/*
   *  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/init.h>

  #include <linux/cpufreq.h>

  #include <linux/cpu.h>

  #include <linux/jiffies.h>
  #include <linux/kernel_stat.h>

  #include <linux/mutex.h>

  #include <linux/hrtimer.h>
  #include <linux/tick.h>
  #include <linux/ktime.h>

  #include <linux/sched.h>

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

  #define DEF_FREQUENCY_DOWN_DIFFERENTIAL		(10)

  #define DEF_FREQUENCY_UP_THRESHOLD		(80)

  #define DEF_SAMPLING_DOWN_FACTOR		(1)
  #define MAX_SAMPLING_DOWN_FACTOR		(100000)

  #define MICRO_FREQUENCY_DOWN_DIFFERENTIAL	(3)
  #define MICRO_FREQUENCY_UP_THRESHOLD		(95)

  #define MICRO_FREQUENCY_MIN_SAMPLE_RATE		(10000)

  #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.
   */

  #define MIN_SAMPLING_RATE_RATIO			(2)

  static unsigned int min_sampling_rate;

  #define LATENCY_MULTIPLIER			(1000)

  #define MIN_LATENCY_MULTIPLIER			(100)

  #define TRANSITION_LATENCY_LIMIT		(10 * 1000 * 1000)

  static void do_dbs_timer(struct work_struct *work);

  static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
  				unsigned int event);
  
  #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
  static
  #endif
  struct cpufreq_governor cpufreq_gov_ondemand = {
         .name                   = "ondemand",
         .governor               = cpufreq_governor_dbs,
         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
         .owner                  = THIS_MODULE,
  };

  
  /* Sampling types */

  enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE};

  
  struct cpu_dbs_info_s {

  	cputime64_t prev_cpu_idle;

  	cputime64_t prev_cpu_iowait;

  	cputime64_t prev_cpu_wall;

  	cputime64_t prev_cpu_nice;

  	struct cpufreq_policy *cur_policy;

  	struct delayed_work work;

  	struct cpufreq_frequency_table *freq_table;
  	unsigned int freq_lo;
  	unsigned int freq_lo_jiffies;
  	unsigned int freq_hi_jiffies;

  	unsigned int rate_mult;

  	int cpu;

  	unsigned int sample_type:1;
  	/*
  	 * percpu mutex that serializes governor limit change with
  	 * do_dbs_timer invocation. We do not want do_dbs_timer to run
  	 * when user is changing the governor or limits.
  	 */
  	struct mutex timer_mutex;

  };

  static DEFINE_PER_CPU(struct cpu_dbs_info_s, od_cpu_dbs_info);

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

  /*

   * dbs_mutex protects dbs_enable in governor start/stop.

   */

  static DEFINE_MUTEX(dbs_mutex);

  static struct dbs_tuners {

  	unsigned int sampling_rate;

  	unsigned int up_threshold;

  	unsigned int down_differential;

  	unsigned int ignore_nice;

  	unsigned int sampling_down_factor;

  	unsigned int powersave_bias;

  	unsigned int io_is_busy;

  } dbs_tuners_ins = {

  	.up_threshold = DEF_FREQUENCY_UP_THRESHOLD,

  	.sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,

  	.down_differential = DEF_FREQUENCY_DOWN_DIFFERENTIAL,

  	.ignore_nice = 0,

  	.powersave_bias = 0,

  };

  static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)

  {

  	u64 idle_time;

  	u64 cur_wall_time;

  	u64 busy_time;

  	cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());

  	busy_time  = kcpustat_cpu(cpu).cpustat[CPUTIME_USER];
  	busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SYSTEM];

  	busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_IRQ];
  	busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SOFTIRQ];
  	busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_STEAL];
  	busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_NICE];

  
  	idle_time = cur_wall_time - busy_time;

  	if (wall)

  		*wall = jiffies_to_usecs(cur_wall_time);

  	return jiffies_to_usecs(idle_time);

  }

  static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
  {

  	u64 idle_time = get_cpu_idle_time_us(cpu, NULL);

  
  	if (idle_time == -1ULL)
  		return get_cpu_idle_time_jiffy(cpu, wall);

  	else
  		idle_time += get_cpu_iowait_time_us(cpu, wall);

  	return idle_time;
  }

  static inline cputime64_t get_cpu_iowait_time(unsigned int cpu, cputime64_t *wall)
  {
  	u64 iowait_time = get_cpu_iowait_time_us(cpu, wall);
  
  	if (iowait_time == -1ULL)
  		return 0;
  
  	return iowait_time;
  }

  /*
   * Find right freq to be set now with powersave_bias on.
   * Returns the freq_hi to be used right now and will set freq_hi_jiffies,
   * freq_lo, and freq_lo_jiffies in percpu area for averaging freqs.
   */

  static unsigned int powersave_bias_target(struct cpufreq_policy *policy,
  					  unsigned int freq_next,
  					  unsigned int relation)

  {
  	unsigned int freq_req, freq_reduc, freq_avg;
  	unsigned int freq_hi, freq_lo;
  	unsigned int index = 0;
  	unsigned int jiffies_total, jiffies_hi, jiffies_lo;

  	struct cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
  						   policy->cpu);

  
  	if (!dbs_info->freq_table) {
  		dbs_info->freq_lo = 0;
  		dbs_info->freq_lo_jiffies = 0;
  		return freq_next;
  	}
  
  	cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_next,
  			relation, &index);
  	freq_req = dbs_info->freq_table[index].frequency;
  	freq_reduc = freq_req * dbs_tuners_ins.powersave_bias / 1000;
  	freq_avg = freq_req - freq_reduc;
  
  	/* Find freq bounds for freq_avg in freq_table */
  	index = 0;
  	cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
  			CPUFREQ_RELATION_H, &index);
  	freq_lo = dbs_info->freq_table[index].frequency;
  	index = 0;
  	cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
  			CPUFREQ_RELATION_L, &index);
  	freq_hi = dbs_info->freq_table[index].frequency;
  
  	/* Find out how long we have to be in hi and lo freqs */
  	if (freq_hi == freq_lo) {
  		dbs_info->freq_lo = 0;
  		dbs_info->freq_lo_jiffies = 0;
  		return freq_lo;
  	}
  	jiffies_total = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
  	jiffies_hi = (freq_avg - freq_lo) * jiffies_total;
  	jiffies_hi += ((freq_hi - freq_lo) / 2);
  	jiffies_hi /= (freq_hi - freq_lo);
  	jiffies_lo = jiffies_total - jiffies_hi;
  	dbs_info->freq_lo = freq_lo;
  	dbs_info->freq_lo_jiffies = jiffies_lo;
  	dbs_info->freq_hi_jiffies = jiffies_hi;
  	return freq_hi;
  }

  static void ondemand_powersave_bias_init_cpu(int cpu)
  {

  	struct cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info, cpu);

  	dbs_info->freq_table = cpufreq_frequency_get_table(cpu);
  	dbs_info->freq_lo = 0;
  }

  static void ondemand_powersave_bias_init(void)
  {
  	int i;
  	for_each_online_cpu(i) {

  		ondemand_powersave_bias_init_cpu(i);

  	}
  }

  /************************** sysfs interface ************************/

  static ssize_t show_sampling_rate_min(struct kobject *kobj,
  				      struct attribute *attr, char *buf)

  {

  	return sprintf(buf, "%u
  ", min_sampling_rate);

  }

  define_one_global_ro(sampling_rate_min);

  
  /* cpufreq_ondemand Governor Tunables */
  #define show_one(file_name, object)					\
  static ssize_t show_##file_name						\

  (struct kobject *kobj, struct attribute *attr, char *buf)              \

  {									\
  	return sprintf(buf, "%u
  ", dbs_tuners_ins.object);		\
  }
  show_one(sampling_rate, sampling_rate);

  show_one(io_is_busy, io_is_busy);

  show_one(up_threshold, up_threshold);

  show_one(sampling_down_factor, sampling_down_factor);

  show_one(ignore_nice_load, ignore_nice);

  show_one(powersave_bias, powersave_bias);

  static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
  				   const char *buf, size_t count)

  {
  	unsigned int input;
  	int ret;

  	ret = sscanf(buf, "%u", &input);

  	if (ret != 1)
  		return -EINVAL;

  	dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);

  	return count;
  }

  static ssize_t store_io_is_busy(struct kobject *a, struct attribute *b,
  				   const char *buf, size_t count)
  {
  	unsigned int input;
  	int ret;
  
  	ret = sscanf(buf, "%u", &input);
  	if (ret != 1)
  		return -EINVAL;

  	dbs_tuners_ins.io_is_busy = !!input;

  	return count;
  }

  static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
  				  const char *buf, size_t count)

  {
  	unsigned int input;
  	int ret;

  	ret = sscanf(buf, "%u", &input);

  	if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||

  			input < MIN_FREQUENCY_UP_THRESHOLD) {

  		return -EINVAL;
  	}

  	dbs_tuners_ins.up_threshold = input;

  	return count;
  }

  static ssize_t store_sampling_down_factor(struct kobject *a,
  			struct attribute *b, const char *buf, size_t count)
  {
  	unsigned int input, j;
  	int ret;
  	ret = sscanf(buf, "%u", &input);
  
  	if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
  		return -EINVAL;

  	dbs_tuners_ins.sampling_down_factor = input;
  
  	/* Reset down sampling multiplier in case it was active */
  	for_each_online_cpu(j) {
  		struct cpu_dbs_info_s *dbs_info;
  		dbs_info = &per_cpu(od_cpu_dbs_info, j);
  		dbs_info->rate_mult = 1;
  	}

  	return count;
  }

  static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
  				      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;

  	if (input == dbs_tuners_ins.ignore_nice) { /* nothing to do */

  		return count;
  	}
  	dbs_tuners_ins.ignore_nice = input;

  	/* we need to re-evaluate prev_cpu_idle */

  	for_each_online_cpu(j) {

  		struct cpu_dbs_info_s *dbs_info;

  		dbs_info = &per_cpu(od_cpu_dbs_info, j);

  		dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
  						&dbs_info->prev_cpu_wall);

  		if (dbs_tuners_ins.ignore_nice)

  			dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];

  	}

  	return count;
  }

  static ssize_t store_powersave_bias(struct kobject *a, struct attribute *b,
  				    const char *buf, size_t count)

  {
  	unsigned int input;
  	int ret;
  	ret = sscanf(buf, "%u", &input);
  
  	if (ret != 1)
  		return -EINVAL;
  
  	if (input > 1000)
  		input = 1000;

  	dbs_tuners_ins.powersave_bias = input;
  	ondemand_powersave_bias_init();

  	return count;
  }

  define_one_global_rw(sampling_rate);

  define_one_global_rw(io_is_busy);

  define_one_global_rw(up_threshold);

  define_one_global_rw(sampling_down_factor);

  define_one_global_rw(ignore_nice_load);
  define_one_global_rw(powersave_bias);

  static struct attribute *dbs_attributes[] = {

  	&sampling_rate_min.attr,
  	&sampling_rate.attr,

  	&up_threshold.attr,

  	&sampling_down_factor.attr,

  	&ignore_nice_load.attr,

  	&powersave_bias.attr,

  	&io_is_busy.attr,

  	NULL
  };
  
  static struct attribute_group dbs_attr_group = {
  	.attrs = dbs_attributes,
  	.name = "ondemand",
  };
  
  /************************** sysfs end ************************/

  static void dbs_freq_increase(struct cpufreq_policy *p, unsigned int freq)
  {
  	if (dbs_tuners_ins.powersave_bias)
  		freq = powersave_bias_target(p, freq, CPUFREQ_RELATION_H);
  	else if (p->cur == p->max)
  		return;
  
  	__cpufreq_driver_target(p, freq, dbs_tuners_ins.powersave_bias ?
  			CPUFREQ_RELATION_L : CPUFREQ_RELATION_H);
  }

  static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)

  {

  	unsigned int max_load_freq;

  
  	struct cpufreq_policy *policy;
  	unsigned int j;

  	this_dbs_info->freq_lo = 0;

  	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, 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

  	 */

  	/* Get Absolute Load - in terms of freq */
  	max_load_freq = 0;

  	for_each_cpu(j, policy->cpus) {

  		struct cpu_dbs_info_s *j_dbs_info;

  		cputime64_t cur_wall_time, cur_idle_time, cur_iowait_time;
  		unsigned int idle_time, wall_time, iowait_time;

  		unsigned int load, load_freq;
  		int freq_avg;

  		j_dbs_info = &per_cpu(od_cpu_dbs_info, j);

  
  		cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);

  		cur_iowait_time = get_cpu_iowait_time(j, &cur_wall_time);

  		wall_time = (unsigned int)
  			(cur_wall_time - j_dbs_info->prev_cpu_wall);

  		j_dbs_info->prev_cpu_wall = cur_wall_time;

  		idle_time = (unsigned int)
  			(cur_idle_time - j_dbs_info->prev_cpu_idle);

  		j_dbs_info->prev_cpu_idle = cur_idle_time;

  		iowait_time = (unsigned int)
  			(cur_iowait_time - j_dbs_info->prev_cpu_iowait);

  		j_dbs_info->prev_cpu_iowait = cur_iowait_time;

  		if (dbs_tuners_ins.ignore_nice) {

  			u64 cur_nice;

  			unsigned long cur_nice_jiffies;

  			cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE] -
  					 j_dbs_info->prev_cpu_nice;

  			/*
  			 * Assumption: nice time between sampling periods will
  			 * be less than 2^32 jiffies for 32 bit sys
  			 */
  			cur_nice_jiffies = (unsigned long)
  					cputime64_to_jiffies64(cur_nice);

  			j_dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];

  			idle_time += jiffies_to_usecs(cur_nice_jiffies);
  		}

  		/*
  		 * For the purpose of ondemand, waiting for disk IO is an
  		 * indication that you're performance critical, and not that
  		 * the system is actually idle. So subtract the iowait time
  		 * from the cpu idle time.
  		 */

  		if (dbs_tuners_ins.io_is_busy && idle_time >= iowait_time)

  			idle_time -= iowait_time;

  		if (unlikely(!wall_time || wall_time < idle_time))

  			continue;

  
  		load = 100 * (wall_time - idle_time) / wall_time;
  
  		freq_avg = __cpufreq_driver_getavg(policy, j);
  		if (freq_avg <= 0)
  			freq_avg = policy->cur;
  
  		load_freq = load * freq_avg;
  		if (load_freq > max_load_freq)
  			max_load_freq = load_freq;

  	}

  	/* Check for frequency increase */

  	if (max_load_freq > dbs_tuners_ins.up_threshold * policy->cur) {

  		/* If switching to max speed, apply sampling_down_factor */
  		if (policy->cur < policy->max)
  			this_dbs_info->rate_mult =
  				dbs_tuners_ins.sampling_down_factor;

  		dbs_freq_increase(policy, policy->max);

  		return;
  	}
  
  	/* Check for frequency decrease */

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

  	/*
  	 * 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.
  	 */

  	if (max_load_freq <
  	    (dbs_tuners_ins.up_threshold - dbs_tuners_ins.down_differential) *
  	     policy->cur) {

  		unsigned int freq_next;

  		freq_next = max_load_freq /
  				(dbs_tuners_ins.up_threshold -
  				 dbs_tuners_ins.down_differential);

  		/* No longer fully busy, reset rate_mult */
  		this_dbs_info->rate_mult = 1;

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

  		if (!dbs_tuners_ins.powersave_bias) {
  			__cpufreq_driver_target(policy, freq_next,
  					CPUFREQ_RELATION_L);
  		} else {
  			int freq = powersave_bias_target(policy, freq_next,
  					CPUFREQ_RELATION_L);
  			__cpufreq_driver_target(policy, freq,
  				CPUFREQ_RELATION_L);
  		}

  	}

  }

  static void do_dbs_timer(struct work_struct *work)

  {

  	struct cpu_dbs_info_s *dbs_info =
  		container_of(work, struct cpu_dbs_info_s, work.work);
  	unsigned int cpu = dbs_info->cpu;
  	int sample_type = dbs_info->sample_type;

  	int delay;

  	mutex_lock(&dbs_info->timer_mutex);

  	/* Common NORMAL_SAMPLE setup */

  	dbs_info->sample_type = DBS_NORMAL_SAMPLE;

  	if (!dbs_tuners_ins.powersave_bias ||

  	    sample_type == DBS_NORMAL_SAMPLE) {

  		dbs_check_cpu(dbs_info);

  		if (dbs_info->freq_lo) {
  			/* Setup timer for SUB_SAMPLE */

  			dbs_info->sample_type = DBS_SUB_SAMPLE;

  			delay = dbs_info->freq_hi_jiffies;

  		} else {
  			/* We want all CPUs to do sampling nearly on
  			 * same jiffy
  			 */
  			delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate
  				* dbs_info->rate_mult);
  
  			if (num_online_cpus() > 1)
  				delay -= jiffies % delay;

  		}
  	} else {
  		__cpufreq_driver_target(dbs_info->cur_policy,

  			dbs_info->freq_lo, CPUFREQ_RELATION_H);

  		delay = dbs_info->freq_lo_jiffies;

  	}

  	schedule_delayed_work_on(cpu, &dbs_info->work, delay);

  	mutex_unlock(&dbs_info->timer_mutex);

  }

  static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)

  {

  	/* We want all CPUs to do sampling nearly on same jiffy */
  	int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);

  
  	if (num_online_cpus() > 1)
  		delay -= jiffies % delay;

  	dbs_info->sample_type = DBS_NORMAL_SAMPLE;

  	INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);

  	schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work, delay);

  }

  static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)

  {

  	cancel_delayed_work_sync(&dbs_info->work);

  }

  /*
   * Not all CPUs want IO time to be accounted as busy; this dependson how
   * efficient idling at a higher frequency/voltage is.
   * Pavel Machek says this is not so for various generations of AMD and old
   * Intel systems.
   * Mike Chan (androidlcom) calis this is also not true for ARM.
   * Because of this, whitelist specific known (series) of CPUs by default, and
   * leave all others up to the user.
   */
  static int should_io_be_busy(void)
  {
  #if defined(CONFIG_X86)
  	/*
  	 * For Intel, Core 2 (model 15) andl later have an efficient idle.
  	 */
  	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
  	    boot_cpu_data.x86 == 6 &&
  	    boot_cpu_data.x86_model >= 15)
  		return 1;
  #endif
  	return 0;
  }

  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;

  	int rc;

  	this_dbs_info = &per_cpu(od_cpu_dbs_info, cpu);

  
  	switch (event) {
  	case CPUFREQ_GOV_START:

  		if ((!cpu_online(cpu)) || (!policy->cur))

  			return -EINVAL;

  		mutex_lock(&dbs_mutex);

  		dbs_enable++;

  		for_each_cpu(j, policy->cpus) {

  			struct cpu_dbs_info_s *j_dbs_info;

  			j_dbs_info = &per_cpu(od_cpu_dbs_info, j);

  			j_dbs_info->cur_policy = policy;

  			j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
  						&j_dbs_info->prev_cpu_wall);

  			if (dbs_tuners_ins.ignore_nice)

  				j_dbs_info->prev_cpu_nice =

  						kcpustat_cpu(j).cpustat[CPUTIME_NICE];

  		}

  		this_dbs_info->cpu = cpu;

  		this_dbs_info->rate_mult = 1;

  		ondemand_powersave_bias_init_cpu(cpu);

  		/*
  		 * Start the timerschedule work, when this governor
  		 * is used for first time
  		 */
  		if (dbs_enable == 1) {
  			unsigned int latency;

  
  			rc = sysfs_create_group(cpufreq_global_kobject,
  						&dbs_attr_group);
  			if (rc) {
  				mutex_unlock(&dbs_mutex);
  				return rc;
  			}

  			/* policy latency is in nS. Convert it to uS first */

  			latency = policy->cpuinfo.transition_latency / 1000;
  			if (latency == 0)
  				latency = 1;

  			/* Bring kernel and HW constraints together */
  			min_sampling_rate = max(min_sampling_rate,
  					MIN_LATENCY_MULTIPLIER * latency);
  			dbs_tuners_ins.sampling_rate =
  				max(min_sampling_rate,
  				    latency * LATENCY_MULTIPLIER);

  			dbs_tuners_ins.io_is_busy = should_io_be_busy();

  		}

  		mutex_unlock(&dbs_mutex);

  		mutex_init(&this_dbs_info->timer_mutex);

  		dbs_timer_init(this_dbs_info);

  		break;
  
  	case CPUFREQ_GOV_STOP:

  		dbs_timer_exit(this_dbs_info);

  
  		mutex_lock(&dbs_mutex);

  		mutex_destroy(&this_dbs_info->timer_mutex);

  		dbs_enable--;

  		mutex_unlock(&dbs_mutex);

  		if (!dbs_enable)
  			sysfs_remove_group(cpufreq_global_kobject,
  					   &dbs_attr_group);

  
  		break;
  
  	case CPUFREQ_GOV_LIMITS:

  		mutex_lock(&this_dbs_info->timer_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(&this_dbs_info->timer_mutex);

  		break;
  	}
  	return 0;
  }

  static int __init cpufreq_gov_dbs_init(void)
  {

  	u64 idle_time;
  	int cpu = get_cpu();

  	idle_time = get_cpu_idle_time_us(cpu, NULL);

  	put_cpu();

  	if (idle_time != -1ULL) {
  		/* Idle micro accounting is supported. Use finer thresholds */
  		dbs_tuners_ins.up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
  		dbs_tuners_ins.down_differential =
  					MICRO_FREQUENCY_DOWN_DIFFERENTIAL;

  		/*

  		 * In nohz/micro accounting case we set the minimum frequency

  		 * not depending on HZ, but fixed (very low). The deferred
  		 * timer might skip some samples if idle/sleeping as needed.
  		*/
  		min_sampling_rate = MICRO_FREQUENCY_MIN_SAMPLE_RATE;
  	} else {
  		/* For correct statistics, we need 10 ticks for each measure */
  		min_sampling_rate =
  			MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);

  	}

  	return cpufreq_register_governor(&cpufreq_gov_ondemand);

  }
  
  static void __exit cpufreq_gov_dbs_exit(void)
  {

  	cpufreq_unregister_governor(&cpufreq_gov_ondemand);

  }

  MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
  MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
  MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "

  	"Low Latency Frequency Transition capable processors");

  MODULE_LICENSE("GPL");

  #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
  fs_initcall(cpufreq_gov_dbs_init);
  #else

  module_init(cpufreq_gov_dbs_init);

  #endif

  module_exit(cpufreq_gov_dbs_exit);