linux-stable/drivers/cpufreq/cpufreq_conservative.c
Stratos Karafotis 42d951c851 cpufreq: conservative: Fix comment explaining frequency updates
The original comment about the frequency increase to maximum is wrong.

Both increase and decrease happen at steps.

Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2016-11-16 23:15:56 +01:00

360 lines
9.2 KiB
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) 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"
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;
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 > 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_H);
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_L);
dbs_info->requested_freq = requested_freq;
}
out:
return dbs_data->sampling_rate;
}
/************************** sysfs interface ************************/
static ssize_t store_sampling_down_factor(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 store_up_threshold(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 store_down_threshold(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 11 otherwise freq will not fall */
if (ret != 1 || input < 11 || input > 100 ||
input >= dbs_data->up_threshold)
return -EINVAL;
cs_tuners->down_threshold = input;
return count;
}
static ssize_t store_ignore_nice_load(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 store_freq_step(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_common(min_sampling_rate);
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_ro(min_sampling_rate);
gov_attr_rw(down_threshold);
gov_attr_rw(freq_step);
static struct attribute *cs_attributes[] = {
&min_sampling_rate.attr,
&sampling_rate.attr,
&sampling_down_factor.attr,
&up_threshold.attr,
&down_threshold.attr,
&ignore_nice_load.attr,
&freq_step.attr,
NULL
};
/************************** 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;
dbs_data->min_sampling_rate = MIN_SAMPLING_RATE_RATIO *
jiffies_to_usecs(10);
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_attrs = cs_attributes },
.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)
static int __init cpufreq_gov_dbs_init(void)
{
return cpufreq_register_governor(CPU_FREQ_GOV_CONSERVATIVE);
}
static void __exit cpufreq_gov_dbs_exit(void)
{
cpufreq_unregister_governor(CPU_FREQ_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
struct cpufreq_governor *cpufreq_default_governor(void)
{
return CPU_FREQ_GOV_CONSERVATIVE;
}
fs_initcall(cpufreq_gov_dbs_init);
#else
module_init(cpufreq_gov_dbs_init);
#endif
module_exit(cpufreq_gov_dbs_exit);