2 * drivers/cpufreq/cpufreq_conservative.c
4 * Copyright (C) 2001 Russell King
5 * (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
6 * Jun Nakajima <jun.nakajima@intel.com>
7 * (C) 2004 Alexander Clouter <alex-kernel@digriz.org.uk>
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/smp.h>
17 #include <linux/init.h>
18 #include <linux/interrupt.h>
19 #include <linux/ctype.h>
20 #include <linux/cpufreq.h>
21 #include <linux/sysctl.h>
22 #include <linux/types.h>
24 #include <linux/sysfs.h>
25 #include <linux/sched.h>
26 #include <linux/kmod.h>
27 #include <linux/workqueue.h>
28 #include <linux/jiffies.h>
29 #include <linux/kernel_stat.h>
30 #include <linux/percpu.h>
31 #include <linux/mutex.h>
33 * dbs is used in this file as a shortform for demandbased switching
34 * It helps to keep variable names smaller, simpler
37 #define DEF_FREQUENCY_UP_THRESHOLD (80)
38 #define DEF_FREQUENCY_DOWN_THRESHOLD (20)
41 * The polling frequency of this governor depends on the capability of
42 * the processor. Default polling frequency is 1000 times the transition
43 * latency of the processor. The governor will work on any processor with
44 * transition latency <= 10mS, using appropriate sampling
46 * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
47 * this governor will not work.
48 * All times here are in uS.
50 static unsigned int def_sampling_rate;
51 #define MIN_SAMPLING_RATE_RATIO (2)
52 /* for correct statistics, we need at least 10 ticks between each measure */
53 #define MIN_STAT_SAMPLING_RATE (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
54 #define MIN_SAMPLING_RATE (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
55 #define MAX_SAMPLING_RATE (500 * def_sampling_rate)
56 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000)
57 #define DEF_SAMPLING_DOWN_FACTOR (1)
58 #define MAX_SAMPLING_DOWN_FACTOR (10)
59 #define TRANSITION_LATENCY_LIMIT (10 * 1000)
61 static void do_dbs_timer(void *data);
63 struct cpu_dbs_info_s {
64 struct cpufreq_policy *cur_policy;
65 unsigned int prev_cpu_idle_up;
66 unsigned int prev_cpu_idle_down;
68 unsigned int down_skip;
69 unsigned int requested_freq;
71 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
73 static unsigned int dbs_enable; /* number of CPUs using this policy */
75 static DEFINE_MUTEX (dbs_mutex);
76 static DECLARE_WORK (dbs_work, do_dbs_timer, NULL);
79 unsigned int sampling_rate;
80 unsigned int sampling_down_factor;
81 unsigned int up_threshold;
82 unsigned int down_threshold;
83 unsigned int ignore_nice;
84 unsigned int freq_step;
87 static struct dbs_tuners dbs_tuners_ins = {
88 .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
89 .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
90 .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
95 static inline unsigned int get_cpu_idle_time(unsigned int cpu)
97 return kstat_cpu(cpu).cpustat.idle +
98 kstat_cpu(cpu).cpustat.iowait +
99 ( dbs_tuners_ins.ignore_nice ?
100 kstat_cpu(cpu).cpustat.nice :
104 /************************** sysfs interface ************************/
105 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
107 return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
110 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
112 return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
115 #define define_one_ro(_name) \
116 static struct freq_attr _name = \
117 __ATTR(_name, 0444, show_##_name, NULL)
119 define_one_ro(sampling_rate_max);
120 define_one_ro(sampling_rate_min);
122 /* cpufreq_conservative Governor Tunables */
123 #define show_one(file_name, object) \
124 static ssize_t show_##file_name \
125 (struct cpufreq_policy *unused, char *buf) \
127 return sprintf(buf, "%u\n", dbs_tuners_ins.object); \
129 show_one(sampling_rate, sampling_rate);
130 show_one(sampling_down_factor, sampling_down_factor);
131 show_one(up_threshold, up_threshold);
132 show_one(down_threshold, down_threshold);
133 show_one(ignore_nice_load, ignore_nice);
134 show_one(freq_step, freq_step);
136 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
137 const char *buf, size_t count)
141 ret = sscanf (buf, "%u", &input);
142 if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
145 mutex_lock(&dbs_mutex);
146 dbs_tuners_ins.sampling_down_factor = input;
147 mutex_unlock(&dbs_mutex);
152 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
153 const char *buf, size_t count)
157 ret = sscanf (buf, "%u", &input);
159 mutex_lock(&dbs_mutex);
160 if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
161 mutex_unlock(&dbs_mutex);
165 dbs_tuners_ins.sampling_rate = input;
166 mutex_unlock(&dbs_mutex);
171 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
172 const char *buf, size_t count)
176 ret = sscanf (buf, "%u", &input);
178 mutex_lock(&dbs_mutex);
179 if (ret != 1 || input > 100 || input <= dbs_tuners_ins.down_threshold) {
180 mutex_unlock(&dbs_mutex);
184 dbs_tuners_ins.up_threshold = input;
185 mutex_unlock(&dbs_mutex);
190 static ssize_t store_down_threshold(struct cpufreq_policy *unused,
191 const char *buf, size_t count)
195 ret = sscanf (buf, "%u", &input);
197 mutex_lock(&dbs_mutex);
198 if (ret != 1 || input > 100 || input >= dbs_tuners_ins.up_threshold) {
199 mutex_unlock(&dbs_mutex);
203 dbs_tuners_ins.down_threshold = input;
204 mutex_unlock(&dbs_mutex);
209 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
210 const char *buf, size_t count)
217 ret = sscanf (buf, "%u", &input);
224 mutex_lock(&dbs_mutex);
225 if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
226 mutex_unlock(&dbs_mutex);
229 dbs_tuners_ins.ignore_nice = input;
231 /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
232 for_each_online_cpu(j) {
233 struct cpu_dbs_info_s *j_dbs_info;
234 j_dbs_info = &per_cpu(cpu_dbs_info, j);
235 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
236 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
238 mutex_unlock(&dbs_mutex);
243 static ssize_t store_freq_step(struct cpufreq_policy *policy,
244 const char *buf, size_t count)
249 ret = sscanf (buf, "%u", &input);
257 /* no need to test here if freq_step is zero as the user might actually
258 * want this, they would be crazy though :) */
259 mutex_lock(&dbs_mutex);
260 dbs_tuners_ins.freq_step = input;
261 mutex_unlock(&dbs_mutex);
266 #define define_one_rw(_name) \
267 static struct freq_attr _name = \
268 __ATTR(_name, 0644, show_##_name, store_##_name)
270 define_one_rw(sampling_rate);
271 define_one_rw(sampling_down_factor);
272 define_one_rw(up_threshold);
273 define_one_rw(down_threshold);
274 define_one_rw(ignore_nice_load);
275 define_one_rw(freq_step);
277 static struct attribute * dbs_attributes[] = {
278 &sampling_rate_max.attr,
279 &sampling_rate_min.attr,
281 &sampling_down_factor.attr,
283 &down_threshold.attr,
284 &ignore_nice_load.attr,
289 static struct attribute_group dbs_attr_group = {
290 .attrs = dbs_attributes,
291 .name = "conservative",
294 /************************** sysfs end ************************/
296 static void dbs_check_cpu(int cpu)
298 unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;
299 unsigned int tmp_idle_ticks, total_idle_ticks;
300 unsigned int freq_step;
301 unsigned int freq_down_sampling_rate;
302 struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
303 struct cpufreq_policy *policy;
305 if (!this_dbs_info->enable)
308 policy = this_dbs_info->cur_policy;
311 * The default safe range is 20% to 80%
312 * Every sampling_rate, we check
313 * - If current idle time is less than 20%, then we try to
315 * Every sampling_rate*sampling_down_factor, we check
316 * - If current idle time is more than 80%, then we try to
319 * Any frequency increase takes it to the maximum frequency.
320 * Frequency reduction happens at minimum steps of
321 * 5% (default) of max_frequency
324 /* Check for frequency increase */
325 idle_ticks = UINT_MAX;
327 /* Check for frequency increase */
328 total_idle_ticks = get_cpu_idle_time(cpu);
329 tmp_idle_ticks = total_idle_ticks -
330 this_dbs_info->prev_cpu_idle_up;
331 this_dbs_info->prev_cpu_idle_up = total_idle_ticks;
333 if (tmp_idle_ticks < idle_ticks)
334 idle_ticks = tmp_idle_ticks;
336 /* Scale idle ticks by 100 and compare with up and down ticks */
338 up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
339 usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
341 if (idle_ticks < up_idle_ticks) {
342 this_dbs_info->down_skip = 0;
343 this_dbs_info->prev_cpu_idle_down =
344 this_dbs_info->prev_cpu_idle_up;
346 /* if we are already at full speed then break out early */
347 if (this_dbs_info->requested_freq == policy->max)
350 freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
352 /* max freq cannot be less than 100. But who knows.... */
353 if (unlikely(freq_step == 0))
356 this_dbs_info->requested_freq += freq_step;
357 if (this_dbs_info->requested_freq > policy->max)
358 this_dbs_info->requested_freq = policy->max;
360 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
365 /* Check for frequency decrease */
366 this_dbs_info->down_skip++;
367 if (this_dbs_info->down_skip < dbs_tuners_ins.sampling_down_factor)
370 /* Check for frequency decrease */
371 total_idle_ticks = this_dbs_info->prev_cpu_idle_up;
372 tmp_idle_ticks = total_idle_ticks -
373 this_dbs_info->prev_cpu_idle_down;
374 this_dbs_info->prev_cpu_idle_down = total_idle_ticks;
376 if (tmp_idle_ticks < idle_ticks)
377 idle_ticks = tmp_idle_ticks;
379 /* Scale idle ticks by 100 and compare with up and down ticks */
381 this_dbs_info->down_skip = 0;
383 freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
384 dbs_tuners_ins.sampling_down_factor;
385 down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) *
386 usecs_to_jiffies(freq_down_sampling_rate);
388 if (idle_ticks > down_idle_ticks) {
390 * if we are already at the lowest speed then break out early
391 * or if we 'cannot' reduce the speed as the user might want
392 * freq_step to be zero
394 if (this_dbs_info->requested_freq == policy->min
395 || dbs_tuners_ins.freq_step == 0)
398 freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
400 /* max freq cannot be less than 100. But who knows.... */
401 if (unlikely(freq_step == 0))
404 this_dbs_info->requested_freq -= freq_step;
405 if (this_dbs_info->requested_freq < policy->min)
406 this_dbs_info->requested_freq = policy->min;
408 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
414 static void do_dbs_timer(void *data)
417 mutex_lock(&dbs_mutex);
418 for_each_online_cpu(i)
420 schedule_delayed_work(&dbs_work,
421 usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
422 mutex_unlock(&dbs_mutex);
425 static inline void dbs_timer_init(void)
427 INIT_WORK(&dbs_work, do_dbs_timer, NULL);
428 schedule_delayed_work(&dbs_work,
429 usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
433 static inline void dbs_timer_exit(void)
435 cancel_delayed_work(&dbs_work);
439 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
442 unsigned int cpu = policy->cpu;
443 struct cpu_dbs_info_s *this_dbs_info;
446 this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
449 case CPUFREQ_GOV_START:
450 if ((!cpu_online(cpu)) ||
454 if (policy->cpuinfo.transition_latency >
455 (TRANSITION_LATENCY_LIMIT * 1000))
457 if (this_dbs_info->enable) /* Already enabled */
460 mutex_lock(&dbs_mutex);
461 for_each_cpu_mask(j, policy->cpus) {
462 struct cpu_dbs_info_s *j_dbs_info;
463 j_dbs_info = &per_cpu(cpu_dbs_info, j);
464 j_dbs_info->cur_policy = policy;
466 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(cpu);
467 j_dbs_info->prev_cpu_idle_down
468 = j_dbs_info->prev_cpu_idle_up;
470 this_dbs_info->enable = 1;
471 this_dbs_info->down_skip = 0;
472 this_dbs_info->requested_freq = policy->cur;
473 sysfs_create_group(&policy->kobj, &dbs_attr_group);
476 * Start the timerschedule work, when this governor
477 * is used for first time
479 if (dbs_enable == 1) {
480 unsigned int latency;
481 /* policy latency is in nS. Convert it to uS first */
482 latency = policy->cpuinfo.transition_latency / 1000;
486 def_sampling_rate = 10 * latency *
487 DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
489 if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
490 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
492 dbs_tuners_ins.sampling_rate = def_sampling_rate;
497 mutex_unlock(&dbs_mutex);
500 case CPUFREQ_GOV_STOP:
501 mutex_lock(&dbs_mutex);
502 this_dbs_info->enable = 0;
503 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
506 * Stop the timerschedule work, when this governor
507 * is used for first time
512 mutex_unlock(&dbs_mutex);
516 case CPUFREQ_GOV_LIMITS:
517 mutex_lock(&dbs_mutex);
518 if (policy->max < this_dbs_info->cur_policy->cur)
519 __cpufreq_driver_target(
520 this_dbs_info->cur_policy,
521 policy->max, CPUFREQ_RELATION_H);
522 else if (policy->min > this_dbs_info->cur_policy->cur)
523 __cpufreq_driver_target(
524 this_dbs_info->cur_policy,
525 policy->min, CPUFREQ_RELATION_L);
526 mutex_unlock(&dbs_mutex);
532 static struct cpufreq_governor cpufreq_gov_dbs = {
533 .name = "conservative",
534 .governor = cpufreq_governor_dbs,
535 .owner = THIS_MODULE,
538 static int __init cpufreq_gov_dbs_init(void)
540 return cpufreq_register_governor(&cpufreq_gov_dbs);
543 static void __exit cpufreq_gov_dbs_exit(void)
545 /* Make sure that the scheduled work is indeed not running */
546 flush_scheduled_work();
548 cpufreq_unregister_governor(&cpufreq_gov_dbs);
552 MODULE_AUTHOR ("Alexander Clouter <alex-kernel@digriz.org.uk>");
553 MODULE_DESCRIPTION ("'cpufreq_conservative' - A dynamic cpufreq governor for "
554 "Low Latency Frequency Transition capable processors "
555 "optimised for use in a battery environment");
556 MODULE_LICENSE ("GPL");
558 module_init(cpufreq_gov_dbs_init);
559 module_exit(cpufreq_gov_dbs_exit);