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cpufreq_conservative.c

/*
 *  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)  2004 Alexander Clouter <alex-kernel@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/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/cpu.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 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.
 */
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 * 1000)

static void do_dbs_timer(struct work_struct *work);

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;
      unsigned int down_skip;
      unsigned int requested_freq;
};
static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);

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

/*
 * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
 * lock and dbs_mutex. cpu_hotplug lock should always be held before
 * dbs_mutex. If any function that can potentially take cpu_hotplug lock
 * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
 * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
 * is recursive for the same process. -Venki
 */
static DEFINE_MUTEX (dbs_mutex);
static DECLARE_DELAYED_WORK(dbs_work, do_dbs_timer);

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;
};

static struct dbs_tuners 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 unsigned int get_cpu_idle_time(unsigned int cpu)
{
      unsigned int add_nice = 0, ret;

      if (dbs_tuners_ins.ignore_nice)
            add_nice = kstat_cpu(cpu).cpustat.nice;

      ret = kstat_cpu(cpu).cpustat.idle +
            kstat_cpu(cpu).cpustat.iowait +
            add_nice;

      return ret;
}

/* 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(cpu_dbs_info,
                                          freq->cpu);

      if (!this_dbs_info->enable)
            return 0;

      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_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_conservative 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(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 cpufreq_policy *unused,
            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;

      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 > 100 || input <= dbs_tuners_ins.down_threshold) {
            mutex_unlock(&dbs_mutex);
            return -EINVAL;
      }

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

      return count;
}

static ssize_t store_down_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 > 100 || input >= dbs_tuners_ins.up_threshold) {
            mutex_unlock(&dbs_mutex);
            return -EINVAL;
      }

      dbs_tuners_ins.down_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;
}

static ssize_t store_freq_step(struct cpufreq_policy *policy,
            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 :) */
      mutex_lock(&dbs_mutex);
      dbs_tuners_ins.freq_step = input;
      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(down_threshold);
define_one_rw(ignore_nice_load);
define_one_rw(freq_step);

static struct attribute * dbs_attributes[] = {
      &sampling_rate_max.attr,
      &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(int cpu)
{
      unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;
      unsigned int tmp_idle_ticks, total_idle_ticks;
      unsigned int freq_step;
      unsigned int freq_down_sampling_rate;
      struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
      struct cpufreq_policy *policy;

      if (!this_dbs_info->enable)
            return;

      policy = this_dbs_info->cur_policy;

      /*
       * The default safe range is 20% to 80%
       * Every sampling_rate, we check
       *    - If current idle time is less than 20%, 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 max_frequency
       */

      /* Check for frequency increase */
      idle_ticks = UINT_MAX;

      /* Check for frequency increase */
      total_idle_ticks = get_cpu_idle_time(cpu);
      tmp_idle_ticks = total_idle_ticks -
            this_dbs_info->prev_cpu_idle_up;
      this_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) {
            this_dbs_info->down_skip = 0;
            this_dbs_info->prev_cpu_idle_down =
                  this_dbs_info->prev_cpu_idle_up;

            /* if we are already at full speed then break out early */
            if (this_dbs_info->requested_freq == policy->max)
                  return;

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

            /* max freq cannot be less than 100. But who knows.... */
            if (unlikely(freq_step == 0))
                  freq_step = 5;

            this_dbs_info->requested_freq += freq_step;
            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;
      }

      /* Check for frequency decrease */
      this_dbs_info->down_skip++;
      if (this_dbs_info->down_skip < dbs_tuners_ins.sampling_down_factor)
            return;

      /* Check for frequency decrease */
      total_idle_ticks = this_dbs_info->prev_cpu_idle_up;
      tmp_idle_ticks = total_idle_ticks -
            this_dbs_info->prev_cpu_idle_down;
      this_dbs_info->prev_cpu_idle_down = 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;
      this_dbs_info->down_skip = 0;

      freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
            dbs_tuners_ins.sampling_down_factor;
      down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) *
            usecs_to_jiffies(freq_down_sampling_rate);

      if (idle_ticks > down_idle_ticks) {
            /*
             * if we are already at the lowest speed then break out early
             * or if we 'cannot' reduce the speed as the user might want
             * freq_step to be zero
             */
            if (this_dbs_info->requested_freq == policy->min
                        || dbs_tuners_ins.freq_step == 0)
                  return;

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

            /* max freq cannot be less than 100. But who knows.... */
            if (unlikely(freq_step == 0))
                  freq_step = 5;

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

            __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
                        CPUFREQ_RELATION_H);
            return;
      }
}

static void do_dbs_timer(struct work_struct *work)
{
      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)
{
      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;
      int rc;

      this_dbs_info = &per_cpu(cpu_dbs_info, cpu);

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

            if (this_dbs_info->enable) /* Already enabled */
                  break;

            mutex_lock(&dbs_mutex);

            rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
            if (rc) {
                  mutex_unlock(&dbs_mutex);
                  return rc;
            }

            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(cpu);
                  j_dbs_info->prev_cpu_idle_down
                        = j_dbs_info->prev_cpu_idle_up;
            }
            this_dbs_info->enable = 1;
            this_dbs_info->down_skip = 0;
            this_dbs_info->requested_freq = policy->cur;

            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 = 10 * 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();
                  cpufreq_register_notifier(
                              &dbs_cpufreq_notifier_block,
                              CPUFREQ_TRANSITION_NOTIFIER);
            }

            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();
                  cpufreq_unregister_notifier(
                              &dbs_cpufreq_notifier_block,
                              CPUFREQ_TRANSITION_NOTIFIER);
            }

            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;
}

struct cpufreq_governor cpufreq_gov_conservative = {
      .name             = "conservative",
      .governor         = cpufreq_governor_dbs,
      .max_transition_latency = TRANSITION_LATENCY_LIMIT,
      .owner                  = THIS_MODULE,
};
EXPORT_SYMBOL(cpufreq_gov_conservative);

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

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_conservative);
}


MODULE_AUTHOR ("Alexander Clouter <alex-kernel@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);

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