/* * drivers/cpufreq/cpufreq_ondemand.c * * Copyright (C) 2001 Russell King * (C) 2003 Venkatesh Pallipadi . * Jun Nakajima * * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * 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 (0) #define MAX_FREQUENCY_UP_THRESHOLD (100) #define DEF_FREQUENCY_DOWN_THRESHOLD (20) #define MIN_FREQUENCY_DOWN_THRESHOLD (0) #define MAX_FREQUENCY_DOWN_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 (def_sampling_rate / 2) #define MAX_SAMPLING_RATE (500 * def_sampling_rate) #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000) #define DEF_SAMPLING_DOWN_FACTOR (10) #define TRANSITION_LATENCY_LIMIT (10 * 1000) #define sampling_rate_in_HZ(x) (((x * HZ) < (1000 * 1000))?1:((x * HZ) / (1000 * 1000))) static void do_dbs_timer(void *data); 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; }; static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info); static unsigned int dbs_enable; /* number of CPUs using this policy */ static DECLARE_MUTEX (dbs_sem); static DECLARE_WORK (dbs_work, do_dbs_timer, NULL); struct dbs_tuners { unsigned int sampling_rate; unsigned int sampling_down_factor; unsigned int up_threshold; unsigned int down_threshold; }; 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, }; /************************** 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(sampling_down_factor, sampling_down_factor); show_one(up_threshold, up_threshold); show_one(down_threshold, down_threshold); 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 ) return -EINVAL; down(&dbs_sem); dbs_tuners_ins.sampling_down_factor = input; up(&dbs_sem); 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); down(&dbs_sem); if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) { up(&dbs_sem); return -EINVAL; } dbs_tuners_ins.sampling_rate = input; up(&dbs_sem); 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); down(&dbs_sem); if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD || input < MIN_FREQUENCY_UP_THRESHOLD || input <= dbs_tuners_ins.down_threshold) { up(&dbs_sem); return -EINVAL; } dbs_tuners_ins.up_threshold = input; up(&dbs_sem); 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); down(&dbs_sem); if (ret != 1 || input > MAX_FREQUENCY_DOWN_THRESHOLD || input < MIN_FREQUENCY_DOWN_THRESHOLD || input >= dbs_tuners_ins.up_threshold) { up(&dbs_sem); return -EINVAL; } dbs_tuners_ins.down_threshold = input; up(&dbs_sem); 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); 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, NULL }; static struct attribute_group dbs_attr_group = { .attrs = dbs_attributes, .name = "ondemand", }; /************************** sysfs end ************************/ static void dbs_check_cpu(int cpu) { unsigned int idle_ticks, up_idle_ticks, down_idle_ticks; unsigned int total_idle_ticks; unsigned int freq_down_step; unsigned int freq_down_sampling_rate; static int down_skip[NR_CPUS]; struct cpu_dbs_info_s *this_dbs_info; struct cpufreq_policy *policy; unsigned int j; this_dbs_info = &per_cpu(cpu_dbs_info, cpu); 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% of max_frequency */ /* Check for frequency increase */ total_idle_ticks = kstat_cpu(cpu).cpustat.idle + kstat_cpu(cpu).cpustat.iowait; idle_ticks = total_idle_ticks - this_dbs_info->prev_cpu_idle_up; this_dbs_info->prev_cpu_idle_up = total_idle_ticks; for_each_cpu_mask(j, policy->cpus) { unsigned int tmp_idle_ticks; struct cpu_dbs_info_s *j_dbs_info; if (j == cpu) continue; j_dbs_info = &per_cpu(cpu_dbs_info, j); /* Check for frequency increase */ total_idle_ticks = kstat_cpu(j).cpustat.idle + kstat_cpu(j).cpustat.iowait; tmp_idle_ticks = total_idle_ticks - j_dbs_info->prev_cpu_idle_up; j_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) * sampling_rate_in_HZ(dbs_tuners_ins.sampling_rate); if (idle_ticks < up_idle_ticks) { __cpufreq_driver_target(policy, policy->max, CPUFREQ_RELATION_H); down_skip[cpu] = 0; this_dbs_info->prev_cpu_idle_down = total_idle_ticks; return; } /* Check for frequency decrease */ down_skip[cpu]++; if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor) return; total_idle_ticks = kstat_cpu(cpu).cpustat.idle + kstat_cpu(cpu).cpustat.iowait; idle_ticks = total_idle_ticks - this_dbs_info->prev_cpu_idle_down; this_dbs_info->prev_cpu_idle_down = total_idle_ticks; for_each_cpu_mask(j, policy->cpus) { unsigned int tmp_idle_ticks; struct cpu_dbs_info_s *j_dbs_info; if (j == cpu) continue; j_dbs_info = &per_cpu(cpu_dbs_info, j); /* Check for frequency increase */ total_idle_ticks = kstat_cpu(j).cpustat.idle + kstat_cpu(j).cpustat.iowait; tmp_idle_ticks = total_idle_ticks - j_dbs_info->prev_cpu_idle_down; j_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; down_skip[cpu] = 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) * sampling_rate_in_HZ(freq_down_sampling_rate); if (idle_ticks > down_idle_ticks ) { freq_down_step = (5 * policy->max) / 100; /* max freq cannot be less than 100. But who knows.... */ if (unlikely(freq_down_step == 0)) freq_down_step = 5; __cpufreq_driver_target(policy, policy->cur - freq_down_step, CPUFREQ_RELATION_H); return; } } static void do_dbs_timer(void *data) { int i; down(&dbs_sem); for (i = 0; i < NR_CPUS; i++) if (cpu_online(i)) dbs_check_cpu(i); schedule_delayed_work(&dbs_work, sampling_rate_in_HZ(dbs_tuners_ins.sampling_rate)); up(&dbs_sem); } static inline void dbs_timer_init(void) { INIT_WORK(&dbs_work, do_dbs_timer, NULL); schedule_delayed_work(&dbs_work, sampling_rate_in_HZ(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; this_dbs_info = &per_cpu(cpu_dbs_info, cpu); switch (event) { case CPUFREQ_GOV_START: if ((!cpu_online(cpu)) || (!policy->cur)) return -EINVAL; if (policy->cpuinfo.transition_latency > (TRANSITION_LATENCY_LIMIT * 1000)) return -EINVAL; if (this_dbs_info->enable) /* Already enabled */ break; down(&dbs_sem); 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 = kstat_cpu(j).cpustat.idle + kstat_cpu(j).cpustat.iowait; j_dbs_info->prev_cpu_idle_down = kstat_cpu(j).cpustat.idle + kstat_cpu(j).cpustat.iowait; } this_dbs_info->enable = 1; sysfs_create_group(&policy->kobj, &dbs_attr_group); 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; if (latency < 1000) latency = 1000; def_sampling_rate = (latency / 1000) * DEF_SAMPLING_RATE_LATENCY_MULTIPLIER; dbs_tuners_ins.sampling_rate = def_sampling_rate; dbs_timer_init(); } up(&dbs_sem); break; case CPUFREQ_GOV_STOP: down(&dbs_sem); 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(); up(&dbs_sem); break; case CPUFREQ_GOV_LIMITS: down(&dbs_sem); 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); up(&dbs_sem); break; } return 0; } struct cpufreq_governor cpufreq_gov_dbs = { .name = "ondemand", .governor = cpufreq_governor_dbs, .owner = THIS_MODULE, }; EXPORT_SYMBOL(cpufreq_gov_dbs); static int __init cpufreq_gov_dbs_init(void) { return cpufreq_register_governor(&cpufreq_gov_dbs); } 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_dbs); } MODULE_AUTHOR ("Venkatesh Pallipadi "); MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor for " "Low Latency Frequency Transition capable processors"); MODULE_LICENSE ("GPL"); module_init(cpufreq_gov_dbs_init); module_exit(cpufreq_gov_dbs_exit);