drivers/cpufreq/cpufreq_ondemand.c - arm/linux-arm64-legacy - Git at Google

 /*
  *  drivers/cpufreq/cpufreq_ondemand.c
  *
  *  Copyright (C)  2001 Russell King
  *            (C)  2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
  *                      Jun Nakajima <jun.nakajima@intel.com>
  *
  * 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.
  */

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/smp.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/ctype.h>
 #include <linux/cpufreq.h>
 #include <linux/sysctl.h>
 #include <linux/types.h>
 #include <linux/fs.h>
 #include <linux/sysfs.h>
 #include <linux/sched.h>
 #include <linux/kmod.h>
 #include <linux/workqueue.h>
 #include <linux/jiffies.h>
 #include <linux/kernel_stat.h>
 #include <linux/percpu.h>
 #include <linux/mutex.h>

 /*
  * dbs is used in this file as a shortform for demandbased switching
  * It helps to keep variable names smaller, simpler
  */

 #define DEF_FREQUENCY_UP_THRESHOLD		(80)
 #define MIN_FREQUENCY_UP_THRESHOLD		(11)
 #define MAX_FREQUENCY_UP_THRESHOLD		(100)

 /*
  * The polling frequency of this governor depends on the capability of
  * the processor. Default polling frequency is 1000 times the transition
  * latency of the processor. The governor will work on any processor with
  * transition latency <= 10mS, using appropriate sampling
  * rate.
  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
  * this governor will not work.
  * All times here are in uS.
  */
 static unsigned int def_sampling_rate;
 #define MIN_SAMPLING_RATE_RATIO			(2)
 /* for correct statistics, we need at least 10 ticks between each measure */
 #define MIN_STAT_SAMPLING_RATE			(MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
 #define MIN_SAMPLING_RATE			(def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
 #define MAX_SAMPLING_RATE			(500 * def_sampling_rate)
 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER	(1000)
 #define DEF_SAMPLING_DOWN_FACTOR		(1)
 #define MAX_SAMPLING_DOWN_FACTOR		(10)
 #define TRANSITION_LATENCY_LIMIT		(10 * 1000)

 static void do_dbs_timer(void *data);

 struct cpu_dbs_info_s {
 	struct cpufreq_policy *cur_policy;
 	unsigned int prev_cpu_idle_up;
 	unsigned int prev_cpu_idle_down;
 	unsigned int enable;
 };
 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);

 static unsigned int dbs_enable;	/* number of CPUs using this policy */

 static DEFINE_MUTEX (dbs_mutex);
 static DECLARE_WORK	(dbs_work, do_dbs_timer, NULL);

 struct dbs_tuners {
 	unsigned int sampling_rate;
 	unsigned int sampling_down_factor;
 	unsigned int up_threshold;
 	unsigned int ignore_nice;
 };

 static struct dbs_tuners dbs_tuners_ins = {
 	.up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
 	.sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
 	.ignore_nice = 0,
 };

 static inline unsigned int get_cpu_idle_time(unsigned int cpu)
 {
 	return	kstat_cpu(cpu).cpustat.idle +
 		kstat_cpu(cpu).cpustat.iowait +
 		( dbs_tuners_ins.ignore_nice ?
 		  kstat_cpu(cpu).cpustat.nice :
 		  0);
 }

 /************************** sysfs interface ************************/
 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 {
 	return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
 }

 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 {
 	return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 }

 #define define_one_ro(_name)		\
 static struct freq_attr _name =		\
 __ATTR(_name, 0444, show_##_name, NULL)

 define_one_ro(sampling_rate_max);
 define_one_ro(sampling_rate_min);

 /* cpufreq_ondemand Governor Tunables */
 #define show_one(file_name, object)					\
 static ssize_t show_##file_name						\
 (struct cpufreq_policy *unused, char *buf)				\
 {									\
 	return sprintf(buf, "%u\n", dbs_tuners_ins.object);		\
 }
 show_one(sampling_rate, sampling_rate);
 show_one(sampling_down_factor, sampling_down_factor);
 show_one(up_threshold, up_threshold);
 show_one(ignore_nice_load, ignore_nice);

 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
 		const char *buf, size_t count)
 {
 	unsigned int input;
 	int ret;
 	ret = sscanf (buf, "%u", &input);
 	if (ret != 1 )
 		return -EINVAL;

 	if (input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 		return -EINVAL;

 	mutex_lock(&dbs_mutex);
 	dbs_tuners_ins.sampling_down_factor = input;
 	mutex_unlock(&dbs_mutex);

 	return count;
 }

 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 		const char *buf, size_t count)
 {
 	unsigned int input;
 	int ret;
 	ret = sscanf (buf, "%u", &input);

 	mutex_lock(&dbs_mutex);
 	if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
 		mutex_unlock(&dbs_mutex);
 		return -EINVAL;
 	}

 	dbs_tuners_ins.sampling_rate = input;
 	mutex_unlock(&dbs_mutex);

 	return count;
 }

 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 		const char *buf, size_t count)
 {
 	unsigned int input;
 	int ret;
 	ret = sscanf (buf, "%u", &input);

 	mutex_lock(&dbs_mutex);
 	if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 			input < MIN_FREQUENCY_UP_THRESHOLD) {
 		mutex_unlock(&dbs_mutex);
 		return -EINVAL;
 	}

 	dbs_tuners_ins.up_threshold = input;
 	mutex_unlock(&dbs_mutex);

 	return count;
 }

 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 		const char *buf, size_t count)
 {
 	unsigned int input;
 	int ret;

 	unsigned int j;

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

 	if ( input > 1 )
 		input = 1;

 	mutex_lock(&dbs_mutex);
 	if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
 		mutex_unlock(&dbs_mutex);
 		return count;
 	}
 	dbs_tuners_ins.ignore_nice = input;

 	/* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
 	for_each_online_cpu(j) {
 		struct cpu_dbs_info_s *j_dbs_info;
 		j_dbs_info = &per_cpu(cpu_dbs_info, j);
 		j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 		j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
 	}
 	mutex_unlock(&dbs_mutex);

 	return count;
 }

 #define define_one_rw(_name) \
 static struct freq_attr _name = \
 __ATTR(_name, 0644, show_##_name, store_##_name)

 define_one_rw(sampling_rate);
 define_one_rw(sampling_down_factor);
 define_one_rw(up_threshold);
 define_one_rw(ignore_nice_load);

 static struct attribute * dbs_attributes[] = {
 	&sampling_rate_max.attr,
 	&sampling_rate_min.attr,
 	&sampling_rate.attr,
 	&sampling_down_factor.attr,
 	&up_threshold.attr,
 	&ignore_nice_load.attr,
 	NULL
 };

 static struct attribute_group dbs_attr_group = {
 	.attrs = dbs_attributes,
 	.name = "ondemand",
 };

 /************************** sysfs end ************************/

 static void dbs_check_cpu(int cpu)
 {
 	unsigned int idle_ticks, up_idle_ticks, total_ticks;
 	unsigned int freq_next;
 	unsigned int freq_down_sampling_rate;
 	static int down_skip[NR_CPUS];
 	struct cpu_dbs_info_s *this_dbs_info;

 	struct cpufreq_policy *policy;
 	unsigned int j;

 	this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 	if (!this_dbs_info->enable)
 		return;

 	policy = this_dbs_info->cur_policy;
 	/*
 	 * Every sampling_rate, we check, if current idle time is less
 	 * than 20% (default), then we try to increase frequency
 	 * Every sampling_rate*sampling_down_factor, we look for a the lowest
 	 * frequency which can sustain the load while keeping idle time over
 	 * 30%. If such a frequency exist, we try to decrease to this frequency.
 	 *
 	 * Any frequency increase takes it to the maximum frequency.
 	 * Frequency reduction happens at minimum steps of
 	 * 5% (default) of current frequency
 	 */

 	/* Check for frequency increase */
 	idle_ticks = UINT_MAX;
 	for_each_cpu_mask(j, policy->cpus) {
 		unsigned int tmp_idle_ticks, total_idle_ticks;
 		struct cpu_dbs_info_s *j_dbs_info;

 		j_dbs_info = &per_cpu(cpu_dbs_info, j);
 		total_idle_ticks = get_cpu_idle_time(j);
 		tmp_idle_ticks = total_idle_ticks -
 			j_dbs_info->prev_cpu_idle_up;
 		j_dbs_info->prev_cpu_idle_up = total_idle_ticks;

 		if (tmp_idle_ticks < idle_ticks)
 			idle_ticks = tmp_idle_ticks;
 	}

 	/* Scale idle ticks by 100 and compare with up and down ticks */
 	idle_ticks *= 100;
 	up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
 			usecs_to_jiffies(dbs_tuners_ins.sampling_rate);

 	if (idle_ticks < up_idle_ticks) {
 		down_skip[cpu] = 0;
 		for_each_cpu_mask(j, policy->cpus) {
 			struct cpu_dbs_info_s *j_dbs_info;

 			j_dbs_info = &per_cpu(cpu_dbs_info, j);
 			j_dbs_info->prev_cpu_idle_down =
 					j_dbs_info->prev_cpu_idle_up;
 		}
 		/* if we are already at full speed then break out early */
 		if (policy->cur == policy->max)
 			return;

 		__cpufreq_driver_target(policy, policy->max,
 			CPUFREQ_RELATION_H);
 		return;
 	}

 	/* Check for frequency decrease */
 	down_skip[cpu]++;
 	if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
 		return;

 	idle_ticks = UINT_MAX;
 	for_each_cpu_mask(j, policy->cpus) {
 		unsigned int tmp_idle_ticks, total_idle_ticks;
 		struct cpu_dbs_info_s *j_dbs_info;

 		j_dbs_info = &per_cpu(cpu_dbs_info, j);
 		/* Check for frequency decrease */
 		total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
 		tmp_idle_ticks = total_idle_ticks -
 			j_dbs_info->prev_cpu_idle_down;
 		j_dbs_info->prev_cpu_idle_down = total_idle_ticks;

 		if (tmp_idle_ticks < idle_ticks)
 			idle_ticks = tmp_idle_ticks;
 	}

 	down_skip[cpu] = 0;
 	/* if we cannot reduce the frequency anymore, break out early */
 	if (policy->cur == policy->min)
 		return;

 	/* Compute how many ticks there are between two measurements */
 	freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
 		dbs_tuners_ins.sampling_down_factor;
 	total_ticks = usecs_to_jiffies(freq_down_sampling_rate);

 	/*
 	 * The optimal frequency is the frequency that is the lowest that
 	 * can support the current CPU usage without triggering the up
 	 * policy. To be safe, we focus 10 points under the threshold.
 	 */
 	freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks;
 	freq_next = (freq_next * policy->cur) /
 			(dbs_tuners_ins.up_threshold - 10);

 	if (freq_next < policy->min)
 		freq_next = policy->min;

 	if (freq_next <= ((policy->cur * 95) / 100))
 		__cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);
 }

 static void do_dbs_timer(void *data)
 {
 	int i;
 	mutex_lock(&dbs_mutex);
 	for_each_online_cpu(i)
 		dbs_check_cpu(i);
 	schedule_delayed_work(&dbs_work,
 			usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 	mutex_unlock(&dbs_mutex);
 }

 static inline void dbs_timer_init(void)
 {
 	INIT_WORK(&dbs_work, do_dbs_timer, NULL);
 	schedule_delayed_work(&dbs_work,
 			usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 	return;
 }

 static inline void dbs_timer_exit(void)
 {
 	cancel_delayed_work(&dbs_work);
 	return;
 }

 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 				   unsigned int event)
 {
 	unsigned int cpu = policy->cpu;
 	struct cpu_dbs_info_s *this_dbs_info;
 	unsigned int j;

 	this_dbs_info = &per_cpu(cpu_dbs_info, cpu);

 	switch (event) {
 	case CPUFREQ_GOV_START:
 		if ((!cpu_online(cpu)) ||
 		    (!policy->cur))
 			return -EINVAL;

 		if (policy->cpuinfo.transition_latency >
 				(TRANSITION_LATENCY_LIMIT * 1000)) {
 			printk(KERN_WARNING "ondemand governor failed to load "
 			       "due to too long transition latency\n");
 			return -EINVAL;
 		}
 		if (this_dbs_info->enable) /* Already enabled */
 			break;

 		mutex_lock(&dbs_mutex);
 		for_each_cpu_mask(j, policy->cpus) {
 			struct cpu_dbs_info_s *j_dbs_info;
 			j_dbs_info = &per_cpu(cpu_dbs_info, j);
 			j_dbs_info->cur_policy = policy;

 			j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 			j_dbs_info->prev_cpu_idle_down
 				= j_dbs_info->prev_cpu_idle_up;
 		}
 		this_dbs_info->enable = 1;
 		sysfs_create_group(&policy->kobj, &dbs_attr_group);
 		dbs_enable++;
 		/*
 		 * Start the timerschedule work, when this governor
 		 * is used for first time
 		 */
 		if (dbs_enable == 1) {
 			unsigned int latency;
 			/* policy latency is in nS. Convert it to uS first */
 			latency = policy->cpuinfo.transition_latency / 1000;
 			if (latency == 0)
 				latency = 1;

 			def_sampling_rate = latency *
 					DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;

 			if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
 				def_sampling_rate = MIN_STAT_SAMPLING_RATE;

 			dbs_tuners_ins.sampling_rate = def_sampling_rate;
 			dbs_timer_init();
 		}

 		mutex_unlock(&dbs_mutex);
 		break;

 	case CPUFREQ_GOV_STOP:
 		mutex_lock(&dbs_mutex);
 		this_dbs_info->enable = 0;
 		sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 		dbs_enable--;
 		/*
 		 * Stop the timerschedule work, when this governor
 		 * is used for first time
 		 */
 		if (dbs_enable == 0)
 			dbs_timer_exit();

 		mutex_unlock(&dbs_mutex);

 		break;

 	case CPUFREQ_GOV_LIMITS:
 		mutex_lock(&dbs_mutex);
 		if (policy->max < this_dbs_info->cur_policy->cur)
 			__cpufreq_driver_target(
 					this_dbs_info->cur_policy,
 					policy->max, CPUFREQ_RELATION_H);
 		else if (policy->min > this_dbs_info->cur_policy->cur)
 			__cpufreq_driver_target(
 					this_dbs_info->cur_policy,
 					policy->min, CPUFREQ_RELATION_L);
 		mutex_unlock(&dbs_mutex);
 		break;
 	}
 	return 0;
 }

 static struct cpufreq_governor cpufreq_gov_dbs = {
 	.name		= "ondemand",
 	.governor	= cpufreq_governor_dbs,
 	.owner		= THIS_MODULE,
 };

 static int __init cpufreq_gov_dbs_init(void)
 {
 	return cpufreq_register_governor(&cpufreq_gov_dbs);
 }

 static void __exit cpufreq_gov_dbs_exit(void)
 {
 	/* Make sure that the scheduled work is indeed not running */
 	flush_scheduled_work();

 	cpufreq_unregister_governor(&cpufreq_gov_dbs);
 }


 MODULE_AUTHOR ("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 		"Low Latency Frequency Transition capable processors");
 MODULE_LICENSE ("GPL");

 module_init(cpufreq_gov_dbs_init);
 module_exit(cpufreq_gov_dbs_exit);
	/*
	* drivers/cpufreq/cpufreq_ondemand.c
	*
	* Copyright (C) 2001 Russell King
	* (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
	* Jun Nakajima <jun.nakajima@intel.com>
	*
	* 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.
	*/

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/smp.h>
	#include <linux/init.h>
	#include <linux/interrupt.h>
	#include <linux/ctype.h>
	#include <linux/cpufreq.h>
	#include <linux/sysctl.h>
	#include <linux/types.h>
	#include <linux/fs.h>
	#include <linux/sysfs.h>
	#include <linux/sched.h>
	#include <linux/kmod.h>
	#include <linux/workqueue.h>
	#include <linux/jiffies.h>
	#include <linux/kernel_stat.h>
	#include <linux/percpu.h>
	#include <linux/mutex.h>

	/*
	* dbs is used in this file as a shortform for demandbased switching
	* It helps to keep variable names smaller, simpler
	*/

	#define DEF_FREQUENCY_UP_THRESHOLD (80)
	#define MIN_FREQUENCY_UP_THRESHOLD (11)
	#define MAX_FREQUENCY_UP_THRESHOLD (100)

	/*
	* The polling frequency of this governor depends on the capability of
	* the processor. Default polling frequency is 1000 times the transition
	* latency of the processor. The governor will work on any processor with
	* transition latency <= 10mS, using appropriate sampling
	* rate.
	* For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
	* this governor will not work.
	* All times here are in uS.
	*/
	static unsigned int def_sampling_rate;
	#define MIN_SAMPLING_RATE_RATIO (2)
	/* for correct statistics, we need at least 10 ticks between each measure */
	#define MIN_STAT_SAMPLING_RATE (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
	#define MIN_SAMPLING_RATE (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
	#define MAX_SAMPLING_RATE (500 * def_sampling_rate)
	#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000)
	#define DEF_SAMPLING_DOWN_FACTOR (1)
	#define MAX_SAMPLING_DOWN_FACTOR (10)
	#define TRANSITION_LATENCY_LIMIT (10 * 1000)

	static void do_dbs_timer(void *data);

	struct cpu_dbs_info_s {
	struct cpufreq_policy *cur_policy;
	unsigned int prev_cpu_idle_up;
	unsigned int prev_cpu_idle_down;
	unsigned int enable;
	};
	static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);

	static unsigned int dbs_enable; /* number of CPUs using this policy */

	static DEFINE_MUTEX (dbs_mutex);
	static DECLARE_WORK (dbs_work, do_dbs_timer, NULL);

	struct dbs_tuners {
	unsigned int sampling_rate;
	unsigned int sampling_down_factor;
	unsigned int up_threshold;
	unsigned int ignore_nice;
	};

	static struct dbs_tuners dbs_tuners_ins = {
	.up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
	.sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
	.ignore_nice = 0,
	};

	static inline unsigned int get_cpu_idle_time(unsigned int cpu)
	{
	return kstat_cpu(cpu).cpustat.idle +
	kstat_cpu(cpu).cpustat.iowait +
	( dbs_tuners_ins.ignore_nice ?
	kstat_cpu(cpu).cpustat.nice :
	0);
	}

	/************************ sysfs interface **********************/
	static ssize_t show_sampling_rate_max(struct cpufreq_policy policy, char buf)
	{
	return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
	}

	static ssize_t show_sampling_rate_min(struct cpufreq_policy policy, char buf)
	{
	return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
	}

	#define define_one_ro(_name) \
	static struct freq_attr _name = \
	__ATTR(_name, 0444, show_##_name, NULL)

	define_one_ro(sampling_rate_max);
	define_one_ro(sampling_rate_min);

	/* cpufreq_ondemand Governor Tunables */
	#define show_one(file_name, object) \
	static ssize_t show_##file_name \
	(struct cpufreq_policy unused, char buf) \
	{ \
	return sprintf(buf, "%u\n", dbs_tuners_ins.object); \
	}
	show_one(sampling_rate, sampling_rate);
	show_one(sampling_down_factor, sampling_down_factor);
	show_one(up_threshold, up_threshold);
	show_one(ignore_nice_load, ignore_nice);

	static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
	const char *buf, size_t count)
	{
	unsigned int input;
	int ret;
	ret = sscanf (buf, "%u", &input);
	if (ret != 1 )
	return -EINVAL;

	if (input > MAX_SAMPLING_DOWN_FACTOR \|\| input < 1)
	return -EINVAL;

	mutex_lock(&dbs_mutex);
	dbs_tuners_ins.sampling_down_factor = input;
	mutex_unlock(&dbs_mutex);

	return count;
	}

	static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
	const char *buf, size_t count)
	{
	unsigned int input;
	int ret;
	ret = sscanf (buf, "%u", &input);

	mutex_lock(&dbs_mutex);
	if (ret != 1 \|\| input > MAX_SAMPLING_RATE \|\| input < MIN_SAMPLING_RATE) {
	mutex_unlock(&dbs_mutex);
	return -EINVAL;
	}

	dbs_tuners_ins.sampling_rate = input;
	mutex_unlock(&dbs_mutex);

	return count;
	}

	static ssize_t store_up_threshold(struct cpufreq_policy *unused,
	const char *buf, size_t count)
	{
	unsigned int input;
	int ret;
	ret = sscanf (buf, "%u", &input);

	mutex_lock(&dbs_mutex);
	if (ret != 1 \|\| input > MAX_FREQUENCY_UP_THRESHOLD \|\|
	input < MIN_FREQUENCY_UP_THRESHOLD) {
	mutex_unlock(&dbs_mutex);
	return -EINVAL;
	}

	dbs_tuners_ins.up_threshold = input;
	mutex_unlock(&dbs_mutex);

	return count;
	}

	static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
	const char *buf, size_t count)
	{
	unsigned int input;
	int ret;

	unsigned int j;

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

	if ( input > 1 )
	input = 1;

	mutex_lock(&dbs_mutex);
	if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
	mutex_unlock(&dbs_mutex);
	return count;
	}
	dbs_tuners_ins.ignore_nice = input;

	/* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
	for_each_online_cpu(j) {
	struct cpu_dbs_info_s *j_dbs_info;
	j_dbs_info = &per_cpu(cpu_dbs_info, j);
	j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
	j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
	}
	mutex_unlock(&dbs_mutex);

	return count;
	}

	#define define_one_rw(_name) \
	static struct freq_attr _name = \
	__ATTR(_name, 0644, show_##_name, store_##_name)

	define_one_rw(sampling_rate);
	define_one_rw(sampling_down_factor);
	define_one_rw(up_threshold);
	define_one_rw(ignore_nice_load);

	static struct attribute * dbs_attributes[] = {
	&sampling_rate_max.attr,
	&sampling_rate_min.attr,
	&sampling_rate.attr,
	&sampling_down_factor.attr,
	&up_threshold.attr,
	&ignore_nice_load.attr,
	NULL
	};

	static struct attribute_group dbs_attr_group = {
	.attrs = dbs_attributes,
	.name = "ondemand",
	};

	/************************ sysfs end **********************/

	static void dbs_check_cpu(int cpu)
	{
	unsigned int idle_ticks, up_idle_ticks, total_ticks;
	unsigned int freq_next;
	unsigned int freq_down_sampling_rate;
	static int down_skip[NR_CPUS];
	struct cpu_dbs_info_s *this_dbs_info;

	struct cpufreq_policy *policy;
	unsigned int j;

	this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
	if (!this_dbs_info->enable)
	return;

	policy = this_dbs_info->cur_policy;
	/*
	* Every sampling_rate, we check, if current idle time is less
	* than 20% (default), then we try to increase frequency
	* Every sampling_rate*sampling_down_factor, we look for a the lowest
	* frequency which can sustain the load while keeping idle time over
	* 30%. If such a frequency exist, we try to decrease to this frequency.
	*
	* Any frequency increase takes it to the maximum frequency.
	* Frequency reduction happens at minimum steps of
	* 5% (default) of current frequency
	*/

	/* Check for frequency increase */
	idle_ticks = UINT_MAX;
	for_each_cpu_mask(j, policy->cpus) {
	unsigned int tmp_idle_ticks, total_idle_ticks;
	struct cpu_dbs_info_s *j_dbs_info;

	j_dbs_info = &per_cpu(cpu_dbs_info, j);
	total_idle_ticks = get_cpu_idle_time(j);
	tmp_idle_ticks = total_idle_ticks -
	j_dbs_info->prev_cpu_idle_up;
	j_dbs_info->prev_cpu_idle_up = total_idle_ticks;

	if (tmp_idle_ticks < idle_ticks)
	idle_ticks = tmp_idle_ticks;
	}

	/* Scale idle ticks by 100 and compare with up and down ticks */
	idle_ticks *= 100;
	up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
	usecs_to_jiffies(dbs_tuners_ins.sampling_rate);

	if (idle_ticks < up_idle_ticks) {
	down_skip[cpu] = 0;
	for_each_cpu_mask(j, policy->cpus) {
	struct cpu_dbs_info_s *j_dbs_info;

	j_dbs_info = &per_cpu(cpu_dbs_info, j);
	j_dbs_info->prev_cpu_idle_down =
	j_dbs_info->prev_cpu_idle_up;
	}
	/* if we are already at full speed then break out early */
	if (policy->cur == policy->max)
	return;

	__cpufreq_driver_target(policy, policy->max,
	CPUFREQ_RELATION_H);
	return;
	}

	/* Check for frequency decrease */
	down_skip[cpu]++;
	if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
	return;

	idle_ticks = UINT_MAX;
	for_each_cpu_mask(j, policy->cpus) {
	unsigned int tmp_idle_ticks, total_idle_ticks;
	struct cpu_dbs_info_s *j_dbs_info;

	j_dbs_info = &per_cpu(cpu_dbs_info, j);
	/* Check for frequency decrease */
	total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
	tmp_idle_ticks = total_idle_ticks -
	j_dbs_info->prev_cpu_idle_down;
	j_dbs_info->prev_cpu_idle_down = total_idle_ticks;

	if (tmp_idle_ticks < idle_ticks)
	idle_ticks = tmp_idle_ticks;
	}

	down_skip[cpu] = 0;
	/* if we cannot reduce the frequency anymore, break out early */
	if (policy->cur == policy->min)
	return;

	/* Compute how many ticks there are between two measurements */
	freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
	dbs_tuners_ins.sampling_down_factor;
	total_ticks = usecs_to_jiffies(freq_down_sampling_rate);

	/*
	* The optimal frequency is the frequency that is the lowest that
	* can support the current CPU usage without triggering the up
	* policy. To be safe, we focus 10 points under the threshold.
	*/
	freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks;
	freq_next = (freq_next * policy->cur) /
	(dbs_tuners_ins.up_threshold - 10);

	if (freq_next < policy->min)
	freq_next = policy->min;

	if (freq_next <= ((policy->cur * 95) / 100))
	__cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);
	}

	static void do_dbs_timer(void *data)
	{
	int i;
	mutex_lock(&dbs_mutex);
	for_each_online_cpu(i)
	dbs_check_cpu(i);
	schedule_delayed_work(&dbs_work,
	usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
	mutex_unlock(&dbs_mutex);
	}

	static inline void dbs_timer_init(void)
	{
	INIT_WORK(&dbs_work, do_dbs_timer, NULL);
	schedule_delayed_work(&dbs_work,
	usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
	return;
	}

	static inline void dbs_timer_exit(void)
	{
	cancel_delayed_work(&dbs_work);
	return;
	}

	static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
	unsigned int event)
	{
	unsigned int cpu = policy->cpu;
	struct cpu_dbs_info_s *this_dbs_info;
	unsigned int j;

	this_dbs_info = &per_cpu(cpu_dbs_info, cpu);

	switch (event) {
	case CPUFREQ_GOV_START:
	if ((!cpu_online(cpu)) \|\|
	(!policy->cur))
	return -EINVAL;

	if (policy->cpuinfo.transition_latency >
	(TRANSITION_LATENCY_LIMIT * 1000)) {
	printk(KERN_WARNING "ondemand governor failed to load "
	"due to too long transition latency\n");
	return -EINVAL;
	}
	if (this_dbs_info->enable) /* Already enabled */
	break;

	mutex_lock(&dbs_mutex);
	for_each_cpu_mask(j, policy->cpus) {
	struct cpu_dbs_info_s *j_dbs_info;
	j_dbs_info = &per_cpu(cpu_dbs_info, j);
	j_dbs_info->cur_policy = policy;

	j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
	j_dbs_info->prev_cpu_idle_down
	= j_dbs_info->prev_cpu_idle_up;
	}
	this_dbs_info->enable = 1;
	sysfs_create_group(&policy->kobj, &dbs_attr_group);
	dbs_enable++;
	/*
	* Start the timerschedule work, when this governor
	* is used for first time
	*/
	if (dbs_enable == 1) {
	unsigned int latency;
	/* policy latency is in nS. Convert it to uS first */
	latency = policy->cpuinfo.transition_latency / 1000;
	if (latency == 0)
	latency = 1;

	def_sampling_rate = latency *
	DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;

	if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
	def_sampling_rate = MIN_STAT_SAMPLING_RATE;

	dbs_tuners_ins.sampling_rate = def_sampling_rate;
	dbs_timer_init();
	}

	mutex_unlock(&dbs_mutex);
	break;

	case CPUFREQ_GOV_STOP:
	mutex_lock(&dbs_mutex);
	this_dbs_info->enable = 0;
	sysfs_remove_group(&policy->kobj, &dbs_attr_group);
	dbs_enable--;
	/*
	* Stop the timerschedule work, when this governor
	* is used for first time
	*/
	if (dbs_enable == 0)
	dbs_timer_exit();

	mutex_unlock(&dbs_mutex);

	break;

	case CPUFREQ_GOV_LIMITS:
	mutex_lock(&dbs_mutex);
	if (policy->max < this_dbs_info->cur_policy->cur)
	__cpufreq_driver_target(
	this_dbs_info->cur_policy,
	policy->max, CPUFREQ_RELATION_H);
	else if (policy->min > this_dbs_info->cur_policy->cur)
	__cpufreq_driver_target(
	this_dbs_info->cur_policy,
	policy->min, CPUFREQ_RELATION_L);
	mutex_unlock(&dbs_mutex);
	break;
	}
	return 0;
	}

	static struct cpufreq_governor cpufreq_gov_dbs = {
	.name = "ondemand",
	.governor = cpufreq_governor_dbs,
	.owner = THIS_MODULE,
	};

	static int __init cpufreq_gov_dbs_init(void)
	{
	return cpufreq_register_governor(&cpufreq_gov_dbs);
	}

	static void __exit cpufreq_gov_dbs_exit(void)
	{
	/* Make sure that the scheduled work is indeed not running */
	flush_scheduled_work();

	cpufreq_unregister_governor(&cpufreq_gov_dbs);
	}


	MODULE_AUTHOR ("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
	MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor for "
	"Low Latency Frequency Transition capable processors");
	MODULE_LICENSE ("GPL");

	module_init(cpufreq_gov_dbs_init);
	module_exit(cpufreq_gov_dbs_exit);