Quelle  cpufreq_conservative.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  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>
 */

#include <linux/slab.h>
#include "cpufreq_governor.h"

struct cs_policy_dbs_info {
 struct policy_dbs_info policy_dbs;
 unsigned int down_skip;
 unsigned int requested_freq;
};

static inline struct cs_policy_dbs_info *to_dbs_info(struct policy_dbs_info *policy_dbs)
{
 return container_of(policy_dbs, struct cs_policy_dbs_info, policy_dbs);
}

struct cs_dbs_tuners {
 unsigned int down_threshold;
 unsigned int freq_step;
};

/* 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 inline unsigned int get_freq_step(struct cs_dbs_tuners *cs_tuners,
      struct cpufreq_policy *policy)
{
 unsigned int freq_step = (cs_tuners->freq_step * policy->max) / 100;

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

 return freq_step;
}

/*
 * 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
 *
 * Frequency updates happen at minimum steps of 5% (default) of maximum
 * frequency
 */
static unsigned int cs_dbs_update(struct cpufreq_policy *policy)
{
 struct policy_dbs_info *policy_dbs = policy->governor_data;
 struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy_dbs);
 unsigned int requested_freq = dbs_info->requested_freq;
 struct dbs_data *dbs_data = policy_dbs->dbs_data;
 struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
 unsigned int load = dbs_update(policy);
 unsigned int freq_step;

 /*
 * break out if we 'cannot' reduce the speed as the user might
 * want freq_step to be zero
 */
 if (cs_tuners->freq_step == 0)
  goto out;

 /*
 * If requested_freq is out of range, it is likely that the limits
 * changed in the meantime, so fall back to current frequency in that
 * case.
 */
 if (requested_freq > policy->max || requested_freq < policy->min) {
  requested_freq = policy->cur;
  dbs_info->requested_freq = requested_freq;
 }

 freq_step = get_freq_step(cs_tuners, policy);

 /*
 * Decrease requested_freq one freq_step for each idle period that
 * we didn't update the frequency.
 */
 if (policy_dbs->idle_periods < UINT_MAX) {
  unsigned int freq_steps = policy_dbs->idle_periods * freq_step;

  if (requested_freq > policy->min + freq_steps)
   requested_freq -= freq_steps;
  else
   requested_freq = policy->min;

  policy_dbs->idle_periods = UINT_MAX;
 }

 /* Check for frequency increase */
 if (load > dbs_data->up_threshold) {
  dbs_info->down_skip = 0;

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

  requested_freq += freq_step;
  if (requested_freq > policy->max)
   requested_freq = policy->max;

  __cpufreq_driver_target(policy, requested_freq,
     CPUFREQ_RELATION_HE);
  dbs_info->requested_freq = requested_freq;
  goto out;
 }

 /* if sampling_down_factor is active break out early */
 if (++dbs_info->down_skip < dbs_data->sampling_down_factor)
  goto out;
 dbs_info->down_skip = 0;

 /* Check for frequency decrease */
 if (load < cs_tuners->down_threshold) {
  /*
 * if we cannot reduce the frequency anymore, break out early
 */
  if (requested_freq == policy->min)
   goto out;

  if (requested_freq > freq_step)
   requested_freq -= freq_step;
  else
   requested_freq = policy->min;

  __cpufreq_driver_target(policy, requested_freq,
     CPUFREQ_RELATION_LE);
  dbs_info->requested_freq = requested_freq;
 }

 out:
 return dbs_data->sampling_rate;
}

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

static ssize_t sampling_down_factor_store(struct gov_attr_set *attr_set,
       const char *buf, size_t count)
{
 struct dbs_data *dbs_data = to_dbs_data(attr_set);
 unsigned int input;
 int ret;
 ret = sscanf(buf, "%u", &input);

 if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
  return -EINVAL;

 dbs_data->sampling_down_factor = input;
 return count;
}

static ssize_t up_threshold_store(struct gov_attr_set *attr_set,
      const char *buf, size_t count)
{
 struct dbs_data *dbs_data = to_dbs_data(attr_set);
 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;

 dbs_data->up_threshold = input;
 return count;
}

static ssize_t down_threshold_store(struct gov_attr_set *attr_set,
        const char *buf, size_t count)
{
 struct dbs_data *dbs_data = to_dbs_data(attr_set);
 struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
 unsigned int input;
 int ret;
 ret = sscanf(buf, "%u", &input);

 /* cannot be lower than 1 otherwise freq will not fall */
 if (ret != 1 || input < 1 || input >= dbs_data->up_threshold)
  return -EINVAL;

 cs_tuners->down_threshold = input;
 return count;
}

static ssize_t ignore_nice_load_store(struct gov_attr_set *attr_set,
          const char *buf, size_t count)
{
 struct dbs_data *dbs_data = to_dbs_data(attr_set);
 unsigned int input;
 int ret;

 ret = sscanf(buf, "%u", &input);
 if (ret != 1)
  return -EINVAL;

 if (input > 1)
  input = 1;

 if (input == dbs_data->ignore_nice_load) /* nothing to do */
  return count;

 dbs_data->ignore_nice_load = input;

 /* we need to re-evaluate prev_cpu_idle */
 gov_update_cpu_data(dbs_data);

 return count;
}

static ssize_t freq_step_store(struct gov_attr_set *attr_set, const char *buf,
          size_t count)
{
 struct dbs_data *dbs_data = to_dbs_data(attr_set);
 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;
}

gov_show_one_common(sampling_rate);
gov_show_one_common(sampling_down_factor);
gov_show_one_common(up_threshold);
gov_show_one_common(ignore_nice_load);
gov_show_one(cs, down_threshold);
gov_show_one(cs, freq_step);

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

static struct attribute *cs_attrs[] = {
 &sampling_rate.attr,
 &sampling_down_factor.attr,
 &up_threshold.attr,
 &down_threshold.attr,
 &ignore_nice_load.attr,
 &freq_step.attr,
 NULL
};
ATTRIBUTE_GROUPS(cs);

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

static struct policy_dbs_info *cs_alloc(void)
{
 struct cs_policy_dbs_info *dbs_info;

 dbs_info = kzalloc(sizeof(*dbs_info), GFP_KERNEL);
 return dbs_info ? &dbs_info->policy_dbs : NULL;
}

static void cs_free(struct policy_dbs_info *policy_dbs)
{
 kfree(to_dbs_info(policy_dbs));
}

static int cs_init(struct dbs_data *dbs_data)
{
 struct cs_dbs_tuners *tuners;

 tuners = kzalloc(sizeof(*tuners), GFP_KERNEL);
 if (!tuners)
  return -ENOMEM;

 tuners->down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD;
 tuners->freq_step = DEF_FREQUENCY_STEP;
 dbs_data->up_threshold = DEF_FREQUENCY_UP_THRESHOLD;
 dbs_data->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
 dbs_data->ignore_nice_load = 0;
 dbs_data->tuners = tuners;

 return 0;
}

static void cs_exit(struct dbs_data *dbs_data)
{
 kfree(dbs_data->tuners);
}

static void cs_start(struct cpufreq_policy *policy)
{
 struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy->governor_data);

 dbs_info->down_skip = 0;
 dbs_info->requested_freq = policy->cur;
}

static struct dbs_governor cs_governor = {
 .gov = CPUFREQ_DBS_GOVERNOR_INITIALIZER("conservative"),
 .kobj_type = { .default_groups = cs_groups },
 .gov_dbs_update = cs_dbs_update,
 .alloc = cs_alloc,
 .free = cs_free,
 .init = cs_init,
 .exit = cs_exit,
 .start = cs_start,
};

#define CPU_FREQ_GOV_CONSERVATIVE (cs_governor.gov)

MODULE_AUTHOR("Alexander Clouter ");
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
struct cpufreq_governor *cpufreq_default_governor(void)
{
 return &CPU_FREQ_GOV_CONSERVATIVE;
}
#endif

cpufreq_governor_init(CPU_FREQ_GOV_CONSERVATIVE);
cpufreq_governor_exit(CPU_FREQ_GOV_CONSERVATIVE);