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

   *            (C)  2009 Alexander Clouter <alex@digriz.org.uk>

   *
   * 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_UP_THRESHOLD		(80)

  #define DEF_FREQUENCY_DOWN_THRESHOLD		(20)

  /*
   * 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 DEF_SAMPLING_DOWN_FACTOR		(1)
  #define MAX_SAMPLING_DOWN_FACTOR		(10)

  #define TRANSITION_LATENCY_LIMIT		(10 * 1000 * 1000)

  static void do_dbs_timer(struct work_struct *work);

  
  struct cpu_dbs_info_s {

  	cputime64_t prev_cpu_idle;
  	cputime64_t prev_cpu_wall;
  	cputime64_t prev_cpu_nice;

  	struct cpufreq_policy *cur_policy;

  	struct delayed_work work;

  	unsigned int down_skip;
  	unsigned int requested_freq;

  	int cpu;
  	unsigned int enable: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, cs_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 sampling_down_factor;
  	unsigned int up_threshold;
  	unsigned int down_threshold;
  	unsigned int ignore_nice;
  	unsigned int freq_step;

  } dbs_tuners_ins = {

  	.up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
  	.down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
  	.sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
  	.ignore_nice = 0,
  	.freq_step = 5,

  };

  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;

  }

  /* keep track of frequency transitions */
  static int
  dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
  		     void *data)
  {
  	struct cpufreq_freqs *freq = data;

  	struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cs_cpu_dbs_info,

  							freq->cpu);

  	struct cpufreq_policy *policy;

  	if (!this_dbs_info->enable)
  		return 0;

  	policy = this_dbs_info->cur_policy;
  
  	/*
  	 * we only care if our internally tracked freq moves outside
  	 * the 'valid' ranges of freqency available to us otherwise
  	 * we do not change it
  	*/
  	if (this_dbs_info->requested_freq > policy->max
  			|| this_dbs_info->requested_freq < policy->min)
  		this_dbs_info->requested_freq = freq->new;

  
  	return 0;
  }
  
  static struct notifier_block dbs_cpufreq_notifier_block = {
  	.notifier_call = dbs_cpufreq_notifier
  };

  /************************** 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_conservative 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(sampling_down_factor, sampling_down_factor);
  show_one(up_threshold, up_threshold);
  show_one(down_threshold, down_threshold);

  show_one(ignore_nice_load, ignore_nice);

  show_one(freq_step, freq_step);

  static ssize_t store_sampling_down_factor(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_SAMPLING_DOWN_FACTOR || input < 1)

  		return -EINVAL;

  	dbs_tuners_ins.sampling_down_factor = input;

  	return count;
  }

  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_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 > 100 ||

  			input <= dbs_tuners_ins.down_threshold)

  		return -EINVAL;

  
  	dbs_tuners_ins.up_threshold = input;

  	return count;
  }

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

  {
  	unsigned int input;
  	int ret;

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

  	/* cannot be lower than 11 otherwise freq will not fall */
  	if (ret != 1 || input < 11 || input > 100 ||

  			input >= dbs_tuners_ins.up_threshold)

  		return -EINVAL;

  
  	dbs_tuners_ins.down_threshold = input;

  	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(cs_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_freq_step(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 > 100)

  		input = 100;

  	/* no need to test here if freq_step is zero as the user might actually
  	 * want this, they would be crazy though :) */

  	dbs_tuners_ins.freq_step = input;

  	return count;
  }

  define_one_global_rw(sampling_rate);
  define_one_global_rw(sampling_down_factor);
  define_one_global_rw(up_threshold);
  define_one_global_rw(down_threshold);
  define_one_global_rw(ignore_nice_load);
  define_one_global_rw(freq_step);

  static struct attribute *dbs_attributes[] = {

  	&sampling_rate_min.attr,
  	&sampling_rate.attr,
  	&sampling_down_factor.attr,
  	&up_threshold.attr,
  	&down_threshold.attr,

  	&ignore_nice_load.attr,

  	&freq_step.attr,
  	NULL
  };
  
  static struct attribute_group dbs_attr_group = {
  	.attrs = dbs_attributes,
  	.name = "conservative",
  };
  
  /************************** sysfs end ************************/

  static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)

  {

  	unsigned int load = 0;

  	unsigned int max_load = 0;

  	unsigned int freq_target;

  	struct cpufreq_policy *policy;
  	unsigned int j;

  	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 check, if current
  	 * idle time is more than 80%, then we try to decrease frequency

  	 *

  	 * Any frequency increase takes it to the maximum frequency.
  	 * Frequency reduction happens at minimum steps of

  	 * 5% (default) of maximum frequency

  	 */

  	/* Get Absolute Load */
  	for_each_cpu(j, policy->cpus) {
  		struct cpu_dbs_info_s *j_dbs_info;
  		cputime64_t cur_wall_time, cur_idle_time;
  		unsigned int idle_time, wall_time;

  		j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);

  
  		cur_idle_time = get_cpu_idle_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;

  		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);
  		}
  
  		if (unlikely(!wall_time || wall_time < idle_time))
  			continue;
  
  		load = 100 * (wall_time - idle_time) / wall_time;

  
  		if (load > max_load)
  			max_load = load;

  	}
  
  	/*
  	 * break out if we 'cannot' reduce the speed as the user might
  	 * want freq_step to be zero
  	 */
  	if (dbs_tuners_ins.freq_step == 0)
  		return;

  	/* Check for frequency increase */

  	if (max_load > dbs_tuners_ins.up_threshold) {

  		this_dbs_info->down_skip = 0;

  		/* if we are already at full speed then break out early */

  		if (this_dbs_info->requested_freq == policy->max)

  			return;

  		freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;

  
  		/* max freq cannot be less than 100. But who knows.... */

  		if (unlikely(freq_target == 0))
  			freq_target = 5;

  		this_dbs_info->requested_freq += freq_target;

  		if (this_dbs_info->requested_freq > policy->max)
  			this_dbs_info->requested_freq = policy->max;

  		__cpufreq_driver_target(policy, this_dbs_info->requested_freq,

  			CPUFREQ_RELATION_H);

  		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 < (dbs_tuners_ins.down_threshold - 10)) {

  		freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;

  		this_dbs_info->requested_freq -= freq_target;

  		if (this_dbs_info->requested_freq < policy->min)
  			this_dbs_info->requested_freq = policy->min;

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

  		__cpufreq_driver_target(policy, this_dbs_info->requested_freq,

  				CPUFREQ_RELATION_H);

  		return;
  	}
  }

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

  	mutex_lock(&dbs_info->timer_mutex);

  
  	dbs_check_cpu(dbs_info);

  	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);
  	delay -= jiffies % delay;
  
  	dbs_info->enable = 1;
  	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)

  {

  	dbs_info->enable = 0;

  	cancel_delayed_work_sync(&dbs_info->work);

  }
  
  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(cs_cpu_dbs_info, cpu);

  
  	switch (event) {
  	case CPUFREQ_GOV_START:

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

  			return -EINVAL;

  		mutex_lock(&dbs_mutex);

  		for_each_cpu(j, policy->cpus) {

  			struct cpu_dbs_info_s *j_dbs_info;

  			j_dbs_info = &per_cpu(cs_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->down_skip = 0;
  		this_dbs_info->requested_freq = policy->cur;

  		mutex_init(&this_dbs_info->timer_mutex);

  		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;

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

  			/*
  			 * conservative does not implement micro like ondemand
  			 * governor, thus we are bound to jiffes/HZ
  			 */
  			min_sampling_rate =
  				MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
  			/* 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);

  			cpufreq_register_notifier(
  					&dbs_cpufreq_notifier_block,
  					CPUFREQ_TRANSITION_NOTIFIER);

  		}

  		mutex_unlock(&dbs_mutex);

  		dbs_timer_init(this_dbs_info);

  		break;
  
  	case CPUFREQ_GOV_STOP:

  		dbs_timer_exit(this_dbs_info);

  
  		mutex_lock(&dbs_mutex);

  		dbs_enable--;

  		mutex_destroy(&this_dbs_info->timer_mutex);

  		/*
  		 * Stop the timerschedule work, when this governor
  		 * is used for first time
  		 */

  		if (dbs_enable == 0)

  			cpufreq_unregister_notifier(
  					&dbs_cpufreq_notifier_block,
  					CPUFREQ_TRANSITION_NOTIFIER);

  		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;
  }

  #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
  static
  #endif

  struct cpufreq_governor cpufreq_gov_conservative = {
  	.name			= "conservative",
  	.governor		= cpufreq_governor_dbs,
  	.max_transition_latency	= TRANSITION_LATENCY_LIMIT,
  	.owner			= THIS_MODULE,

  };
  
  static int __init cpufreq_gov_dbs_init(void)
  {

  	return cpufreq_register_governor(&cpufreq_gov_conservative);

  }
  
  static void __exit cpufreq_gov_dbs_exit(void)
  {

  	cpufreq_unregister_governor(&cpufreq_gov_conservative);

  }

  MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");

  MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "

  		"Low Latency Frequency Transition capable processors "
  		"optimised for use in a battery environment");

  MODULE_LICENSE("GPL");

  #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
  fs_initcall(cpufreq_gov_dbs_init);
  #else

  module_init(cpufreq_gov_dbs_init);

  #endif

  module_exit(cpufreq_gov_dbs_exit);