drivers/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/pm_domain.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);

static void dev_pm_opp_get(struct dev_pm_opp *opp);

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;
}

static struct opp_table *_find_opp_table_unlocked(struct device *dev)
{
	struct opp_table *opp_table;

	list_for_each_entry(opp_table, &opp_tables, node) {
		if (_find_opp_dev(dev, opp_table)) {
			_get_opp_table_kref(opp_table);

			return opp_table;
		}
	}

	return ERR_PTR(-ENODEV);
}

/**
 * _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.
 *
 * Return: pointer to 'struct opp_table' if found, otherwise -ENODEV or
 * -EINVAL based on type of error.
 *
 * The callers must call dev_pm_opp_put_opp_table() after the table is used.
 */
struct opp_table *_find_opp_table(struct device *dev)
{
	struct opp_table *opp_table;

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

	mutex_lock(&opp_table_lock);
	opp_table = _find_opp_table_unlocked(dev);
	mutex_unlock(&opp_table_lock);

	return opp_table;
}

/**
 * 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
 *
 * This is useful only for devices with single power supply.
 */
unsigned long dev_pm_opp_get_voltage(struct dev_pm_opp *opp)
{
	if (IS_ERR_OR_NULL(opp)) {
		pr_err("%s: Invalid parameters\n", __func__);
		return 0;
	}

	return opp->supplies[0].u_volt;
}
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
 */
unsigned long dev_pm_opp_get_freq(struct dev_pm_opp *opp)
{
	if (IS_ERR_OR_NULL(opp) || !opp->available) {
		pr_err("%s: Invalid parameters\n", __func__);
		return 0;
	}

	return opp->rate;
}
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.
 */
bool dev_pm_opp_is_turbo(struct dev_pm_opp *opp)
{
	if (IS_ERR_OR_NULL(opp) || !opp->available) {
		pr_err("%s: Invalid parameters\n", __func__);
		return false;
	}

	return 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.
 */
unsigned long dev_pm_opp_get_max_clock_latency(struct device *dev)
{
	struct opp_table *opp_table;
	unsigned long clock_latency_ns;

	opp_table = _find_opp_table(dev);
	if (IS_ERR(opp_table))
		return 0;

	clock_latency_ns = opp_table->clock_latency_ns_max;

	dev_pm_opp_put_opp_table(opp_table);

	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.
 */
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;
	int ret, i, count;
	struct {
		unsigned long min;
		unsigned long max;
	} *uV;

	opp_table = _find_opp_table(dev);
	if (IS_ERR(opp_table))
		return 0;

	count = opp_table->regulator_count;

	/* Regulator may not be required for the device */
	if (!count)
		goto put_opp_table;

	uV = kmalloc_array(count, sizeof(*uV), GFP_KERNEL);
	if (!uV)
		goto put_opp_table;

	mutex_lock(&opp_table->lock);

	for (i = 0; i < count; i++) {
		uV[i].min = ~0;
		uV[i].max = 0;

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

			if (opp->supplies[i].u_volt_min < uV[i].min)
				uV[i].min = opp->supplies[i].u_volt_min;
			if (opp->supplies[i].u_volt_max > uV[i].max)
				uV[i].max = opp->supplies[i].u_volt_max;
		}
	}

	mutex_unlock(&opp_table->lock);

	/*
	 * The caller needs to ensure that opp_table (and hence the regulator)
	 * isn't freed, while we are executing this routine.
	 */
	for (i = 0; i < count; i++) {
		reg = opp_table->regulators[i];
		ret = regulator_set_voltage_time(reg, uV[i].min, uV[i].max);
		if (ret > 0)
			latency_ns += ret * 1000;
	}

	kfree(uV);
put_opp_table:
	dev_pm_opp_put_opp_table(opp_table);

	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.
 */
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_freq() - Get frequency of suspend opp in Hz
 * @dev:	device for which we do this operation
 *
 * Return: This function returns the frequency of the OPP marked as suspend_opp
 * if one is available, else returns 0;
 */
unsigned long dev_pm_opp_get_suspend_opp_freq(struct device *dev)
{
	struct opp_table *opp_table;
	unsigned long freq = 0;

	opp_table = _find_opp_table(dev);
	if (IS_ERR(opp_table))
		return 0;

	if (opp_table->suspend_opp && opp_table->suspend_opp->available)
		freq = dev_pm_opp_get_freq(opp_table->suspend_opp);

	dev_pm_opp_put_opp_table(opp_table);

	return freq;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_get_suspend_opp_freq);

/**
 * 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.
 */
int dev_pm_opp_get_opp_count(struct device *dev)
{
	struct opp_table *opp_table;
	struct dev_pm_opp *temp_opp;
	int count = 0;

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

	mutex_lock(&opp_table->lock);

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

	mutex_unlock(&opp_table->lock);
	dev_pm_opp_put_opp_table(opp_table);

	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.
 *
 * The callers are required to call dev_pm_opp_put() for the returned OPP after
 * use.
 */
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_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);
	}

	mutex_lock(&opp_table->lock);

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

			/* Increment the reference count of OPP */
			dev_pm_opp_get(opp);
			break;
		}
	}

	mutex_unlock(&opp_table->lock);
	dev_pm_opp_put_opp_table(opp_table);

	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);

	mutex_lock(&opp_table->lock);

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

			/* Increment the reference count of OPP */
			dev_pm_opp_get(opp);
			break;
		}
	}

	mutex_unlock(&opp_table->lock);

	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
 *
 * The callers are required to call dev_pm_opp_put() for the returned OPP after
 * use.
 */
struct dev_pm_opp *dev_pm_opp_find_freq_ceil(struct device *dev,
					     unsigned long *freq)
{
	struct opp_table *opp_table;
	struct dev_pm_opp *opp;

	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);

	opp = _find_freq_ceil(opp_table, freq);

	dev_pm_opp_put_opp_table(opp_table);

	return opp;
}
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
 *
 * The callers are required to call dev_pm_opp_put() for the returned OPP after
 * use.
 */
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);

	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);

	mutex_lock(&opp_table->lock);

	list_for_each_entry(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;
		}
	}

	/* Increment the reference count of OPP */
	if (!IS_ERR(opp))
		dev_pm_opp_get(opp);
	mutex_unlock(&opp_table->lock);
	dev_pm_opp_put_opp_table(opp_table);

	if (!IS_ERR(opp))
		*freq = opp->rate;

	return opp;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_find_freq_floor);

static int _set_opp_voltage(struct device *dev, struct regulator *reg,
			    struct dev_pm_opp_supply *supply)
{
	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__,
		supply->u_volt_min, supply->u_volt, supply->u_volt_max);

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

	return ret;
}

static inline int
_generic_set_opp_clk_only(struct device *dev, struct clk *clk,
			  unsigned long old_freq, unsigned long freq)
{
	int ret;

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

	return ret;
}

static inline int
_generic_set_opp_domain(struct device *dev, struct clk *clk,
			unsigned long old_freq, unsigned long freq,
			unsigned int old_pstate, unsigned int new_pstate)
{
	int ret;

	/* Scaling up? Scale domain performance state before frequency */
	if (freq > old_freq) {
		ret = dev_pm_genpd_set_performance_state(dev, new_pstate);
		if (ret)
			return ret;
	}

	ret = _generic_set_opp_clk_only(dev, clk, old_freq, freq);
	if (ret)
		goto restore_domain_state;

	/* Scaling down? Scale domain performance state after frequency */
	if (freq < old_freq) {
		ret = dev_pm_genpd_set_performance_state(dev, new_pstate);
		if (ret)
			goto restore_freq;
	}

	return 0;

restore_freq:
	if (_generic_set_opp_clk_only(dev, clk, freq, old_freq))
		dev_err(dev, "%s: failed to restore old-freq (%lu Hz)\n",
			__func__, old_freq);
restore_domain_state:
	if (freq > old_freq)
		dev_pm_genpd_set_performance_state(dev, old_pstate);

	return ret;
}

static int _generic_set_opp_regulator(const struct opp_table *opp_table,
				      struct device *dev,
				      unsigned long old_freq,
				      unsigned long freq,
				      struct dev_pm_opp_supply *old_supply,
				      struct dev_pm_opp_supply *new_supply)
{
	struct regulator *reg = opp_table->regulators[0];
	int ret;

	/* This function only supports single regulator per device */
	if (WARN_ON(opp_table->regulator_count > 1)) {
		dev_err(dev, "multiple regulators are not supported\n");
		return -EINVAL;
	}

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

	/* Change frequency */
	ret = _generic_set_opp_clk_only(dev, opp_table->clk, old_freq, freq);
	if (ret)
		goto restore_voltage;

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

	return 0;

restore_freq:
	if (_generic_set_opp_clk_only(dev, opp_table->clk, freq, 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 (old_supply)
		_set_opp_voltage(dev, reg, old_supply);

	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.
 */
int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
{
	struct opp_table *opp_table;
	unsigned long freq, old_freq;
	struct dev_pm_opp *old_opp, *opp;
	struct clk *clk;
	int ret, size;

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

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

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

	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);
		ret = 0;
		goto put_opp_table;
	}

	old_opp = _find_freq_ceil(opp_table, &old_freq);
	if (IS_ERR(old_opp)) {
		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);
		goto put_old_opp;
	}

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

	/* Only frequency scaling */
	if (!opp_table->regulators) {
		/*
		 * We don't support devices with both regulator and
		 * domain performance-state for now.
		 */
		if (opp_table->genpd_performance_state)
			ret = _generic_set_opp_domain(dev, clk, old_freq, freq,
						      IS_ERR(old_opp) ? 0 : old_opp->pstate,
						      opp->pstate);
		else
			ret = _generic_set_opp_clk_only(dev, clk, old_freq, freq);
	} else if (!opp_table->set_opp) {
		ret = _generic_set_opp_regulator(opp_table, dev, old_freq, freq,
						 IS_ERR(old_opp) ? NULL : old_opp->supplies,
						 opp->supplies);
	} else {
		struct dev_pm_set_opp_data *data;

		data = opp_table->set_opp_data;
		data->regulators = opp_table->regulators;
		data->regulator_count = opp_table->regulator_count;
		data->clk = clk;
		data->dev = dev;

		data->old_opp.rate = old_freq;
		size = sizeof(*opp->supplies) * opp_table->regulator_count;
		if (IS_ERR(old_opp))
			memset(data->old_opp.supplies, 0, size);
		else
			memcpy(data->old_opp.supplies, old_opp->supplies, size);

		data->new_opp.rate = freq;
		memcpy(data->new_opp.supplies, opp->supplies, size);

		ret = opp_table->set_opp(data);
	}

	dev_pm_opp_put(opp);
put_old_opp:
	if (!IS_ERR(old_opp))
		dev_pm_opp_put(old_opp);
put_opp_table:
	dev_pm_opp_put_opp_table(opp_table);
	return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_set_rate);

/* OPP-dev Helpers */
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);
	kfree(opp_dev);
}

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(&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;
}

static struct opp_table *_allocate_opp_table(struct device *dev)
{
	struct opp_table *opp_table;
	struct opp_device *opp_dev;
	int ret;

	/*
	 * 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);

	/* 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);
	}

	BLOCKING_INIT_NOTIFIER_HEAD(&opp_table->head);
	INIT_LIST_HEAD(&opp_table->opp_list);
	mutex_init(&opp_table->lock);
	kref_init(&opp_table->kref);

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

void _get_opp_table_kref(struct opp_table *opp_table)
{
	kref_get(&opp_table->kref);
}

struct opp_table *dev_pm_opp_get_opp_table(struct device *dev)
{
	struct opp_table *opp_table;

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

	opp_table = _find_opp_table_unlocked(dev);
	if (!IS_ERR(opp_table))
		goto unlock;

	opp_table = _allocate_opp_table(dev);

unlock:
	mutex_unlock(&opp_table_lock);

	return opp_table;
}
EXPORT_SYMBOL_GPL(dev_pm_opp_get_opp_table);

static void _opp_table_kref_release(struct kref *kref)
{
	struct opp_table *opp_table = container_of(kref, struct opp_table, kref);
	struct opp_device *opp_dev;

	/* 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));

	mutex_destroy(&opp_table->lock);
	list_del(&opp_table->node);
	kfree(opp_table);

	mutex_unlock(&opp_table_lock);
}

void dev_pm_opp_put_opp_table(struct opp_table *opp_table)
{
	kref_put_mutex(&opp_table->kref, _opp_table_kref_release,
		       &opp_table_lock);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_put_opp_table);

void _opp_free(struct dev_pm_opp *opp)
{
	kfree(opp);
}

static void _opp_kref_release(struct kref *kref)
{
	struct dev_pm_opp *opp = container_of(kref, struct dev_pm_opp, kref);
	struct opp_table *opp_table = opp->opp_table;

	/*
	 * Notify the changes in the availability of the operable
	 * frequency/voltage list.
	 */
	blocking_notifier_call_chain(&opp_table->head, OPP_EVENT_REMOVE, opp);
	opp_debug_remove_one(opp);
	list_del(&opp->node);
	kfree(opp);

	mutex_unlock(&opp_table->lock);
	dev_pm_opp_put_opp_table(opp_table);
}

static void dev_pm_opp_get(struct dev_pm_opp *opp)
{
	kref_get(&opp->kref);
}

void dev_pm_opp_put(struct dev_pm_opp *opp)
{
	kref_put_mutex(&opp->kref, _opp_kref_release, &opp->opp_table->lock);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_put);

/**
 * 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.
 */
void dev_pm_opp_remove(struct device *dev, unsigned long freq)
{
	struct dev_pm_opp *opp;
	struct opp_table *opp_table;
	bool found = false;

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

	mutex_lock(&opp_table->lock);

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

	mutex_unlock(&opp_table->lock);

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

	dev_pm_opp_put_opp_table(opp_table);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_remove);

struct dev_pm_opp *_opp_allocate(struct opp_table *table)
{
	struct dev_pm_opp *opp;
	int count, supply_size;

	/* Allocate space for at least one supply */
	count = table->regulator_count ? table->regulator_count : 1;
	supply_size = sizeof(*opp->supplies) * count;

	/* allocate new OPP node and supplies structures */
	opp = kzalloc(sizeof(*opp) + supply_size, GFP_KERNEL);
	if (!opp)
		return NULL;

	/* Put the supplies at the end of the OPP structure as an empty array */
	opp->supplies = (struct dev_pm_opp_supply *)(opp + 1);
	INIT_LIST_HEAD(&opp->node);

	return opp;
}

static bool _opp_supported_by_regulators(struct dev_pm_opp *opp,
					 struct opp_table *opp_table)
{
	struct regulator *reg;
	int i;

	for (i = 0; i < opp_table->regulator_count; i++) {
		reg = opp_table->regulators[i];

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

	return true;
}

/*
 * Returns:
 * 0: On success. And appropriate error message for duplicate OPPs.
 * -EBUSY: For OPP with same freq/volt and is available. The callers of
 *  _opp_add() must return 0 if they receive -EBUSY from it. This is to make
 *  sure we don't print error messages unnecessarily if different parts of
 *  kernel try to initialize the OPP table.
 * -EEXIST: For OPP with same freq but different volt or is unavailable. This
 *  should be considered an error by the callers of _opp_add().
 */
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;
	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.
	 */
	mutex_lock(&opp_table->lock);
	head = &opp_table->opp_list;

	list_for_each_entry(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->supplies[0].u_volt,
			 opp->available, new_opp->rate,
			 new_opp->supplies[0].u_volt, new_opp->available);

		/* Should we compare voltages for all regulators here ? */
		ret = opp->available &&
		      new_opp->supplies[0].u_volt == opp->supplies[0].u_volt ? -EBUSY : -EEXIST;

		mutex_unlock(&opp_table->lock);
		return ret;
	}

	list_add(&new_opp->node, head);
	mutex_unlock(&opp_table->lock);

	new_opp->opp_table = opp_table;
	kref_init(&new_opp->kref);

	/* Get a reference to the OPP table */
	_get_opp_table_kref(opp_table);

	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.
 * @opp_table:	OPP table
 * @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.
 *
 * 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 opp_table *opp_table, struct device *dev,
		unsigned long freq, long u_volt, bool dynamic)
{
	struct dev_pm_opp *new_opp;
	unsigned long tol;
	int ret;

	new_opp = _opp_allocate(opp_table);
	if (!new_opp)
		return -ENOMEM;

	/* populate the opp table */
	new_opp->rate = freq;
	tol = u_volt * opp_table->voltage_tolerance_v1 / 100;
	new_opp->supplies[0].u_volt = u_volt;
	new_opp->supplies[0].u_volt_min = u_volt - tol;
	new_opp->supplies[0].u_volt_max = u_volt + tol;
	new_opp->available = true;
	new_opp->dynamic = dynamic;

	ret = _opp_add(dev, new_opp, opp_table);
	if (ret) {
		/* Don't return error for duplicate OPPs */
		if (ret == -EBUSY)
			ret = 0;
		goto free_opp;
	}

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

free_opp:
	_opp_free(new_opp);

	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.
 */
struct opp_table *dev_pm_opp_set_supported_hw(struct device *dev,
			const u32 *versions, unsigned int count)
{
	struct opp_table *opp_table;
	int ret;

	opp_table = dev_pm_opp_get_opp_table(dev);
	if (!opp_table)
		return ERR_PTR(-ENOMEM);

	/* 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;

	return opp_table;

err:
	dev_pm_opp_put_opp_table(opp_table);

	return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_set_supported_hw);

/**
 * dev_pm_opp_put_supported_hw() - Releases resources blocked for supported hw
 * @opp_table: OPP table returned by dev_pm_opp_set_supported_hw().
 *
 * 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.
 */
void dev_pm_opp_put_supported_hw(struct opp_table *opp_table)
{
	/* Make sure there are no concurrent readers while updating opp_table */
	WARN_ON(!list_empty(&opp_table->opp_list));

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

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

	dev_pm_opp_put_opp_table(opp_table);
}
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.
 */
struct opp_table *dev_pm_opp_set_prop_name(struct device *dev, const char *name)
{
	struct opp_table *opp_table;
	int ret;

	opp_table = dev_pm_opp_get_opp_table(dev);
	if (!opp_table)
		return ERR_PTR(-ENOMEM);

	/* 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;
	}

	return opp_table;

err:
	dev_pm_opp_put_opp_table(opp_table);

	return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_set_prop_name);

/**
 * dev_pm_opp_put_prop_name() - Releases resources blocked for prop-name
 * @opp_table: OPP table returned by dev_pm_opp_set_prop_name().
 *
 * 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.
 */
void dev_pm_opp_put_prop_name(struct opp_table *opp_table)
{
	/* Make sure there are no concurrent readers while updating opp_table */
	WARN_ON(!list_empty(&opp_table->opp_list));

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

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

	dev_pm_opp_put_opp_table(opp_table);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_put_prop_name);

static int _allocate_set_opp_data(struct opp_table *opp_table)
{
	struct dev_pm_set_opp_data *data;
	int len, count = opp_table->regulator_count;

	if (WARN_ON(!count))
		return -EINVAL;

	/* space for set_opp_data */
	len = sizeof(*data);

	/* space for old_opp.supplies and new_opp.supplies */
	len += 2 * sizeof(struct dev_pm_opp_supply) * count;

	data = kzalloc(len, GFP_KERNEL);
	if (!data)
		return -ENOMEM;

	data->old_opp.supplies = (void *)(data + 1);
	data->new_opp.supplies = data->old_opp.supplies + count;

	opp_table->set_opp_data = data;

	return 0;
}

static void _free_set_opp_data(struct opp_table *opp_table)
{
	kfree(opp_table->set_opp_data);
	opp_table->set_opp_data = NULL;
}

/**
 * dev_pm_opp_set_regulators() - Set regulator names for the device
 * @dev: Device for which regulator name is being set.
 * @names: Array of pointers to the names of the regulator.
 * @count: Number of regulators.
 *
 * In order to support OPP switching, OPP layer needs to know the name of the
 * device's regulators, as the core would be required to switch voltages as
 * well.
 *
 * This must be called before any OPPs are initialized for the device.
 */
struct opp_table *dev_pm_opp_set_regulators(struct device *dev,
					    const char * const names[],
					    unsigned int count)
{
	struct opp_table *opp_table;
	struct regulator *reg;
	int ret, i;

	opp_table = dev_pm_opp_get_opp_table(dev);
	if (!opp_table)
		return ERR_PTR(-ENOMEM);

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

	/* Already have regulators set */
	if (opp_table->regulators) {
		ret = -EBUSY;
		goto err;
	}

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

	for (i = 0; i < count; i++) {
		reg = regulator_get_optional(dev, names[i]);
		if (IS_ERR(reg)) {
			ret = PTR_ERR(reg);
			if (ret != -EPROBE_DEFER)
				dev_err(dev, "%s: no regulator (%s) found: %d\n",
					__func__, names[i], ret);
			goto free_regulators;
		}

		opp_table->regulators[i] = reg;
	}

	opp_table->regulator_count = count;

	/* Allocate block only once to pass to set_opp() routines */
	ret = _allocate_set_opp_data(opp_table);
	if (ret)
		goto free_regulators;

	return opp_table;

free_regulators:
	while (i != 0)
		regulator_put(opp_table->regulators[--i]);

	kfree(opp_table->regulators);
	opp_table->regulators = NULL;
	opp_table->regulator_count = 0;
err:
	dev_pm_opp_put_opp_table(opp_table);

	return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_set_regulators);

/**
 * dev_pm_opp_put_regulators() - Releases resources blocked for regulator
 * @opp_table: OPP table returned from dev_pm_opp_set_regulators().
 */
void dev_pm_opp_put_regulators(struct opp_table *opp_table)
{
	int i;

	if (!opp_table->regulators) {
		pr_err("%s: Doesn't have regulators set\n", __func__);
		return;
	}

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

	for (i = opp_table->regulator_count - 1; i >= 0; i--)
		regulator_put(opp_table->regulators[i]);

	_free_set_opp_data(opp_table);

	kfree(opp_table->regulators);
	opp_table->regulators = NULL;
	opp_table->regulator_count = 0;

	dev_pm_opp_put_opp_table(opp_table);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_put_regulators);

/**
 * dev_pm_opp_set_clkname() - Set clk name for the device
 * @dev: Device for which clk name is being set.
 * @name: Clk name.
 *
 * In order to support OPP switching, OPP layer needs to get pointer to the
 * clock for the device. Simple cases work fine without using this routine (i.e.
 * by passing connection-id as NULL), but for a device with multiple clocks
 * available, the OPP core needs to know the exact name of the clk to use.
 *
 * This must be called before any OPPs are initialized for the device.
 */
struct opp_table *dev_pm_opp_set_clkname(struct device *dev, const char *name)
{
	struct opp_table *opp_table;
	int ret;

	opp_table = dev_pm_opp_get_opp_table(dev);
	if (!opp_table)
		return ERR_PTR(-ENOMEM);

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

	/* Already have default clk set, free it */
	if (!IS_ERR(opp_table->clk))
		clk_put(opp_table->clk);

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

	return opp_table;

err:
	dev_pm_opp_put_opp_table(opp_table);

	return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_set_clkname);

/**
 * dev_pm_opp_put_clkname() - Releases resources blocked for clk.
 * @opp_table: OPP table returned from dev_pm_opp_set_clkname().
 */
void dev_pm_opp_put_clkname(struct opp_table *opp_table)
{
	/* Make sure there are no concurrent readers while updating opp_table */
	WARN_ON(!list_empty(&opp_table->opp_list));

	clk_put(opp_table->clk);
	opp_table->clk = ERR_PTR(-EINVAL);

	dev_pm_opp_put_opp_table(opp_table);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_put_clkname);

/**
 * dev_pm_opp_register_set_opp_helper() - Register custom set OPP helper
 * @dev: Device for which the helper is getting registered.
 * @set_opp: Custom set OPP helper.
 *
 * This is useful to support complex platforms (like platforms with multiple
 * regulators per device), instead of the generic OPP set rate helper.
 *
 * This must be called before any OPPs are initialized for the device.
 */
struct opp_table *dev_pm_opp_register_set_opp_helper(struct device *dev,
			int (*set_opp)(struct dev_pm_set_opp_data *data))
{
	struct opp_table *opp_table;
	int ret;

	if (!set_opp)
		return ERR_PTR(-EINVAL);

	opp_table = dev_pm_opp_get_opp_table(dev);
	if (!opp_table)
		return ERR_PTR(-ENOMEM);

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

	/* Already have custom set_opp helper */
	if (WARN_ON(opp_table->set_opp)) {
		ret = -EBUSY;
		goto err;
	}

	opp_table->set_opp = set_opp;

	return opp_table;

err:
	dev_pm_opp_put_opp_table(opp_table);

	return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_register_set_opp_helper);

/**
 * dev_pm_opp_unregister_set_opp_helper() - Releases resources blocked for
 *					   set_opp helper
 * @opp_table: OPP table returned from dev_pm_opp_register_set_opp_helper().
 *
 * Release resources blocked for platform specific set_opp helper.
 */
void dev_pm_opp_unregister_set_opp_helper(struct opp_table *opp_table)
{
	if (!opp_table->set_opp) {
		pr_err("%s: Doesn't have custom set_opp helper set\n",
		       __func__);
		return;
	}

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

	opp_table->set_opp = NULL;

	dev_pm_opp_put_opp_table(opp_table);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_unregister_set_opp_helper);

/**
 * 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.
 *
 * 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)
{
	struct opp_table *opp_table;
	int ret;

	opp_table = dev_pm_opp_get_opp_table(dev);
	if (!opp_table)
		return -ENOMEM;

	ret = _opp_add_v1(opp_table, dev, freq, u_volt, true);

	dev_pm_opp_put_opp_table(opp_table);
	return ret;
}
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, 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.
 */
static int _opp_set_availability(struct device *dev, unsigned long freq,
				 bool availability_req)
{
	struct opp_table *opp_table;
	struct dev_pm_opp *tmp_opp, *opp = ERR_PTR(-ENODEV);
	int r = 0;

	/* 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);
		return r;
	}

	mutex_lock(&opp_table->lock);

	/* 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;

	opp->available = availability_req;

	dev_pm_opp_get(opp);
	mutex_unlock(&opp_table->lock);

	/* Notify the change of the OPP availability */
	if (availability_req)
		blocking_notifier_call_chain(&opp_table->head, OPP_EVENT_ENABLE,
					     opp);
	else
		blocking_notifier_call_chain(&opp_table->head,
					     OPP_EVENT_DISABLE, opp);

	dev_pm_opp_put(opp);
	goto put_table;

unlock:
	mutex_unlock(&opp_table->lock);
put_table:
	dev_pm_opp_put_opp_table(opp_table);
	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.
 *
 * 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).
 *
 * 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_register_notifier() - Register OPP notifier for the device
 * @dev:	Device for which notifier needs to be registered
 * @nb:		Notifier block to be registered
 *
 * Return: 0 on success or a negative error value.
 */
int dev_pm_opp_register_notifier(struct device *dev, struct notifier_block *nb)
{
	struct opp_table *opp_table;
	int ret;

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

	ret = blocking_notifier_chain_register(&opp_table->head, nb);

	dev_pm_opp_put_opp_table(opp_table);

	return ret;
}
EXPORT_SYMBOL(dev_pm_opp_register_notifier);

/**
 * dev_pm_opp_unregister_notifier() - Unregister OPP notifier for the device
 * @dev:	Device for which notifier needs to be unregistered
 * @nb:		Notifier block to be unregistered
 *
 * Return: 0 on success or a negative error value.
 */
int dev_pm_opp_unregister_notifier(struct device *dev,
				   struct notifier_block *nb)
{
	struct opp_table *opp_table;
	int ret;

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

	ret = blocking_notifier_chain_unregister(&opp_table->head, nb);

	dev_pm_opp_put_opp_table(opp_table);

	return ret;
}
EXPORT_SYMBOL(dev_pm_opp_unregister_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 opp_table *opp_table, struct device *dev,
			      bool remove_all)
{
	struct dev_pm_opp *opp, *tmp;

	/* 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)
				dev_pm_opp_put(opp);
		}

		/*
		 * The OPP table is getting removed, drop the performance state
		 * constraints.
		 */
		if (opp_table->genpd_performance_state)
			dev_pm_genpd_set_performance_state(dev, 0);
	} else {
		_remove_opp_dev(_find_opp_dev(dev, opp_table), opp_table);
	}
}

void _dev_pm_opp_find_and_remove_table(struct device *dev, bool remove_all)
{
	struct opp_table *opp_table;

	/* 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);
		return;
	}

	_dev_pm_opp_remove_table(opp_table, dev, remove_all);

	dev_pm_opp_put_opp_table(opp_table);
}

/**
 * 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.
 */
void dev_pm_opp_remove_table(struct device *dev)
{
	_dev_pm_opp_find_and_remove_table(dev, true);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_remove_table);