Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...
[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 define_one_ro(_name)            \
182 static struct global_attr _name =       \
183 __ATTR(_name, 0444, show_##_name, NULL)
184
185 define_one_ro(sampling_rate_max);
186 define_one_ro(sampling_rate_min);
187
188 /* cpufreq_conservative Governor Tunables */
189 #define show_one(file_name, object)                                     \
190 static ssize_t show_##file_name                                         \
191 (struct kobject *kobj, struct attribute *attr, char *buf)               \
192 {                                                                       \
193         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
194 }
195 show_one(sampling_rate, sampling_rate);
196 show_one(sampling_down_factor, sampling_down_factor);
197 show_one(up_threshold, up_threshold);
198 show_one(down_threshold, down_threshold);
199 show_one(ignore_nice_load, ignore_nice);
200 show_one(freq_step, freq_step);
201
202 /*** delete after deprecation time ***/
203 #define DEPRECATION_MSG(file_name)                                      \
204         printk_once(KERN_INFO "CPUFREQ: Per core conservative sysfs "   \
205                 "interface is deprecated - " #file_name "\n");
206
207 #define show_one_old(file_name)                                         \
208 static ssize_t show_##file_name##_old                                   \
209 (struct cpufreq_policy *unused, char *buf)                              \
210 {                                                                       \
211         printk_once(KERN_INFO "CPUFREQ: Per core conservative sysfs "   \
212                 "interface is deprecated - " #file_name "\n");          \
213         return show_##file_name(NULL, NULL, buf);                       \
214 }
215 show_one_old(sampling_rate);
216 show_one_old(sampling_down_factor);
217 show_one_old(up_threshold);
218 show_one_old(down_threshold);
219 show_one_old(ignore_nice_load);
220 show_one_old(freq_step);
221 show_one_old(sampling_rate_min);
222 show_one_old(sampling_rate_max);
223
224 #define define_one_ro_old(object, _name)        \
225 static struct freq_attr object =                \
226 __ATTR(_name, 0444, show_##_name##_old, NULL)
227
228 define_one_ro_old(sampling_rate_min_old, sampling_rate_min);
229 define_one_ro_old(sampling_rate_max_old, sampling_rate_max);
230
231 /*** delete after deprecation time ***/
232
233 static ssize_t store_sampling_down_factor(struct kobject *a,
234                                           struct attribute *b,
235                                           const char *buf, size_t count)
236 {
237         unsigned int input;
238         int ret;
239         ret = sscanf(buf, "%u", &input);
240
241         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
242                 return -EINVAL;
243
244         mutex_lock(&dbs_mutex);
245         dbs_tuners_ins.sampling_down_factor = input;
246         mutex_unlock(&dbs_mutex);
247
248         return count;
249 }
250
251 static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
252                                    const char *buf, size_t count)
253 {
254         unsigned int input;
255         int ret;
256         ret = sscanf(buf, "%u", &input);
257
258         if (ret != 1)
259                 return -EINVAL;
260
261         mutex_lock(&dbs_mutex);
262         dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);
263         mutex_unlock(&dbs_mutex);
264
265         return count;
266 }
267
268 static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
269                                   const char *buf, size_t count)
270 {
271         unsigned int input;
272         int ret;
273         ret = sscanf(buf, "%u", &input);
274
275         mutex_lock(&dbs_mutex);
276         if (ret != 1 || input > 100 ||
277                         input <= dbs_tuners_ins.down_threshold) {
278                 mutex_unlock(&dbs_mutex);
279                 return -EINVAL;
280         }
281
282         dbs_tuners_ins.up_threshold = input;
283         mutex_unlock(&dbs_mutex);
284
285         return count;
286 }
287
288 static ssize_t store_down_threshold(struct kobject *a, struct attribute *b,
289                                     const char *buf, size_t count)
290 {
291         unsigned int input;
292         int ret;
293         ret = sscanf(buf, "%u", &input);
294
295         mutex_lock(&dbs_mutex);
296         /* cannot be lower than 11 otherwise freq will not fall */
297         if (ret != 1 || input < 11 || input > 100 ||
298                         input >= dbs_tuners_ins.up_threshold) {
299                 mutex_unlock(&dbs_mutex);
300                 return -EINVAL;
301         }
302
303         dbs_tuners_ins.down_threshold = input;
304         mutex_unlock(&dbs_mutex);
305
306         return count;
307 }
308
309 static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
310                                       const char *buf, size_t count)
311 {
312         unsigned int input;
313         int ret;
314
315         unsigned int j;
316
317         ret = sscanf(buf, "%u", &input);
318         if (ret != 1)
319                 return -EINVAL;
320
321         if (input > 1)
322                 input = 1;
323
324         mutex_lock(&dbs_mutex);
325         if (input == dbs_tuners_ins.ignore_nice) { /* nothing to do */
326                 mutex_unlock(&dbs_mutex);
327                 return count;
328         }
329         dbs_tuners_ins.ignore_nice = input;
330
331         /* we need to re-evaluate prev_cpu_idle */
332         for_each_online_cpu(j) {
333                 struct cpu_dbs_info_s *dbs_info;
334                 dbs_info = &per_cpu(cs_cpu_dbs_info, j);
335                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
336                                                 &dbs_info->prev_cpu_wall);
337                 if (dbs_tuners_ins.ignore_nice)
338                         dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
339         }
340         mutex_unlock(&dbs_mutex);
341
342         return count;
343 }
344
345 static ssize_t store_freq_step(struct kobject *a, struct attribute *b,
346                                const char *buf, size_t count)
347 {
348         unsigned int input;
349         int ret;
350         ret = sscanf(buf, "%u", &input);
351
352         if (ret != 1)
353                 return -EINVAL;
354
355         if (input > 100)
356                 input = 100;
357
358         /* no need to test here if freq_step is zero as the user might actually
359          * want this, they would be crazy though :) */
360         mutex_lock(&dbs_mutex);
361         dbs_tuners_ins.freq_step = input;
362         mutex_unlock(&dbs_mutex);
363
364         return count;
365 }
366
367 #define define_one_rw(_name) \
368 static struct global_attr _name = \
369 __ATTR(_name, 0644, show_##_name, store_##_name)
370
371 define_one_rw(sampling_rate);
372 define_one_rw(sampling_down_factor);
373 define_one_rw(up_threshold);
374 define_one_rw(down_threshold);
375 define_one_rw(ignore_nice_load);
376 define_one_rw(freq_step);
377
378 static struct attribute *dbs_attributes[] = {
379         &sampling_rate_max.attr,
380         &sampling_rate_min.attr,
381         &sampling_rate.attr,
382         &sampling_down_factor.attr,
383         &up_threshold.attr,
384         &down_threshold.attr,
385         &ignore_nice_load.attr,
386         &freq_step.attr,
387         NULL
388 };
389
390 static struct attribute_group dbs_attr_group = {
391         .attrs = dbs_attributes,
392         .name = "conservative",
393 };
394
395 /*** delete after deprecation time ***/
396
397 #define write_one_old(file_name)                                        \
398 static ssize_t store_##file_name##_old                                  \
399 (struct cpufreq_policy *unused, const char *buf, size_t count)          \
400 {                                                                       \
401         printk_once(KERN_INFO "CPUFREQ: Per core conservative sysfs "   \
402                 "interface is deprecated - " #file_name "\n");  \
403         return store_##file_name(NULL, NULL, buf, count);               \
404 }
405 write_one_old(sampling_rate);
406 write_one_old(sampling_down_factor);
407 write_one_old(up_threshold);
408 write_one_old(down_threshold);
409 write_one_old(ignore_nice_load);
410 write_one_old(freq_step);
411
412 #define define_one_rw_old(object, _name)        \
413 static struct freq_attr object =                \
414 __ATTR(_name, 0644, show_##_name##_old, store_##_name##_old)
415
416 define_one_rw_old(sampling_rate_old, sampling_rate);
417 define_one_rw_old(sampling_down_factor_old, sampling_down_factor);
418 define_one_rw_old(up_threshold_old, up_threshold);
419 define_one_rw_old(down_threshold_old, down_threshold);
420 define_one_rw_old(ignore_nice_load_old, ignore_nice_load);
421 define_one_rw_old(freq_step_old, freq_step);
422
423 static struct attribute *dbs_attributes_old[] = {
424         &sampling_rate_max_old.attr,
425         &sampling_rate_min_old.attr,
426         &sampling_rate_old.attr,
427         &sampling_down_factor_old.attr,
428         &up_threshold_old.attr,
429         &down_threshold_old.attr,
430         &ignore_nice_load_old.attr,
431         &freq_step_old.attr,
432         NULL
433 };
434
435 static struct attribute_group dbs_attr_group_old = {
436         .attrs = dbs_attributes_old,
437         .name = "conservative",
438 };
439
440 /*** delete after deprecation time ***/
441
442 /************************** sysfs end ************************/
443
444 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
445 {
446         unsigned int load = 0;
447         unsigned int freq_target;
448
449         struct cpufreq_policy *policy;
450         unsigned int j;
451
452         policy = this_dbs_info->cur_policy;
453
454         /*
455          * Every sampling_rate, we check, if current idle time is less
456          * than 20% (default), then we try to increase frequency
457          * Every sampling_rate*sampling_down_factor, we check, if current
458          * idle time is more than 80%, then we try to decrease frequency
459          *
460          * Any frequency increase takes it to the maximum frequency.
461          * Frequency reduction happens at minimum steps of
462          * 5% (default) of maximum frequency
463          */
464
465         /* Get Absolute Load */
466         for_each_cpu(j, policy->cpus) {
467                 struct cpu_dbs_info_s *j_dbs_info;
468                 cputime64_t cur_wall_time, cur_idle_time;
469                 unsigned int idle_time, wall_time;
470
471                 j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
472
473                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
474
475                 wall_time = (unsigned int) cputime64_sub(cur_wall_time,
476                                 j_dbs_info->prev_cpu_wall);
477                 j_dbs_info->prev_cpu_wall = cur_wall_time;
478
479                 idle_time = (unsigned int) cputime64_sub(cur_idle_time,
480                                 j_dbs_info->prev_cpu_idle);
481                 j_dbs_info->prev_cpu_idle = cur_idle_time;
482
483                 if (dbs_tuners_ins.ignore_nice) {
484                         cputime64_t cur_nice;
485                         unsigned long cur_nice_jiffies;
486
487                         cur_nice = cputime64_sub(kstat_cpu(j).cpustat.nice,
488                                          j_dbs_info->prev_cpu_nice);
489                         /*
490                          * Assumption: nice time between sampling periods will
491                          * be less than 2^32 jiffies for 32 bit sys
492                          */
493                         cur_nice_jiffies = (unsigned long)
494                                         cputime64_to_jiffies64(cur_nice);
495
496                         j_dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
497                         idle_time += jiffies_to_usecs(cur_nice_jiffies);
498                 }
499
500                 if (unlikely(!wall_time || wall_time < idle_time))
501                         continue;
502
503                 load = 100 * (wall_time - idle_time) / wall_time;
504         }
505
506         /*
507          * break out if we 'cannot' reduce the speed as the user might
508          * want freq_step to be zero
509          */
510         if (dbs_tuners_ins.freq_step == 0)
511                 return;
512
513         /* Check for frequency increase */
514         if (load > dbs_tuners_ins.up_threshold) {
515                 this_dbs_info->down_skip = 0;
516
517                 /* if we are already at full speed then break out early */
518                 if (this_dbs_info->requested_freq == policy->max)
519                         return;
520
521                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
522
523                 /* max freq cannot be less than 100. But who knows.... */
524                 if (unlikely(freq_target == 0))
525                         freq_target = 5;
526
527                 this_dbs_info->requested_freq += freq_target;
528                 if (this_dbs_info->requested_freq > policy->max)
529                         this_dbs_info->requested_freq = policy->max;
530
531                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
532                         CPUFREQ_RELATION_H);
533                 return;
534         }
535
536         /*
537          * The optimal frequency is the frequency that is the lowest that
538          * can support the current CPU usage without triggering the up
539          * policy. To be safe, we focus 10 points under the threshold.
540          */
541         if (load < (dbs_tuners_ins.down_threshold - 10)) {
542                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
543
544                 this_dbs_info->requested_freq -= freq_target;
545                 if (this_dbs_info->requested_freq < policy->min)
546                         this_dbs_info->requested_freq = policy->min;
547
548                 /*
549                  * if we cannot reduce the frequency anymore, break out early
550                  */
551                 if (policy->cur == policy->min)
552                         return;
553
554                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
555                                 CPUFREQ_RELATION_H);
556                 return;
557         }
558 }
559
560 static void do_dbs_timer(struct work_struct *work)
561 {
562         struct cpu_dbs_info_s *dbs_info =
563                 container_of(work, struct cpu_dbs_info_s, work.work);
564         unsigned int cpu = dbs_info->cpu;
565
566         /* We want all CPUs to do sampling nearly on same jiffy */
567         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
568
569         delay -= jiffies % delay;
570
571         mutex_lock(&dbs_info->timer_mutex);
572
573         dbs_check_cpu(dbs_info);
574
575         queue_delayed_work_on(cpu, kconservative_wq, &dbs_info->work, delay);
576         mutex_unlock(&dbs_info->timer_mutex);
577 }
578
579 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
580 {
581         /* We want all CPUs to do sampling nearly on same jiffy */
582         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
583         delay -= jiffies % delay;
584
585         dbs_info->enable = 1;
586         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
587         queue_delayed_work_on(dbs_info->cpu, kconservative_wq, &dbs_info->work,
588                                 delay);
589 }
590
591 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
592 {
593         dbs_info->enable = 0;
594         cancel_delayed_work_sync(&dbs_info->work);
595 }
596
597 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
598                                    unsigned int event)
599 {
600         unsigned int cpu = policy->cpu;
601         struct cpu_dbs_info_s *this_dbs_info;
602         unsigned int j;
603         int rc;
604
605         this_dbs_info = &per_cpu(cs_cpu_dbs_info, cpu);
606
607         switch (event) {
608         case CPUFREQ_GOV_START:
609                 if ((!cpu_online(cpu)) || (!policy->cur))
610                         return -EINVAL;
611
612                 mutex_lock(&dbs_mutex);
613
614                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group_old);
615                 if (rc) {
616                         mutex_unlock(&dbs_mutex);
617                         return rc;
618                 }
619
620                 for_each_cpu(j, policy->cpus) {
621                         struct cpu_dbs_info_s *j_dbs_info;
622                         j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
623                         j_dbs_info->cur_policy = policy;
624
625                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
626                                                 &j_dbs_info->prev_cpu_wall);
627                         if (dbs_tuners_ins.ignore_nice) {
628                                 j_dbs_info->prev_cpu_nice =
629                                                 kstat_cpu(j).cpustat.nice;
630                         }
631                 }
632                 this_dbs_info->down_skip = 0;
633                 this_dbs_info->requested_freq = policy->cur;
634
635                 mutex_init(&this_dbs_info->timer_mutex);
636                 dbs_enable++;
637                 /*
638                  * Start the timerschedule work, when this governor
639                  * is used for first time
640                  */
641                 if (dbs_enable == 1) {
642                         unsigned int latency;
643                         /* policy latency is in nS. Convert it to uS first */
644                         latency = policy->cpuinfo.transition_latency / 1000;
645                         if (latency == 0)
646                                 latency = 1;
647
648                         rc = sysfs_create_group(cpufreq_global_kobject,
649                                                 &dbs_attr_group);
650                         if (rc) {
651                                 mutex_unlock(&dbs_mutex);
652                                 return rc;
653                         }
654
655                         /*
656                          * conservative does not implement micro like ondemand
657                          * governor, thus we are bound to jiffes/HZ
658                          */
659                         min_sampling_rate =
660                                 MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
661                         /* Bring kernel and HW constraints together */
662                         min_sampling_rate = max(min_sampling_rate,
663                                         MIN_LATENCY_MULTIPLIER * latency);
664                         dbs_tuners_ins.sampling_rate =
665                                 max(min_sampling_rate,
666                                     latency * LATENCY_MULTIPLIER);
667
668                         cpufreq_register_notifier(
669                                         &dbs_cpufreq_notifier_block,
670                                         CPUFREQ_TRANSITION_NOTIFIER);
671                 }
672                 mutex_unlock(&dbs_mutex);
673
674                 dbs_timer_init(this_dbs_info);
675
676                 break;
677
678         case CPUFREQ_GOV_STOP:
679                 dbs_timer_exit(this_dbs_info);
680
681                 mutex_lock(&dbs_mutex);
682                 sysfs_remove_group(&policy->kobj, &dbs_attr_group_old);
683                 dbs_enable--;
684                 mutex_destroy(&this_dbs_info->timer_mutex);
685
686                 /*
687                  * Stop the timerschedule work, when this governor
688                  * is used for first time
689                  */
690                 if (dbs_enable == 0)
691                         cpufreq_unregister_notifier(
692                                         &dbs_cpufreq_notifier_block,
693                                         CPUFREQ_TRANSITION_NOTIFIER);
694
695                 mutex_unlock(&dbs_mutex);
696                 if (!dbs_enable)
697                         sysfs_remove_group(cpufreq_global_kobject,
698                                            &dbs_attr_group);
699
700                 break;
701
702         case CPUFREQ_GOV_LIMITS:
703                 mutex_lock(&this_dbs_info->timer_mutex);
704                 if (policy->max < this_dbs_info->cur_policy->cur)
705                         __cpufreq_driver_target(
706                                         this_dbs_info->cur_policy,
707                                         policy->max, CPUFREQ_RELATION_H);
708                 else if (policy->min > this_dbs_info->cur_policy->cur)
709                         __cpufreq_driver_target(
710                                         this_dbs_info->cur_policy,
711                                         policy->min, CPUFREQ_RELATION_L);
712                 mutex_unlock(&this_dbs_info->timer_mutex);
713
714                 break;
715         }
716         return 0;
717 }
718
719 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
720 static
721 #endif
722 struct cpufreq_governor cpufreq_gov_conservative = {
723         .name                   = "conservative",
724         .governor               = cpufreq_governor_dbs,
725         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
726         .owner                  = THIS_MODULE,
727 };
728
729 static int __init cpufreq_gov_dbs_init(void)
730 {
731         int err;
732
733         kconservative_wq = create_workqueue("kconservative");
734         if (!kconservative_wq) {
735                 printk(KERN_ERR "Creation of kconservative failed\n");
736                 return -EFAULT;
737         }
738
739         err = cpufreq_register_governor(&cpufreq_gov_conservative);
740         if (err)
741                 destroy_workqueue(kconservative_wq);
742
743         return err;
744 }
745
746 static void __exit cpufreq_gov_dbs_exit(void)
747 {
748         cpufreq_unregister_governor(&cpufreq_gov_conservative);
749         destroy_workqueue(kconservative_wq);
750 }
751
752
753 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
754 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
755                 "Low Latency Frequency Transition capable processors "
756                 "optimised for use in a battery environment");
757 MODULE_LICENSE("GPL");
758
759 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
760 fs_initcall(cpufreq_gov_dbs_init);
761 #else
762 module_init(cpufreq_gov_dbs_init);
763 #endif
764 module_exit(cpufreq_gov_dbs_exit);