[CPUFREQ] conservative: remove 10x from def_sampling_rate
[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 static unsigned int def_sampling_rate;
46 #define MIN_SAMPLING_RATE_RATIO                 (2)
47 /* for correct statistics, we need at least 10 ticks between each measure */
48 #define MIN_STAT_SAMPLING_RATE                  \
49                         (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
50 #define MIN_SAMPLING_RATE                       \
51                         (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
52 /* Above MIN_SAMPLING_RATE will vanish with its sysfs file soon
53  * Define the minimal settable sampling rate to the greater of:
54  *   - "HW transition latency" * 100 (same as default sampling / 10)
55  *   - MIN_STAT_SAMPLING_RATE
56  * To avoid that userspace shoots itself.
57 */
58 static unsigned int minimum_sampling_rate(void)
59 {
60         return max(def_sampling_rate / 10, MIN_STAT_SAMPLING_RATE);
61 }
62
63 /* This will also vanish soon with removing sampling_rate_max */
64 #define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
65 #define LATENCY_MULTIPLIER                      (1000)
66 #define DEF_SAMPLING_DOWN_FACTOR                (1)
67 #define MAX_SAMPLING_DOWN_FACTOR                (10)
68 #define TRANSITION_LATENCY_LIMIT                (10 * 1000 * 1000)
69
70 static void do_dbs_timer(struct work_struct *work);
71
72 struct cpu_dbs_info_s {
73         cputime64_t prev_cpu_idle;
74         cputime64_t prev_cpu_wall;
75         cputime64_t prev_cpu_nice;
76         struct cpufreq_policy *cur_policy;
77         struct delayed_work work;
78         unsigned int down_skip;
79         unsigned int requested_freq;
80         int cpu;
81         unsigned int enable:1;
82 };
83 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
84
85 static unsigned int dbs_enable; /* number of CPUs using this policy */
86
87 /*
88  * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
89  * lock and dbs_mutex. cpu_hotplug lock should always be held before
90  * dbs_mutex. If any function that can potentially take cpu_hotplug lock
91  * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
92  * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
93  * is recursive for the same process. -Venki
94  */
95 static DEFINE_MUTEX(dbs_mutex);
96
97 static struct workqueue_struct  *kconservative_wq;
98
99 static struct dbs_tuners {
100         unsigned int sampling_rate;
101         unsigned int sampling_down_factor;
102         unsigned int up_threshold;
103         unsigned int down_threshold;
104         unsigned int ignore_nice;
105         unsigned int freq_step;
106 } dbs_tuners_ins = {
107         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
108         .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
109         .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
110         .ignore_nice = 0,
111         .freq_step = 5,
112 };
113
114 static inline cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu,
115                                                         cputime64_t *wall)
116 {
117         cputime64_t idle_time;
118         cputime64_t cur_wall_time;
119         cputime64_t busy_time;
120
121         cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
122         busy_time = cputime64_add(kstat_cpu(cpu).cpustat.user,
123                         kstat_cpu(cpu).cpustat.system);
124
125         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.irq);
126         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.softirq);
127         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.steal);
128         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.nice);
129
130         idle_time = cputime64_sub(cur_wall_time, busy_time);
131         if (wall)
132                 *wall = cur_wall_time;
133
134         return idle_time;
135 }
136
137 static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
138 {
139         u64 idle_time = get_cpu_idle_time_us(cpu, wall);
140
141         if (idle_time == -1ULL)
142                 return get_cpu_idle_time_jiffy(cpu, wall);
143
144         return idle_time;
145 }
146
147 /* keep track of frequency transitions */
148 static int
149 dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
150                      void *data)
151 {
152         struct cpufreq_freqs *freq = data;
153         struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info,
154                                                         freq->cpu);
155
156         struct cpufreq_policy *policy;
157
158         if (!this_dbs_info->enable)
159                 return 0;
160
161         policy = this_dbs_info->cur_policy;
162
163         /*
164          * we only care if our internally tracked freq moves outside
165          * the 'valid' ranges of freqency available to us otherwise
166          * we do not change it
167         */
168         if (this_dbs_info->requested_freq > policy->max
169                         || this_dbs_info->requested_freq < policy->min)
170                 this_dbs_info->requested_freq = freq->new;
171
172         return 0;
173 }
174
175 static struct notifier_block dbs_cpufreq_notifier_block = {
176         .notifier_call = dbs_cpufreq_notifier
177 };
178
179 /************************** sysfs interface ************************/
180 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
181 {
182         static int print_once;
183
184         if (!print_once) {
185                 printk(KERN_INFO "CPUFREQ: conservative sampling_rate_max "
186                        "sysfs file is deprecated - used by: %s\n",
187                        current->comm);
188                 print_once = 1;
189         }
190         return sprintf(buf, "%u\n", MAX_SAMPLING_RATE);
191 }
192
193 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
194 {
195         static int print_once;
196
197         if (!print_once) {
198                 printk(KERN_INFO "CPUFREQ: conservative sampling_rate_max "
199                        "sysfs file is deprecated - used by: %s\n", current->comm);
200                 print_once = 1;
201         }
202         return sprintf(buf, "%u\n", MIN_SAMPLING_RATE);
203 }
204
205 #define define_one_ro(_name)            \
206 static struct freq_attr _name =         \
207 __ATTR(_name, 0444, show_##_name, NULL)
208
209 define_one_ro(sampling_rate_max);
210 define_one_ro(sampling_rate_min);
211
212 /* cpufreq_conservative Governor Tunables */
213 #define show_one(file_name, object)                                     \
214 static ssize_t show_##file_name                                         \
215 (struct cpufreq_policy *unused, char *buf)                              \
216 {                                                                       \
217         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
218 }
219 show_one(sampling_rate, sampling_rate);
220 show_one(sampling_down_factor, sampling_down_factor);
221 show_one(up_threshold, up_threshold);
222 show_one(down_threshold, down_threshold);
223 show_one(ignore_nice_load, ignore_nice);
224 show_one(freq_step, freq_step);
225
226 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
227                 const char *buf, size_t count)
228 {
229         unsigned int input;
230         int ret;
231         ret = sscanf(buf, "%u", &input);
232
233         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
234                 return -EINVAL;
235
236         mutex_lock(&dbs_mutex);
237         dbs_tuners_ins.sampling_down_factor = input;
238         mutex_unlock(&dbs_mutex);
239
240         return count;
241 }
242
243 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
244                 const char *buf, size_t count)
245 {
246         unsigned int input;
247         int ret;
248         ret = sscanf(buf, "%u", &input);
249
250         if (ret != 1)
251                 return -EINVAL;
252
253         mutex_lock(&dbs_mutex);
254         dbs_tuners_ins.sampling_rate = max(input, minimum_sampling_rate());
255         mutex_unlock(&dbs_mutex);
256
257         return count;
258 }
259
260 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
261                 const char *buf, size_t count)
262 {
263         unsigned int input;
264         int ret;
265         ret = sscanf(buf, "%u", &input);
266
267         mutex_lock(&dbs_mutex);
268         if (ret != 1 || input > 100 ||
269                         input <= dbs_tuners_ins.down_threshold) {
270                 mutex_unlock(&dbs_mutex);
271                 return -EINVAL;
272         }
273
274         dbs_tuners_ins.up_threshold = input;
275         mutex_unlock(&dbs_mutex);
276
277         return count;
278 }
279
280 static ssize_t store_down_threshold(struct cpufreq_policy *unused,
281                 const char *buf, size_t count)
282 {
283         unsigned int input;
284         int ret;
285         ret = sscanf(buf, "%u", &input);
286
287         mutex_lock(&dbs_mutex);
288         /* cannot be lower than 11 otherwise freq will not fall */
289         if (ret != 1 || input < 11 || input > 100 ||
290                         input >= dbs_tuners_ins.up_threshold) {
291                 mutex_unlock(&dbs_mutex);
292                 return -EINVAL;
293         }
294
295         dbs_tuners_ins.down_threshold = input;
296         mutex_unlock(&dbs_mutex);
297
298         return count;
299 }
300
301 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
302                 const char *buf, size_t count)
303 {
304         unsigned int input;
305         int ret;
306
307         unsigned int j;
308
309         ret = sscanf(buf, "%u", &input);
310         if (ret != 1)
311                 return -EINVAL;
312
313         if (input > 1)
314                 input = 1;
315
316         mutex_lock(&dbs_mutex);
317         if (input == dbs_tuners_ins.ignore_nice) { /* nothing to do */
318                 mutex_unlock(&dbs_mutex);
319                 return count;
320         }
321         dbs_tuners_ins.ignore_nice = input;
322
323         /* we need to re-evaluate prev_cpu_idle */
324         for_each_online_cpu(j) {
325                 struct cpu_dbs_info_s *dbs_info;
326                 dbs_info = &per_cpu(cpu_dbs_info, j);
327                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
328                                                 &dbs_info->prev_cpu_wall);
329                 if (dbs_tuners_ins.ignore_nice)
330                         dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
331         }
332         mutex_unlock(&dbs_mutex);
333
334         return count;
335 }
336
337 static ssize_t store_freq_step(struct cpufreq_policy *policy,
338                 const char *buf, size_t count)
339 {
340         unsigned int input;
341         int ret;
342         ret = sscanf(buf, "%u", &input);
343
344         if (ret != 1)
345                 return -EINVAL;
346
347         if (input > 100)
348                 input = 100;
349
350         /* no need to test here if freq_step is zero as the user might actually
351          * want this, they would be crazy though :) */
352         mutex_lock(&dbs_mutex);
353         dbs_tuners_ins.freq_step = input;
354         mutex_unlock(&dbs_mutex);
355
356         return count;
357 }
358
359 #define define_one_rw(_name) \
360 static struct freq_attr _name = \
361 __ATTR(_name, 0644, show_##_name, store_##_name)
362
363 define_one_rw(sampling_rate);
364 define_one_rw(sampling_down_factor);
365 define_one_rw(up_threshold);
366 define_one_rw(down_threshold);
367 define_one_rw(ignore_nice_load);
368 define_one_rw(freq_step);
369
370 static struct attribute *dbs_attributes[] = {
371         &sampling_rate_max.attr,
372         &sampling_rate_min.attr,
373         &sampling_rate.attr,
374         &sampling_down_factor.attr,
375         &up_threshold.attr,
376         &down_threshold.attr,
377         &ignore_nice_load.attr,
378         &freq_step.attr,
379         NULL
380 };
381
382 static struct attribute_group dbs_attr_group = {
383         .attrs = dbs_attributes,
384         .name = "conservative",
385 };
386
387 /************************** sysfs end ************************/
388
389 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
390 {
391         unsigned int load = 0;
392         unsigned int freq_target;
393
394         struct cpufreq_policy *policy;
395         unsigned int j;
396
397         policy = this_dbs_info->cur_policy;
398
399         /*
400          * Every sampling_rate, we check, if current idle time is less
401          * than 20% (default), then we try to increase frequency
402          * Every sampling_rate*sampling_down_factor, we check, if current
403          * idle time is more than 80%, then we try to decrease frequency
404          *
405          * Any frequency increase takes it to the maximum frequency.
406          * Frequency reduction happens at minimum steps of
407          * 5% (default) of maximum frequency
408          */
409
410         /* Get Absolute Load */
411         for_each_cpu(j, policy->cpus) {
412                 struct cpu_dbs_info_s *j_dbs_info;
413                 cputime64_t cur_wall_time, cur_idle_time;
414                 unsigned int idle_time, wall_time;
415
416                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
417
418                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
419
420                 wall_time = (unsigned int) cputime64_sub(cur_wall_time,
421                                 j_dbs_info->prev_cpu_wall);
422                 j_dbs_info->prev_cpu_wall = cur_wall_time;
423
424                 idle_time = (unsigned int) cputime64_sub(cur_idle_time,
425                                 j_dbs_info->prev_cpu_idle);
426                 j_dbs_info->prev_cpu_idle = cur_idle_time;
427
428                 if (dbs_tuners_ins.ignore_nice) {
429                         cputime64_t cur_nice;
430                         unsigned long cur_nice_jiffies;
431
432                         cur_nice = cputime64_sub(kstat_cpu(j).cpustat.nice,
433                                          j_dbs_info->prev_cpu_nice);
434                         /*
435                          * Assumption: nice time between sampling periods will
436                          * be less than 2^32 jiffies for 32 bit sys
437                          */
438                         cur_nice_jiffies = (unsigned long)
439                                         cputime64_to_jiffies64(cur_nice);
440
441                         j_dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
442                         idle_time += jiffies_to_usecs(cur_nice_jiffies);
443                 }
444
445                 if (unlikely(!wall_time || wall_time < idle_time))
446                         continue;
447
448                 load = 100 * (wall_time - idle_time) / wall_time;
449         }
450
451         /*
452          * break out if we 'cannot' reduce the speed as the user might
453          * want freq_step to be zero
454          */
455         if (dbs_tuners_ins.freq_step == 0)
456                 return;
457
458         /* Check for frequency increase */
459         if (load > dbs_tuners_ins.up_threshold) {
460                 this_dbs_info->down_skip = 0;
461
462                 /* if we are already at full speed then break out early */
463                 if (this_dbs_info->requested_freq == policy->max)
464                         return;
465
466                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
467
468                 /* max freq cannot be less than 100. But who knows.... */
469                 if (unlikely(freq_target == 0))
470                         freq_target = 5;
471
472                 this_dbs_info->requested_freq += freq_target;
473                 if (this_dbs_info->requested_freq > policy->max)
474                         this_dbs_info->requested_freq = policy->max;
475
476                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
477                         CPUFREQ_RELATION_H);
478                 return;
479         }
480
481         /*
482          * The optimal frequency is the frequency that is the lowest that
483          * can support the current CPU usage without triggering the up
484          * policy. To be safe, we focus 10 points under the threshold.
485          */
486         if (load < (dbs_tuners_ins.down_threshold - 10)) {
487                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
488
489                 this_dbs_info->requested_freq -= freq_target;
490                 if (this_dbs_info->requested_freq < policy->min)
491                         this_dbs_info->requested_freq = policy->min;
492
493                 /*
494                  * if we cannot reduce the frequency anymore, break out early
495                  */
496                 if (policy->cur == policy->min)
497                         return;
498
499                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
500                                 CPUFREQ_RELATION_H);
501                 return;
502         }
503 }
504
505 static void do_dbs_timer(struct work_struct *work)
506 {
507         struct cpu_dbs_info_s *dbs_info =
508                 container_of(work, struct cpu_dbs_info_s, work.work);
509         unsigned int cpu = dbs_info->cpu;
510
511         /* We want all CPUs to do sampling nearly on same jiffy */
512         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
513
514         delay -= jiffies % delay;
515
516         if (lock_policy_rwsem_write(cpu) < 0)
517                 return;
518
519         if (!dbs_info->enable) {
520                 unlock_policy_rwsem_write(cpu);
521                 return;
522         }
523
524         dbs_check_cpu(dbs_info);
525
526         queue_delayed_work_on(cpu, kconservative_wq, &dbs_info->work, delay);
527         unlock_policy_rwsem_write(cpu);
528 }
529
530 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
531 {
532         /* We want all CPUs to do sampling nearly on same jiffy */
533         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
534         delay -= jiffies % delay;
535
536         dbs_info->enable = 1;
537         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
538         queue_delayed_work_on(dbs_info->cpu, kconservative_wq, &dbs_info->work,
539                                 delay);
540 }
541
542 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
543 {
544         dbs_info->enable = 0;
545         cancel_delayed_work(&dbs_info->work);
546 }
547
548 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
549                                    unsigned int event)
550 {
551         unsigned int cpu = policy->cpu;
552         struct cpu_dbs_info_s *this_dbs_info;
553         unsigned int j;
554         int rc;
555
556         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
557
558         switch (event) {
559         case CPUFREQ_GOV_START:
560                 if ((!cpu_online(cpu)) || (!policy->cur))
561                         return -EINVAL;
562
563                 if (this_dbs_info->enable) /* Already enabled */
564                         break;
565
566                 mutex_lock(&dbs_mutex);
567
568                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
569                 if (rc) {
570                         mutex_unlock(&dbs_mutex);
571                         return rc;
572                 }
573
574                 for_each_cpu(j, policy->cpus) {
575                         struct cpu_dbs_info_s *j_dbs_info;
576                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
577                         j_dbs_info->cur_policy = policy;
578
579                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
580                                                 &j_dbs_info->prev_cpu_wall);
581                         if (dbs_tuners_ins.ignore_nice) {
582                                 j_dbs_info->prev_cpu_nice =
583                                                 kstat_cpu(j).cpustat.nice;
584                         }
585                 }
586                 this_dbs_info->down_skip = 0;
587                 this_dbs_info->requested_freq = policy->cur;
588
589                 dbs_enable++;
590                 /*
591                  * Start the timerschedule work, when this governor
592                  * is used for first time
593                  */
594                 if (dbs_enable == 1) {
595                         unsigned int latency;
596                         /* policy latency is in nS. Convert it to uS first */
597                         latency = policy->cpuinfo.transition_latency / 1000;
598                         if (latency == 0)
599                                 latency = 1;
600
601                         def_sampling_rate =
602                                 max(latency * LATENCY_MULTIPLIER,
603                                     MIN_STAT_SAMPLING_RATE);
604
605                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
606
607                         cpufreq_register_notifier(
608                                         &dbs_cpufreq_notifier_block,
609                                         CPUFREQ_TRANSITION_NOTIFIER);
610                 }
611                 dbs_timer_init(this_dbs_info);
612
613                 mutex_unlock(&dbs_mutex);
614
615                 break;
616
617         case CPUFREQ_GOV_STOP:
618                 mutex_lock(&dbs_mutex);
619                 dbs_timer_exit(this_dbs_info);
620                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
621                 dbs_enable--;
622
623                 /*
624                  * Stop the timerschedule work, when this governor
625                  * is used for first time
626                  */
627                 if (dbs_enable == 0)
628                         cpufreq_unregister_notifier(
629                                         &dbs_cpufreq_notifier_block,
630                                         CPUFREQ_TRANSITION_NOTIFIER);
631
632                 mutex_unlock(&dbs_mutex);
633
634                 break;
635
636         case CPUFREQ_GOV_LIMITS:
637                 mutex_lock(&dbs_mutex);
638                 if (policy->max < this_dbs_info->cur_policy->cur)
639                         __cpufreq_driver_target(
640                                         this_dbs_info->cur_policy,
641                                         policy->max, CPUFREQ_RELATION_H);
642                 else if (policy->min > this_dbs_info->cur_policy->cur)
643                         __cpufreq_driver_target(
644                                         this_dbs_info->cur_policy,
645                                         policy->min, CPUFREQ_RELATION_L);
646                 mutex_unlock(&dbs_mutex);
647
648                 break;
649         }
650         return 0;
651 }
652
653 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
654 static
655 #endif
656 struct cpufreq_governor cpufreq_gov_conservative = {
657         .name                   = "conservative",
658         .governor               = cpufreq_governor_dbs,
659         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
660         .owner                  = THIS_MODULE,
661 };
662
663 static int __init cpufreq_gov_dbs_init(void)
664 {
665         int err;
666
667         kconservative_wq = create_workqueue("kconservative");
668         if (!kconservative_wq) {
669                 printk(KERN_ERR "Creation of kconservative failed\n");
670                 return -EFAULT;
671         }
672
673         err = cpufreq_register_governor(&cpufreq_gov_conservative);
674         if (err)
675                 destroy_workqueue(kconservative_wq);
676
677         return err;
678 }
679
680 static void __exit cpufreq_gov_dbs_exit(void)
681 {
682         cpufreq_unregister_governor(&cpufreq_gov_conservative);
683         destroy_workqueue(kconservative_wq);
684 }
685
686
687 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
688 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
689                 "Low Latency Frequency Transition capable processors "
690                 "optimised for use in a battery environment");
691 MODULE_LICENSE("GPL");
692
693 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
694 fs_initcall(cpufreq_gov_dbs_init);
695 #else
696 module_init(cpufreq_gov_dbs_init);
697 #endif
698 module_exit(cpufreq_gov_dbs_exit);