[CPUFREQ] fix BUG on cpufreq policy init failure
[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 data in dbs_tuners_ins from concurrent changes on
80  * different CPUs. It protects dbs_enable in governor start/stop.
81  */
82 static DEFINE_MUTEX(dbs_mutex);
83
84 static struct workqueue_struct  *kconservative_wq;
85
86 static struct dbs_tuners {
87         unsigned int sampling_rate;
88         unsigned int sampling_down_factor;
89         unsigned int up_threshold;
90         unsigned int down_threshold;
91         unsigned int ignore_nice;
92         unsigned int freq_step;
93 } dbs_tuners_ins = {
94         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
95         .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
96         .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
97         .ignore_nice = 0,
98         .freq_step = 5,
99 };
100
101 static inline cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu,
102                                                         cputime64_t *wall)
103 {
104         cputime64_t idle_time;
105         cputime64_t cur_wall_time;
106         cputime64_t busy_time;
107
108         cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
109         busy_time = cputime64_add(kstat_cpu(cpu).cpustat.user,
110                         kstat_cpu(cpu).cpustat.system);
111
112         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.irq);
113         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.softirq);
114         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.steal);
115         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.nice);
116
117         idle_time = cputime64_sub(cur_wall_time, busy_time);
118         if (wall)
119                 *wall = (cputime64_t)jiffies_to_usecs(cur_wall_time);
120
121         return (cputime64_t)jiffies_to_usecs(idle_time);;
122 }
123
124 static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
125 {
126         u64 idle_time = get_cpu_idle_time_us(cpu, wall);
127
128         if (idle_time == -1ULL)
129                 return get_cpu_idle_time_jiffy(cpu, wall);
130
131         return idle_time;
132 }
133
134 /* keep track of frequency transitions */
135 static int
136 dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
137                      void *data)
138 {
139         struct cpufreq_freqs *freq = data;
140         struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cs_cpu_dbs_info,
141                                                         freq->cpu);
142
143         struct cpufreq_policy *policy;
144
145         if (!this_dbs_info->enable)
146                 return 0;
147
148         policy = this_dbs_info->cur_policy;
149
150         /*
151          * we only care if our internally tracked freq moves outside
152          * the 'valid' ranges of freqency available to us otherwise
153          * we do not change it
154         */
155         if (this_dbs_info->requested_freq > policy->max
156                         || this_dbs_info->requested_freq < policy->min)
157                 this_dbs_info->requested_freq = freq->new;
158
159         return 0;
160 }
161
162 static struct notifier_block dbs_cpufreq_notifier_block = {
163         .notifier_call = dbs_cpufreq_notifier
164 };
165
166 /************************** sysfs interface ************************/
167 static ssize_t show_sampling_rate_max(struct kobject *kobj,
168                                       struct attribute *attr, char *buf)
169 {
170         printk_once(KERN_INFO "CPUFREQ: conservative sampling_rate_max "
171                     "sysfs file is deprecated - used by: %s\n", current->comm);
172         return sprintf(buf, "%u\n", -1U);
173 }
174
175 static ssize_t show_sampling_rate_min(struct kobject *kobj,
176                                       struct attribute *attr, char *buf)
177 {
178         return sprintf(buf, "%u\n", min_sampling_rate);
179 }
180
181 define_one_global_ro(sampling_rate_max);
182 define_one_global_ro(sampling_rate_min);
183
184 /* cpufreq_conservative Governor Tunables */
185 #define show_one(file_name, object)                                     \
186 static ssize_t show_##file_name                                         \
187 (struct kobject *kobj, struct attribute *attr, char *buf)               \
188 {                                                                       \
189         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
190 }
191 show_one(sampling_rate, sampling_rate);
192 show_one(sampling_down_factor, sampling_down_factor);
193 show_one(up_threshold, up_threshold);
194 show_one(down_threshold, down_threshold);
195 show_one(ignore_nice_load, ignore_nice);
196 show_one(freq_step, freq_step);
197
198 /*** delete after deprecation time ***/
199 #define DEPRECATION_MSG(file_name)                                      \
200         printk_once(KERN_INFO "CPUFREQ: Per core conservative sysfs "   \
201                 "interface is deprecated - " #file_name "\n");
202
203 #define show_one_old(file_name)                                         \
204 static ssize_t show_##file_name##_old                                   \
205 (struct cpufreq_policy *unused, char *buf)                              \
206 {                                                                       \
207         printk_once(KERN_INFO "CPUFREQ: Per core conservative sysfs "   \
208                 "interface is deprecated - " #file_name "\n");          \
209         return show_##file_name(NULL, NULL, buf);                       \
210 }
211 show_one_old(sampling_rate);
212 show_one_old(sampling_down_factor);
213 show_one_old(up_threshold);
214 show_one_old(down_threshold);
215 show_one_old(ignore_nice_load);
216 show_one_old(freq_step);
217 show_one_old(sampling_rate_min);
218 show_one_old(sampling_rate_max);
219
220 cpufreq_freq_attr_ro_old(sampling_rate_min);
221 cpufreq_freq_attr_ro_old(sampling_rate_max);
222
223 /*** delete after deprecation time ***/
224
225 static ssize_t store_sampling_down_factor(struct kobject *a,
226                                           struct attribute *b,
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 kobject *a, struct attribute *b,
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, min_sampling_rate);
255         mutex_unlock(&dbs_mutex);
256
257         return count;
258 }
259
260 static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
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 kobject *a, struct attribute *b,
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 kobject *a, struct attribute *b,
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(cs_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 kobject *a, struct attribute *b,
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_one_global_rw(sampling_rate);
360 define_one_global_rw(sampling_down_factor);
361 define_one_global_rw(up_threshold);
362 define_one_global_rw(down_threshold);
363 define_one_global_rw(ignore_nice_load);
364 define_one_global_rw(freq_step);
365
366 static struct attribute *dbs_attributes[] = {
367         &sampling_rate_max.attr,
368         &sampling_rate_min.attr,
369         &sampling_rate.attr,
370         &sampling_down_factor.attr,
371         &up_threshold.attr,
372         &down_threshold.attr,
373         &ignore_nice_load.attr,
374         &freq_step.attr,
375         NULL
376 };
377
378 static struct attribute_group dbs_attr_group = {
379         .attrs = dbs_attributes,
380         .name = "conservative",
381 };
382
383 /*** delete after deprecation time ***/
384
385 #define write_one_old(file_name)                                        \
386 static ssize_t store_##file_name##_old                                  \
387 (struct cpufreq_policy *unused, const char *buf, size_t count)          \
388 {                                                                       \
389         printk_once(KERN_INFO "CPUFREQ: Per core conservative sysfs "   \
390                 "interface is deprecated - " #file_name "\n");  \
391         return store_##file_name(NULL, NULL, buf, count);               \
392 }
393 write_one_old(sampling_rate);
394 write_one_old(sampling_down_factor);
395 write_one_old(up_threshold);
396 write_one_old(down_threshold);
397 write_one_old(ignore_nice_load);
398 write_one_old(freq_step);
399
400 cpufreq_freq_attr_rw_old(sampling_rate);
401 cpufreq_freq_attr_rw_old(sampling_down_factor);
402 cpufreq_freq_attr_rw_old(up_threshold);
403 cpufreq_freq_attr_rw_old(down_threshold);
404 cpufreq_freq_attr_rw_old(ignore_nice_load);
405 cpufreq_freq_attr_rw_old(freq_step);
406
407 static struct attribute *dbs_attributes_old[] = {
408         &sampling_rate_max_old.attr,
409         &sampling_rate_min_old.attr,
410         &sampling_rate_old.attr,
411         &sampling_down_factor_old.attr,
412         &up_threshold_old.attr,
413         &down_threshold_old.attr,
414         &ignore_nice_load_old.attr,
415         &freq_step_old.attr,
416         NULL
417 };
418
419 static struct attribute_group dbs_attr_group_old = {
420         .attrs = dbs_attributes_old,
421         .name = "conservative",
422 };
423
424 /*** delete after deprecation time ***/
425
426 /************************** sysfs end ************************/
427
428 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
429 {
430         unsigned int load = 0;
431         unsigned int max_load = 0;
432         unsigned int freq_target;
433
434         struct cpufreq_policy *policy;
435         unsigned int j;
436
437         policy = this_dbs_info->cur_policy;
438
439         /*
440          * Every sampling_rate, we check, if current idle time is less
441          * than 20% (default), then we try to increase frequency
442          * Every sampling_rate*sampling_down_factor, we check, if current
443          * idle time is more than 80%, then we try to decrease frequency
444          *
445          * Any frequency increase takes it to the maximum frequency.
446          * Frequency reduction happens at minimum steps of
447          * 5% (default) of maximum frequency
448          */
449
450         /* Get Absolute Load */
451         for_each_cpu(j, policy->cpus) {
452                 struct cpu_dbs_info_s *j_dbs_info;
453                 cputime64_t cur_wall_time, cur_idle_time;
454                 unsigned int idle_time, wall_time;
455
456                 j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
457
458                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
459
460                 wall_time = (unsigned int) cputime64_sub(cur_wall_time,
461                                 j_dbs_info->prev_cpu_wall);
462                 j_dbs_info->prev_cpu_wall = cur_wall_time;
463
464                 idle_time = (unsigned int) cputime64_sub(cur_idle_time,
465                                 j_dbs_info->prev_cpu_idle);
466                 j_dbs_info->prev_cpu_idle = cur_idle_time;
467
468                 if (dbs_tuners_ins.ignore_nice) {
469                         cputime64_t cur_nice;
470                         unsigned long cur_nice_jiffies;
471
472                         cur_nice = cputime64_sub(kstat_cpu(j).cpustat.nice,
473                                          j_dbs_info->prev_cpu_nice);
474                         /*
475                          * Assumption: nice time between sampling periods will
476                          * be less than 2^32 jiffies for 32 bit sys
477                          */
478                         cur_nice_jiffies = (unsigned long)
479                                         cputime64_to_jiffies64(cur_nice);
480
481                         j_dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
482                         idle_time += jiffies_to_usecs(cur_nice_jiffies);
483                 }
484
485                 if (unlikely(!wall_time || wall_time < idle_time))
486                         continue;
487
488                 load = 100 * (wall_time - idle_time) / wall_time;
489
490                 if (load > max_load)
491                         max_load = load;
492         }
493
494         /*
495          * break out if we 'cannot' reduce the speed as the user might
496          * want freq_step to be zero
497          */
498         if (dbs_tuners_ins.freq_step == 0)
499                 return;
500
501         /* Check for frequency increase */
502         if (max_load > dbs_tuners_ins.up_threshold) {
503                 this_dbs_info->down_skip = 0;
504
505                 /* if we are already at full speed then break out early */
506                 if (this_dbs_info->requested_freq == policy->max)
507                         return;
508
509                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
510
511                 /* max freq cannot be less than 100. But who knows.... */
512                 if (unlikely(freq_target == 0))
513                         freq_target = 5;
514
515                 this_dbs_info->requested_freq += freq_target;
516                 if (this_dbs_info->requested_freq > policy->max)
517                         this_dbs_info->requested_freq = policy->max;
518
519                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
520                         CPUFREQ_RELATION_H);
521                 return;
522         }
523
524         /*
525          * The optimal frequency is the frequency that is the lowest that
526          * can support the current CPU usage without triggering the up
527          * policy. To be safe, we focus 10 points under the threshold.
528          */
529         if (max_load < (dbs_tuners_ins.down_threshold - 10)) {
530                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
531
532                 this_dbs_info->requested_freq -= freq_target;
533                 if (this_dbs_info->requested_freq < policy->min)
534                         this_dbs_info->requested_freq = policy->min;
535
536                 /*
537                  * if we cannot reduce the frequency anymore, break out early
538                  */
539                 if (policy->cur == policy->min)
540                         return;
541
542                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
543                                 CPUFREQ_RELATION_H);
544                 return;
545         }
546 }
547
548 static void do_dbs_timer(struct work_struct *work)
549 {
550         struct cpu_dbs_info_s *dbs_info =
551                 container_of(work, struct cpu_dbs_info_s, work.work);
552         unsigned int cpu = dbs_info->cpu;
553
554         /* We want all CPUs to do sampling nearly on same jiffy */
555         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
556
557         delay -= jiffies % delay;
558
559         mutex_lock(&dbs_info->timer_mutex);
560
561         dbs_check_cpu(dbs_info);
562
563         queue_delayed_work_on(cpu, kconservative_wq, &dbs_info->work, delay);
564         mutex_unlock(&dbs_info->timer_mutex);
565 }
566
567 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
568 {
569         /* We want all CPUs to do sampling nearly on same jiffy */
570         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
571         delay -= jiffies % delay;
572
573         dbs_info->enable = 1;
574         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
575         queue_delayed_work_on(dbs_info->cpu, kconservative_wq, &dbs_info->work,
576                                 delay);
577 }
578
579 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
580 {
581         dbs_info->enable = 0;
582         cancel_delayed_work_sync(&dbs_info->work);
583 }
584
585 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
586                                    unsigned int event)
587 {
588         unsigned int cpu = policy->cpu;
589         struct cpu_dbs_info_s *this_dbs_info;
590         unsigned int j;
591         int rc;
592
593         this_dbs_info = &per_cpu(cs_cpu_dbs_info, cpu);
594
595         switch (event) {
596         case CPUFREQ_GOV_START:
597                 if ((!cpu_online(cpu)) || (!policy->cur))
598                         return -EINVAL;
599
600                 mutex_lock(&dbs_mutex);
601
602                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group_old);
603                 if (rc) {
604                         mutex_unlock(&dbs_mutex);
605                         return rc;
606                 }
607
608                 for_each_cpu(j, policy->cpus) {
609                         struct cpu_dbs_info_s *j_dbs_info;
610                         j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
611                         j_dbs_info->cur_policy = policy;
612
613                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
614                                                 &j_dbs_info->prev_cpu_wall);
615                         if (dbs_tuners_ins.ignore_nice) {
616                                 j_dbs_info->prev_cpu_nice =
617                                                 kstat_cpu(j).cpustat.nice;
618                         }
619                 }
620                 this_dbs_info->down_skip = 0;
621                 this_dbs_info->requested_freq = policy->cur;
622
623                 mutex_init(&this_dbs_info->timer_mutex);
624                 dbs_enable++;
625                 /*
626                  * Start the timerschedule work, when this governor
627                  * is used for first time
628                  */
629                 if (dbs_enable == 1) {
630                         unsigned int latency;
631                         /* policy latency is in nS. Convert it to uS first */
632                         latency = policy->cpuinfo.transition_latency / 1000;
633                         if (latency == 0)
634                                 latency = 1;
635
636                         rc = sysfs_create_group(cpufreq_global_kobject,
637                                                 &dbs_attr_group);
638                         if (rc) {
639                                 mutex_unlock(&dbs_mutex);
640                                 return rc;
641                         }
642
643                         /*
644                          * conservative does not implement micro like ondemand
645                          * governor, thus we are bound to jiffes/HZ
646                          */
647                         min_sampling_rate =
648                                 MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
649                         /* Bring kernel and HW constraints together */
650                         min_sampling_rate = max(min_sampling_rate,
651                                         MIN_LATENCY_MULTIPLIER * latency);
652                         dbs_tuners_ins.sampling_rate =
653                                 max(min_sampling_rate,
654                                     latency * LATENCY_MULTIPLIER);
655
656                         cpufreq_register_notifier(
657                                         &dbs_cpufreq_notifier_block,
658                                         CPUFREQ_TRANSITION_NOTIFIER);
659                 }
660                 mutex_unlock(&dbs_mutex);
661
662                 dbs_timer_init(this_dbs_info);
663
664                 break;
665
666         case CPUFREQ_GOV_STOP:
667                 dbs_timer_exit(this_dbs_info);
668
669                 mutex_lock(&dbs_mutex);
670                 sysfs_remove_group(&policy->kobj, &dbs_attr_group_old);
671                 dbs_enable--;
672                 mutex_destroy(&this_dbs_info->timer_mutex);
673
674                 /*
675                  * Stop the timerschedule work, when this governor
676                  * is used for first time
677                  */
678                 if (dbs_enable == 0)
679                         cpufreq_unregister_notifier(
680                                         &dbs_cpufreq_notifier_block,
681                                         CPUFREQ_TRANSITION_NOTIFIER);
682
683                 mutex_unlock(&dbs_mutex);
684                 if (!dbs_enable)
685                         sysfs_remove_group(cpufreq_global_kobject,
686                                            &dbs_attr_group);
687
688                 break;
689
690         case CPUFREQ_GOV_LIMITS:
691                 mutex_lock(&this_dbs_info->timer_mutex);
692                 if (policy->max < this_dbs_info->cur_policy->cur)
693                         __cpufreq_driver_target(
694                                         this_dbs_info->cur_policy,
695                                         policy->max, CPUFREQ_RELATION_H);
696                 else if (policy->min > this_dbs_info->cur_policy->cur)
697                         __cpufreq_driver_target(
698                                         this_dbs_info->cur_policy,
699                                         policy->min, CPUFREQ_RELATION_L);
700                 mutex_unlock(&this_dbs_info->timer_mutex);
701
702                 break;
703         }
704         return 0;
705 }
706
707 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
708 static
709 #endif
710 struct cpufreq_governor cpufreq_gov_conservative = {
711         .name                   = "conservative",
712         .governor               = cpufreq_governor_dbs,
713         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
714         .owner                  = THIS_MODULE,
715 };
716
717 static int __init cpufreq_gov_dbs_init(void)
718 {
719         int err;
720
721         kconservative_wq = create_workqueue("kconservative");
722         if (!kconservative_wq) {
723                 printk(KERN_ERR "Creation of kconservative failed\n");
724                 return -EFAULT;
725         }
726
727         err = cpufreq_register_governor(&cpufreq_gov_conservative);
728         if (err)
729                 destroy_workqueue(kconservative_wq);
730
731         return err;
732 }
733
734 static void __exit cpufreq_gov_dbs_exit(void)
735 {
736         cpufreq_unregister_governor(&cpufreq_gov_conservative);
737         destroy_workqueue(kconservative_wq);
738 }
739
740
741 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
742 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
743                 "Low Latency Frequency Transition capable processors "
744                 "optimised for use in a battery environment");
745 MODULE_LICENSE("GPL");
746
747 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
748 fs_initcall(cpufreq_gov_dbs_init);
749 #else
750 module_init(cpufreq_gov_dbs_init);
751 #endif
752 module_exit(cpufreq_gov_dbs_exit);