/*
   *  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/slab.h>
  #include "cpufreq_governor.h"
  
  /* Conservative governor macros */
  #define DEF_FREQUENCY_UP_THRESHOLD		(80)
  #define DEF_FREQUENCY_DOWN_THRESHOLD		(20)
  #define DEF_FREQUENCY_STEP			(5)
  #define DEF_SAMPLING_DOWN_FACTOR		(1)
  #define MAX_SAMPLING_DOWN_FACTOR		(10)
  
  static DEFINE_PER_CPU(struct cs_cpu_dbs_info_s, cs_cpu_dbs_info);
  
  static inline unsigned int get_freq_target(struct cs_dbs_tuners *cs_tuners,
  					   struct cpufreq_policy *policy)
  {
  	unsigned int freq_target = (cs_tuners->freq_step * policy->max) / 100;
  
  	/* max freq cannot be less than 100. But who knows... */
  	if (unlikely(freq_target == 0))
  		freq_target = DEF_FREQUENCY_STEP;
  
  	return freq_target;
  }
  
  /*
   * 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%
   * (default), 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
   */
  static void cs_check_cpu(int cpu, unsigned int load)
  {
  	struct cs_cpu_dbs_info_s *dbs_info = &per_cpu(cs_cpu_dbs_info, cpu);
  	struct cpufreq_policy *policy = dbs_info->cdbs.cur_policy;
  	struct dbs_data *dbs_data = policy->governor_data;
  	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
  
  	/*
  	 * break out if we 'cannot' reduce the speed as the user might
  	 * want freq_step to be zero
  	 */
  	if (cs_tuners->freq_step == 0)
  		return;
  
  	/* Check for frequency increase */
  	if (load > cs_tuners->up_threshold) {
  		dbs_info->down_skip = 0;
  
  		/* if we are already at full speed then break out early */
  		if (dbs_info->requested_freq == policy->max)
  			return;
  
  		dbs_info->requested_freq += get_freq_target(cs_tuners, policy);
  
  		if (dbs_info->requested_freq > policy->max)
  			dbs_info->requested_freq = policy->max;
  
  		__cpufreq_driver_target(policy, dbs_info->requested_freq,
  			CPUFREQ_RELATION_H);
  		return;
  	}
  
  	/* if sampling_down_factor is active break out early */
  	if (++dbs_info->down_skip < cs_tuners->sampling_down_factor)
  		return;
  	dbs_info->down_skip = 0;
  
  	/* Check for frequency decrease */
  	if (load < cs_tuners->down_threshold) {
  		unsigned int freq_target;
  		/*
  		 * if we cannot reduce the frequency anymore, break out early
  		 */
  		if (policy->cur == policy->min)
  			return;
  
  		freq_target = get_freq_target(cs_tuners, policy);
  		if (dbs_info->requested_freq > freq_target)
  			dbs_info->requested_freq -= freq_target;
  		else
  			dbs_info->requested_freq = policy->min;
  
  		__cpufreq_driver_target(policy, dbs_info->requested_freq,
  				CPUFREQ_RELATION_L);
  		return;
  	}
  }
  
  static void cs_dbs_timer(struct work_struct *work)
  {
  	struct cs_cpu_dbs_info_s *dbs_info = container_of(work,
  			struct cs_cpu_dbs_info_s, cdbs.work.work);
  	unsigned int cpu = dbs_info->cdbs.cur_policy->cpu;
  	struct cs_cpu_dbs_info_s *core_dbs_info = &per_cpu(cs_cpu_dbs_info,
  			cpu);
  	struct dbs_data *dbs_data = dbs_info->cdbs.cur_policy->governor_data;
  	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
  	int delay = delay_for_sampling_rate(cs_tuners->sampling_rate);
  	bool modify_all = true;
  
  	mutex_lock(&core_dbs_info->cdbs.timer_mutex);
  	if (!need_load_eval(&core_dbs_info->cdbs, cs_tuners->sampling_rate))
  		modify_all = false;
  	else
  		dbs_check_cpu(dbs_data, cpu);
  
  	gov_queue_work(dbs_data, dbs_info->cdbs.cur_policy, delay, modify_all);
  	mutex_unlock(&core_dbs_info->cdbs.timer_mutex);
  }
  
  static int dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
  		void *data)
  {
  	struct cpufreq_freqs *freq = data;
  	struct cs_cpu_dbs_info_s *dbs_info =
  					&per_cpu(cs_cpu_dbs_info, freq->cpu);
  	struct cpufreq_policy *policy;
  
  	if (!dbs_info->enable)
  		return 0;
  
  	policy = dbs_info->cdbs.cur_policy;
  
  	/*
  	 * we only care if our internally tracked freq moves outside the 'valid'
  	 * ranges of frequency available to us otherwise we do not change it
  	*/
  	if (dbs_info->requested_freq > policy->max
  			|| dbs_info->requested_freq < policy->min)
  		dbs_info->requested_freq = freq->new;
  
  	return 0;
  }
  
  /************************** sysfs interface ************************/
  static struct common_dbs_data cs_dbs_cdata;
  
  static ssize_t store_sampling_down_factor(struct dbs_data *dbs_data,
  		const char *buf, size_t count)
  {
  	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
  	unsigned int input;
  	int ret;
  	ret = sscanf(buf, "%u", &input);
  
  	if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
  		return -EINVAL;
  
  	cs_tuners->sampling_down_factor = input;
  	return count;
  }
  
  static ssize_t store_sampling_rate(struct dbs_data *dbs_data, const char *buf,
  		size_t count)
  {
  	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
  	unsigned int input;
  	int ret;
  	ret = sscanf(buf, "%u", &input);
  
  	if (ret != 1)
  		return -EINVAL;
  
  	cs_tuners->sampling_rate = max(input, dbs_data->min_sampling_rate);
  	return count;
  }
  
  static ssize_t store_up_threshold(struct dbs_data *dbs_data, const char *buf,
  		size_t count)
  {
  	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
  	unsigned int input;
  	int ret;
  	ret = sscanf(buf, "%u", &input);
  
  	if (ret != 1 || input > 100 || input <= cs_tuners->down_threshold)
  		return -EINVAL;
  
  	cs_tuners->up_threshold = input;
  	return count;
  }
  
  static ssize_t store_down_threshold(struct dbs_data *dbs_data, const char *buf,
  		size_t count)
  {
  	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
  	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 >= cs_tuners->up_threshold)
  		return -EINVAL;
  
  	cs_tuners->down_threshold = input;
  	return count;
  }
  
  static ssize_t store_ignore_nice_load(struct dbs_data *dbs_data,
  		const char *buf, size_t count)
  {
  	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
  	unsigned int input, j;
  	int ret;
  
  	ret = sscanf(buf, "%u", &input);
  	if (ret != 1)
  		return -EINVAL;
  
  	if (input > 1)
  		input = 1;
  
  	if (input == cs_tuners->ignore_nice_load) /* nothing to do */
  		return count;
  
  	cs_tuners->ignore_nice_load = input;
  
  	/* we need to re-evaluate prev_cpu_idle */
  	for_each_online_cpu(j) {
  		struct cs_cpu_dbs_info_s *dbs_info;
  		dbs_info = &per_cpu(cs_cpu_dbs_info, j);
  		dbs_info->cdbs.prev_cpu_idle = get_cpu_idle_time(j,
  					&dbs_info->cdbs.prev_cpu_wall, 0);
  		if (cs_tuners->ignore_nice_load)
  			dbs_info->cdbs.prev_cpu_nice =
  				kcpustat_cpu(j).cpustat[CPUTIME_NICE];
  	}
  	return count;
  }
  
  static ssize_t store_freq_step(struct dbs_data *dbs_data, const char *buf,
  		size_t count)
  {
  	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
  	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 :)
  	 */
  	cs_tuners->freq_step = input;
  	return count;
  }
  
  show_store_one(cs, sampling_rate);
  show_store_one(cs, sampling_down_factor);
  show_store_one(cs, up_threshold);
  show_store_one(cs, down_threshold);
  show_store_one(cs, ignore_nice_load);
  show_store_one(cs, freq_step);
  declare_show_sampling_rate_min(cs);
  
  gov_sys_pol_attr_rw(sampling_rate);
  gov_sys_pol_attr_rw(sampling_down_factor);
  gov_sys_pol_attr_rw(up_threshold);
  gov_sys_pol_attr_rw(down_threshold);
  gov_sys_pol_attr_rw(ignore_nice_load);
  gov_sys_pol_attr_rw(freq_step);
  gov_sys_pol_attr_ro(sampling_rate_min);
  
  static struct attribute *dbs_attributes_gov_sys[] = {
  	&sampling_rate_min_gov_sys.attr,
  	&sampling_rate_gov_sys.attr,
  	&sampling_down_factor_gov_sys.attr,
  	&up_threshold_gov_sys.attr,
  	&down_threshold_gov_sys.attr,
  	&ignore_nice_load_gov_sys.attr,
  	&freq_step_gov_sys.attr,
  	NULL
  };
  
  static struct attribute_group cs_attr_group_gov_sys = {
  	.attrs = dbs_attributes_gov_sys,
  	.name = "conservative",
  };
  
  static struct attribute *dbs_attributes_gov_pol[] = {
  	&sampling_rate_min_gov_pol.attr,
  	&sampling_rate_gov_pol.attr,
  	&sampling_down_factor_gov_pol.attr,
  	&up_threshold_gov_pol.attr,
  	&down_threshold_gov_pol.attr,
  	&ignore_nice_load_gov_pol.attr,
  	&freq_step_gov_pol.attr,
  	NULL
  };
  
  static struct attribute_group cs_attr_group_gov_pol = {
  	.attrs = dbs_attributes_gov_pol,
  	.name = "conservative",
  };
  
  /************************** sysfs end ************************/
  
  static int cs_init(struct dbs_data *dbs_data)
  {
  	struct cs_dbs_tuners *tuners;
  
  	tuners = kzalloc(sizeof(*tuners), GFP_KERNEL);
  	if (!tuners) {
  		pr_err("%s: kzalloc failed
  ", __func__);
  		return -ENOMEM;
  	}
  
  	tuners->up_threshold = DEF_FREQUENCY_UP_THRESHOLD;
  	tuners->down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD;
  	tuners->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
  	tuners->ignore_nice_load = 0;
  	tuners->freq_step = DEF_FREQUENCY_STEP;
  
  	dbs_data->tuners = tuners;
  	dbs_data->min_sampling_rate = MIN_SAMPLING_RATE_RATIO *
  		jiffies_to_usecs(10);
  	mutex_init(&dbs_data->mutex);
  	return 0;
  }
  
  static void cs_exit(struct dbs_data *dbs_data)
  {
  	kfree(dbs_data->tuners);
  }
  
  define_get_cpu_dbs_routines(cs_cpu_dbs_info);
  
  static struct notifier_block cs_cpufreq_notifier_block = {
  	.notifier_call = dbs_cpufreq_notifier,
  };
  
  static struct cs_ops cs_ops = {
  	.notifier_block = &cs_cpufreq_notifier_block,
  };
  
  static struct common_dbs_data cs_dbs_cdata = {
  	.governor = GOV_CONSERVATIVE,
  	.attr_group_gov_sys = &cs_attr_group_gov_sys,
  	.attr_group_gov_pol = &cs_attr_group_gov_pol,
  	.get_cpu_cdbs = get_cpu_cdbs,
  	.get_cpu_dbs_info_s = get_cpu_dbs_info_s,
  	.gov_dbs_timer = cs_dbs_timer,
  	.gov_check_cpu = cs_check_cpu,
  	.gov_ops = &cs_ops,
  	.init = cs_init,
  	.exit = cs_exit,
  };
  
  static int cs_cpufreq_governor_dbs(struct cpufreq_policy *policy,
  				   unsigned int event)
  {
  	return cpufreq_governor_dbs(policy, &cs_dbs_cdata, event);
  }
  
  #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
  static
  #endif
  struct cpufreq_governor cpufreq_gov_conservative = {
  	.name			= "conservative",
  	.governor		= cs_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);