drivers/devfreq/governor_cache_hwmon.c - kernel/msm-4.9 - Gitiles

 /*
  * Copyright (c) 2014-2015, The Linux Foundation. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 and
  * only version 2 as published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  */

 #define pr_fmt(fmt) "cache-hwmon: " fmt

 #include <linux/kernel.h>
 #include <linux/sizes.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/io.h>
 #include <linux/delay.h>
 #include <linux/ktime.h>
 #include <linux/time.h>
 #include <linux/err.h>
 #include <linux/errno.h>
 #include <linux/mutex.h>
 #include <linux/interrupt.h>
 #include <linux/platform_device.h>
 #include <linux/of.h>
 #include <linux/devfreq.h>
 #include <trace/events/power.h>
 #include "governor.h"
 #include "governor_cache_hwmon.h"

 struct cache_hwmon_node {
 	unsigned int cycles_per_low_req;
 	unsigned int cycles_per_med_req;
 	unsigned int cycles_per_high_req;
 	unsigned int min_busy;
 	unsigned int max_busy;
 	unsigned int tolerance_mrps;
 	unsigned int guard_band_mhz;
 	unsigned int decay_rate;
 	unsigned long prev_mhz;
 	ktime_t prev_ts;
 	bool mon_started;
 	struct list_head list;
 	void *orig_data;
 	struct cache_hwmon *hw;
 	struct attribute_group *attr_grp;
 };

 static LIST_HEAD(cache_hwmon_list);
 static DEFINE_MUTEX(list_lock);

 static int use_cnt;
 static DEFINE_MUTEX(register_lock);

 static DEFINE_MUTEX(monitor_lock);

 #define show_attr(name) \
 static ssize_t show_##name(struct device *dev,				\
 			struct device_attribute *attr, char *buf)	\
 {									\
 	struct devfreq *df = to_devfreq(dev);				\
 	struct cache_hwmon_node *hw = df->data;				\
 	return snprintf(buf, PAGE_SIZE, "%u\n", hw->name);		\
 }

 #define store_attr(name, _min, _max) \
 static ssize_t store_##name(struct device *dev,				\
 			struct device_attribute *attr, const char *buf,	\
 			size_t count)					\
 {									\
 	int ret;							\
 	unsigned int val;						\
 	struct devfreq *df = to_devfreq(dev);				\
 	struct cache_hwmon_node *hw = df->data;				\
 	ret = kstrtoint(buf, 10, &val);					\
 	if (ret)							\
 		return ret;						\
 	val = max(val, _min);						\
 	val = min(val, _max);						\
 	hw->name = val;							\
 	return count;							\
 }

 #define gov_attr(__attr, min, max)	\
 show_attr(__attr)			\
 store_attr(__attr, (min), (max))	\
 static DEVICE_ATTR(__attr, 0644, show_##__attr, store_##__attr)

 #define MIN_MS	10U
 #define MAX_MS	500U

 static struct cache_hwmon_node *find_hwmon_node(struct devfreq *df)
 {
 	struct cache_hwmon_node *node, *found = NULL;

 	mutex_lock(&list_lock);
 	list_for_each_entry(node, &cache_hwmon_list, list)
 		if (node->hw->dev == df->dev.parent ||
 		    node->hw->of_node == df->dev.parent->of_node) {
 			found = node;
 			break;
 		}
 	mutex_unlock(&list_lock);

 	return found;
 }

 static unsigned long measure_mrps_and_set_irq(struct cache_hwmon_node *node,
 			struct mrps_stats *stat)
 {
 	ktime_t ts;
 	unsigned int us;
 	struct cache_hwmon *hw = node->hw;

 	/*
 	 * Since we are stopping the counters, we don't want this short work
 	 * to be interrupted by other tasks and cause the measurements to be
 	 * wrong. Not blocking interrupts to avoid affecting interrupt
 	 * latency and since they should be short anyway because they run in
 	 * atomic context.
 	 */
 	preempt_disable();

 	ts = ktime_get();
 	us = ktime_to_us(ktime_sub(ts, node->prev_ts));
 	if (!us)
 		us = 1;

 	hw->meas_mrps_and_set_irq(hw, node->tolerance_mrps, us, stat);
 	node->prev_ts = ts;

 	preempt_enable();

 	trace_cache_hwmon_meas(dev_name(hw->df->dev.parent), stat->mrps[HIGH],
 			       stat->mrps[MED], stat->mrps[LOW],
 			       stat->busy_percent, us);
 	return 0;
 }

 static void compute_cache_freq(struct cache_hwmon_node *node,
 		struct mrps_stats *mrps, unsigned long *freq)
 {
 	unsigned long new_mhz;
 	unsigned int busy;

 	new_mhz = mrps->mrps[HIGH] * node->cycles_per_high_req
 		+ mrps->mrps[MED] * node->cycles_per_med_req
 		+ mrps->mrps[LOW] * node->cycles_per_low_req;

 	busy = max(node->min_busy, mrps->busy_percent);
 	busy = min(node->max_busy, busy);

 	new_mhz *= 100;
 	new_mhz /= busy;

 	if (new_mhz < node->prev_mhz) {
 		new_mhz = new_mhz * node->decay_rate + node->prev_mhz
 				* (100 - node->decay_rate);
 		new_mhz /= 100;
 	}
 	node->prev_mhz = new_mhz;

 	new_mhz += node->guard_band_mhz;
 	*freq = new_mhz * 1000;
 	trace_cache_hwmon_update(dev_name(node->hw->df->dev.parent), *freq);
 }

 #define TOO_SOON_US	(1 * USEC_PER_MSEC)
 int update_cache_hwmon(struct cache_hwmon *hwmon)
 {
 	struct cache_hwmon_node *node;
 	struct devfreq *df;
 	ktime_t ts;
 	unsigned int us;
 	int ret;

 	if (!hwmon)
 		return -EINVAL;
 	df = hwmon->df;
 	if (!df)
 		return -ENODEV;
 	node = df->data;
 	if (!node)
 		return -ENODEV;

 	mutex_lock(&monitor_lock);
 	if (!node->mon_started) {
 		mutex_unlock(&monitor_lock);
 		return -EBUSY;
 	}

 	dev_dbg(df->dev.parent, "Got update request\n");
 	devfreq_monitor_stop(df);

 	/*
 	 * Don't recalc cache freq if the interrupt comes right after a
 	 * previous cache freq calculation.  This is done for two reasons:
 	 *
 	 * 1. Sampling the cache request during a very short duration can
 	 *    result in a very inaccurate measurement due to very short
 	 *    bursts.
 	 * 2. This can only happen if the limit was hit very close to the end
 	 *    of the previous sample period. Which means the current cache
 	 *    request estimate is not very off and doesn't need to be
 	 *    readjusted.
 	 */
 	ts = ktime_get();
 	us = ktime_to_us(ktime_sub(ts, node->prev_ts));
 	if (us > TOO_SOON_US) {
 		mutex_lock(&df->lock);
 		ret = update_devfreq(df);
 		if (ret)
 			dev_err(df->dev.parent,
 				"Unable to update freq on request!\n");
 		mutex_unlock(&df->lock);
 	}

 	devfreq_monitor_start(df);

 	mutex_unlock(&monitor_lock);
 	return 0;
 }

 static int devfreq_cache_hwmon_get_freq(struct devfreq *df,
 					unsigned long *freq)
 {
 	struct mrps_stats stat;
 	struct cache_hwmon_node *node = df->data;

 	memset(&stat, 0, sizeof(stat));
 	measure_mrps_and_set_irq(node, &stat);
 	compute_cache_freq(node, &stat, freq);

 	return 0;
 }

 gov_attr(cycles_per_low_req, 1U, 100U);
 gov_attr(cycles_per_med_req, 1U, 100U);
 gov_attr(cycles_per_high_req, 1U, 100U);
 gov_attr(min_busy, 1U, 100U);
 gov_attr(max_busy, 1U, 100U);
 gov_attr(tolerance_mrps, 0U, 100U);
 gov_attr(guard_band_mhz, 0U, 500U);
 gov_attr(decay_rate, 0U, 100U);

 static struct attribute *dev_attr[] = {
 	&dev_attr_cycles_per_low_req.attr,
 	&dev_attr_cycles_per_med_req.attr,
 	&dev_attr_cycles_per_high_req.attr,
 	&dev_attr_min_busy.attr,
 	&dev_attr_max_busy.attr,
 	&dev_attr_tolerance_mrps.attr,
 	&dev_attr_guard_band_mhz.attr,
 	&dev_attr_decay_rate.attr,
 	NULL,
 };

 static struct attribute_group dev_attr_group = {
 	.name = "cache_hwmon",
 	.attrs = dev_attr,
 };

 static int start_monitoring(struct devfreq *df)
 {
 	int ret;
 	struct mrps_stats mrps;
 	struct device *dev = df->dev.parent;
 	struct cache_hwmon_node *node;
 	struct cache_hwmon *hw;

 	node = find_hwmon_node(df);
 	if (!node) {
 		dev_err(dev, "Unable to find HW monitor!\n");
 		return -ENODEV;
 	}
 	hw = node->hw;
 	hw->df = df;
 	node->orig_data = df->data;
 	df->data = node;

 	node->prev_ts = ktime_get();
 	node->prev_mhz = 0;
 	mrps.mrps[HIGH] = (df->previous_freq / 1000) - node->guard_band_mhz;
 	mrps.mrps[HIGH] /= node->cycles_per_high_req;
 	mrps.mrps[MED] = mrps.mrps[LOW] = 0;

 	ret = hw->start_hwmon(hw, &mrps);
 	if (ret) {
 		dev_err(dev, "Unable to start HW monitor!\n");
 		goto err_start;
 	}

 	mutex_lock(&monitor_lock);
 	devfreq_monitor_start(df);
 	node->mon_started = true;
 	mutex_unlock(&monitor_lock);

 	ret = sysfs_create_group(&df->dev.kobj, &dev_attr_group);
 	if (ret) {
 		dev_err(dev, "Error creating sys entries!\n");
 		goto sysfs_fail;
 	}

 	return 0;

 sysfs_fail:
 	mutex_lock(&monitor_lock);
 	node->mon_started = false;
 	devfreq_monitor_stop(df);
 	mutex_unlock(&monitor_lock);
 	hw->stop_hwmon(hw);
 err_start:
 	df->data = node->orig_data;
 	node->orig_data = NULL;
 	hw->df = NULL;
 	return ret;
 }

 static void stop_monitoring(struct devfreq *df)
 {
 	struct cache_hwmon_node *node = df->data;
 	struct cache_hwmon *hw = node->hw;

 	sysfs_remove_group(&df->dev.kobj, &dev_attr_group);
 	mutex_lock(&monitor_lock);
 	node->mon_started = false;
 	devfreq_monitor_stop(df);
 	mutex_unlock(&monitor_lock);
 	hw->stop_hwmon(hw);
 	df->data = node->orig_data;
 	node->orig_data = NULL;
 	hw->df = NULL;
 }

 static int devfreq_cache_hwmon_ev_handler(struct devfreq *df,
 					unsigned int event, void *data)
 {
 	int ret;
 	unsigned int sample_ms;

 	switch (event) {
 	case DEVFREQ_GOV_START:
 		sample_ms = df->profile->polling_ms;
 		sample_ms = max(MIN_MS, sample_ms);
 		sample_ms = min(MAX_MS, sample_ms);
 		df->profile->polling_ms = sample_ms;

 		ret = start_monitoring(df);
 		if (ret)
 			return ret;

 		dev_dbg(df->dev.parent, "Enabled Cache HW monitor governor\n");
 		break;

 	case DEVFREQ_GOV_STOP:
 		stop_monitoring(df);
 		dev_dbg(df->dev.parent, "Disabled Cache HW monitor governor\n");
 		break;

 	case DEVFREQ_GOV_INTERVAL:
 		sample_ms = *(unsigned int *)data;
 		sample_ms = max(MIN_MS, sample_ms);
 		sample_ms = min(MAX_MS, sample_ms);
 		devfreq_interval_update(df, &sample_ms);
 		break;
 	}

 	return 0;
 }

 static struct devfreq_governor devfreq_cache_hwmon = {
 	.name = "cache_hwmon",
 	.get_target_freq = devfreq_cache_hwmon_get_freq,
 	.event_handler = devfreq_cache_hwmon_ev_handler,
 };

 int register_cache_hwmon(struct device *dev, struct cache_hwmon *hwmon)
 {
 	int ret = 0;
 	struct cache_hwmon_node *node;

 	if (!hwmon->dev && !hwmon->of_node)
 		return -EINVAL;

 	node = devm_kzalloc(dev, sizeof(*node), GFP_KERNEL);
 	if (!node)
 		return -ENOMEM;

 	node->cycles_per_med_req = 20;
 	node->cycles_per_high_req = 35;
 	node->min_busy = 100;
 	node->max_busy = 100;
 	node->tolerance_mrps = 5;
 	node->guard_band_mhz = 100;
 	node->decay_rate = 90;
 	node->hw = hwmon;
 	node->attr_grp = &dev_attr_group;

 	mutex_lock(&register_lock);
 	if (!use_cnt) {
 		ret = devfreq_add_governor(&devfreq_cache_hwmon);
 		if (!ret)
 			use_cnt++;
 	}
 	mutex_unlock(&register_lock);

 	if (!ret) {
 		dev_info(dev, "Cache HWmon governor registered.\n");
 	} else {
 		dev_err(dev, "Failed to add Cache HWmon governor\n");
 		return ret;
 	}

 	mutex_lock(&list_lock);
 	list_add_tail(&node->list, &cache_hwmon_list);
 	mutex_unlock(&list_lock);

 	return ret;
 }

 MODULE_DESCRIPTION("HW monitor based cache freq driver");
 MODULE_LICENSE("GPL v2");
	/*
	* Copyright (c) 2014-2015, The Linux Foundation. All rights reserved.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 and
	* only version 2 as published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*/

	#define pr_fmt(fmt) "cache-hwmon: " fmt

	#include <linux/kernel.h>
	#include <linux/sizes.h>
	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/io.h>
	#include <linux/delay.h>
	#include <linux/ktime.h>
	#include <linux/time.h>
	#include <linux/err.h>
	#include <linux/errno.h>
	#include <linux/mutex.h>
	#include <linux/interrupt.h>
	#include <linux/platform_device.h>
	#include <linux/of.h>
	#include <linux/devfreq.h>
	#include <trace/events/power.h>
	#include "governor.h"
	#include "governor_cache_hwmon.h"

	struct cache_hwmon_node {
	unsigned int cycles_per_low_req;
	unsigned int cycles_per_med_req;
	unsigned int cycles_per_high_req;
	unsigned int min_busy;
	unsigned int max_busy;
	unsigned int tolerance_mrps;
	unsigned int guard_band_mhz;
	unsigned int decay_rate;
	unsigned long prev_mhz;
	ktime_t prev_ts;
	bool mon_started;
	struct list_head list;
	void *orig_data;
	struct cache_hwmon *hw;
	struct attribute_group *attr_grp;
	};

	static LIST_HEAD(cache_hwmon_list);
	static DEFINE_MUTEX(list_lock);

	static int use_cnt;
	static DEFINE_MUTEX(register_lock);

	static DEFINE_MUTEX(monitor_lock);

	#define show_attr(name) \
	static ssize_t show_##name(struct device *dev, \
	struct device_attribute attr, char buf) \
	{ \
	struct devfreq *df = to_devfreq(dev); \
	struct cache_hwmon_node *hw = df->data; \
	return snprintf(buf, PAGE_SIZE, "%u\n", hw->name); \
	}

	#define store_attr(name, _min, _max) \
	static ssize_t store_##name(struct device *dev, \
	struct device_attribute attr, const char buf, \
	size_t count) \
	{ \
	int ret; \
	unsigned int val; \
	struct devfreq *df = to_devfreq(dev); \
	struct cache_hwmon_node *hw = df->data; \
	ret = kstrtoint(buf, 10, &val); \
	if (ret) \
	return ret; \
	val = max(val, _min); \
	val = min(val, _max); \
	hw->name = val; \
	return count; \
	}

	#define gov_attr(__attr, min, max) \
	show_attr(__attr) \
	store_attr(__attr, (min), (max)) \
	static DEVICE_ATTR(__attr, 0644, show_##__attr, store_##__attr)

	#define MIN_MS 10U
	#define MAX_MS 500U

	static struct cache_hwmon_node find_hwmon_node(struct devfreq df)
	{
	struct cache_hwmon_node node, found = NULL;

	mutex_lock(&list_lock);
	list_for_each_entry(node, &cache_hwmon_list, list)
	if (node->hw->dev == df->dev.parent \|\|
	node->hw->of_node == df->dev.parent->of_node) {
	found = node;
	break;
	}
	mutex_unlock(&list_lock);

	return found;
	}

	static unsigned long measure_mrps_and_set_irq(struct cache_hwmon_node *node,
	struct mrps_stats *stat)
	{
	ktime_t ts;
	unsigned int us;
	struct cache_hwmon *hw = node->hw;

	/*
	* Since we are stopping the counters, we don't want this short work
	* to be interrupted by other tasks and cause the measurements to be
	* wrong. Not blocking interrupts to avoid affecting interrupt
	* latency and since they should be short anyway because they run in
	* atomic context.
	*/
	preempt_disable();

	ts = ktime_get();
	us = ktime_to_us(ktime_sub(ts, node->prev_ts));
	if (!us)
	us = 1;

	hw->meas_mrps_and_set_irq(hw, node->tolerance_mrps, us, stat);
	node->prev_ts = ts;

	preempt_enable();

	trace_cache_hwmon_meas(dev_name(hw->df->dev.parent), stat->mrps[HIGH],
	stat->mrps[MED], stat->mrps[LOW],
	stat->busy_percent, us);
	return 0;
	}

	static void compute_cache_freq(struct cache_hwmon_node *node,
	struct mrps_stats mrps, unsigned long freq)
	{
	unsigned long new_mhz;
	unsigned int busy;

	new_mhz = mrps->mrps[HIGH] * node->cycles_per_high_req
	+ mrps->mrps[MED] * node->cycles_per_med_req
	+ mrps->mrps[LOW] * node->cycles_per_low_req;

	busy = max(node->min_busy, mrps->busy_percent);
	busy = min(node->max_busy, busy);

	new_mhz *= 100;
	new_mhz /= busy;

	if (new_mhz < node->prev_mhz) {
	new_mhz = new_mhz * node->decay_rate + node->prev_mhz
	* (100 - node->decay_rate);
	new_mhz /= 100;
	}
	node->prev_mhz = new_mhz;

	new_mhz += node->guard_band_mhz;
	freq = new_mhz 1000;
	trace_cache_hwmon_update(dev_name(node->hw->df->dev.parent), *freq);
	}

	#define TOO_SOON_US (1 * USEC_PER_MSEC)
	int update_cache_hwmon(struct cache_hwmon *hwmon)
	{
	struct cache_hwmon_node *node;
	struct devfreq *df;
	ktime_t ts;
	unsigned int us;
	int ret;

	if (!hwmon)
	return -EINVAL;
	df = hwmon->df;
	if (!df)
	return -ENODEV;
	node = df->data;
	if (!node)
	return -ENODEV;

	mutex_lock(&monitor_lock);
	if (!node->mon_started) {
	mutex_unlock(&monitor_lock);
	return -EBUSY;
	}

	dev_dbg(df->dev.parent, "Got update request\n");
	devfreq_monitor_stop(df);

	/*
	* Don't recalc cache freq if the interrupt comes right after a
	* previous cache freq calculation. This is done for two reasons:
	*
	* 1. Sampling the cache request during a very short duration can
	* result in a very inaccurate measurement due to very short
	* bursts.
	* 2. This can only happen if the limit was hit very close to the end
	* of the previous sample period. Which means the current cache
	* request estimate is not very off and doesn't need to be
	* readjusted.
	*/
	ts = ktime_get();
	us = ktime_to_us(ktime_sub(ts, node->prev_ts));
	if (us > TOO_SOON_US) {
	mutex_lock(&df->lock);
	ret = update_devfreq(df);
	if (ret)
	dev_err(df->dev.parent,
	"Unable to update freq on request!\n");
	mutex_unlock(&df->lock);
	}

	devfreq_monitor_start(df);

	mutex_unlock(&monitor_lock);
	return 0;
	}

	static int devfreq_cache_hwmon_get_freq(struct devfreq *df,
	unsigned long *freq)
	{
	struct mrps_stats stat;
	struct cache_hwmon_node *node = df->data;

	memset(&stat, 0, sizeof(stat));
	measure_mrps_and_set_irq(node, &stat);
	compute_cache_freq(node, &stat, freq);

	return 0;
	}

	gov_attr(cycles_per_low_req, 1U, 100U);
	gov_attr(cycles_per_med_req, 1U, 100U);
	gov_attr(cycles_per_high_req, 1U, 100U);
	gov_attr(min_busy, 1U, 100U);
	gov_attr(max_busy, 1U, 100U);
	gov_attr(tolerance_mrps, 0U, 100U);
	gov_attr(guard_band_mhz, 0U, 500U);
	gov_attr(decay_rate, 0U, 100U);

	static struct attribute *dev_attr[] = {
	&dev_attr_cycles_per_low_req.attr,
	&dev_attr_cycles_per_med_req.attr,
	&dev_attr_cycles_per_high_req.attr,
	&dev_attr_min_busy.attr,
	&dev_attr_max_busy.attr,
	&dev_attr_tolerance_mrps.attr,
	&dev_attr_guard_band_mhz.attr,
	&dev_attr_decay_rate.attr,
	NULL,
	};

	static struct attribute_group dev_attr_group = {
	.name = "cache_hwmon",
	.attrs = dev_attr,
	};

	static int start_monitoring(struct devfreq *df)
	{
	int ret;
	struct mrps_stats mrps;
	struct device *dev = df->dev.parent;
	struct cache_hwmon_node *node;
	struct cache_hwmon *hw;

	node = find_hwmon_node(df);
	if (!node) {
	dev_err(dev, "Unable to find HW monitor!\n");
	return -ENODEV;
	}
	hw = node->hw;
	hw->df = df;
	node->orig_data = df->data;
	df->data = node;

	node->prev_ts = ktime_get();
	node->prev_mhz = 0;
	mrps.mrps[HIGH] = (df->previous_freq / 1000) - node->guard_band_mhz;
	mrps.mrps[HIGH] /= node->cycles_per_high_req;
	mrps.mrps[MED] = mrps.mrps[LOW] = 0;

	ret = hw->start_hwmon(hw, &mrps);
	if (ret) {
	dev_err(dev, "Unable to start HW monitor!\n");
	goto err_start;
	}

	mutex_lock(&monitor_lock);
	devfreq_monitor_start(df);
	node->mon_started = true;
	mutex_unlock(&monitor_lock);

	ret = sysfs_create_group(&df->dev.kobj, &dev_attr_group);
	if (ret) {
	dev_err(dev, "Error creating sys entries!\n");
	goto sysfs_fail;
	}

	return 0;

	sysfs_fail:
	mutex_lock(&monitor_lock);
	node->mon_started = false;
	devfreq_monitor_stop(df);
	mutex_unlock(&monitor_lock);
	hw->stop_hwmon(hw);
	err_start:
	df->data = node->orig_data;
	node->orig_data = NULL;
	hw->df = NULL;
	return ret;
	}

	static void stop_monitoring(struct devfreq *df)
	{
	struct cache_hwmon_node *node = df->data;
	struct cache_hwmon *hw = node->hw;

	sysfs_remove_group(&df->dev.kobj, &dev_attr_group);
	mutex_lock(&monitor_lock);
	node->mon_started = false;
	devfreq_monitor_stop(df);
	mutex_unlock(&monitor_lock);
	hw->stop_hwmon(hw);
	df->data = node->orig_data;
	node->orig_data = NULL;
	hw->df = NULL;
	}

	static int devfreq_cache_hwmon_ev_handler(struct devfreq *df,
	unsigned int event, void *data)
	{
	int ret;
	unsigned int sample_ms;

	switch (event) {
	case DEVFREQ_GOV_START:
	sample_ms = df->profile->polling_ms;
	sample_ms = max(MIN_MS, sample_ms);
	sample_ms = min(MAX_MS, sample_ms);
	df->profile->polling_ms = sample_ms;

	ret = start_monitoring(df);
	if (ret)
	return ret;

	dev_dbg(df->dev.parent, "Enabled Cache HW monitor governor\n");
	break;

	case DEVFREQ_GOV_STOP:
	stop_monitoring(df);
	dev_dbg(df->dev.parent, "Disabled Cache HW monitor governor\n");
	break;

	case DEVFREQ_GOV_INTERVAL:
	sample_ms = (unsigned int )data;
	sample_ms = max(MIN_MS, sample_ms);
	sample_ms = min(MAX_MS, sample_ms);
	devfreq_interval_update(df, &sample_ms);
	break;
	}

	return 0;
	}

	static struct devfreq_governor devfreq_cache_hwmon = {
	.name = "cache_hwmon",
	.get_target_freq = devfreq_cache_hwmon_get_freq,
	.event_handler = devfreq_cache_hwmon_ev_handler,
	};

	int register_cache_hwmon(struct device dev, struct cache_hwmon hwmon)
	{
	int ret = 0;
	struct cache_hwmon_node *node;

	if (!hwmon->dev && !hwmon->of_node)
	return -EINVAL;

	node = devm_kzalloc(dev, sizeof(*node), GFP_KERNEL);
	if (!node)
	return -ENOMEM;

	node->cycles_per_med_req = 20;
	node->cycles_per_high_req = 35;
	node->min_busy = 100;
	node->max_busy = 100;
	node->tolerance_mrps = 5;
	node->guard_band_mhz = 100;
	node->decay_rate = 90;
	node->hw = hwmon;
	node->attr_grp = &dev_attr_group;

	mutex_lock(&register_lock);
	if (!use_cnt) {
	ret = devfreq_add_governor(&devfreq_cache_hwmon);
	if (!ret)
	use_cnt++;
	}
	mutex_unlock(&register_lock);

	if (!ret) {
	dev_info(dev, "Cache HWmon governor registered.\n");
	} else {
	dev_err(dev, "Failed to add Cache HWmon governor\n");
	return ret;
	}

	mutex_lock(&list_lock);
	list_add_tail(&node->list, &cache_hwmon_list);
	mutex_unlock(&list_lock);

	return ret;
	}

	MODULE_DESCRIPTION("HW monitor based cache freq driver");
	MODULE_LICENSE("GPL v2");