Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2275 insertions, 0 deletions

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
new file mode 100644
index 000000000..2951a87cc
--- /dev/null
+++ b/drivers/devfreq/devfreq.c
@@ -0,0 +1,2275 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * devfreq: Generic Dynamic Voltage and Frequency Scaling (DVFS) Framework
+ *	    for Non-CPU Devices.
+ *
+ * Copyright (C) 2011 Samsung Electronics
+ *	MyungJoo Ham <myungjoo.ham@samsung.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/kmod.h>
+#include <linux/sched.h>
+#include <linux/debugfs.h>
+#include <linux/devfreq_cooling.h>
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/export.h>
+#include <linux/slab.h>
+#include <linux/stat.h>
+#include <linux/pm_opp.h>
+#include <linux/devfreq.h>
+#include <linux/workqueue.h>
+#include <linux/platform_device.h>
+#include <linux/list.h>
+#include <linux/printk.h>
+#include <linux/hrtimer.h>
+#include <linux/of.h>
+#include <linux/pm_qos.h>
+#include <linux/units.h>
+#include "governor.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/devfreq.h>
+
+#define IS_SUPPORTED_FLAG(f, name) ((f & DEVFREQ_GOV_FLAG_##name) ? true : false)
+#define IS_SUPPORTED_ATTR(f, name) ((f & DEVFREQ_GOV_ATTR_##name) ? true : false)
+
+static struct class *devfreq_class;
+static struct dentry *devfreq_debugfs;
+
+/*
+ * devfreq core provides delayed work based load monitoring helper
+ * functions. Governors can use these or can implement their own
+ * monitoring mechanism.
+ */
+static struct workqueue_struct *devfreq_wq;
+
+/* The list of all device-devfreq governors */
+static LIST_HEAD(devfreq_governor_list);
+/* The list of all device-devfreq */
+static LIST_HEAD(devfreq_list);
+static DEFINE_MUTEX(devfreq_list_lock);
+
+static const char timer_name[][DEVFREQ_NAME_LEN] = {
+	[DEVFREQ_TIMER_DEFERRABLE] = { "deferrable" },
+	[DEVFREQ_TIMER_DELAYED] = { "delayed" },
+};
+
+/**
+ * find_device_devfreq() - find devfreq struct using device pointer
+ * @dev:	device pointer used to lookup device devfreq.
+ *
+ * Search the list of device devfreqs and return the matched device's
+ * devfreq info. devfreq_list_lock should be held by the caller.
+ */
+static struct devfreq *find_device_devfreq(struct device *dev)
+{
+	struct devfreq *tmp_devfreq;
+
+	lockdep_assert_held(&devfreq_list_lock);
+
+	if (IS_ERR_OR_NULL(dev)) {
+		pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
+		return ERR_PTR(-EINVAL);
+	}
+
+	list_for_each_entry(tmp_devfreq, &devfreq_list, node) {
+		if (tmp_devfreq->dev.parent == dev)
+			return tmp_devfreq;
+	}
+
+	return ERR_PTR(-ENODEV);
+}
+
+static unsigned long find_available_min_freq(struct devfreq *devfreq)
+{
+	struct dev_pm_opp *opp;
+	unsigned long min_freq = 0;
+
+	opp = dev_pm_opp_find_freq_ceil(devfreq->dev.parent, &min_freq);
+	if (IS_ERR(opp))
+		min_freq = 0;
+	else
+		dev_pm_opp_put(opp);
+
+	return min_freq;
+}
+
+static unsigned long find_available_max_freq(struct devfreq *devfreq)
+{
+	struct dev_pm_opp *opp;
+	unsigned long max_freq = ULONG_MAX;
+
+	opp = dev_pm_opp_find_freq_floor(devfreq->dev.parent, &max_freq);
+	if (IS_ERR(opp))
+		max_freq = 0;
+	else
+		dev_pm_opp_put(opp);
+
+	return max_freq;
+}
+
+/**
+ * devfreq_get_freq_range() - Get the current freq range
+ * @devfreq:	the devfreq instance
+ * @min_freq:	the min frequency
+ * @max_freq:	the max frequency
+ *
+ * This takes into consideration all constraints.
+ */
+void devfreq_get_freq_range(struct devfreq *devfreq,
+			    unsigned long *min_freq,
+			    unsigned long *max_freq)
+{
+	unsigned long *freq_table = devfreq->freq_table;
+	s32 qos_min_freq, qos_max_freq;
+
+	lockdep_assert_held(&devfreq->lock);
+
+	/*
+	 * Initialize minimum/maximum frequency from freq table.
+	 * The devfreq drivers can initialize this in either ascending or
+	 * descending order and devfreq core supports both.
+	 */
+	if (freq_table[0] < freq_table[devfreq->max_state - 1]) {
+		*min_freq = freq_table[0];
+		*max_freq = freq_table[devfreq->max_state - 1];
+	} else {
+		*min_freq = freq_table[devfreq->max_state - 1];
+		*max_freq = freq_table[0];
+	}
+
+	/* Apply constraints from PM QoS */
+	qos_min_freq = dev_pm_qos_read_value(devfreq->dev.parent,
+					     DEV_PM_QOS_MIN_FREQUENCY);
+	qos_max_freq = dev_pm_qos_read_value(devfreq->dev.parent,
+					     DEV_PM_QOS_MAX_FREQUENCY);
+	*min_freq = max(*min_freq, (unsigned long)HZ_PER_KHZ * qos_min_freq);
+	if (qos_max_freq != PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE)
+		*max_freq = min(*max_freq,
+				(unsigned long)HZ_PER_KHZ * qos_max_freq);
+
+	/* Apply constraints from OPP interface */
+	*min_freq = max(*min_freq, devfreq->scaling_min_freq);
+	*max_freq = min(*max_freq, devfreq->scaling_max_freq);
+
+	if (*min_freq > *max_freq)
+		*min_freq = *max_freq;
+}
+EXPORT_SYMBOL(devfreq_get_freq_range);
+
+/**
+ * devfreq_get_freq_level() - Lookup freq_table for the frequency
+ * @devfreq:	the devfreq instance
+ * @freq:	the target frequency
+ */
+static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
+{
+	int lev;
+
+	for (lev = 0; lev < devfreq->max_state; lev++)
+		if (freq == devfreq->freq_table[lev])
+			return lev;
+
+	return -EINVAL;
+}
+
+static int set_freq_table(struct devfreq *devfreq)
+{
+	struct dev_pm_opp *opp;
+	unsigned long freq;
+	int i, count;
+
+	/* Initialize the freq_table from OPP table */
+	count = dev_pm_opp_get_opp_count(devfreq->dev.parent);
+	if (count <= 0)
+		return -EINVAL;
+
+	devfreq->max_state = count;
+	devfreq->freq_table = devm_kcalloc(devfreq->dev.parent,
+					   devfreq->max_state,
+					   sizeof(*devfreq->freq_table),
+					   GFP_KERNEL);
+	if (!devfreq->freq_table)
+		return -ENOMEM;
+
+	for (i = 0, freq = 0; i < devfreq->max_state; i++, freq++) {
+		opp = dev_pm_opp_find_freq_ceil(devfreq->dev.parent, &freq);
+		if (IS_ERR(opp)) {
+			devm_kfree(devfreq->dev.parent, devfreq->freq_table);
+			return PTR_ERR(opp);
+		}
+		dev_pm_opp_put(opp);
+		devfreq->freq_table[i] = freq;
+	}
+
+	return 0;
+}
+
+/**
+ * devfreq_update_status() - Update statistics of devfreq behavior
+ * @devfreq:	the devfreq instance
+ * @freq:	the update target frequency
+ */
+int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
+{
+	int lev, prev_lev, ret = 0;
+	u64 cur_time;
+
+	lockdep_assert_held(&devfreq->lock);
+	cur_time = get_jiffies_64();
+
+	/* Immediately exit if previous_freq is not initialized yet. */
+	if (!devfreq->previous_freq)
+		goto out;
+
+	prev_lev = devfreq_get_freq_level(devfreq, devfreq->previous_freq);
+	if (prev_lev < 0) {
+		ret = prev_lev;
+		goto out;
+	}
+
+	devfreq->stats.time_in_state[prev_lev] +=
+			cur_time - devfreq->stats.last_update;
+
+	lev = devfreq_get_freq_level(devfreq, freq);
+	if (lev < 0) {
+		ret = lev;
+		goto out;
+	}
+
+	if (lev != prev_lev) {
+		devfreq->stats.trans_table[
+			(prev_lev * devfreq->max_state) + lev]++;
+		devfreq->stats.total_trans++;
+	}
+
+out:
+	devfreq->stats.last_update = cur_time;
+	return ret;
+}
+EXPORT_SYMBOL(devfreq_update_status);
+
+/**
+ * find_devfreq_governor() - find devfreq governor from name
+ * @name:	name of the governor
+ *
+ * Search the list of devfreq governors and return the matched
+ * governor's pointer. devfreq_list_lock should be held by the caller.
+ */
+static struct devfreq_governor *find_devfreq_governor(const char *name)
+{
+	struct devfreq_governor *tmp_governor;
+
+	lockdep_assert_held(&devfreq_list_lock);
+
+	if (IS_ERR_OR_NULL(name)) {
+		pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
+		return ERR_PTR(-EINVAL);
+	}
+
+	list_for_each_entry(tmp_governor, &devfreq_governor_list, node) {
+		if (!strncmp(tmp_governor->name, name, DEVFREQ_NAME_LEN))
+			return tmp_governor;
+	}
+
+	return ERR_PTR(-ENODEV);
+}
+
+/**
+ * try_then_request_governor() - Try to find the governor and request the
+ *                               module if is not found.
+ * @name:	name of the governor
+ *
+ * Search the list of devfreq governors and request the module and try again
+ * if is not found. This can happen when both drivers (the governor driver
+ * and the driver that call devfreq_add_device) are built as modules.
+ * devfreq_list_lock should be held by the caller. Returns the matched
+ * governor's pointer or an error pointer.
+ */
+static struct devfreq_governor *try_then_request_governor(const char *name)
+{
+	struct devfreq_governor *governor;
+	int err = 0;
+
+	lockdep_assert_held(&devfreq_list_lock);
+
+	if (IS_ERR_OR_NULL(name)) {
+		pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
+		return ERR_PTR(-EINVAL);
+	}
+
+	governor = find_devfreq_governor(name);
+	if (IS_ERR(governor)) {
+		mutex_unlock(&devfreq_list_lock);
+
+		if (!strncmp(name, DEVFREQ_GOV_SIMPLE_ONDEMAND,
+			     DEVFREQ_NAME_LEN))
+			err = request_module("governor_%s", "simpleondemand");
+		else
+			err = request_module("governor_%s", name);
+		/* Restore previous state before return */
+		mutex_lock(&devfreq_list_lock);
+		if (err)
+			return (err < 0) ? ERR_PTR(err) : ERR_PTR(-EINVAL);
+
+		governor = find_devfreq_governor(name);
+	}
+
+	return governor;
+}
+
+static int devfreq_notify_transition(struct devfreq *devfreq,
+		struct devfreq_freqs *freqs, unsigned int state)
+{
+	if (!devfreq)
+		return -EINVAL;
+
+	switch (state) {
+	case DEVFREQ_PRECHANGE:
+		srcu_notifier_call_chain(&devfreq->transition_notifier_list,
+				DEVFREQ_PRECHANGE, freqs);
+		break;
+
+	case DEVFREQ_POSTCHANGE:
+		srcu_notifier_call_chain(&devfreq->transition_notifier_list,
+				DEVFREQ_POSTCHANGE, freqs);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
+			      u32 flags)
+{
+	struct devfreq_freqs freqs;
+	unsigned long cur_freq;
+	int err = 0;
+
+	if (devfreq->profile->get_cur_freq)
+		devfreq->profile->get_cur_freq(devfreq->dev.parent, &cur_freq);
+	else
+		cur_freq = devfreq->previous_freq;
+
+	freqs.old = cur_freq;
+	freqs.new = new_freq;
+	devfreq_notify_transition(devfreq, &freqs, DEVFREQ_PRECHANGE);
+
+	err = devfreq->profile->target(devfreq->dev.parent, &new_freq, flags);
+	if (err) {
+		freqs.new = cur_freq;
+		devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
+		return err;
+	}
+
+	/*
+	 * Print devfreq_frequency trace information between DEVFREQ_PRECHANGE
+	 * and DEVFREQ_POSTCHANGE because for showing the correct frequency
+	 * change order of between devfreq device and passive devfreq device.
+	 */
+	if (trace_devfreq_frequency_enabled() && new_freq != cur_freq)
+		trace_devfreq_frequency(devfreq, new_freq, cur_freq);
+
+	freqs.new = new_freq;
+	devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
+
+	if (devfreq_update_status(devfreq, new_freq))
+		dev_warn(&devfreq->dev,
+			 "Couldn't update frequency transition information.\n");
+
+	devfreq->previous_freq = new_freq;
+
+	if (devfreq->suspend_freq)
+		devfreq->resume_freq = new_freq;
+
+	return err;
+}
+
+/**
+ * devfreq_update_target() - Reevaluate the device and configure frequency
+ *			   on the final stage.
+ * @devfreq:	the devfreq instance.
+ * @freq:	the new frequency of parent device. This argument
+ *		is only used for devfreq device using passive governor.
+ *
+ * Note: Lock devfreq->lock before calling devfreq_update_target. This function
+ *	 should be only used by both update_devfreq() and devfreq governors.
+ */
+int devfreq_update_target(struct devfreq *devfreq, unsigned long freq)
+{
+	unsigned long min_freq, max_freq;
+	int err = 0;
+	u32 flags = 0;
+
+	lockdep_assert_held(&devfreq->lock);
+
+	if (!devfreq->governor)
+		return -EINVAL;
+
+	/* Reevaluate the proper frequency */
+	err = devfreq->governor->get_target_freq(devfreq, &freq);
+	if (err)
+		return err;
+	devfreq_get_freq_range(devfreq, &min_freq, &max_freq);
+
+	if (freq < min_freq) {
+		freq = min_freq;
+		flags &= ~DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use GLB */
+	}
+	if (freq > max_freq) {
+		freq = max_freq;
+		flags |= DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use LUB */
+	}
+
+	return devfreq_set_target(devfreq, freq, flags);
+}
+EXPORT_SYMBOL(devfreq_update_target);
+
+/* Load monitoring helper functions for governors use */
+
+/**
+ * update_devfreq() - Reevaluate the device and configure frequency.
+ * @devfreq:	the devfreq instance.
+ *
+ * Note: Lock devfreq->lock before calling update_devfreq
+ *	 This function is exported for governors.
+ */
+int update_devfreq(struct devfreq *devfreq)
+{
+	return devfreq_update_target(devfreq, 0L);
+}
+EXPORT_SYMBOL(update_devfreq);
+
+/**
+ * devfreq_monitor() - Periodically poll devfreq objects.
+ * @work:	the work struct used to run devfreq_monitor periodically.
+ *
+ */
+static void devfreq_monitor(struct work_struct *work)
+{
+	int err;
+	struct devfreq *devfreq = container_of(work,
+					struct devfreq, work.work);
+
+	mutex_lock(&devfreq->lock);
+	err = update_devfreq(devfreq);
+	if (err)
+		dev_err(&devfreq->dev, "dvfs failed with (%d) error\n", err);
+
+	queue_delayed_work(devfreq_wq, &devfreq->work,
+				msecs_to_jiffies(devfreq->profile->polling_ms));
+	mutex_unlock(&devfreq->lock);
+
+	trace_devfreq_monitor(devfreq);
+}
+
+/**
+ * devfreq_monitor_start() - Start load monitoring of devfreq instance
+ * @devfreq:	the devfreq instance.
+ *
+ * Helper function for starting devfreq device load monitoring. By
+ * default delayed work based monitoring is supported. Function
+ * to be called from governor in response to DEVFREQ_GOV_START
+ * event when device is added to devfreq framework.
+ */
+void devfreq_monitor_start(struct devfreq *devfreq)
+{
+	if (IS_SUPPORTED_FLAG(devfreq->governor->flags, IRQ_DRIVEN))
+		return;
+
+	switch (devfreq->profile->timer) {
+	case DEVFREQ_TIMER_DEFERRABLE:
+		INIT_DEFERRABLE_WORK(&devfreq->work, devfreq_monitor);
+		break;
+	case DEVFREQ_TIMER_DELAYED:
+		INIT_DELAYED_WORK(&devfreq->work, devfreq_monitor);
+		break;
+	default:
+		return;
+	}
+
+	if (devfreq->profile->polling_ms)
+		queue_delayed_work(devfreq_wq, &devfreq->work,
+			msecs_to_jiffies(devfreq->profile->polling_ms));
+}
+EXPORT_SYMBOL(devfreq_monitor_start);
+
+/**
+ * devfreq_monitor_stop() - Stop load monitoring of a devfreq instance
+ * @devfreq:	the devfreq instance.
+ *
+ * Helper function to stop devfreq device load monitoring. Function
+ * to be called from governor in response to DEVFREQ_GOV_STOP
+ * event when device is removed from devfreq framework.
+ */
+void devfreq_monitor_stop(struct devfreq *devfreq)
+{
+	if (IS_SUPPORTED_FLAG(devfreq->governor->flags, IRQ_DRIVEN))
+		return;
+
+	cancel_delayed_work_sync(&devfreq->work);
+}
+EXPORT_SYMBOL(devfreq_monitor_stop);
+
+/**
+ * devfreq_monitor_suspend() - Suspend load monitoring of a devfreq instance
+ * @devfreq:	the devfreq instance.
+ *
+ * Helper function to suspend devfreq device load monitoring. Function
+ * to be called from governor in response to DEVFREQ_GOV_SUSPEND
+ * event or when polling interval is set to zero.
+ *
+ * Note: Though this function is same as devfreq_monitor_stop(),
+ * intentionally kept separate to provide hooks for collecting
+ * transition statistics.
+ */
+void devfreq_monitor_suspend(struct devfreq *devfreq)
+{
+	mutex_lock(&devfreq->lock);
+	if (devfreq->stop_polling) {
+		mutex_unlock(&devfreq->lock);
+		return;
+	}
+
+	devfreq_update_status(devfreq, devfreq->previous_freq);
+	devfreq->stop_polling = true;
+	mutex_unlock(&devfreq->lock);
+
+	if (IS_SUPPORTED_FLAG(devfreq->governor->flags, IRQ_DRIVEN))
+		return;
+
+	cancel_delayed_work_sync(&devfreq->work);
+}
+EXPORT_SYMBOL(devfreq_monitor_suspend);
+
+/**
+ * devfreq_monitor_resume() - Resume load monitoring of a devfreq instance
+ * @devfreq:    the devfreq instance.
+ *
+ * Helper function to resume devfreq device load monitoring. Function
+ * to be called from governor in response to DEVFREQ_GOV_RESUME
+ * event or when polling interval is set to non-zero.
+ */
+void devfreq_monitor_resume(struct devfreq *devfreq)
+{
+	unsigned long freq;
+
+	mutex_lock(&devfreq->lock);
+
+	if (IS_SUPPORTED_FLAG(devfreq->governor->flags, IRQ_DRIVEN))
+		goto out_update;
+
+	if (!devfreq->stop_polling)
+		goto out;
+
+	if (!delayed_work_pending(&devfreq->work) &&
+			devfreq->profile->polling_ms)
+		queue_delayed_work(devfreq_wq, &devfreq->work,
+			msecs_to_jiffies(devfreq->profile->polling_ms));
+
+out_update:
+	devfreq->stats.last_update = get_jiffies_64();
+	devfreq->stop_polling = false;
+
+	if (devfreq->profile->get_cur_freq &&
+		!devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq))
+		devfreq->previous_freq = freq;
+
+out:
+	mutex_unlock(&devfreq->lock);
+}
+EXPORT_SYMBOL(devfreq_monitor_resume);
+
+/**
+ * devfreq_update_interval() - Update device devfreq monitoring interval
+ * @devfreq:    the devfreq instance.
+ * @delay:      new polling interval to be set.
+ *
+ * Helper function to set new load monitoring polling interval. Function
+ * to be called from governor in response to DEVFREQ_GOV_UPDATE_INTERVAL event.
+ */
+void devfreq_update_interval(struct devfreq *devfreq, unsigned int *delay)
+{
+	unsigned int cur_delay = devfreq->profile->polling_ms;
+	unsigned int new_delay = *delay;
+
+	mutex_lock(&devfreq->lock);
+	devfreq->profile->polling_ms = new_delay;
+
+	if (IS_SUPPORTED_FLAG(devfreq->governor->flags, IRQ_DRIVEN))
+		goto out;
+
+	if (devfreq->stop_polling)
+		goto out;
+
+	/* if new delay is zero, stop polling */
+	if (!new_delay) {
+		mutex_unlock(&devfreq->lock);
+		cancel_delayed_work_sync(&devfreq->work);
+		return;
+	}
+
+	/* if current delay is zero, start polling with new delay */
+	if (!cur_delay) {
+		queue_delayed_work(devfreq_wq, &devfreq->work,
+			msecs_to_jiffies(devfreq->profile->polling_ms));
+		goto out;
+	}
+
+	/* if current delay is greater than new delay, restart polling */
+	if (cur_delay > new_delay) {
+		mutex_unlock(&devfreq->lock);
+		cancel_delayed_work_sync(&devfreq->work);
+		mutex_lock(&devfreq->lock);
+		if (!devfreq->stop_polling)
+			queue_delayed_work(devfreq_wq, &devfreq->work,
+				msecs_to_jiffies(devfreq->profile->polling_ms));
+	}
+out:
+	mutex_unlock(&devfreq->lock);
+}
+EXPORT_SYMBOL(devfreq_update_interval);
+
+/**
+ * devfreq_notifier_call() - Notify that the device frequency requirements
+ *			     has been changed out of devfreq framework.
+ * @nb:		the notifier_block (supposed to be devfreq->nb)
+ * @type:	not used
+ * @devp:	not used
+ *
+ * Called by a notifier that uses devfreq->nb.
+ */
+static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
+				 void *devp)
+{
+	struct devfreq *devfreq = container_of(nb, struct devfreq, nb);
+	int err = -EINVAL;
+
+	mutex_lock(&devfreq->lock);
+
+	devfreq->scaling_min_freq = find_available_min_freq(devfreq);
+	if (!devfreq->scaling_min_freq)
+		goto out;
+
+	devfreq->scaling_max_freq = find_available_max_freq(devfreq);
+	if (!devfreq->scaling_max_freq) {
+		devfreq->scaling_max_freq = ULONG_MAX;
+		goto out;
+	}
+
+	err = update_devfreq(devfreq);
+
+out:
+	mutex_unlock(&devfreq->lock);
+	if (err)
+		dev_err(devfreq->dev.parent,
+			"failed to update frequency from OPP notifier (%d)\n",
+			err);
+
+	return NOTIFY_OK;
+}
+
+/**
+ * qos_notifier_call() - Common handler for QoS constraints.
+ * @devfreq:    the devfreq instance.
+ */
+static int qos_notifier_call(struct devfreq *devfreq)
+{
+	int err;
+
+	mutex_lock(&devfreq->lock);
+	err = update_devfreq(devfreq);
+	mutex_unlock(&devfreq->lock);
+	if (err)
+		dev_err(devfreq->dev.parent,
+			"failed to update frequency from PM QoS (%d)\n",
+			err);
+
+	return NOTIFY_OK;
+}
+
+/**
+ * qos_min_notifier_call() - Callback for QoS min_freq changes.
+ * @nb:		Should be devfreq->nb_min
+ * @val:	not used
+ * @ptr:	not used
+ */
+static int qos_min_notifier_call(struct notifier_block *nb,
+					 unsigned long val, void *ptr)
+{
+	return qos_notifier_call(container_of(nb, struct devfreq, nb_min));
+}
+
+/**
+ * qos_max_notifier_call() - Callback for QoS max_freq changes.
+ * @nb:		Should be devfreq->nb_max
+ * @val:	not used
+ * @ptr:	not used
+ */
+static int qos_max_notifier_call(struct notifier_block *nb,
+					 unsigned long val, void *ptr)
+{
+	return qos_notifier_call(container_of(nb, struct devfreq, nb_max));
+}
+
+/**
+ * devfreq_dev_release() - Callback for struct device to release the device.
+ * @dev:	the devfreq device
+ *
+ * Remove devfreq from the list and release its resources.
+ */
+static void devfreq_dev_release(struct device *dev)
+{
+	struct devfreq *devfreq = to_devfreq(dev);
+	int err;
+
+	mutex_lock(&devfreq_list_lock);
+	list_del(&devfreq->node);
+	mutex_unlock(&devfreq_list_lock);
+
+	err = dev_pm_qos_remove_notifier(devfreq->dev.parent, &devfreq->nb_max,
+					 DEV_PM_QOS_MAX_FREQUENCY);
+	if (err && err != -ENOENT)
+		dev_warn(dev->parent,
+			"Failed to remove max_freq notifier: %d\n", err);
+	err = dev_pm_qos_remove_notifier(devfreq->dev.parent, &devfreq->nb_min,
+					 DEV_PM_QOS_MIN_FREQUENCY);
+	if (err && err != -ENOENT)
+		dev_warn(dev->parent,
+			"Failed to remove min_freq notifier: %d\n", err);
+
+	if (dev_pm_qos_request_active(&devfreq->user_max_freq_req)) {
+		err = dev_pm_qos_remove_request(&devfreq->user_max_freq_req);
+		if (err < 0)
+			dev_warn(dev->parent,
+				"Failed to remove max_freq request: %d\n", err);
+	}
+	if (dev_pm_qos_request_active(&devfreq->user_min_freq_req)) {
+		err = dev_pm_qos_remove_request(&devfreq->user_min_freq_req);
+		if (err < 0)
+			dev_warn(dev->parent,
+				"Failed to remove min_freq request: %d\n", err);
+	}
+
+	if (devfreq->profile->exit)
+		devfreq->profile->exit(devfreq->dev.parent);
+
+	if (devfreq->opp_table)
+		dev_pm_opp_put_opp_table(devfreq->opp_table);
+
+	mutex_destroy(&devfreq->lock);
+	srcu_cleanup_notifier_head(&devfreq->transition_notifier_list);
+	kfree(devfreq);
+}
+
+static void create_sysfs_files(struct devfreq *devfreq,
+				const struct devfreq_governor *gov);
+static void remove_sysfs_files(struct devfreq *devfreq,
+				const struct devfreq_governor *gov);
+
+/**
+ * devfreq_add_device() - Add devfreq feature to the device
+ * @dev:	the device to add devfreq feature.
+ * @profile:	device-specific profile to run devfreq.
+ * @governor_name:	name of the policy to choose frequency.
+ * @data:	devfreq driver pass to governors, governor should not change it.
+ */
+struct devfreq *devfreq_add_device(struct device *dev,
+				   struct devfreq_dev_profile *profile,
+				   const char *governor_name,
+				   void *data)
+{
+	struct devfreq *devfreq;
+	struct devfreq_governor *governor;
+	unsigned long min_freq, max_freq;
+	int err = 0;
+
+	if (!dev || !profile || !governor_name) {
+		dev_err(dev, "%s: Invalid parameters.\n", __func__);
+		return ERR_PTR(-EINVAL);
+	}
+
+	mutex_lock(&devfreq_list_lock);
+	devfreq = find_device_devfreq(dev);
+	mutex_unlock(&devfreq_list_lock);
+	if (!IS_ERR(devfreq)) {
+		dev_err(dev, "%s: devfreq device already exists!\n",
+			__func__);
+		err = -EINVAL;
+		goto err_out;
+	}
+
+	devfreq = kzalloc(sizeof(struct devfreq), GFP_KERNEL);
+	if (!devfreq) {
+		err = -ENOMEM;
+		goto err_out;
+	}
+
+	mutex_init(&devfreq->lock);
+	mutex_lock(&devfreq->lock);
+	devfreq->dev.parent = dev;
+	devfreq->dev.class = devfreq_class;
+	devfreq->dev.release = devfreq_dev_release;
+	INIT_LIST_HEAD(&devfreq->node);
+	devfreq->profile = profile;
+	devfreq->previous_freq = profile->initial_freq;
+	devfreq->last_status.current_frequency = profile->initial_freq;
+	devfreq->data = data;
+	devfreq->nb.notifier_call = devfreq_notifier_call;
+
+	if (devfreq->profile->timer < 0
+		|| devfreq->profile->timer >= DEVFREQ_TIMER_NUM) {
+		mutex_unlock(&devfreq->lock);
+		err = -EINVAL;
+		goto err_dev;
+	}
+
+	if (!devfreq->profile->max_state || !devfreq->profile->freq_table) {
+		mutex_unlock(&devfreq->lock);
+		err = set_freq_table(devfreq);
+		if (err < 0)
+			goto err_dev;
+		mutex_lock(&devfreq->lock);
+	} else {
+		devfreq->freq_table = devfreq->profile->freq_table;
+		devfreq->max_state = devfreq->profile->max_state;
+	}
+
+	devfreq->scaling_min_freq = find_available_min_freq(devfreq);
+	if (!devfreq->scaling_min_freq) {
+		mutex_unlock(&devfreq->lock);
+		err = -EINVAL;
+		goto err_dev;
+	}
+
+	devfreq->scaling_max_freq = find_available_max_freq(devfreq);
+	if (!devfreq->scaling_max_freq) {
+		mutex_unlock(&devfreq->lock);
+		err = -EINVAL;
+		goto err_dev;
+	}
+
+	devfreq_get_freq_range(devfreq, &min_freq, &max_freq);
+
+	devfreq->suspend_freq = dev_pm_opp_get_suspend_opp_freq(dev);
+	devfreq->opp_table = dev_pm_opp_get_opp_table(dev);
+	if (IS_ERR(devfreq->opp_table))
+		devfreq->opp_table = NULL;
+
+	atomic_set(&devfreq->suspend_count, 0);
+
+	dev_set_name(&devfreq->dev, "%s", dev_name(dev));
+	err = device_register(&devfreq->dev);
+	if (err) {
+		mutex_unlock(&devfreq->lock);
+		put_device(&devfreq->dev);
+		goto err_out;
+	}
+
+	devfreq->stats.trans_table = devm_kzalloc(&devfreq->dev,
+			array3_size(sizeof(unsigned int),
+				    devfreq->max_state,
+				    devfreq->max_state),
+			GFP_KERNEL);
+	if (!devfreq->stats.trans_table) {
+		mutex_unlock(&devfreq->lock);
+		err = -ENOMEM;
+		goto err_devfreq;
+	}
+
+	devfreq->stats.time_in_state = devm_kcalloc(&devfreq->dev,
+			devfreq->max_state,
+			sizeof(*devfreq->stats.time_in_state),
+			GFP_KERNEL);
+	if (!devfreq->stats.time_in_state) {
+		mutex_unlock(&devfreq->lock);
+		err = -ENOMEM;
+		goto err_devfreq;
+	}
+
+	devfreq->stats.total_trans = 0;
+	devfreq->stats.last_update = get_jiffies_64();
+
+	srcu_init_notifier_head(&devfreq->transition_notifier_list);
+
+	mutex_unlock(&devfreq->lock);
+
+	err = dev_pm_qos_add_request(dev, &devfreq->user_min_freq_req,
+				     DEV_PM_QOS_MIN_FREQUENCY, 0);
+	if (err < 0)
+		goto err_devfreq;
+	err = dev_pm_qos_add_request(dev, &devfreq->user_max_freq_req,
+				     DEV_PM_QOS_MAX_FREQUENCY,
+				     PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE);
+	if (err < 0)
+		goto err_devfreq;
+
+	devfreq->nb_min.notifier_call = qos_min_notifier_call;
+	err = dev_pm_qos_add_notifier(dev, &devfreq->nb_min,
+				      DEV_PM_QOS_MIN_FREQUENCY);
+	if (err)
+		goto err_devfreq;
+
+	devfreq->nb_max.notifier_call = qos_max_notifier_call;
+	err = dev_pm_qos_add_notifier(dev, &devfreq->nb_max,
+				      DEV_PM_QOS_MAX_FREQUENCY);
+	if (err)
+		goto err_devfreq;
+
+	mutex_lock(&devfreq_list_lock);
+
+	governor = try_then_request_governor(governor_name);
+	if (IS_ERR(governor)) {
+		dev_err(dev, "%s: Unable to find governor for the device\n",
+			__func__);
+		err = PTR_ERR(governor);
+		goto err_init;
+	}
+
+	devfreq->governor = governor;
+	err = devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_START,
+						NULL);
+	if (err) {
+		dev_err_probe(dev, err,
+			"%s: Unable to start governor for the device\n",
+			 __func__);
+		goto err_init;
+	}
+	create_sysfs_files(devfreq, devfreq->governor);
+
+	list_add(&devfreq->node, &devfreq_list);
+
+	mutex_unlock(&devfreq_list_lock);
+
+	if (devfreq->profile->is_cooling_device) {
+		devfreq->cdev = devfreq_cooling_em_register(devfreq, NULL);
+		if (IS_ERR(devfreq->cdev))
+			devfreq->cdev = NULL;
+	}
+
+	return devfreq;
+
+err_init:
+	mutex_unlock(&devfreq_list_lock);
+err_devfreq:
+	devfreq_remove_device(devfreq);
+	devfreq = NULL;
+err_dev:
+	kfree(devfreq);
+err_out:
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL(devfreq_add_device);
+
+/**
+ * devfreq_remove_device() - Remove devfreq feature from a device.
+ * @devfreq:	the devfreq instance to be removed
+ *
+ * The opposite of devfreq_add_device().
+ */
+int devfreq_remove_device(struct devfreq *devfreq)
+{
+	if (!devfreq)
+		return -EINVAL;
+
+	devfreq_cooling_unregister(devfreq->cdev);
+
+	if (devfreq->governor) {
+		devfreq->governor->event_handler(devfreq,
+						 DEVFREQ_GOV_STOP, NULL);
+		remove_sysfs_files(devfreq, devfreq->governor);
+	}
+
+	device_unregister(&devfreq->dev);
+
+	return 0;
+}
+EXPORT_SYMBOL(devfreq_remove_device);
+
+static int devm_devfreq_dev_match(struct device *dev, void *res, void *data)
+{
+	struct devfreq **r = res;
+
+	if (WARN_ON(!r || !*r))
+		return 0;
+
+	return *r == data;
+}
+
+static void devm_devfreq_dev_release(struct device *dev, void *res)
+{
+	devfreq_remove_device(*(struct devfreq **)res);
+}
+
+/**
+ * devm_devfreq_add_device() - Resource-managed devfreq_add_device()
+ * @dev:	the device to add devfreq feature.
+ * @profile:	device-specific profile to run devfreq.
+ * @governor_name:	name of the policy to choose frequency.
+ * @data:	 devfreq driver pass to governors, governor should not change it.
+ *
+ * This function manages automatically the memory of devfreq device using device
+ * resource management and simplify the free operation for memory of devfreq
+ * device.
+ */
+struct devfreq *devm_devfreq_add_device(struct device *dev,
+					struct devfreq_dev_profile *profile,
+					const char *governor_name,
+					void *data)
+{
+	struct devfreq **ptr, *devfreq;
+
+	ptr = devres_alloc(devm_devfreq_dev_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	devfreq = devfreq_add_device(dev, profile, governor_name, data);
+	if (IS_ERR(devfreq)) {
+		devres_free(ptr);
+		return devfreq;
+	}
+
+	*ptr = devfreq;
+	devres_add(dev, ptr);
+
+	return devfreq;
+}
+EXPORT_SYMBOL(devm_devfreq_add_device);
+
+#ifdef CONFIG_OF
+/*
+ * devfreq_get_devfreq_by_node - Get the devfreq device from devicetree
+ * @node - pointer to device_node
+ *
+ * return the instance of devfreq device
+ */
+struct devfreq *devfreq_get_devfreq_by_node(struct device_node *node)
+{
+	struct devfreq *devfreq;
+
+	if (!node)
+		return ERR_PTR(-EINVAL);
+
+	mutex_lock(&devfreq_list_lock);
+	list_for_each_entry(devfreq, &devfreq_list, node) {
+		if (devfreq->dev.parent
+			&& devfreq->dev.parent->of_node == node) {
+			mutex_unlock(&devfreq_list_lock);
+			return devfreq;
+		}
+	}
+	mutex_unlock(&devfreq_list_lock);
+
+	return ERR_PTR(-ENODEV);
+}
+
+/*
+ * devfreq_get_devfreq_by_phandle - Get the devfreq device from devicetree
+ * @dev - instance to the given device
+ * @phandle_name - name of property holding a phandle value
+ * @index - index into list of devfreq
+ *
+ * return the instance of devfreq device
+ */
+struct devfreq *devfreq_get_devfreq_by_phandle(struct device *dev,
+					const char *phandle_name, int index)
+{
+	struct device_node *node;
+	struct devfreq *devfreq;
+
+	if (!dev || !phandle_name)
+		return ERR_PTR(-EINVAL);
+
+	if (!dev->of_node)
+		return ERR_PTR(-EINVAL);
+
+	node = of_parse_phandle(dev->of_node, phandle_name, index);
+	if (!node)
+		return ERR_PTR(-ENODEV);
+
+	devfreq = devfreq_get_devfreq_by_node(node);
+	of_node_put(node);
+
+	return devfreq;
+}
+
+#else
+struct devfreq *devfreq_get_devfreq_by_node(struct device_node *node)
+{
+	return ERR_PTR(-ENODEV);
+}
+
+struct devfreq *devfreq_get_devfreq_by_phandle(struct device *dev,
+					const char *phandle_name, int index)
+{
+	return ERR_PTR(-ENODEV);
+}
+#endif /* CONFIG_OF */
+EXPORT_SYMBOL_GPL(devfreq_get_devfreq_by_node);
+EXPORT_SYMBOL_GPL(devfreq_get_devfreq_by_phandle);
+
+/**
+ * devm_devfreq_remove_device() - Resource-managed devfreq_remove_device()
+ * @dev:	the device from which to remove devfreq feature.
+ * @devfreq:	the devfreq instance to be removed
+ */
+void devm_devfreq_remove_device(struct device *dev, struct devfreq *devfreq)
+{
+	WARN_ON(devres_release(dev, devm_devfreq_dev_release,
+			       devm_devfreq_dev_match, devfreq));
+}
+EXPORT_SYMBOL(devm_devfreq_remove_device);
+
+/**
+ * devfreq_suspend_device() - Suspend devfreq of a device.
+ * @devfreq: the devfreq instance to be suspended
+ *
+ * This function is intended to be called by the pm callbacks
+ * (e.g., runtime_suspend, suspend) of the device driver that
+ * holds the devfreq.
+ */
+int devfreq_suspend_device(struct devfreq *devfreq)
+{
+	int ret;
+
+	if (!devfreq)
+		return -EINVAL;
+
+	if (atomic_inc_return(&devfreq->suspend_count) > 1)
+		return 0;
+
+	if (devfreq->governor) {
+		ret = devfreq->governor->event_handler(devfreq,
+					DEVFREQ_GOV_SUSPEND, NULL);
+		if (ret)
+			return ret;
+	}
+
+	if (devfreq->suspend_freq) {
+		mutex_lock(&devfreq->lock);
+		ret = devfreq_set_target(devfreq, devfreq->suspend_freq, 0);
+		mutex_unlock(&devfreq->lock);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(devfreq_suspend_device);
+
+/**
+ * devfreq_resume_device() - Resume devfreq of a device.
+ * @devfreq: the devfreq instance to be resumed
+ *
+ * This function is intended to be called by the pm callbacks
+ * (e.g., runtime_resume, resume) of the device driver that
+ * holds the devfreq.
+ */
+int devfreq_resume_device(struct devfreq *devfreq)
+{
+	int ret;
+
+	if (!devfreq)
+		return -EINVAL;
+
+	if (atomic_dec_return(&devfreq->suspend_count) >= 1)
+		return 0;
+
+	if (devfreq->resume_freq) {
+		mutex_lock(&devfreq->lock);
+		ret = devfreq_set_target(devfreq, devfreq->resume_freq, 0);
+		mutex_unlock(&devfreq->lock);
+		if (ret)
+			return ret;
+	}
+
+	if (devfreq->governor) {
+		ret = devfreq->governor->event_handler(devfreq,
+					DEVFREQ_GOV_RESUME, NULL);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(devfreq_resume_device);
+
+/**
+ * devfreq_suspend() - Suspend devfreq governors and devices
+ *
+ * Called during system wide Suspend/Hibernate cycles for suspending governors
+ * and devices preserving the state for resume. On some platforms the devfreq
+ * device must have precise state (frequency) after resume in order to provide
+ * fully operating setup.
+ */
+void devfreq_suspend(void)
+{
+	struct devfreq *devfreq;
+	int ret;
+
+	mutex_lock(&devfreq_list_lock);
+	list_for_each_entry(devfreq, &devfreq_list, node) {
+		ret = devfreq_suspend_device(devfreq);
+		if (ret)
+			dev_err(&devfreq->dev,
+				"failed to suspend devfreq device\n");
+	}
+	mutex_unlock(&devfreq_list_lock);
+}
+
+/**
+ * devfreq_resume() - Resume devfreq governors and devices
+ *
+ * Called during system wide Suspend/Hibernate cycle for resuming governors and
+ * devices that are suspended with devfreq_suspend().
+ */
+void devfreq_resume(void)
+{
+	struct devfreq *devfreq;
+	int ret;
+
+	mutex_lock(&devfreq_list_lock);
+	list_for_each_entry(devfreq, &devfreq_list, node) {
+		ret = devfreq_resume_device(devfreq);
+		if (ret)
+			dev_warn(&devfreq->dev,
+				 "failed to resume devfreq device\n");
+	}
+	mutex_unlock(&devfreq_list_lock);
+}
+
+/**
+ * devfreq_add_governor() - Add devfreq governor
+ * @governor:	the devfreq governor to be added
+ */
+int devfreq_add_governor(struct devfreq_governor *governor)
+{
+	struct devfreq_governor *g;
+	struct devfreq *devfreq;
+	int err = 0;
+
+	if (!governor) {
+		pr_err("%s: Invalid parameters.\n", __func__);
+		return -EINVAL;
+	}
+
+	mutex_lock(&devfreq_list_lock);
+	g = find_devfreq_governor(governor->name);
+	if (!IS_ERR(g)) {
+		pr_err("%s: governor %s already registered\n", __func__,
+		       g->name);
+		err = -EINVAL;
+		goto err_out;
+	}
+
+	list_add(&governor->node, &devfreq_governor_list);
+
+	list_for_each_entry(devfreq, &devfreq_list, node) {
+		int ret = 0;
+		struct device *dev = devfreq->dev.parent;
+
+		if (!strncmp(devfreq->governor->name, governor->name,
+			     DEVFREQ_NAME_LEN)) {
+			/* The following should never occur */
+			if (devfreq->governor) {
+				dev_warn(dev,
+					 "%s: Governor %s already present\n",
+					 __func__, devfreq->governor->name);
+				ret = devfreq->governor->event_handler(devfreq,
+							DEVFREQ_GOV_STOP, NULL);
+				if (ret) {
+					dev_warn(dev,
+						 "%s: Governor %s stop = %d\n",
+						 __func__,
+						 devfreq->governor->name, ret);
+				}
+				/* Fall through */
+			}
+			devfreq->governor = governor;
+			ret = devfreq->governor->event_handler(devfreq,
+						DEVFREQ_GOV_START, NULL);
+			if (ret) {
+				dev_warn(dev, "%s: Governor %s start=%d\n",
+					 __func__, devfreq->governor->name,
+					 ret);
+			}
+		}
+	}
+
+err_out:
+	mutex_unlock(&devfreq_list_lock);
+
+	return err;
+}
+EXPORT_SYMBOL(devfreq_add_governor);
+
+static void devm_devfreq_remove_governor(void *governor)
+{
+	WARN_ON(devfreq_remove_governor(governor));
+}
+
+/**
+ * devm_devfreq_add_governor() - Add devfreq governor
+ * @dev:	device which adds devfreq governor
+ * @governor:	the devfreq governor to be added
+ *
+ * This is a resource-managed variant of devfreq_add_governor().
+ */
+int devm_devfreq_add_governor(struct device *dev,
+			      struct devfreq_governor *governor)
+{
+	int err;
+
+	err = devfreq_add_governor(governor);
+	if (err)
+		return err;
+
+	return devm_add_action_or_reset(dev, devm_devfreq_remove_governor,
+					governor);
+}
+EXPORT_SYMBOL(devm_devfreq_add_governor);
+
+/**
+ * devfreq_remove_governor() - Remove devfreq feature from a device.
+ * @governor:	the devfreq governor to be removed
+ */
+int devfreq_remove_governor(struct devfreq_governor *governor)
+{
+	struct devfreq_governor *g;
+	struct devfreq *devfreq;
+	int err = 0;
+
+	if (!governor) {
+		pr_err("%s: Invalid parameters.\n", __func__);
+		return -EINVAL;
+	}
+
+	mutex_lock(&devfreq_list_lock);
+	g = find_devfreq_governor(governor->name);
+	if (IS_ERR(g)) {
+		pr_err("%s: governor %s not registered\n", __func__,
+		       governor->name);
+		err = PTR_ERR(g);
+		goto err_out;
+	}
+	list_for_each_entry(devfreq, &devfreq_list, node) {
+		int ret;
+		struct device *dev = devfreq->dev.parent;
+
+		if (!strncmp(devfreq->governor->name, governor->name,
+			     DEVFREQ_NAME_LEN)) {
+			/* we should have a devfreq governor! */
+			if (!devfreq->governor) {
+				dev_warn(dev, "%s: Governor %s NOT present\n",
+					 __func__, governor->name);
+				continue;
+				/* Fall through */
+			}
+			ret = devfreq->governor->event_handler(devfreq,
+						DEVFREQ_GOV_STOP, NULL);
+			if (ret) {
+				dev_warn(dev, "%s: Governor %s stop=%d\n",
+					 __func__, devfreq->governor->name,
+					 ret);
+			}
+			devfreq->governor = NULL;
+		}
+	}
+
+	list_del(&governor->node);
+err_out:
+	mutex_unlock(&devfreq_list_lock);
+
+	return err;
+}
+EXPORT_SYMBOL(devfreq_remove_governor);
+
+static ssize_t name_show(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct devfreq *df = to_devfreq(dev);
+	return sprintf(buf, "%s\n", dev_name(df->dev.parent));
+}
+static DEVICE_ATTR_RO(name);
+
+static ssize_t governor_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct devfreq *df = to_devfreq(dev);
+
+	if (!df->governor)
+		return -EINVAL;
+
+	return sprintf(buf, "%s\n", df->governor->name);
+}
+
+static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct devfreq *df = to_devfreq(dev);
+	int ret;
+	char str_governor[DEVFREQ_NAME_LEN + 1];
+	const struct devfreq_governor *governor, *prev_governor;
+
+	if (!df->governor)
+		return -EINVAL;
+
+	ret = sscanf(buf, "%" __stringify(DEVFREQ_NAME_LEN) "s", str_governor);
+	if (ret != 1)
+		return -EINVAL;
+
+	mutex_lock(&devfreq_list_lock);
+	governor = try_then_request_governor(str_governor);
+	if (IS_ERR(governor)) {
+		ret = PTR_ERR(governor);
+		goto out;
+	}
+	if (df->governor == governor) {
+		ret = 0;
+		goto out;
+	} else if (IS_SUPPORTED_FLAG(df->governor->flags, IMMUTABLE)
+		|| IS_SUPPORTED_FLAG(governor->flags, IMMUTABLE)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/*
+	 * Stop the current governor and remove the specific sysfs files
+	 * which depend on current governor.
+	 */
+	ret = df->governor->event_handler(df, DEVFREQ_GOV_STOP, NULL);
+	if (ret) {
+		dev_warn(dev, "%s: Governor %s not stopped(%d)\n",
+			 __func__, df->governor->name, ret);
+		goto out;
+	}
+	remove_sysfs_files(df, df->governor);
+
+	/*
+	 * Start the new governor and create the specific sysfs files
+	 * which depend on the new governor.
+	 */
+	prev_governor = df->governor;
+	df->governor = governor;
+	ret = df->governor->event_handler(df, DEVFREQ_GOV_START, NULL);
+	if (ret) {
+		dev_warn(dev, "%s: Governor %s not started(%d)\n",
+			 __func__, df->governor->name, ret);
+
+		/* Restore previous governor */
+		df->governor = prev_governor;
+		ret = df->governor->event_handler(df, DEVFREQ_GOV_START, NULL);
+		if (ret) {
+			dev_err(dev,
+				"%s: reverting to Governor %s failed (%d)\n",
+				__func__, prev_governor->name, ret);
+			df->governor = NULL;
+			goto out;
+		}
+	}
+
+	/*
+	 * Create the sysfs files for the new governor. But if failed to start
+	 * the new governor, restore the sysfs files of previous governor.
+	 */
+	create_sysfs_files(df, df->governor);
+
+out:
+	mutex_unlock(&devfreq_list_lock);
+
+	if (!ret)
+		ret = count;
+	return ret;
+}
+static DEVICE_ATTR_RW(governor);
+
+static ssize_t available_governors_show(struct device *d,
+					struct device_attribute *attr,
+					char *buf)
+{
+	struct devfreq *df = to_devfreq(d);
+	ssize_t count = 0;
+
+	if (!df->governor)
+		return -EINVAL;
+
+	mutex_lock(&devfreq_list_lock);
+
+	/*
+	 * The devfreq with immutable governor (e.g., passive) shows
+	 * only own governor.
+	 */
+	if (IS_SUPPORTED_FLAG(df->governor->flags, IMMUTABLE)) {
+		count = scnprintf(&buf[count], DEVFREQ_NAME_LEN,
+				  "%s ", df->governor->name);
+	/*
+	 * The devfreq device shows the registered governor except for
+	 * immutable governors such as passive governor .
+	 */
+	} else {
+		struct devfreq_governor *governor;
+
+		list_for_each_entry(governor, &devfreq_governor_list, node) {
+			if (IS_SUPPORTED_FLAG(governor->flags, IMMUTABLE))
+				continue;
+			count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
+					   "%s ", governor->name);
+		}
+	}
+
+	mutex_unlock(&devfreq_list_lock);
+
+	/* Truncate the trailing space */
+	if (count)
+		count--;
+
+	count += sprintf(&buf[count], "\n");
+
+	return count;
+}
+static DEVICE_ATTR_RO(available_governors);
+
+static ssize_t cur_freq_show(struct device *dev, struct device_attribute *attr,
+			     char *buf)
+{
+	unsigned long freq;
+	struct devfreq *df = to_devfreq(dev);
+
+	if (!df->profile)
+		return -EINVAL;
+
+	if (df->profile->get_cur_freq &&
+		!df->profile->get_cur_freq(df->dev.parent, &freq))
+		return sprintf(buf, "%lu\n", freq);
+
+	return sprintf(buf, "%lu\n", df->previous_freq);
+}
+static DEVICE_ATTR_RO(cur_freq);
+
+static ssize_t target_freq_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct devfreq *df = to_devfreq(dev);
+
+	return sprintf(buf, "%lu\n", df->previous_freq);
+}
+static DEVICE_ATTR_RO(target_freq);
+
+static ssize_t min_freq_store(struct device *dev, struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct devfreq *df = to_devfreq(dev);
+	unsigned long value;
+	int ret;
+
+	/*
+	 * Protect against theoretical sysfs writes between
+	 * device_add and dev_pm_qos_add_request
+	 */
+	if (!dev_pm_qos_request_active(&df->user_min_freq_req))
+		return -EAGAIN;
+
+	ret = sscanf(buf, "%lu", &value);
+	if (ret != 1)
+		return -EINVAL;
+
+	/* Round down to kHz for PM QoS */
+	ret = dev_pm_qos_update_request(&df->user_min_freq_req,
+					value / HZ_PER_KHZ);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+static ssize_t min_freq_show(struct device *dev, struct device_attribute *attr,
+			     char *buf)
+{
+	struct devfreq *df = to_devfreq(dev);
+	unsigned long min_freq, max_freq;
+
+	mutex_lock(&df->lock);
+	devfreq_get_freq_range(df, &min_freq, &max_freq);
+	mutex_unlock(&df->lock);
+
+	return sprintf(buf, "%lu\n", min_freq);
+}
+static DEVICE_ATTR_RW(min_freq);
+
+static ssize_t max_freq_store(struct device *dev, struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct devfreq *df = to_devfreq(dev);
+	unsigned long value;
+	int ret;
+
+	/*
+	 * Protect against theoretical sysfs writes between
+	 * device_add and dev_pm_qos_add_request
+	 */
+	if (!dev_pm_qos_request_active(&df->user_max_freq_req))
+		return -EINVAL;
+
+	ret = sscanf(buf, "%lu", &value);
+	if (ret != 1)
+		return -EINVAL;
+
+	/*
+	 * PM QoS frequencies are in kHz so we need to convert. Convert by
+	 * rounding upwards so that the acceptable interval never shrinks.
+	 *
+	 * For example if the user writes "666666666" to sysfs this value will
+	 * be converted to 666667 kHz and back to 666667000 Hz before an OPP
+	 * lookup, this ensures that an OPP of 666666666Hz is still accepted.
+	 *
+	 * A value of zero means "no limit".
+	 */
+	if (value)
+		value = DIV_ROUND_UP(value, HZ_PER_KHZ);
+	else
+		value = PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE;
+
+	ret = dev_pm_qos_update_request(&df->user_max_freq_req, value);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+static ssize_t max_freq_show(struct device *dev, struct device_attribute *attr,
+			     char *buf)
+{
+	struct devfreq *df = to_devfreq(dev);
+	unsigned long min_freq, max_freq;
+
+	mutex_lock(&df->lock);
+	devfreq_get_freq_range(df, &min_freq, &max_freq);
+	mutex_unlock(&df->lock);
+
+	return sprintf(buf, "%lu\n", max_freq);
+}
+static DEVICE_ATTR_RW(max_freq);
+
+static ssize_t available_frequencies_show(struct device *d,
+					  struct device_attribute *attr,
+					  char *buf)
+{
+	struct devfreq *df = to_devfreq(d);
+	ssize_t count = 0;
+	int i;
+
+	if (!df->profile)
+		return -EINVAL;
+
+	mutex_lock(&df->lock);
+
+	for (i = 0; i < df->max_state; i++)
+		count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
+				"%lu ", df->freq_table[i]);
+
+	mutex_unlock(&df->lock);
+	/* Truncate the trailing space */
+	if (count)
+		count--;
+
+	count += sprintf(&buf[count], "\n");
+
+	return count;
+}
+static DEVICE_ATTR_RO(available_frequencies);
+
+static ssize_t trans_stat_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct devfreq *df = to_devfreq(dev);
+	ssize_t len = 0;
+	int i, j;
+	unsigned int max_state;
+
+	if (!df->profile)
+		return -EINVAL;
+	max_state = df->max_state;
+
+	if (max_state == 0)
+		return scnprintf(buf, PAGE_SIZE, "Not Supported.\n");
+
+	mutex_lock(&df->lock);
+	if (!df->stop_polling &&
+			devfreq_update_status(df, df->previous_freq)) {
+		mutex_unlock(&df->lock);
+		return 0;
+	}
+	mutex_unlock(&df->lock);
+
+	len += scnprintf(buf + len, PAGE_SIZE - len, "     From  :   To\n");
+	len += scnprintf(buf + len, PAGE_SIZE - len, "           :");
+	for (i = 0; i < max_state; i++) {
+		if (len >= PAGE_SIZE - 1)
+			break;
+		len += scnprintf(buf + len, PAGE_SIZE - len, "%10lu",
+				 df->freq_table[i]);
+	}
+	if (len >= PAGE_SIZE - 1)
+		return PAGE_SIZE - 1;
+
+	len += scnprintf(buf + len, PAGE_SIZE - len, "   time(ms)\n");
+
+	for (i = 0; i < max_state; i++) {
+		if (len >= PAGE_SIZE - 1)
+			break;
+		if (df->freq_table[i] == df->previous_freq)
+			len += scnprintf(buf + len, PAGE_SIZE - len, "*");
+		else
+			len += scnprintf(buf + len, PAGE_SIZE - len, " ");
+		if (len >= PAGE_SIZE - 1)
+			break;
+
+		len += scnprintf(buf + len, PAGE_SIZE - len, "%10lu:",
+				 df->freq_table[i]);
+		for (j = 0; j < max_state; j++) {
+			if (len >= PAGE_SIZE - 1)
+				break;
+			len += scnprintf(buf + len, PAGE_SIZE - len, "%10u",
+					 df->stats.trans_table[(i * max_state) + j]);
+		}
+		if (len >= PAGE_SIZE - 1)
+			break;
+		len += scnprintf(buf + len, PAGE_SIZE - len, "%10llu\n", (u64)
+				 jiffies64_to_msecs(df->stats.time_in_state[i]));
+	}
+
+	if (len < PAGE_SIZE - 1)
+		len += scnprintf(buf + len, PAGE_SIZE - len, "Total transition : %u\n",
+				 df->stats.total_trans);
+
+	if (len >= PAGE_SIZE - 1) {
+		pr_warn_once("devfreq transition table exceeds PAGE_SIZE. Disabling\n");
+		return -EFBIG;
+	}
+
+	return len;
+}
+
+static ssize_t trans_stat_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	struct devfreq *df = to_devfreq(dev);
+	int err, value;
+
+	if (!df->profile)
+		return -EINVAL;
+
+	if (df->max_state == 0)
+		return count;
+
+	err = kstrtoint(buf, 10, &value);
+	if (err || value != 0)
+		return -EINVAL;
+
+	mutex_lock(&df->lock);
+	memset(df->stats.time_in_state, 0, (df->max_state *
+					sizeof(*df->stats.time_in_state)));
+	memset(df->stats.trans_table, 0, array3_size(sizeof(unsigned int),
+					df->max_state,
+					df->max_state));
+	df->stats.total_trans = 0;
+	df->stats.last_update = get_jiffies_64();
+	mutex_unlock(&df->lock);
+
+	return count;
+}
+static DEVICE_ATTR_RW(trans_stat);
+
+static struct attribute *devfreq_attrs[] = {
+	&dev_attr_name.attr,
+	&dev_attr_governor.attr,
+	&dev_attr_available_governors.attr,
+	&dev_attr_cur_freq.attr,
+	&dev_attr_available_frequencies.attr,
+	&dev_attr_target_freq.attr,
+	&dev_attr_min_freq.attr,
+	&dev_attr_max_freq.attr,
+	&dev_attr_trans_stat.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(devfreq);
+
+static ssize_t polling_interval_show(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	struct devfreq *df = to_devfreq(dev);
+
+	if (!df->profile)
+		return -EINVAL;
+
+	return sprintf(buf, "%d\n", df->profile->polling_ms);
+}
+
+static ssize_t polling_interval_store(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf, size_t count)
+{
+	struct devfreq *df = to_devfreq(dev);
+	unsigned int value;
+	int ret;
+
+	if (!df->governor)
+		return -EINVAL;
+
+	ret = sscanf(buf, "%u", &value);
+	if (ret != 1)
+		return -EINVAL;
+
+	df->governor->event_handler(df, DEVFREQ_GOV_UPDATE_INTERVAL, &value);
+	ret = count;
+
+	return ret;
+}
+static DEVICE_ATTR_RW(polling_interval);
+
+static ssize_t timer_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct devfreq *df = to_devfreq(dev);
+
+	if (!df->profile)
+		return -EINVAL;
+
+	return sprintf(buf, "%s\n", timer_name[df->profile->timer]);
+}
+
+static ssize_t timer_store(struct device *dev, struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct devfreq *df = to_devfreq(dev);
+	char str_timer[DEVFREQ_NAME_LEN + 1];
+	int timer = -1;
+	int ret = 0, i;
+
+	if (!df->governor || !df->profile)
+		return -EINVAL;
+
+	ret = sscanf(buf, "%16s", str_timer);
+	if (ret != 1)
+		return -EINVAL;
+
+	for (i = 0; i < DEVFREQ_TIMER_NUM; i++) {
+		if (!strncmp(timer_name[i], str_timer, DEVFREQ_NAME_LEN)) {
+			timer = i;
+			break;
+		}
+	}
+
+	if (timer < 0) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (df->profile->timer == timer) {
+		ret = 0;
+		goto out;
+	}
+
+	mutex_lock(&df->lock);
+	df->profile->timer = timer;
+	mutex_unlock(&df->lock);
+
+	ret = df->governor->event_handler(df, DEVFREQ_GOV_STOP, NULL);
+	if (ret) {
+		dev_warn(dev, "%s: Governor %s not stopped(%d)\n",
+			 __func__, df->governor->name, ret);
+		goto out;
+	}
+
+	ret = df->governor->event_handler(df, DEVFREQ_GOV_START, NULL);
+	if (ret)
+		dev_warn(dev, "%s: Governor %s not started(%d)\n",
+			 __func__, df->governor->name, ret);
+out:
+	return ret ? ret : count;
+}
+static DEVICE_ATTR_RW(timer);
+
+#define CREATE_SYSFS_FILE(df, name)					\
+{									\
+	int ret;							\
+	ret = sysfs_create_file(&df->dev.kobj, &dev_attr_##name.attr);	\
+	if (ret < 0) {							\
+		dev_warn(&df->dev,					\
+			"Unable to create attr(%s)\n", "##name");	\
+	}								\
+}									\
+
+/* Create the specific sysfs files which depend on each governor. */
+static void create_sysfs_files(struct devfreq *devfreq,
+				const struct devfreq_governor *gov)
+{
+	if (IS_SUPPORTED_ATTR(gov->attrs, POLLING_INTERVAL))
+		CREATE_SYSFS_FILE(devfreq, polling_interval);
+	if (IS_SUPPORTED_ATTR(gov->attrs, TIMER))
+		CREATE_SYSFS_FILE(devfreq, timer);
+}
+
+/* Remove the specific sysfs files which depend on each governor. */
+static void remove_sysfs_files(struct devfreq *devfreq,
+				const struct devfreq_governor *gov)
+{
+	if (IS_SUPPORTED_ATTR(gov->attrs, POLLING_INTERVAL))
+		sysfs_remove_file(&devfreq->dev.kobj,
+				&dev_attr_polling_interval.attr);
+	if (IS_SUPPORTED_ATTR(gov->attrs, TIMER))
+		sysfs_remove_file(&devfreq->dev.kobj, &dev_attr_timer.attr);
+}
+
+/**
+ * devfreq_summary_show() - Show the summary of the devfreq devices
+ * @s:		seq_file instance to show the summary of devfreq devices
+ * @data:	not used
+ *
+ * Show the summary of the devfreq devices via 'devfreq_summary' debugfs file.
+ * It helps that user can know the detailed information of the devfreq devices.
+ *
+ * Return 0 always because it shows the information without any data change.
+ */
+static int devfreq_summary_show(struct seq_file *s, void *data)
+{
+	struct devfreq *devfreq;
+	struct devfreq *p_devfreq = NULL;
+	unsigned long cur_freq, min_freq, max_freq;
+	unsigned int polling_ms;
+	unsigned int timer;
+
+	seq_printf(s, "%-30s %-30s %-15s %-10s %10s %12s %12s %12s\n",
+			"dev",
+			"parent_dev",
+			"governor",
+			"timer",
+			"polling_ms",
+			"cur_freq_Hz",
+			"min_freq_Hz",
+			"max_freq_Hz");
+	seq_printf(s, "%30s %30s %15s %10s %10s %12s %12s %12s\n",
+			"------------------------------",
+			"------------------------------",
+			"---------------",
+			"----------",
+			"----------",
+			"------------",
+			"------------",
+			"------------");
+
+	mutex_lock(&devfreq_list_lock);
+
+	list_for_each_entry_reverse(devfreq, &devfreq_list, node) {
+#if IS_ENABLED(CONFIG_DEVFREQ_GOV_PASSIVE)
+		if (!strncmp(devfreq->governor->name, DEVFREQ_GOV_PASSIVE,
+							DEVFREQ_NAME_LEN)) {
+			struct devfreq_passive_data *data = devfreq->data;
+
+			if (data)
+				p_devfreq = data->parent;
+		} else {
+			p_devfreq = NULL;
+		}
+#endif
+
+		mutex_lock(&devfreq->lock);
+		cur_freq = devfreq->previous_freq;
+		devfreq_get_freq_range(devfreq, &min_freq, &max_freq);
+		timer = devfreq->profile->timer;
+
+		if (IS_SUPPORTED_ATTR(devfreq->governor->attrs, POLLING_INTERVAL))
+			polling_ms = devfreq->profile->polling_ms;
+		else
+			polling_ms = 0;
+		mutex_unlock(&devfreq->lock);
+
+		seq_printf(s,
+			"%-30s %-30s %-15s %-10s %10d %12ld %12ld %12ld\n",
+			dev_name(&devfreq->dev),
+			p_devfreq ? dev_name(&p_devfreq->dev) : "null",
+			devfreq->governor->name,
+			polling_ms ? timer_name[timer] : "null",
+			polling_ms,
+			cur_freq,
+			min_freq,
+			max_freq);
+	}
+
+	mutex_unlock(&devfreq_list_lock);
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(devfreq_summary);
+
+static int __init devfreq_init(void)
+{
+	devfreq_class = class_create(THIS_MODULE, "devfreq");
+	if (IS_ERR(devfreq_class)) {
+		pr_err("%s: couldn't create class\n", __FILE__);
+		return PTR_ERR(devfreq_class);
+	}
+
+	devfreq_wq = create_freezable_workqueue("devfreq_wq");
+	if (!devfreq_wq) {
+		class_destroy(devfreq_class);
+		pr_err("%s: couldn't create workqueue\n", __FILE__);
+		return -ENOMEM;
+	}
+	devfreq_class->dev_groups = devfreq_groups;
+
+	devfreq_debugfs = debugfs_create_dir("devfreq", NULL);
+	debugfs_create_file("devfreq_summary", 0444,
+				devfreq_debugfs, NULL,
+				&devfreq_summary_fops);
+
+	return 0;
+}
+subsys_initcall(devfreq_init);
+
+/*
+ * The following are helper functions for devfreq user device drivers with
+ * OPP framework.
+ */
+
+/**
+ * devfreq_recommended_opp() - Helper function to get proper OPP for the
+ *			     freq value given to target callback.
+ * @dev:	The devfreq user device. (parent of devfreq)
+ * @freq:	The frequency given to target function
+ * @flags:	Flags handed from devfreq framework.
+ *
+ * The callers are required to call dev_pm_opp_put() for the returned OPP after
+ * use.
+ */
+struct dev_pm_opp *devfreq_recommended_opp(struct device *dev,
+					   unsigned long *freq,
+					   u32 flags)
+{
+	struct dev_pm_opp *opp;
+
+	if (flags & DEVFREQ_FLAG_LEAST_UPPER_BOUND) {
+		/* The freq is an upper bound. opp should be lower */
+		opp = dev_pm_opp_find_freq_floor(dev, freq);
+
+		/* If not available, use the closest opp */
+		if (opp == ERR_PTR(-ERANGE))
+			opp = dev_pm_opp_find_freq_ceil(dev, freq);
+	} else {
+		/* The freq is an lower bound. opp should be higher */
+		opp = dev_pm_opp_find_freq_ceil(dev, freq);
+
+		/* If not available, use the closest opp */
+		if (opp == ERR_PTR(-ERANGE))
+			opp = dev_pm_opp_find_freq_floor(dev, freq);
+	}
+
+	return opp;
+}
+EXPORT_SYMBOL(devfreq_recommended_opp);
+
+/**
+ * devfreq_register_opp_notifier() - Helper function to get devfreq notified
+ *				     for any changes in the OPP availability
+ *				     changes
+ * @dev:	The devfreq user device. (parent of devfreq)
+ * @devfreq:	The devfreq object.
+ */
+int devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq)
+{
+	return dev_pm_opp_register_notifier(dev, &devfreq->nb);
+}
+EXPORT_SYMBOL(devfreq_register_opp_notifier);
+
+/**
+ * devfreq_unregister_opp_notifier() - Helper function to stop getting devfreq
+ *				       notified for any changes in the OPP
+ *				       availability changes anymore.
+ * @dev:	The devfreq user device. (parent of devfreq)
+ * @devfreq:	The devfreq object.
+ *
+ * At exit() callback of devfreq_dev_profile, this must be included if
+ * devfreq_recommended_opp is used.
+ */
+int devfreq_unregister_opp_notifier(struct device *dev, struct devfreq *devfreq)
+{
+	return dev_pm_opp_unregister_notifier(dev, &devfreq->nb);
+}
+EXPORT_SYMBOL(devfreq_unregister_opp_notifier);
+
+static void devm_devfreq_opp_release(struct device *dev, void *res)
+{
+	devfreq_unregister_opp_notifier(dev, *(struct devfreq **)res);
+}
+
+/**
+ * devm_devfreq_register_opp_notifier() - Resource-managed
+ *					  devfreq_register_opp_notifier()
+ * @dev:	The devfreq user device. (parent of devfreq)
+ * @devfreq:	The devfreq object.
+ */
+int devm_devfreq_register_opp_notifier(struct device *dev,
+				       struct devfreq *devfreq)
+{
+	struct devfreq **ptr;
+	int ret;
+
+	ptr = devres_alloc(devm_devfreq_opp_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	ret = devfreq_register_opp_notifier(dev, devfreq);
+	if (ret) {
+		devres_free(ptr);
+		return ret;
+	}
+
+	*ptr = devfreq;
+	devres_add(dev, ptr);
+
+	return 0;
+}
+EXPORT_SYMBOL(devm_devfreq_register_opp_notifier);
+
+/**
+ * devm_devfreq_unregister_opp_notifier() - Resource-managed
+ *					    devfreq_unregister_opp_notifier()
+ * @dev:	The devfreq user device. (parent of devfreq)
+ * @devfreq:	The devfreq object.
+ */
+void devm_devfreq_unregister_opp_notifier(struct device *dev,
+					 struct devfreq *devfreq)
+{
+	WARN_ON(devres_release(dev, devm_devfreq_opp_release,
+			       devm_devfreq_dev_match, devfreq));
+}
+EXPORT_SYMBOL(devm_devfreq_unregister_opp_notifier);
+
+/**
+ * devfreq_register_notifier() - Register a driver with devfreq
+ * @devfreq:	The devfreq object.
+ * @nb:		The notifier block to register.
+ * @list:	DEVFREQ_TRANSITION_NOTIFIER.
+ */
+int devfreq_register_notifier(struct devfreq *devfreq,
+			      struct notifier_block *nb,
+			      unsigned int list)
+{
+	int ret = 0;
+
+	if (!devfreq)
+		return -EINVAL;
+
+	switch (list) {
+	case DEVFREQ_TRANSITION_NOTIFIER:
+		ret = srcu_notifier_chain_register(
+				&devfreq->transition_notifier_list, nb);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(devfreq_register_notifier);
+
+/*
+ * devfreq_unregister_notifier() - Unregister a driver with devfreq
+ * @devfreq:	The devfreq object.
+ * @nb:		The notifier block to be unregistered.
+ * @list:	DEVFREQ_TRANSITION_NOTIFIER.
+ */
+int devfreq_unregister_notifier(struct devfreq *devfreq,
+				struct notifier_block *nb,
+				unsigned int list)
+{
+	int ret = 0;
+
+	if (!devfreq)
+		return -EINVAL;
+
+	switch (list) {
+	case DEVFREQ_TRANSITION_NOTIFIER:
+		ret = srcu_notifier_chain_unregister(
+				&devfreq->transition_notifier_list, nb);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(devfreq_unregister_notifier);
+
+struct devfreq_notifier_devres {
+	struct devfreq *devfreq;
+	struct notifier_block *nb;
+	unsigned int list;
+};
+
+static void devm_devfreq_notifier_release(struct device *dev, void *res)
+{
+	struct devfreq_notifier_devres *this = res;
+
+	devfreq_unregister_notifier(this->devfreq, this->nb, this->list);
+}
+
+/**
+ * devm_devfreq_register_notifier()
+ *	- Resource-managed devfreq_register_notifier()
+ * @dev:	The devfreq user device. (parent of devfreq)
+ * @devfreq:	The devfreq object.
+ * @nb:		The notifier block to be unregistered.
+ * @list:	DEVFREQ_TRANSITION_NOTIFIER.
+ */
+int devm_devfreq_register_notifier(struct device *dev,
+				struct devfreq *devfreq,
+				struct notifier_block *nb,
+				unsigned int list)
+{
+	struct devfreq_notifier_devres *ptr;
+	int ret;
+
+	ptr = devres_alloc(devm_devfreq_notifier_release, sizeof(*ptr),
+				GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	ret = devfreq_register_notifier(devfreq, nb, list);
+	if (ret) {
+		devres_free(ptr);
+		return ret;
+	}
+
+	ptr->devfreq = devfreq;
+	ptr->nb = nb;
+	ptr->list = list;
+	devres_add(dev, ptr);
+
+	return 0;
+}
+EXPORT_SYMBOL(devm_devfreq_register_notifier);
+
+/**
+ * devm_devfreq_unregister_notifier()
+ *	- Resource-managed devfreq_unregister_notifier()
+ * @dev:	The devfreq user device. (parent of devfreq)
+ * @devfreq:	The devfreq object.
+ * @nb:		The notifier block to be unregistered.
+ * @list:	DEVFREQ_TRANSITION_NOTIFIER.
+ */
+void devm_devfreq_unregister_notifier(struct device *dev,
+				      struct devfreq *devfreq,
+				      struct notifier_block *nb,
+				      unsigned int list)
+{
+	WARN_ON(devres_release(dev, devm_devfreq_notifier_release,
+			       devm_devfreq_dev_match, devfreq));
+}
+EXPORT_SYMBOL(devm_devfreq_unregister_notifier);