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cpufreq_ondemand.c

/*
 *  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>

/*
 * 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 TRANSITION_LATENCY_LIMIT          (10 * 1000 * 1000)

static void do_dbs_timer(struct work_struct *work);

/* Sampling types */
enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE};

struct cpu_dbs_info_s {
      cputime64_t prev_cpu_idle;
      cputime64_t prev_cpu_wall;
      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;
      int cpu;
      unsigned int enable:1,
                   sample_type:1;
};
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 struct workqueue_struct      *kondemand_wq;

static struct dbs_tuners {
      unsigned int sampling_rate;
      unsigned int up_threshold;
      unsigned int ignore_nice;
      unsigned int powersave_bias;
} dbs_tuners_ins = {
      .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
      .ignore_nice = 0,
      .powersave_bias = 0,
};

static inline cputime64_t get_cpu_idle_time(unsigned int cpu)
{
      cputime64_t idle_time;
      cputime64_t cur_jiffies;
      cputime64_t busy_time;

      cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());
      busy_time = cputime64_add(kstat_cpu(cpu).cpustat.user,
                  kstat_cpu(cpu).cpustat.system);

      busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.irq);
      busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.softirq);
      busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.steal);

      if (!dbs_tuners_ins.ignore_nice) {
            busy_time = cputime64_add(busy_time,
                        kstat_cpu(cpu).cpustat.nice);
      }

      idle_time = cputime64_sub(cur_jiffies, busy_time);
      return idle_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(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(void)
{
      int i;
      for_each_online_cpu(i) {
            struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, i);
            dbs_info->freq_table = cpufreq_frequency_get_table(i);
            dbs_info->freq_lo = 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(up_threshold, up_threshold);
show_one(ignore_nice_load, ignore_nice);
show_one(powersave_bias, powersave_bias);

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 */
      for_each_online_cpu(j) {
            struct cpu_dbs_info_s *dbs_info;
            dbs_info = &per_cpu(cpu_dbs_info, j);
            dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
            dbs_info->prev_cpu_wall = get_jiffies_64();
      }
      mutex_unlock(&dbs_mutex);

      return count;
}

static ssize_t store_powersave_bias(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 > 1000)
            input = 1000;

      mutex_lock(&dbs_mutex);
      dbs_tuners_ins.powersave_bias = input;
      ondemand_powersave_bias_init();
      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(up_threshold);
define_one_rw(ignore_nice_load);
define_one_rw(powersave_bias);

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

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

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

static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
{
      unsigned int idle_ticks, total_ticks;
      unsigned int load = 0;
      cputime64_t cur_jiffies;

      struct cpufreq_policy *policy;
      unsigned int j;

      if (!this_dbs_info->enable)
            return;

      this_dbs_info->freq_lo = 0;
      policy = this_dbs_info->cur_policy;
      cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());
      total_ticks = (unsigned int) cputime64_sub(cur_jiffies,
                  this_dbs_info->prev_cpu_wall);
      this_dbs_info->prev_cpu_wall = get_jiffies_64();

      if (!total_ticks)
            return;
      /*
       * 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 Idle Time */
      idle_ticks = UINT_MAX;
      for_each_cpu_mask(j, policy->cpus) {
            cputime64_t total_idle_ticks;
            unsigned int tmp_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 = (unsigned int) cputime64_sub(total_idle_ticks,
                        j_dbs_info->prev_cpu_idle);
            j_dbs_info->prev_cpu_idle = total_idle_ticks;

            if (tmp_idle_ticks < idle_ticks)
                  idle_ticks = tmp_idle_ticks;
      }
      if (likely(total_ticks > idle_ticks))
            load = (100 * (total_ticks - idle_ticks)) / total_ticks;

      /* Check for frequency increase */
      if (load > dbs_tuners_ins.up_threshold) {
            /* if we are already at full speed then break out early */
            if (!dbs_tuners_ins.powersave_bias) {
                  if (policy->cur == policy->max)
                        return;

                  __cpufreq_driver_target(policy, policy->max,
                        CPUFREQ_RELATION_H);
            } else {
                  int freq = powersave_bias_target(policy, policy->max,
                              CPUFREQ_RELATION_H);
                  __cpufreq_driver_target(policy, freq,
                        CPUFREQ_RELATION_L);
            }
            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 (load < (dbs_tuners_ins.up_threshold - 10)) {
            unsigned int freq_next, freq_cur;

            freq_cur = __cpufreq_driver_getavg(policy);
            if (!freq_cur)
                  freq_cur = policy->cur;

            freq_next = (freq_cur * load) /
                  (dbs_tuners_ins.up_threshold - 10);

            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;

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

      delay -= jiffies % delay;

      if (lock_policy_rwsem_write(cpu) < 0)
            return;

      if (!dbs_info->enable) {
            unlock_policy_rwsem_write(cpu);
            return;
      }

      /* 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 {
            __cpufreq_driver_target(dbs_info->cur_policy,
                                    dbs_info->freq_lo,
                                    CPUFREQ_RELATION_H);
      }
      queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
      unlock_policy_rwsem_write(cpu);
}

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;
      ondemand_powersave_bias_init();
      dbs_info->sample_type = DBS_NORMAL_SAMPLE;
      INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
      queue_delayed_work_on(dbs_info->cpu, kondemand_wq, &dbs_info->work,
                            delay);
}

static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
{
      dbs_info->enable = 0;
      cancel_delayed_work(&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(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);
            dbs_enable++;

            rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
            if (rc) {
                  dbs_enable--;
                  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 = get_cpu_idle_time(j);
                  j_dbs_info->prev_cpu_wall = get_jiffies_64();
            }
            this_dbs_info->cpu = cpu;
            /*
             * 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(this_dbs_info);

            mutex_unlock(&dbs_mutex);
            break;

      case CPUFREQ_GOV_STOP:
            mutex_lock(&dbs_mutex);
            dbs_timer_exit(this_dbs_info);
            sysfs_remove_group(&policy->kobj, &dbs_attr_group);
            dbs_enable--;
            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_ondemand = {
      .name             = "ondemand",
      .governor         = cpufreq_governor_dbs,
      .max_transition_latency = TRANSITION_LATENCY_LIMIT,
      .owner                  = THIS_MODULE,
};
EXPORT_SYMBOL(cpufreq_gov_ondemand);

static int __init cpufreq_gov_dbs_init(void)
{
      kondemand_wq = create_workqueue("kondemand");
      if (!kondemand_wq) {
            printk(KERN_ERR "Creation of kondemand failed\n");
            return -EFAULT;
      }
      return cpufreq_register_governor(&cpufreq_gov_ondemand);
}

static void __exit cpufreq_gov_dbs_exit(void)
{
      cpufreq_unregister_governor(&cpufreq_gov_ondemand);
      destroy_workqueue(kondemand_wq);
}


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);

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