Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6
[linux-2.6] / drivers / cpufreq / cpufreq_ondemand.c
1 /*
2  *  drivers/cpufreq/cpufreq_ondemand.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  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License version 2 as
10  * published by the Free Software Foundation.
11  */
12
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/init.h>
16 #include <linux/cpufreq.h>
17 #include <linux/cpu.h>
18 #include <linux/jiffies.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/mutex.h>
21 #include <linux/hrtimer.h>
22 #include <linux/tick.h>
23 #include <linux/ktime.h>
24
25 /*
26  * dbs is used in this file as a shortform for demandbased switching
27  * It helps to keep variable names smaller, simpler
28  */
29
30 #define DEF_FREQUENCY_DOWN_DIFFERENTIAL         (10)
31 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
32 #define MICRO_FREQUENCY_DOWN_DIFFERENTIAL       (3)
33 #define MICRO_FREQUENCY_UP_THRESHOLD            (95)
34 #define MIN_FREQUENCY_UP_THRESHOLD              (11)
35 #define MAX_FREQUENCY_UP_THRESHOLD              (100)
36
37 /*
38  * The polling frequency of this governor depends on the capability of
39  * the processor. Default polling frequency is 1000 times the transition
40  * latency of the processor. The governor will work on any processor with
41  * transition latency <= 10mS, using appropriate sampling
42  * rate.
43  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
44  * this governor will not work.
45  * All times here are in uS.
46  */
47 static unsigned int def_sampling_rate;
48 #define MIN_SAMPLING_RATE_RATIO                 (2)
49 /* for correct statistics, we need at least 10 ticks between each measure */
50 #define MIN_STAT_SAMPLING_RATE                  \
51                         (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
52 #define MIN_SAMPLING_RATE                       \
53                         (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
54 #define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
55 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (1000)
56 #define TRANSITION_LATENCY_LIMIT                (10 * 1000 * 1000)
57
58 static void do_dbs_timer(struct work_struct *work);
59
60 /* Sampling types */
61 enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE};
62
63 struct cpu_dbs_info_s {
64         cputime64_t prev_cpu_idle;
65         cputime64_t prev_cpu_wall;
66         cputime64_t prev_cpu_nice;
67         struct cpufreq_policy *cur_policy;
68         struct delayed_work work;
69         struct cpufreq_frequency_table *freq_table;
70         unsigned int freq_lo;
71         unsigned int freq_lo_jiffies;
72         unsigned int freq_hi_jiffies;
73         int cpu;
74         unsigned int enable:1,
75                      sample_type:1;
76 };
77 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
78
79 static unsigned int dbs_enable; /* number of CPUs using this policy */
80
81 /*
82  * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
83  * lock and dbs_mutex. cpu_hotplug lock should always be held before
84  * dbs_mutex. If any function that can potentially take cpu_hotplug lock
85  * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
86  * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
87  * is recursive for the same process. -Venki
88  */
89 static DEFINE_MUTEX(dbs_mutex);
90
91 static struct workqueue_struct  *kondemand_wq;
92
93 static struct dbs_tuners {
94         unsigned int sampling_rate;
95         unsigned int up_threshold;
96         unsigned int down_differential;
97         unsigned int ignore_nice;
98         unsigned int powersave_bias;
99 } dbs_tuners_ins = {
100         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
101         .down_differential = DEF_FREQUENCY_DOWN_DIFFERENTIAL,
102         .ignore_nice = 0,
103         .powersave_bias = 0,
104 };
105
106 static inline cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu,
107                                                         cputime64_t *wall)
108 {
109         cputime64_t idle_time;
110         cputime64_t cur_wall_time;
111         cputime64_t busy_time;
112
113         cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
114         busy_time = cputime64_add(kstat_cpu(cpu).cpustat.user,
115                         kstat_cpu(cpu).cpustat.system);
116
117         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.irq);
118         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.softirq);
119         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.steal);
120
121         if (!dbs_tuners_ins.ignore_nice) {
122                 busy_time = cputime64_add(busy_time,
123                                 kstat_cpu(cpu).cpustat.nice);
124         }
125
126         idle_time = cputime64_sub(cur_wall_time, busy_time);
127         if (wall)
128                 *wall = cur_wall_time;
129
130         return idle_time;
131 }
132
133 static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
134 {
135         u64 idle_time = get_cpu_idle_time_us(cpu, wall);
136
137         if (idle_time == -1ULL)
138                 return get_cpu_idle_time_jiffy(cpu, wall);
139
140         if (dbs_tuners_ins.ignore_nice) {
141                 cputime64_t cur_nice;
142                 unsigned long cur_nice_jiffies;
143                 struct cpu_dbs_info_s *dbs_info;
144
145                 dbs_info = &per_cpu(cpu_dbs_info, cpu);
146                 cur_nice = cputime64_sub(kstat_cpu(cpu).cpustat.nice,
147                                          dbs_info->prev_cpu_nice);
148                 /*
149                  * Assumption: nice time between sampling periods will be
150                  * less than 2^32 jiffies for 32 bit sys
151                  */
152                 cur_nice_jiffies = (unsigned long)
153                                         cputime64_to_jiffies64(cur_nice);
154                 dbs_info->prev_cpu_nice = kstat_cpu(cpu).cpustat.nice;
155                 return idle_time + jiffies_to_usecs(cur_nice_jiffies);
156         }
157         return idle_time;
158 }
159
160 /*
161  * Find right freq to be set now with powersave_bias on.
162  * Returns the freq_hi to be used right now and will set freq_hi_jiffies,
163  * freq_lo, and freq_lo_jiffies in percpu area for averaging freqs.
164  */
165 static unsigned int powersave_bias_target(struct cpufreq_policy *policy,
166                                           unsigned int freq_next,
167                                           unsigned int relation)
168 {
169         unsigned int freq_req, freq_reduc, freq_avg;
170         unsigned int freq_hi, freq_lo;
171         unsigned int index = 0;
172         unsigned int jiffies_total, jiffies_hi, jiffies_lo;
173         struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, policy->cpu);
174
175         if (!dbs_info->freq_table) {
176                 dbs_info->freq_lo = 0;
177                 dbs_info->freq_lo_jiffies = 0;
178                 return freq_next;
179         }
180
181         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_next,
182                         relation, &index);
183         freq_req = dbs_info->freq_table[index].frequency;
184         freq_reduc = freq_req * dbs_tuners_ins.powersave_bias / 1000;
185         freq_avg = freq_req - freq_reduc;
186
187         /* Find freq bounds for freq_avg in freq_table */
188         index = 0;
189         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
190                         CPUFREQ_RELATION_H, &index);
191         freq_lo = dbs_info->freq_table[index].frequency;
192         index = 0;
193         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
194                         CPUFREQ_RELATION_L, &index);
195         freq_hi = dbs_info->freq_table[index].frequency;
196
197         /* Find out how long we have to be in hi and lo freqs */
198         if (freq_hi == freq_lo) {
199                 dbs_info->freq_lo = 0;
200                 dbs_info->freq_lo_jiffies = 0;
201                 return freq_lo;
202         }
203         jiffies_total = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
204         jiffies_hi = (freq_avg - freq_lo) * jiffies_total;
205         jiffies_hi += ((freq_hi - freq_lo) / 2);
206         jiffies_hi /= (freq_hi - freq_lo);
207         jiffies_lo = jiffies_total - jiffies_hi;
208         dbs_info->freq_lo = freq_lo;
209         dbs_info->freq_lo_jiffies = jiffies_lo;
210         dbs_info->freq_hi_jiffies = jiffies_hi;
211         return freq_hi;
212 }
213
214 static void ondemand_powersave_bias_init(void)
215 {
216         int i;
217         for_each_online_cpu(i) {
218                 struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, i);
219                 dbs_info->freq_table = cpufreq_frequency_get_table(i);
220                 dbs_info->freq_lo = 0;
221         }
222 }
223
224 /************************** sysfs interface ************************/
225 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
226 {
227         return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
228 }
229
230 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
231 {
232         return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
233 }
234
235 #define define_one_ro(_name)            \
236 static struct freq_attr _name =         \
237 __ATTR(_name, 0444, show_##_name, NULL)
238
239 define_one_ro(sampling_rate_max);
240 define_one_ro(sampling_rate_min);
241
242 /* cpufreq_ondemand Governor Tunables */
243 #define show_one(file_name, object)                                     \
244 static ssize_t show_##file_name                                         \
245 (struct cpufreq_policy *unused, char *buf)                              \
246 {                                                                       \
247         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
248 }
249 show_one(sampling_rate, sampling_rate);
250 show_one(up_threshold, up_threshold);
251 show_one(ignore_nice_load, ignore_nice);
252 show_one(powersave_bias, powersave_bias);
253
254 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
255                 const char *buf, size_t count)
256 {
257         unsigned int input;
258         int ret;
259         ret = sscanf(buf, "%u", &input);
260
261         mutex_lock(&dbs_mutex);
262         if (ret != 1 || input > MAX_SAMPLING_RATE
263                      || input < MIN_SAMPLING_RATE) {
264                 mutex_unlock(&dbs_mutex);
265                 return -EINVAL;
266         }
267
268         dbs_tuners_ins.sampling_rate = input;
269         mutex_unlock(&dbs_mutex);
270
271         return count;
272 }
273
274 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
275                 const char *buf, size_t count)
276 {
277         unsigned int input;
278         int ret;
279         ret = sscanf(buf, "%u", &input);
280
281         mutex_lock(&dbs_mutex);
282         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
283                         input < MIN_FREQUENCY_UP_THRESHOLD) {
284                 mutex_unlock(&dbs_mutex);
285                 return -EINVAL;
286         }
287
288         dbs_tuners_ins.up_threshold = input;
289         mutex_unlock(&dbs_mutex);
290
291         return count;
292 }
293
294 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
295                 const char *buf, size_t count)
296 {
297         unsigned int input;
298         int ret;
299
300         unsigned int j;
301
302         ret = sscanf(buf, "%u", &input);
303         if ( ret != 1 )
304                 return -EINVAL;
305
306         if ( input > 1 )
307                 input = 1;
308
309         mutex_lock(&dbs_mutex);
310         if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
311                 mutex_unlock(&dbs_mutex);
312                 return count;
313         }
314         dbs_tuners_ins.ignore_nice = input;
315
316         /* we need to re-evaluate prev_cpu_idle */
317         for_each_online_cpu(j) {
318                 struct cpu_dbs_info_s *dbs_info;
319                 dbs_info = &per_cpu(cpu_dbs_info, j);
320                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
321                                                 &dbs_info->prev_cpu_wall);
322         }
323         mutex_unlock(&dbs_mutex);
324
325         return count;
326 }
327
328 static ssize_t store_powersave_bias(struct cpufreq_policy *unused,
329                 const char *buf, size_t count)
330 {
331         unsigned int input;
332         int ret;
333         ret = sscanf(buf, "%u", &input);
334
335         if (ret != 1)
336                 return -EINVAL;
337
338         if (input > 1000)
339                 input = 1000;
340
341         mutex_lock(&dbs_mutex);
342         dbs_tuners_ins.powersave_bias = input;
343         ondemand_powersave_bias_init();
344         mutex_unlock(&dbs_mutex);
345
346         return count;
347 }
348
349 #define define_one_rw(_name) \
350 static struct freq_attr _name = \
351 __ATTR(_name, 0644, show_##_name, store_##_name)
352
353 define_one_rw(sampling_rate);
354 define_one_rw(up_threshold);
355 define_one_rw(ignore_nice_load);
356 define_one_rw(powersave_bias);
357
358 static struct attribute * dbs_attributes[] = {
359         &sampling_rate_max.attr,
360         &sampling_rate_min.attr,
361         &sampling_rate.attr,
362         &up_threshold.attr,
363         &ignore_nice_load.attr,
364         &powersave_bias.attr,
365         NULL
366 };
367
368 static struct attribute_group dbs_attr_group = {
369         .attrs = dbs_attributes,
370         .name = "ondemand",
371 };
372
373 /************************** sysfs end ************************/
374
375 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
376 {
377         unsigned int max_load_freq;
378
379         struct cpufreq_policy *policy;
380         unsigned int j;
381
382         if (!this_dbs_info->enable)
383                 return;
384
385         this_dbs_info->freq_lo = 0;
386         policy = this_dbs_info->cur_policy;
387
388         /*
389          * Every sampling_rate, we check, if current idle time is less
390          * than 20% (default), then we try to increase frequency
391          * Every sampling_rate, we look for a the lowest
392          * frequency which can sustain the load while keeping idle time over
393          * 30%. If such a frequency exist, we try to decrease to this frequency.
394          *
395          * Any frequency increase takes it to the maximum frequency.
396          * Frequency reduction happens at minimum steps of
397          * 5% (default) of current frequency
398          */
399
400         /* Get Absolute Load - in terms of freq */
401         max_load_freq = 0;
402
403         for_each_cpu_mask_nr(j, policy->cpus) {
404                 struct cpu_dbs_info_s *j_dbs_info;
405                 cputime64_t cur_wall_time, cur_idle_time;
406                 unsigned int idle_time, wall_time;
407                 unsigned int load, load_freq;
408                 int freq_avg;
409
410                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
411
412                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
413
414                 wall_time = (unsigned int) cputime64_sub(cur_wall_time,
415                                 j_dbs_info->prev_cpu_wall);
416                 j_dbs_info->prev_cpu_wall = cur_wall_time;
417
418                 idle_time = (unsigned int) cputime64_sub(cur_idle_time,
419                                 j_dbs_info->prev_cpu_idle);
420                 j_dbs_info->prev_cpu_idle = cur_idle_time;
421
422                 if (unlikely(!wall_time || wall_time < idle_time))
423                         continue;
424
425                 load = 100 * (wall_time - idle_time) / wall_time;
426
427                 freq_avg = __cpufreq_driver_getavg(policy, j);
428                 if (freq_avg <= 0)
429                         freq_avg = policy->cur;
430
431                 load_freq = load * freq_avg;
432                 if (load_freq > max_load_freq)
433                         max_load_freq = load_freq;
434         }
435
436         /* Check for frequency increase */
437         if (max_load_freq > dbs_tuners_ins.up_threshold * policy->cur) {
438                 /* if we are already at full speed then break out early */
439                 if (!dbs_tuners_ins.powersave_bias) {
440                         if (policy->cur == policy->max)
441                                 return;
442
443                         __cpufreq_driver_target(policy, policy->max,
444                                 CPUFREQ_RELATION_H);
445                 } else {
446                         int freq = powersave_bias_target(policy, policy->max,
447                                         CPUFREQ_RELATION_H);
448                         __cpufreq_driver_target(policy, freq,
449                                 CPUFREQ_RELATION_L);
450                 }
451                 return;
452         }
453
454         /* Check for frequency decrease */
455         /* if we cannot reduce the frequency anymore, break out early */
456         if (policy->cur == policy->min)
457                 return;
458
459         /*
460          * The optimal frequency is the frequency that is the lowest that
461          * can support the current CPU usage without triggering the up
462          * policy. To be safe, we focus 10 points under the threshold.
463          */
464         if (max_load_freq <
465             (dbs_tuners_ins.up_threshold - dbs_tuners_ins.down_differential) *
466              policy->cur) {
467                 unsigned int freq_next;
468                 freq_next = max_load_freq /
469                                 (dbs_tuners_ins.up_threshold -
470                                  dbs_tuners_ins.down_differential);
471
472                 if (!dbs_tuners_ins.powersave_bias) {
473                         __cpufreq_driver_target(policy, freq_next,
474                                         CPUFREQ_RELATION_L);
475                 } else {
476                         int freq = powersave_bias_target(policy, freq_next,
477                                         CPUFREQ_RELATION_L);
478                         __cpufreq_driver_target(policy, freq,
479                                 CPUFREQ_RELATION_L);
480                 }
481         }
482 }
483
484 static void do_dbs_timer(struct work_struct *work)
485 {
486         struct cpu_dbs_info_s *dbs_info =
487                 container_of(work, struct cpu_dbs_info_s, work.work);
488         unsigned int cpu = dbs_info->cpu;
489         int sample_type = dbs_info->sample_type;
490
491         /* We want all CPUs to do sampling nearly on same jiffy */
492         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
493
494         delay -= jiffies % delay;
495
496         if (lock_policy_rwsem_write(cpu) < 0)
497                 return;
498
499         if (!dbs_info->enable) {
500                 unlock_policy_rwsem_write(cpu);
501                 return;
502         }
503
504         /* Common NORMAL_SAMPLE setup */
505         dbs_info->sample_type = DBS_NORMAL_SAMPLE;
506         if (!dbs_tuners_ins.powersave_bias ||
507             sample_type == DBS_NORMAL_SAMPLE) {
508                 dbs_check_cpu(dbs_info);
509                 if (dbs_info->freq_lo) {
510                         /* Setup timer for SUB_SAMPLE */
511                         dbs_info->sample_type = DBS_SUB_SAMPLE;
512                         delay = dbs_info->freq_hi_jiffies;
513                 }
514         } else {
515                 __cpufreq_driver_target(dbs_info->cur_policy,
516                                         dbs_info->freq_lo,
517                                         CPUFREQ_RELATION_H);
518         }
519         queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
520         unlock_policy_rwsem_write(cpu);
521 }
522
523 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
524 {
525         /* We want all CPUs to do sampling nearly on same jiffy */
526         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
527         delay -= jiffies % delay;
528
529         dbs_info->enable = 1;
530         ondemand_powersave_bias_init();
531         dbs_info->sample_type = DBS_NORMAL_SAMPLE;
532         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
533         queue_delayed_work_on(dbs_info->cpu, kondemand_wq, &dbs_info->work,
534                               delay);
535 }
536
537 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
538 {
539         dbs_info->enable = 0;
540         cancel_delayed_work(&dbs_info->work);
541 }
542
543 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
544                                    unsigned int event)
545 {
546         unsigned int cpu = policy->cpu;
547         struct cpu_dbs_info_s *this_dbs_info;
548         unsigned int j;
549         int rc;
550
551         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
552
553         switch (event) {
554         case CPUFREQ_GOV_START:
555                 if ((!cpu_online(cpu)) || (!policy->cur))
556                         return -EINVAL;
557
558                 if (this_dbs_info->enable) /* Already enabled */
559                         break;
560
561                 mutex_lock(&dbs_mutex);
562                 dbs_enable++;
563
564                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
565                 if (rc) {
566                         dbs_enable--;
567                         mutex_unlock(&dbs_mutex);
568                         return rc;
569                 }
570
571                 for_each_cpu_mask_nr(j, policy->cpus) {
572                         struct cpu_dbs_info_s *j_dbs_info;
573                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
574                         j_dbs_info->cur_policy = policy;
575
576                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
577                                                 &j_dbs_info->prev_cpu_wall);
578                 }
579                 this_dbs_info->cpu = cpu;
580                 /*
581                  * Start the timerschedule work, when this governor
582                  * is used for first time
583                  */
584                 if (dbs_enable == 1) {
585                         unsigned int latency;
586                         /* policy latency is in nS. Convert it to uS first */
587                         latency = policy->cpuinfo.transition_latency / 1000;
588                         if (latency == 0)
589                                 latency = 1;
590
591                         def_sampling_rate = latency *
592                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
593
594                         if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
595                                 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
596
597                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
598                 }
599                 dbs_timer_init(this_dbs_info);
600
601                 mutex_unlock(&dbs_mutex);
602                 break;
603
604         case CPUFREQ_GOV_STOP:
605                 mutex_lock(&dbs_mutex);
606                 dbs_timer_exit(this_dbs_info);
607                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
608                 dbs_enable--;
609                 mutex_unlock(&dbs_mutex);
610
611                 break;
612
613         case CPUFREQ_GOV_LIMITS:
614                 mutex_lock(&dbs_mutex);
615                 if (policy->max < this_dbs_info->cur_policy->cur)
616                         __cpufreq_driver_target(this_dbs_info->cur_policy,
617                                                 policy->max,
618                                                 CPUFREQ_RELATION_H);
619                 else if (policy->min > this_dbs_info->cur_policy->cur)
620                         __cpufreq_driver_target(this_dbs_info->cur_policy,
621                                                 policy->min,
622                                                 CPUFREQ_RELATION_L);
623                 mutex_unlock(&dbs_mutex);
624                 break;
625         }
626         return 0;
627 }
628
629 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
630 static
631 #endif
632 struct cpufreq_governor cpufreq_gov_ondemand = {
633         .name                   = "ondemand",
634         .governor               = cpufreq_governor_dbs,
635         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
636         .owner                  = THIS_MODULE,
637 };
638
639 static int __init cpufreq_gov_dbs_init(void)
640 {
641         int err;
642         cputime64_t wall;
643         u64 idle_time;
644         int cpu = get_cpu();
645
646         idle_time = get_cpu_idle_time_us(cpu, &wall);
647         put_cpu();
648         if (idle_time != -1ULL) {
649                 /* Idle micro accounting is supported. Use finer thresholds */
650                 dbs_tuners_ins.up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
651                 dbs_tuners_ins.down_differential =
652                                         MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
653         }
654
655         kondemand_wq = create_workqueue("kondemand");
656         if (!kondemand_wq) {
657                 printk(KERN_ERR "Creation of kondemand failed\n");
658                 return -EFAULT;
659         }
660         err = cpufreq_register_governor(&cpufreq_gov_ondemand);
661         if (err)
662                 destroy_workqueue(kondemand_wq);
663
664         return err;
665 }
666
667 static void __exit cpufreq_gov_dbs_exit(void)
668 {
669         cpufreq_unregister_governor(&cpufreq_gov_ondemand);
670         destroy_workqueue(kondemand_wq);
671 }
672
673
674 MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
675 MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
676 MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
677                    "Low Latency Frequency Transition capable processors");
678 MODULE_LICENSE("GPL");
679
680 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
681 fs_initcall(cpufreq_gov_dbs_init);
682 #else
683 module_init(cpufreq_gov_dbs_init);
684 #endif
685 module_exit(cpufreq_gov_dbs_exit);