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[linux-2.6.git] / drivers / cpufreq / cpufreq_conservative.c
1 /*
2  *  drivers/cpufreq/cpufreq_conservative.c
3  *
4  *  Copyright (C)  2001 Russell King
5  *            (C)  2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
6  *                      Jun Nakajima <jun.nakajima@intel.com>
7  *            (C)  2009 Alexander Clouter <alex@digriz.org.uk>
8  *
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.
12  */
13
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/init.h>
17 #include <linux/cpufreq.h>
18 #include <linux/cpu.h>
19 #include <linux/jiffies.h>
20 #include <linux/kernel_stat.h>
21 #include <linux/mutex.h>
22 #include <linux/hrtimer.h>
23 #include <linux/tick.h>
24 #include <linux/ktime.h>
25 #include <linux/sched.h>
26
27 /*
28  * dbs is used in this file as a shortform for demandbased switching
29  * It helps to keep variable names smaller, simpler
30  */
31
32 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
33 #define DEF_FREQUENCY_DOWN_THRESHOLD            (20)
34
35 /*
36  * The polling frequency of this governor depends on the capability of
37  * the processor. Default polling frequency is 1000 times the transition
38  * latency of the processor. The governor will work on any processor with
39  * transition latency <= 10mS, using appropriate sampling
40  * rate.
41  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
42  * this governor will not work.
43  * All times here are in uS.
44  */
45 #define MIN_SAMPLING_RATE_RATIO                 (2)
46
47 static unsigned int min_sampling_rate;
48
49 #define LATENCY_MULTIPLIER                      (1000)
50 #define MIN_LATENCY_MULTIPLIER                  (100)
51 #define DEF_SAMPLING_DOWN_FACTOR                (1)
52 #define MAX_SAMPLING_DOWN_FACTOR                (10)
53 #define TRANSITION_LATENCY_LIMIT                (10 * 1000 * 1000)
54
55 static void do_dbs_timer(struct work_struct *work);
56
57 struct cpu_dbs_info_s {
58         cputime64_t prev_cpu_idle;
59         cputime64_t prev_cpu_wall;
60         cputime64_t prev_cpu_nice;
61         struct cpufreq_policy *cur_policy;
62         struct delayed_work work;
63         unsigned int down_skip;
64         unsigned int requested_freq;
65         int cpu;
66         unsigned int enable:1;
67         /*
68          * percpu mutex that serializes governor limit change with
69          * do_dbs_timer invocation. We do not want do_dbs_timer to run
70          * when user is changing the governor or limits.
71          */
72         struct mutex timer_mutex;
73 };
74 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cs_cpu_dbs_info);
75
76 static unsigned int dbs_enable; /* number of CPUs using this policy */
77
78 /*
79  * dbs_mutex protects dbs_enable in governor start/stop.
80  */
81 static DEFINE_MUTEX(dbs_mutex);
82
83 static struct dbs_tuners {
84         unsigned int sampling_rate;
85         unsigned int sampling_down_factor;
86         unsigned int up_threshold;
87         unsigned int down_threshold;
88         unsigned int ignore_nice;
89         unsigned int freq_step;
90 } dbs_tuners_ins = {
91         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
92         .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
93         .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
94         .ignore_nice = 0,
95         .freq_step = 5,
96 };
97
98 static inline cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu,
99                                                         cputime64_t *wall)
100 {
101         cputime64_t idle_time;
102         cputime64_t cur_wall_time;
103         cputime64_t busy_time;
104
105         cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
106         busy_time = cputime64_add(kstat_cpu(cpu).cpustat.user,
107                         kstat_cpu(cpu).cpustat.system);
108
109         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.irq);
110         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.softirq);
111         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.steal);
112         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.nice);
113
114         idle_time = cputime64_sub(cur_wall_time, busy_time);
115         if (wall)
116                 *wall = (cputime64_t)jiffies_to_usecs(cur_wall_time);
117
118         return (cputime64_t)jiffies_to_usecs(idle_time);
119 }
120
121 static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
122 {
123         u64 idle_time = get_cpu_idle_time_us(cpu, wall);
124
125         if (idle_time == -1ULL)
126                 return get_cpu_idle_time_jiffy(cpu, wall);
127
128         return idle_time;
129 }
130
131 /* keep track of frequency transitions */
132 static int
133 dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
134                      void *data)
135 {
136         struct cpufreq_freqs *freq = data;
137         struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cs_cpu_dbs_info,
138                                                         freq->cpu);
139
140         struct cpufreq_policy *policy;
141
142         if (!this_dbs_info->enable)
143                 return 0;
144
145         policy = this_dbs_info->cur_policy;
146
147         /*
148          * we only care if our internally tracked freq moves outside
149          * the 'valid' ranges of freqency available to us otherwise
150          * we do not change it
151         */
152         if (this_dbs_info->requested_freq > policy->max
153                         || this_dbs_info->requested_freq < policy->min)
154                 this_dbs_info->requested_freq = freq->new;
155
156         return 0;
157 }
158
159 static struct notifier_block dbs_cpufreq_notifier_block = {
160         .notifier_call = dbs_cpufreq_notifier
161 };
162
163 /************************** sysfs interface ************************/
164 static ssize_t show_sampling_rate_min(struct kobject *kobj,
165                                       struct attribute *attr, char *buf)
166 {
167         return sprintf(buf, "%u\n", min_sampling_rate);
168 }
169
170 define_one_global_ro(sampling_rate_min);
171
172 /* cpufreq_conservative Governor Tunables */
173 #define show_one(file_name, object)                                     \
174 static ssize_t show_##file_name                                         \
175 (struct kobject *kobj, struct attribute *attr, char *buf)               \
176 {                                                                       \
177         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
178 }
179 show_one(sampling_rate, sampling_rate);
180 show_one(sampling_down_factor, sampling_down_factor);
181 show_one(up_threshold, up_threshold);
182 show_one(down_threshold, down_threshold);
183 show_one(ignore_nice_load, ignore_nice);
184 show_one(freq_step, freq_step);
185
186 static ssize_t store_sampling_down_factor(struct kobject *a,
187                                           struct attribute *b,
188                                           const char *buf, size_t count)
189 {
190         unsigned int input;
191         int ret;
192         ret = sscanf(buf, "%u", &input);
193
194         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
195                 return -EINVAL;
196
197         dbs_tuners_ins.sampling_down_factor = input;
198         return count;
199 }
200
201 static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
202                                    const char *buf, size_t count)
203 {
204         unsigned int input;
205         int ret;
206         ret = sscanf(buf, "%u", &input);
207
208         if (ret != 1)
209                 return -EINVAL;
210
211         dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);
212         return count;
213 }
214
215 static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
216                                   const char *buf, size_t count)
217 {
218         unsigned int input;
219         int ret;
220         ret = sscanf(buf, "%u", &input);
221
222         if (ret != 1 || input > 100 ||
223                         input <= dbs_tuners_ins.down_threshold)
224                 return -EINVAL;
225
226         dbs_tuners_ins.up_threshold = input;
227         return count;
228 }
229
230 static ssize_t store_down_threshold(struct kobject *a, struct attribute *b,
231                                     const char *buf, size_t count)
232 {
233         unsigned int input;
234         int ret;
235         ret = sscanf(buf, "%u", &input);
236
237         /* cannot be lower than 11 otherwise freq will not fall */
238         if (ret != 1 || input < 11 || input > 100 ||
239                         input >= dbs_tuners_ins.up_threshold)
240                 return -EINVAL;
241
242         dbs_tuners_ins.down_threshold = input;
243         return count;
244 }
245
246 static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
247                                       const char *buf, size_t count)
248 {
249         unsigned int input;
250         int ret;
251
252         unsigned int j;
253
254         ret = sscanf(buf, "%u", &input);
255         if (ret != 1)
256                 return -EINVAL;
257
258         if (input > 1)
259                 input = 1;
260
261         if (input == dbs_tuners_ins.ignore_nice) /* nothing to do */
262                 return count;
263
264         dbs_tuners_ins.ignore_nice = input;
265
266         /* we need to re-evaluate prev_cpu_idle */
267         for_each_online_cpu(j) {
268                 struct cpu_dbs_info_s *dbs_info;
269                 dbs_info = &per_cpu(cs_cpu_dbs_info, j);
270                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
271                                                 &dbs_info->prev_cpu_wall);
272                 if (dbs_tuners_ins.ignore_nice)
273                         dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
274         }
275         return count;
276 }
277
278 static ssize_t store_freq_step(struct kobject *a, struct attribute *b,
279                                const char *buf, size_t count)
280 {
281         unsigned int input;
282         int ret;
283         ret = sscanf(buf, "%u", &input);
284
285         if (ret != 1)
286                 return -EINVAL;
287
288         if (input > 100)
289                 input = 100;
290
291         /* no need to test here if freq_step is zero as the user might actually
292          * want this, they would be crazy though :) */
293         dbs_tuners_ins.freq_step = input;
294         return count;
295 }
296
297 define_one_global_rw(sampling_rate);
298 define_one_global_rw(sampling_down_factor);
299 define_one_global_rw(up_threshold);
300 define_one_global_rw(down_threshold);
301 define_one_global_rw(ignore_nice_load);
302 define_one_global_rw(freq_step);
303
304 static struct attribute *dbs_attributes[] = {
305         &sampling_rate_min.attr,
306         &sampling_rate.attr,
307         &sampling_down_factor.attr,
308         &up_threshold.attr,
309         &down_threshold.attr,
310         &ignore_nice_load.attr,
311         &freq_step.attr,
312         NULL
313 };
314
315 static struct attribute_group dbs_attr_group = {
316         .attrs = dbs_attributes,
317         .name = "conservative",
318 };
319
320 /************************** sysfs end ************************/
321
322 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
323 {
324         unsigned int load = 0;
325         unsigned int max_load = 0;
326         unsigned int freq_target;
327
328         struct cpufreq_policy *policy;
329         unsigned int j;
330
331         policy = this_dbs_info->cur_policy;
332
333         /*
334          * Every sampling_rate, we check, if current idle time is less
335          * than 20% (default), then we try to increase frequency
336          * Every sampling_rate*sampling_down_factor, we check, if current
337          * idle time is more than 80%, then we try to decrease frequency
338          *
339          * Any frequency increase takes it to the maximum frequency.
340          * Frequency reduction happens at minimum steps of
341          * 5% (default) of maximum frequency
342          */
343
344         /* Get Absolute Load */
345         for_each_cpu(j, policy->cpus) {
346                 struct cpu_dbs_info_s *j_dbs_info;
347                 cputime64_t cur_wall_time, cur_idle_time;
348                 unsigned int idle_time, wall_time;
349
350                 j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
351
352                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
353
354                 wall_time = (unsigned int) cputime64_sub(cur_wall_time,
355                                 j_dbs_info->prev_cpu_wall);
356                 j_dbs_info->prev_cpu_wall = cur_wall_time;
357
358                 idle_time = (unsigned int) cputime64_sub(cur_idle_time,
359                                 j_dbs_info->prev_cpu_idle);
360                 j_dbs_info->prev_cpu_idle = cur_idle_time;
361
362                 if (dbs_tuners_ins.ignore_nice) {
363                         cputime64_t cur_nice;
364                         unsigned long cur_nice_jiffies;
365
366                         cur_nice = cputime64_sub(kstat_cpu(j).cpustat.nice,
367                                          j_dbs_info->prev_cpu_nice);
368                         /*
369                          * Assumption: nice time between sampling periods will
370                          * be less than 2^32 jiffies for 32 bit sys
371                          */
372                         cur_nice_jiffies = (unsigned long)
373                                         cputime64_to_jiffies64(cur_nice);
374
375                         j_dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
376                         idle_time += jiffies_to_usecs(cur_nice_jiffies);
377                 }
378
379                 if (unlikely(!wall_time || wall_time < idle_time))
380                         continue;
381
382                 load = 100 * (wall_time - idle_time) / wall_time;
383
384                 if (load > max_load)
385                         max_load = load;
386         }
387
388         /*
389          * break out if we 'cannot' reduce the speed as the user might
390          * want freq_step to be zero
391          */
392         if (dbs_tuners_ins.freq_step == 0)
393                 return;
394
395         /* Check for frequency increase */
396         if (max_load > dbs_tuners_ins.up_threshold) {
397                 this_dbs_info->down_skip = 0;
398
399                 /* if we are already at full speed then break out early */
400                 if (this_dbs_info->requested_freq == policy->max)
401                         return;
402
403                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
404
405                 /* max freq cannot be less than 100. But who knows.... */
406                 if (unlikely(freq_target == 0))
407                         freq_target = 5;
408
409                 this_dbs_info->requested_freq += freq_target;
410                 if (this_dbs_info->requested_freq > policy->max)
411                         this_dbs_info->requested_freq = policy->max;
412
413                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
414                         CPUFREQ_RELATION_H);
415                 return;
416         }
417
418         /*
419          * The optimal frequency is the frequency that is the lowest that
420          * can support the current CPU usage without triggering the up
421          * policy. To be safe, we focus 10 points under the threshold.
422          */
423         if (max_load < (dbs_tuners_ins.down_threshold - 10)) {
424                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
425
426                 this_dbs_info->requested_freq -= freq_target;
427                 if (this_dbs_info->requested_freq < policy->min)
428                         this_dbs_info->requested_freq = policy->min;
429
430                 /*
431                  * if we cannot reduce the frequency anymore, break out early
432                  */
433                 if (policy->cur == policy->min)
434                         return;
435
436                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
437                                 CPUFREQ_RELATION_H);
438                 return;
439         }
440 }
441
442 static void do_dbs_timer(struct work_struct *work)
443 {
444         struct cpu_dbs_info_s *dbs_info =
445                 container_of(work, struct cpu_dbs_info_s, work.work);
446         unsigned int cpu = dbs_info->cpu;
447
448         /* We want all CPUs to do sampling nearly on same jiffy */
449         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
450
451         delay -= jiffies % delay;
452
453         mutex_lock(&dbs_info->timer_mutex);
454
455         dbs_check_cpu(dbs_info);
456
457         schedule_delayed_work_on(cpu, &dbs_info->work, delay);
458         mutex_unlock(&dbs_info->timer_mutex);
459 }
460
461 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
462 {
463         /* We want all CPUs to do sampling nearly on same jiffy */
464         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
465         delay -= jiffies % delay;
466
467         dbs_info->enable = 1;
468         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
469         schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work, delay);
470 }
471
472 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
473 {
474         dbs_info->enable = 0;
475         cancel_delayed_work_sync(&dbs_info->work);
476 }
477
478 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
479                                    unsigned int event)
480 {
481         unsigned int cpu = policy->cpu;
482         struct cpu_dbs_info_s *this_dbs_info;
483         unsigned int j;
484         int rc;
485
486         this_dbs_info = &per_cpu(cs_cpu_dbs_info, cpu);
487
488         switch (event) {
489         case CPUFREQ_GOV_START:
490                 if ((!cpu_online(cpu)) || (!policy->cur))
491                         return -EINVAL;
492
493                 mutex_lock(&dbs_mutex);
494
495                 for_each_cpu(j, policy->cpus) {
496                         struct cpu_dbs_info_s *j_dbs_info;
497                         j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
498                         j_dbs_info->cur_policy = policy;
499
500                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
501                                                 &j_dbs_info->prev_cpu_wall);
502                         if (dbs_tuners_ins.ignore_nice) {
503                                 j_dbs_info->prev_cpu_nice =
504                                                 kstat_cpu(j).cpustat.nice;
505                         }
506                 }
507                 this_dbs_info->down_skip = 0;
508                 this_dbs_info->requested_freq = policy->cur;
509
510                 mutex_init(&this_dbs_info->timer_mutex);
511                 dbs_enable++;
512                 /*
513                  * Start the timerschedule work, when this governor
514                  * is used for first time
515                  */
516                 if (dbs_enable == 1) {
517                         unsigned int latency;
518                         /* policy latency is in nS. Convert it to uS first */
519                         latency = policy->cpuinfo.transition_latency / 1000;
520                         if (latency == 0)
521                                 latency = 1;
522
523                         rc = sysfs_create_group(cpufreq_global_kobject,
524                                                 &dbs_attr_group);
525                         if (rc) {
526                                 mutex_unlock(&dbs_mutex);
527                                 return rc;
528                         }
529
530                         /*
531                          * conservative does not implement micro like ondemand
532                          * governor, thus we are bound to jiffes/HZ
533                          */
534                         min_sampling_rate =
535                                 MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
536                         /* Bring kernel and HW constraints together */
537                         min_sampling_rate = max(min_sampling_rate,
538                                         MIN_LATENCY_MULTIPLIER * latency);
539                         dbs_tuners_ins.sampling_rate =
540                                 max(min_sampling_rate,
541                                     latency * LATENCY_MULTIPLIER);
542
543                         cpufreq_register_notifier(
544                                         &dbs_cpufreq_notifier_block,
545                                         CPUFREQ_TRANSITION_NOTIFIER);
546                 }
547                 mutex_unlock(&dbs_mutex);
548
549                 dbs_timer_init(this_dbs_info);
550
551                 break;
552
553         case CPUFREQ_GOV_STOP:
554                 dbs_timer_exit(this_dbs_info);
555
556                 mutex_lock(&dbs_mutex);
557                 dbs_enable--;
558                 mutex_destroy(&this_dbs_info->timer_mutex);
559
560                 /*
561                  * Stop the timerschedule work, when this governor
562                  * is used for first time
563                  */
564                 if (dbs_enable == 0)
565                         cpufreq_unregister_notifier(
566                                         &dbs_cpufreq_notifier_block,
567                                         CPUFREQ_TRANSITION_NOTIFIER);
568
569                 mutex_unlock(&dbs_mutex);
570                 if (!dbs_enable)
571                         sysfs_remove_group(cpufreq_global_kobject,
572                                            &dbs_attr_group);
573
574                 break;
575
576         case CPUFREQ_GOV_LIMITS:
577                 mutex_lock(&this_dbs_info->timer_mutex);
578                 if (policy->max < this_dbs_info->cur_policy->cur)
579                         __cpufreq_driver_target(
580                                         this_dbs_info->cur_policy,
581                                         policy->max, CPUFREQ_RELATION_H);
582                 else if (policy->min > this_dbs_info->cur_policy->cur)
583                         __cpufreq_driver_target(
584                                         this_dbs_info->cur_policy,
585                                         policy->min, CPUFREQ_RELATION_L);
586                 mutex_unlock(&this_dbs_info->timer_mutex);
587
588                 break;
589         }
590         return 0;
591 }
592
593 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
594 static
595 #endif
596 struct cpufreq_governor cpufreq_gov_conservative = {
597         .name                   = "conservative",
598         .governor               = cpufreq_governor_dbs,
599         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
600         .owner                  = THIS_MODULE,
601 };
602
603 static int __init cpufreq_gov_dbs_init(void)
604 {
605         return cpufreq_register_governor(&cpufreq_gov_conservative);
606 }
607
608 static void __exit cpufreq_gov_dbs_exit(void)
609 {
610         cpufreq_unregister_governor(&cpufreq_gov_conservative);
611 }
612
613
614 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
615 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
616                 "Low Latency Frequency Transition capable processors "
617                 "optimised for use in a battery environment");
618 MODULE_LICENSE("GPL");
619
620 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
621 fs_initcall(cpufreq_gov_dbs_init);
622 #else
623 module_init(cpufreq_gov_dbs_init);
624 #endif
625 module_exit(cpufreq_gov_dbs_exit);