure that opp_table (and hence the clk) isn't freed,
 * while clk returned here is used.
 */
static struct clk *_get_opp_clk(struct device *dev)
{
        struct opp_table *opp_table;
        struct clk *clk;

        rcu_read_lock();

        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                dev_err(dev, "%s: device opp doesn't exist\n", __func__);
                clk = ERR_CAST(opp_table);
                goto unlock;
        }

        clk = opp_table->clk;
        if (IS_ERR(clk))
                dev_err(dev, "%s: No clock available for the device\n",
                        __func__);

unlock:
        rcu_read_unlock();
        return clk;
}

static int _set_opp_voltage(struct device *dev, struct regulator *reg,
                            unsigned long u_volt, unsigned long u_volt_min,
                            unsigned long u_volt_max)
{
        int ret;

        /* Regulator not available for device */
        if (IS_ERR(reg)) {
                dev_dbg(dev, "%s: regulator not available: %ld\n", __func__,
                        PTR_ERR(reg));
                return 0;
        }

        dev_dbg(dev, "%s: voltages (mV): %lu %lu %lu\n", __func__, u_volt_min,
                u_volt, u_volt_max);

        ret = regulator_set_voltage_triplet(reg, u_volt_min, u_volt,
                                            u_volt_max);
        if (ret)
                dev_err(dev, "%s: failed to set voltage (%lu %lu %lu mV): %d\n",
                        __func__, u_volt_min, u_volt, u_volt_max, ret);

        return ret;
}

/**
 * dev_pm_opp_set_rate() - Configure new OPP based on frequency
 * @dev:         device for which we do this operation
 * @target_freq: frequency to achieve
 *
 * This configures the power-supplies and clock source to the levels specified
 * by the OPP corresponding to the target_freq.
 *
 * Locking: This function takes rcu_read_lock().
 */
int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
{
        struct opp_table *opp_table;
        struct dev_pm_opp *old_opp, *opp;
        struct regulator *reg;
        struct clk *clk;
        unsigned long freq, old_freq;
        unsigned long u_volt, u_volt_min, u_volt_max;
        unsigned long ou_volt, ou_volt_min, ou_volt_max;
        int ret;

        if (unlikely(!target_freq)) {
                dev_err(dev, "%s: Invalid target frequency %lu\n", __func__,
                        target_freq);
                return -EINVAL;
        }

        clk = _get_opp_clk(dev);
        if (IS_ERR(clk))
                return PTR_ERR(clk);

        freq = clk_round_rate(clk, target_freq);
        if ((long)freq <= 0)
                freq = target_freq;

        old_freq = clk_get_rate(clk);

        /* Return early if nothing to do */
        if (old_freq == freq) {
                dev_dbg(dev, "%s: old/new frequencies (%lu Hz) are same, nothing to do\n",
                        __func__, freq);
                return 0;
        }

        rcu_read_lock();

        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                dev_err(dev, "%s: device opp doesn't exist\n", __func__);
                rcu_read_unlock();
                return PTR_ERR(opp_table);
        }

        old_opp = _find_freq_ceil(opp_table, &old_freq);
        if (!IS_ERR(old_opp)) {
                ou_volt = old_opp->u_volt;
                ou_volt_min = old_opp->u_volt_min;
                ou_volt_max = old_opp->u_volt_max;
        } else {
                dev_err(dev, "%s: failed to find current OPP for freq %lu (%ld)\n",
                        __func__, old_freq, PTR_ERR(old_opp));
        }

        opp = _find_freq_ceil(opp_table, &freq);
        if (IS_ERR(opp)) {
                ret = PTR_ERR(opp);
                dev_err(dev, "%s: failed to find OPP for freq %lu (%d)\n",
                        __func__, freq, ret);
                rcu_read_unlock();
                return ret;
        }

        u_volt = opp->u_volt;
        u_volt_min = opp->u_volt_min;
        u_volt_max = opp->u_volt_max;

        reg = opp_table->regulator;

        rcu_read_unlock();

        /* Scaling up? Scale voltage before frequency */
        if (freq > old_freq) {
                ret = _set_opp_voltage(dev, reg, u_volt, u_volt_min,
                                       u_volt_max);
                if (ret)
                        goto restore_voltage;
        }

        /* Change frequency */

        dev_dbg(dev, "%s: switching OPP: %lu Hz --> %lu Hz\n",
                __func__, old_freq, freq);

        ret = clk_set_rate(clk, freq);
        if (ret) {
                dev_err(dev, "%s: failed to set clock rate: %d\n", __func__,
                        ret);
                goto restore_voltage;
        }

        /* Scaling down? Scale voltage after frequency */
        if (freq < old_freq) {
                ret = _set_opp_voltage(dev, reg, u_volt, u_volt_min,
                                       u_volt_max);
                if (ret)
                        goto restore_freq;
        }

        return 0;

restore_freq:
        if (clk_set_rate(clk, old_freq))
                dev_err(dev, "%s: failed to restore old-freq (%lu Hz)\n",
                        __func__, old_freq);
restore_voltage:
        /* This shouldn't harm even if the voltages weren't updated earlier */
        if (!IS_ERR(old_opp))
                _set_opp_voltage(dev, reg, ou_volt, ou_volt_min, ou_volt_max);

        return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_set_rate);

/* OPP-dev Helpers */
static void _kfree_opp_dev_rcu(struct rcu_head *head)
{
        struct opp_device *opp_dev;

        opp_dev = container_of(head, struct opp_device, rcu_head);
        kfree_rcu(opp_dev, rcu_head);
}

static void _remove_opp_dev(struct opp_device *opp_dev,
                            struct opp_table *opp_table)
{
        opp_debug_unregister(opp_dev, opp_table);
        list_del(&opp_dev->node);
        call_srcu(&opp_table->srcu_head.srcu, &opp_dev->rcu_head,
                  _kfree_opp_dev_rcu);
}

struct opp_device *_add_opp_dev(const struct device *dev,
                                struct opp_table *opp_table)
{
        struct opp_device *opp_dev;
        int ret;

        opp_dev = kzalloc(sizeof(*opp_dev), GFP_KERNEL);
        if (!opp_dev)
                return NULL;

        /* Initialize opp-dev */
        opp_dev->dev = dev;
        list_add_rcu(&opp_dev->node, &opp_table->dev_list);

        /* Create debugfs entries for the opp_table */
        ret = opp_debug_register(opp_dev, opp_table);
        if (ret)
                dev_err(dev, "%s: Failed to register opp debugfs (%d)\n",
                        __func__, ret);

        return opp_dev;
}

/**
 * _add_opp_table() - Find OPP table or allocate a new one
 * @dev:        device for which we do this operation
 *
 * It tries to find an existing table first, if it couldn't find one, it
 * allocates a new OPP table and returns that.
 *
 * Return: valid opp_table pointer if success, else NULL.
 */
static struct opp_table *_add_opp_table(struct device *dev)
{
        struct opp_table *opp_table;
        struct opp_device *opp_dev;
        int ret;

        /* Check for existing table for 'dev' first */
        opp_table = _find_opp_table(dev);
        if (!IS_ERR(opp_table))
                return opp_table;

        /*
         * Allocate a new OPP table. In the infrequent case where a new
         * device is needed to be added, we pay this penalty.
         */
        opp_table = kzalloc(sizeof(*opp_table), GFP_KERNEL);
        if (!opp_table)
                return NULL;

        INIT_LIST_HEAD(&opp_table->dev_list);

        opp_dev = _add_opp_dev(dev, opp_table);
        if (!opp_dev) {
                kfree(opp_table);
                return NULL;
        }

        _of_init_opp_table(opp_table, dev);

        /* Set regulator to a non-NULL error value */
        opp_table->regulator = ERR_PTR(-ENXIO);

        /* Find clk for the device */
        opp_table->clk = clk_get(dev, NULL);
        if (IS_ERR(opp_table->clk)) {
                ret = PTR_ERR(opp_table->clk);
                if (ret != -EPROBE_DEFER)
                        dev_dbg(dev, "%s: Couldn't find clock: %d\n", __func__,
                                ret);
        }

        srcu_init_notifier_head(&opp_table->srcu_head);
        INIT_LIST_HEAD(&opp_table->opp_list);

        /* Secure the device table modification */
        list_add_rcu(&opp_table->node, &opp_tables);
        return opp_table;
}

/**
 * _kfree_device_rcu() - Free opp_table RCU handler
 * @head:       RCU head
 */
static void _kfree_device_rcu(struct rcu_head *head)
{
        struct opp_table *opp_table = container_of(head, struct opp_table,
                                                   rcu_head);

        kfree_rcu(opp_table, rcu_head);
}

/**
 * _remove_opp_table() - Removes a OPP table
 * @opp_table: OPP table to be removed.
 *
 * Removes/frees OPP table if it doesn't contain any OPPs.
 */
static void _remove_opp_table(struct opp_table *opp_table)
{
        struct opp_device *opp_dev;

        if (!list_empty(&opp_table->opp_list))
                return;

        if (opp_table->supported_hw)
                return;

        if (opp_table->prop_name)
                return;

        if (!IS_ERR(opp_table->regulator))
                return;

        /* Release clk */
        if (!IS_ERR(opp_table->clk))
                clk_put(opp_table->clk);

        opp_dev = list_first_entry(&opp_table->dev_list, struct opp_device,
                                   node);

        _remove_opp_dev(opp_dev, opp_table);

        /* dev_list must be empty now */
        WARN_ON(!list_empty(&opp_table->dev_list));

        list_del_rcu(&opp_table->node);
        call_srcu(&opp_table->srcu_head.srcu, &opp_table->rcu_head,
                  _kfree_device_rcu);
}

/**
 * _kfree_opp_rcu() - Free OPP RCU handler
 * @head:       RCU head
 */
static void _kfree_opp_rcu(struct rcu_head *head)
{
        struct dev_pm_opp *opp = container_of(head, struct dev_pm_opp, rcu_head);

        kfree_rcu(opp, rcu_head);
}

/**
 * _opp_remove()  - Remove an OPP from a table definition
 * @opp_table:  points back to the opp_table struct this opp belongs to
 * @opp:        pointer to the OPP to remove
 * @notify:     OPP_EVENT_REMOVE notification should be sent or not
 *
 * This function removes an opp definition from the opp table.
 *
 * Locking: The internal opp_table and opp structures are RCU protected.
 * It is assumed that the caller holds required mutex for an RCU updater
 * strategy.
 */
void _opp_remove(struct opp_table *opp_table, struct dev_pm_opp *opp,
                 bool notify)
{
        /*
         * Notify the changes in the availability of the operable
         * frequency/voltage list.
         */
        if (notify)
                srcu_notifier_call_chain(&opp_table->srcu_head,
                                         OPP_EVENT_REMOVE, opp);
        opp_debug_remove_one(opp);
        list_del_rcu(&opp->node);
        call_srcu(&opp_table->srcu_head.srcu, &opp->rcu_head, _kfree_opp_rcu);

        _remove_opp_table(opp_table);
}

/**
 * dev_pm_opp_remove()  - Remove an OPP from OPP table
 * @dev:        device for which we do this operation
 * @freq:       OPP to remove with matching 'freq'
 *
 * This function removes an opp from the opp table.
 *
 * Locking: The internal opp_table and opp structures are RCU protected.
 * Hence this function internally uses RCU updater strategy with mutex locks
 * to keep the integrity of the internal data structures. Callers should ensure
 * that this function is *NOT* called under RCU protection or in contexts where
 * mutex cannot be locked.
 */
void dev_pm_opp_remove(struct device *dev, unsigned long freq)
{
        struct dev_pm_opp *opp;
        struct opp_table *opp_table;
        bool found = false;

        /* Hold our table modification lock here */
        mutex_lock(&opp_table_lock);

        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table))
                goto unlock;

        list_for_each_entry(opp, &opp_table->opp_list, node) {
                if (opp->rate == freq) {
                        found = true;
                        break;
                }
        }

        if (!found) {
                dev_warn(dev, "%s: Couldn't find OPP with freq: %lu\n",
                         __func__, freq);
                goto unlock;
        }

        _opp_remove(opp_table, opp, true);
unlock:
        mutex_unlock(&opp_table_lock);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_remove);

struct dev_pm_opp *_allocate_opp(struct device *dev,
                                 struct opp_table **opp_table)
{
        struct dev_pm_opp *opp;

        /* allocate new OPP node */
        opp = kzalloc(sizeof(*opp), GFP_KERNEL);
        if (!opp)
                return NULL;

        INIT_LIST_HEAD(&opp->node);

        *opp_table = _add_opp_table(dev);
        if (!*opp_table) {
                kfree(opp);
                return NULL;
        }

        return opp;
}

static bool _opp_supported_by_regulators(struct dev_pm_opp *opp,
                                         struct opp_table *opp_table)
{
        struct regulator *reg = opp_table->regulator;

        if (!IS_ERR(reg) &&
            !regulator_is_supported_voltage(reg, opp->u_volt_min,
                                            opp->u_volt_max)) {
                pr_warn("%s: OPP minuV: %lu maxuV: %lu, not supported by regulator\n",
                        __func__, opp->u_volt_min, opp->u_volt_max);
                return false;
        }

        return true;
}

int _opp_add(struct device *dev, struct dev_pm_opp *new_opp,
             struct opp_table *opp_table)
{
        struct dev_pm_opp *opp;
        struct list_head *head = &opp_table->opp_list;
        int ret;

        /*
         * Insert new OPP in order of increasing frequency and discard if
         * already present.
         *
         * Need to use &opp_table->opp_list in the condition part of the 'for'
         * loop, don't replace it with head otherwise it will become an infinite
         * loop.
         */
        list_for_each_entry_rcu(opp, &opp_table->opp_list, node) {
                if (new_opp->rate > opp->rate) {
                        head = &opp->node;
                        continue;
                }

                if (new_opp->rate < opp->rate)
                        break;

                /* Duplicate OPPs */
                dev_warn(dev, "%s: duplicate OPPs detected. Existing: freq: %lu, volt: %lu, enabled: %d. New: freq: %lu, volt: %lu, enabled: %d\n",
                         __func__, opp->rate, opp->u_volt, opp->available,
                         new_opp->rate, new_opp->u_volt, new_opp->available);

                return opp->available && new_opp->u_volt == opp->u_volt ?
                        0 : -EEXIST;
        }

        new_opp->opp_table = opp_table;
        list_add_rcu(&new_opp->node, head);

        ret = opp_debug_create_one(new_opp, opp_table);
        if (ret)
                dev_err(dev, "%s: Failed to register opp to debugfs (%d)\n",
                        __func__, ret);

        if (!_opp_supported_by_regulators(new_opp, opp_table)) {
                new_opp->available = false;
                dev_warn(dev, "%s: OPP not supported by regulators (%lu)\n",
                         __func__, new_opp->rate);
        }

        return 0;
}

/**
 * _opp_add_v1() - Allocate a OPP based on v1 bindings.
 * @dev:        device for which we do this operation
 * @freq:       Frequency in Hz for this OPP
 * @u_volt:     Voltage in uVolts for this OPP
 * @dynamic:    Dynamically added OPPs.
 *
 * This function adds an opp definition to the opp table and returns status.
 * The opp is made available by default and it can be controlled using
 * dev_pm_opp_enable/disable functions and may be removed by dev_pm_opp_remove.
 *
 * NOTE: "dynamic" parameter impacts OPPs added by the dev_pm_opp_of_add_table
 * and freed by dev_pm_opp_of_remove_table.
 *
 * Locking: The internal opp_table and opp structures are RCU protected.
 * Hence this function internally uses RCU updater strategy with mutex locks
 * to keep the integrity of the internal data structures. Callers should ensure
 * that this function is *NOT* called under RCU protection or in contexts where
 * mutex cannot be locked.
 *
 * Return:
 * 0            On success OR
 *              Duplicate OPPs (both freq and volt are same) and opp->available
 * -EEXIST      Freq are same and volt are different OR
 *              Duplicate OPPs (both freq and volt are same) and !opp->available
 * -ENOMEM      Memory allocation failure
 */
int _opp_add_v1(struct device *dev, unsigned long freq, long u_volt,
                bool dynamic)
{
        struct opp_table *opp_table;
        struct dev_pm_opp *new_opp;
        unsigned long tol;
        int ret;

        /* Hold our table modification lock here */
        mutex_lock(&opp_table_lock);

        new_opp = _allocate_opp(dev, &opp_table);
        if (!new_opp) {
                ret = -ENOMEM;
                goto unlock;
        }

        /* populate the opp table */
        new_opp->rate = freq;
        tol = u_volt * opp_table->voltage_tolerance_v1 / 100;
        new_opp->u_volt = u_volt;
        new_opp->u_volt_min = u_volt - tol;
        new_opp->u_volt_max = u_volt + tol;
        new_opp->available = true;
        new_opp->dynamic = dynamic;

        ret = _opp_add(dev, new_opp, opp_table);
        if (ret)
                goto free_opp;

        mutex_unlock(&opp_table_lock);

        /*
         * Notify the changes in the availability of the operable
         * frequency/voltage list.
         */
        srcu_notifier_call_chain(&opp_table->srcu_head, OPP_EVENT_ADD, new_opp);
        return 0;

free_opp:
        _opp_remove(opp_table, new_opp, false);
unlock:
        mutex_unlock(&opp_table_lock);
        return ret;
}

/**
 * dev_pm_opp_set_supported_hw() - Set supported platforms
 * @dev: Device for which supported-hw has to be set.
 * @versions: Array of hierarchy of versions to match.
 * @count: Number of elements in the array.
 *
 * This is required only for the V2 bindings, and it enables a platform to
 * specify the hierarchy of versions it supports. OPP layer will then enable
 * OPPs, which are available for those versions, based on its 'opp-supported-hw'
 * property.
 *
 * Locking: The internal opp_table and opp structures are RCU protected.
 * Hence this function internally uses RCU updater strategy with mutex locks
 * to keep the integrity of the internal data structures. Callers should ensure
 * that this function is *NOT* called under RCU protection or in contexts where
 * mutex cannot be locked.
 */
int dev_pm_opp_set_supported_hw(struct device *dev, const u32 *versions,
                                unsigned int count)
{
        struct opp_table *opp_table;
        int ret = 0;

        /* Hold our table modification lock here */
        mutex_lock(&opp_table_lock);

        opp_table = _add_opp_table(dev);
        if (!opp_table) {
                ret = -ENOMEM;
                goto unlock;
        }

        /* Make sure there are no concurrent readers while updating opp_table */
        WARN_ON(!list_empty(&opp_table->opp_list));

        /* Do we already have a version hierarchy associated with opp_table? */
        if (opp_table->supported_hw) {
                dev_err(dev, "%s: Already have supported hardware list\n",
                        __func__);
                ret = -EBUSY;
                goto err;
        }

        opp_table->supported_hw = kmemdup(versions, count * sizeof(*versions),
                                        GFP_KERNEL);
        if (!opp_table->supported_hw) {
                ret = -ENOMEM;
                goto err;
        }

        opp_table->supported_hw_count = count;
        mutex_unlock(&opp_table_lock);
        return 0;

err:
        _remove_opp_table(opp_table);
unlock:
        mutex_unlock(&opp_table_lock);

        return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_set_supported_hw);

/**
 * dev_pm_opp_put_supported_hw() - Releases resources blocked for supported hw
 * @dev: Device for which supported-hw has to be put.
 *
 * This is required only for the V2 bindings, and is called for a matching
 * dev_pm_opp_set_supported_hw(). Until this is called, the opp_table structure
 * will not be freed.
 *
 * Locking: The internal opp_table and opp structures are RCU protected.
 * Hence this function internally uses RCU updater strategy with mutex locks
 * to keep the integrity of the internal data structures. Callers should ensure
 * that this function is *NOT* called under RCU protection or in contexts where
 * mutex cannot be locked.
 */
void dev_pm_opp_put_supported_hw(struct device *dev)
{
        struct opp_table *opp_table;

        /* Hold our table modification lock here */
        mutex_lock(&opp_table_lock);

        /* Check for existing table for 'dev' first */
        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                dev_err(dev, "Failed to find opp_table: %ld\n",
                        PTR_ERR(opp_table));
                goto unlock;
        }

        /* Make sure there are no concurrent readers while updating opp_table */
        WARN_ON(!list_empty(&opp_table->opp_list));

        if (!opp_table->supported_hw) {
                dev_err(dev, "%s: Doesn't have supported hardware list\n",
                        __func__);
                goto unlock;
        }

        kfree(opp_table->supported_hw);
        opp_table->supported_hw = NULL;
        opp_table->supported_hw_count = 0;

        /* Try freeing opp_table if this was the last blocking resource */
        _remove_opp_table(opp_table);

unlock:
        mutex_unlock(&opp_table_lock);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_put_supported_hw);

/**
 * dev_pm_opp_set_prop_name() - Set prop-extn name
 * @dev: Device for which the prop-name has to be set.
 * @name: name to postfix to properties.
 *
 * This is required only for the V2 bindings, and it enables a platform to
 * specify the extn to be used for certain property names. The properties to
 * which the extension will apply are opp-microvolt and opp-microamp. OPP core
 * should postfix the property name with -<name> while looking for them.
 *
 * Locking: The internal opp_table and opp structures are RCU protected.
 * Hence this function internally uses RCU updater strategy with mutex locks
 * to keep the integrity of the internal data structures. Callers should ensure
 * that this function is *NOT* called under RCU protection or in contexts where
 * mutex cannot be locked.
 */
int dev_pm_opp_set_prop_name(struct device *dev, const char *name)
{
        struct opp_table *opp_table;
        int ret = 0;

        /* Hold our table modification lock here */
        mutex_lock(&opp_table_lock);

        opp_table = _add_opp_table(dev);
        if (!opp_table) {
                ret = -ENOMEM;
                goto unlock;
        }

        /* Make sure there are no concurrent readers while updating opp_table */
        WARN_ON(!list_empty(&opp_table->opp_list));

        /* Do we already have a prop-name associated with opp_table? */
        if (opp_table->prop_name) {
                dev_err(dev, "%s: Already have prop-name %s\n", __func__,
                        opp_table->prop_name);
                ret = -EBUSY;
                goto err;
        }

        opp_table->prop_name = kstrdup(name, GFP_KERNEL);
        if (!opp_table->prop_name) {
                ret = -ENOMEM;
                goto err;
        }

        mutex_unlock(&opp_table_lock);
        return 0;

err:
        _remove_opp_table(opp_table);
unlock:
        mutex_unlock(&opp_table_lock);

        return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_set_prop_name);

/**
 * dev_pm_opp_put_prop_name() - Releases resources blocked for prop-name
 * @dev: Device for which the prop-name has to be put.
 *
 * This is required only for the V2 bindings, and is called for a matching
 * dev_pm_opp_set_prop_name(). Until this is called, the opp_table structure
 * will not be freed.
 *
 * Locking: The internal opp_table and opp structures are RCU protected.
 * Hence this function internally uses RCU updater strategy with mutex locks
 * to keep the integrity of the internal data structures. Callers should ensure
 * that this function is *NOT* called under RCU protection or in contexts where
 * mutex cannot be locked.
 */
void dev_pm_opp_put_prop_name(struct device *dev)
{
        struct opp_table *opp_table;

        /* Hold our table modification lock here */
        mutex_lock(&opp_table_lock);

        /* Check for existing table for 'dev' first */
        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                dev_err(dev, "Failed to find opp_table: %ld\n",
                        PTR_ERR(opp_table));
                goto unlock;
        }

        /* Make sure there are no concurrent readers while updating opp_table */
        WARN_ON(!list_empty(&opp_table->opp_list));

        if (!opp_table->prop_name) {
                dev_err(dev, "%s: Doesn't have a prop-name\n", __func__);
                goto unlock;
        }

        kfree(opp_table->prop_name);
        opp_table->prop_name = NULL;

        /* Try freeing opp_table if this was the last blocking resource */
        _remove_opp_table(opp_table);

unlock:
        mutex_unlock(&opp_table_lock);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_put_prop_name);

/**
 * dev_pm_opp_set_regulator() - Set regulator name for the device
 * @dev: Device for which regulator name is being set.
 * @name: Name of the regulator.
 *
 * In order to support OPP switching, OPP layer needs to know the name of the
 * device's regulator, as the core would be required to switch voltages as well.
 *
 * This must be called before any OPPs are initialized for the device.
 *
 * Locking: The internal opp_table and opp structures are RCU protected.
 * Hence this function internally uses RCU updater strategy with mutex locks
 * to keep the integrity of the internal data structures. Callers should ensure
 * that this function is *NOT* called under RCU protection or in contexts where
 * mutex cannot be locked.
 */
int dev_pm_opp_set_regulator(struct device *dev, const char *name)
{
        struct opp_table *opp_table;
        struct regulator *reg;
        int ret;

        mutex_lock(&opp_table_lock);

        opp_table = _add_opp_table(dev);
        if (!opp_table) {
                ret = -ENOMEM;
                goto unlock;
        }

        /* This should be called before OPPs are initialized */
        if (WARN_ON(!list_empty(&opp_table->opp_list))) {
                ret = -EBUSY;
                goto err;
        }

        /* Already have a regulator set */
        if (WARN_ON(!IS_ERR(opp_table->regulator))) {
                ret = -EBUSY;
                goto err;
        }
        /* Allocate the regulator */
        reg = regulator_get_optional(dev, name);
        if (IS_ERR(reg)) {
                ret = PTR_ERR(reg);
                if (ret != -EPROBE_DEFER)
                        dev_err(dev, "%s: no regulator (%s) found: %d\n",
                                __func__, name, ret);
                goto err;
        }

        opp_table->regulator = reg;

        mutex_unlock(&opp_table_lock);
        return 0;

err:
        _remove_opp_table(opp_table);
unlock:
        mutex_unlock(&opp_table_lock);

        return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_set_regulator);

/**
 * dev_pm_opp_put_regulator() - Releases resources blocked for regulator
 * @dev: Device for which regulator was set.
 *
 * Locking: The internal opp_table and opp structures are RCU protected.
 * Hence this function internally uses RCU updater strategy with mutex locks
 * to keep the integrity of the internal data structures. Callers should ensure
 * that this function is *NOT* called under RCU protection or in contexts where
 * mutex cannot be locked.
 */
void dev_pm_opp_put_regulator(struct device *dev)
{
        struct opp_table *opp_table;

        mutex_lock(&opp_table_lock);

        /* Check for existing table for 'dev' first */
        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                dev_err(dev, "Failed to find opp_table: %ld\n",
                        PTR_ERR(opp_table));
                goto unlock;
        }

        if (IS_ERR(opp_table->regulator)) {
                dev_err(dev, "%s: Doesn't have regulator set\n", __func__);
                goto unlock;
        }

        /* Make sure there are no concurrent readers while updating opp_table */
        WARN_ON(!list_empty(&opp_table->opp_list));

        regulator_put(opp_table->regulator);
        opp_table->regulator = ERR_PTR(-ENXIO);

        /* Try freeing opp_table if this was the last blocking resource */
        _remove_opp_table(opp_table);

unlock:
        mutex_unlock(&opp_table_lock);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_put_regulator);

/**
 * dev_pm_opp_add()  - Add an OPP table from a table definitions
 * @dev:        device for which we do this operation
 * @freq:       Frequency in Hz for this OPP
 * @u_volt:     Voltage in uVolts for this OPP
 *
 * This function adds an opp definition to the opp table and returns status.
 * The opp is made available by default and it can be controlled using
 * dev_pm_opp_enable/disable functions.
 *
 * Locking: The internal opp_table and opp structures are RCU protected.
 * Hence this function internally uses RCU updater strategy with mutex locks
 * to keep the integrity of the internal data structures. Callers should ensure
 * that this function is *NOT* called under RCU protection or in contexts where
 * mutex cannot be locked.
 *
 * Return:
 * 0            On success OR
 *              Duplicate OPPs (both freq and volt are same) and opp->available
 * -EEXIST      Freq are same and volt are different OR
 *              Duplicate OPPs (both freq and volt are same) and !opp->available
 * -ENOMEM      Memory allocation failure
 */
int dev_pm_opp_add(struct device *dev, unsigned long freq, unsigned long u_volt)
{
        return _opp_add_v1(dev, freq, u_volt, true);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_add);

/**
 * _opp_set_availability() - helper to set the availability of an opp
 * @dev:                device for which we do this operation
 * @freq:               OPP frequency to modify availability
 * @availability_req:   availability status requested for this opp
 *
 * Set the availability of an OPP with an RCU operation, opp_{enable,disable}
 * share a common logic which is isolated here.
 *
 * Return: -EINVAL for bad pointers, -ENOMEM if no memory available for the
 * copy operation, returns 0 if no modification was done OR modification was
 * successful.
 *
 * Locking: The internal opp_table and opp structures are RCU protected.
 * Hence this function internally uses RCU updater strategy with mutex locks to
 * keep the integrity of the internal data structures. Callers should ensure
 * that this function is *NOT* called under RCU protection or in contexts where
 * mutex locking or synchronize_rcu() blocking calls cannot be used.
 */
static int _opp_set_availability(struct device *dev, unsigned long freq,
                                 bool availability_req)
{
        struct opp_table *opp_table;
        struct dev_pm_opp *new_opp, *tmp_opp, *opp = ERR_PTR(-ENODEV);
        int r = 0;

        /* keep the node allocated */
        new_opp = kmalloc(sizeof(*new_opp), GFP_KERNEL);
        if (!new_opp)
                return -ENOMEM;

        mutex_lock(&opp_table_lock);

        /* Find the opp_table */
        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                r = PTR_ERR(opp_table);
                dev_warn(dev, "%s: Device OPP not found (%d)\n", __func__, r);
                goto unlock;
        }

        /* Do we have the frequency? */
        list_for_each_entry(tmp_opp, &opp_table->opp_list, node) {
                if (tmp_opp->rate == freq) {
                        opp = tmp_opp;
                        break;
                }
        }
        if (IS_ERR(opp)) {
                r = PTR_ERR(opp);
                goto unlock;
        }

        /* Is update really needed? */
        if (opp->available == availability_req)
                goto unlock;
        /* copy the old data over */
        *new_opp = *opp;

        /* plug in new node */
        new_opp->available = availability_req;

        list_replace_rcu(&opp->node, &new_opp->node);
        mutex_unlock(&opp_table_lock);
        call_srcu(&opp_table->srcu_head.srcu, &opp->rcu_head, _kfree_opp_rcu);

        /* Notify the change of the OPP availability */
        if (availability_req)
                srcu_notifier_call_chain(&opp_table->srcu_head,
                                         OPP_EVENT_ENABLE, new_opp);
        else
                srcu_notifier_call_chain(&opp_table->srcu_head,
                                         OPP_EVENT_DISABLE, new_opp);

        return 0;

unlock:
        mutex_unlock(&opp_table_lock);
        kfree(new_opp);
        return r;
}

/**
 * dev_pm_opp_enable() - Enable a specific OPP
 * @dev:        device for which we do this operation
 * @freq:       OPP frequency to enable
 *
 * Enables a provided opp. If the operation is valid, this returns 0, else the
 * corresponding error value. It is meant to be used for users an OPP available
 * after being temporarily made unavailable with dev_pm_opp_disable.
 *
 * Locking: The internal opp_table and opp structures are RCU protected.
 * Hence this function indirectly uses RCU and mutex locks to keep the
 * integrity of the internal data structures. Callers should ensure that
 * this function is *NOT* called under RCU protection or in contexts where
 * mutex locking or synchronize_rcu() blocking calls cannot be used.
 *
 * Return: -EINVAL for bad pointers, -ENOMEM if no memory available for the
 * copy operation, returns 0 if no modification was done OR modification was
 * successful.
 */
int dev_pm_opp_enable(struct device *dev, unsigned long freq)
{
        return _opp_set_availability(dev, freq, true);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_enable);

/**
 * dev_pm_opp_disable() - Disable a specific OPP
 * @dev:        device for which we do this operation
 * @freq:       OPP frequency to disable
 *
 * Disables a provided opp. If the operation is valid, this returns
 * 0, else the corresponding error value. It is meant to be a temporary
 * control by users to make this OPP not available until the circumstances are
 * right to make it available again (with a call to dev_pm_opp_enable).
 *
 * Locking: The internal opp_table and opp structures are RCU protected.
 * Hence this function indirectly uses RCU and mutex locks to keep the
 * integrity of the internal data structures. Callers should ensure that
 * this function is *NOT* called under RCU protection or in contexts where
 * mutex locking or synchronize_rcu() blocking calls cannot be used.
 *
 * Return: -EINVAL for bad pointers, -ENOMEM if no memory available for the
 * copy operation, returns 0 if no modification was done OR modification was
 * successful.
 */
int dev_pm_opp_disable(struct device *dev, unsigned long freq)
{
        return _opp_set_availability(dev, freq, false);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_disable);

/**
 * dev_pm_opp_get_notifier() - find notifier_head of the device with opp
 * @dev:        device pointer used to lookup OPP table.
 *
 * Return: pointer to  notifier head if found, otherwise -ENODEV or
 * -EINVAL based on type of error casted as pointer. value must be checked
 *  with IS_ERR to determine valid pointer or error result.
 *
 * Locking: This function must be called under rcu_read_lock(). opp_table is a
 * RCU protected pointer. The reason for the same is that the opp pointer which
 * is returned will remain valid for use with opp_get_{voltage, freq} only while
 * under the locked area. The pointer returned must be used prior to unlocking
 * with rcu_read_unlock() to maintain the integrity of the pointer.
 */
struct srcu_notifier_head *dev_pm_opp_get_notifier(struct device *dev)
{
        struct opp_table *opp_table = _find_opp_table(dev);

        if (IS_ERR(opp_table))
                return ERR_CAST(opp_table); /* matching type */

        return &opp_table->srcu_head;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_get_notifier);

/*
 * Free OPPs either created using static entries present in DT or even the
 * dynamically added entries based on remove_all param.
 */
void _dev_pm_opp_remove_table(struct device *dev, bool remove_all)
{
        struct opp_table *opp_table;
        struct dev_pm_opp *opp, *tmp;

        /* Hold our table modification lock here */
        mutex_lock(&opp_table_lock);

        /* Check for existing table for 'dev' */
        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                int error = PTR_ERR(opp_table);

                if (error != -ENODEV)
                        WARN(1, "%s: opp_table: %d\n",
                             IS_ERR_OR_NULL(dev) ?
                                        "Invalid device" : dev_name(dev),
                             error);
                goto unlock;
        }

        /* Find if opp_table manages a single device */
        if (list_is_singular(&opp_table->dev_list)) {
                /* Free static OPPs */
                list_for_each_entry_safe(opp, tmp, &opp_table->opp_list, node) {
                        if (remove_all || !opp->dynamic)
                                _opp_remove(opp_table, opp, true);
                }
        } else {
                _remove_opp_dev(_find_opp_dev(dev, opp_table), opp_table);
        }

unlock:
        mutex_unlock(&opp_table_lock);
}

/**
 * dev_pm_opp_remove_table() - Free all OPPs associated with the device
 * @dev:        device pointer used to lookup OPP table.
 *
 * Free both OPPs created using static entries present in DT and the
 * dynamically added entries.
 *
 * Locking: The internal opp_table and opp structures are RCU protected.
 * Hence this function indirectly uses RCU updater strategy with mutex locks
 * to keep the integrity of the internal data structures. Callers should ensure
 * that this function is *NOT* called under RCU protection or in contexts where
 * mutex cannot be locked.
 */
void dev_pm_opp_remove_table(struct device *dev)
{
        _dev_pm_opp_remove_table(dev, true);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_remove_table);