[CPUFREQ] use max load in conservative governor
[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 max_load = 0;
448         unsigned int freq_target;
449
450         struct cpufreq_policy *policy;
451         unsigned int j;
452
453         policy = this_dbs_info->cur_policy;
454
455         /*
456          * Every sampling_rate, we check, if current idle time is less
457          * than 20% (default), then we try to increase frequency
458          * Every sampling_rate*sampling_down_factor, we check, if current
459          * idle time is more than 80%, then we try to decrease frequency
460          *
461          * Any frequency increase takes it to the maximum frequency.
462          * Frequency reduction happens at minimum steps of
463          * 5% (default) of maximum frequency
464          */
465
466         /* Get Absolute Load */
467         for_each_cpu(j, policy->cpus) {
468                 struct cpu_dbs_info_s *j_dbs_info;
469                 cputime64_t cur_wall_time, cur_idle_time;
470                 unsigned int idle_time, wall_time;
471
472                 j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
473
474                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
475
476                 wall_time = (unsigned int) cputime64_sub(cur_wall_time,
477                                 j_dbs_info->prev_cpu_wall);
478                 j_dbs_info->prev_cpu_wall = cur_wall_time;
479
480                 idle_time = (unsigned int) cputime64_sub(cur_idle_time,
481                                 j_dbs_info->prev_cpu_idle);
482                 j_dbs_info->prev_cpu_idle = cur_idle_time;
483
484                 if (dbs_tuners_ins.ignore_nice) {
485                         cputime64_t cur_nice;
486                         unsigned long cur_nice_jiffies;
487
488                         cur_nice = cputime64_sub(kstat_cpu(j).cpustat.nice,
489                                          j_dbs_info->prev_cpu_nice);
490                         /*
491                          * Assumption: nice time between sampling periods will
492                          * be less than 2^32 jiffies for 32 bit sys
493                          */
494                         cur_nice_jiffies = (unsigned long)
495                                         cputime64_to_jiffies64(cur_nice);
496
497                         j_dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
498                         idle_time += jiffies_to_usecs(cur_nice_jiffies);
499                 }
500
501                 if (unlikely(!wall_time || wall_time < idle_time))
502                         continue;
503
504                 load = 100 * (wall_time - idle_time) / wall_time;
505
506                 if (load > max_load)
507                         max_load = load;
508         }
509
510         /*
511          * break out if we 'cannot' reduce the speed as the user might
512          * want freq_step to be zero
513          */
514         if (dbs_tuners_ins.freq_step == 0)
515                 return;
516
517         /* Check for frequency increase */
518         if (max_load > dbs_tuners_ins.up_threshold) {
519                 this_dbs_info->down_skip = 0;
520
521                 /* if we are already at full speed then break out early */
522                 if (this_dbs_info->requested_freq == policy->max)
523                         return;
524
525                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
526
527                 /* max freq cannot be less than 100. But who knows.... */
528                 if (unlikely(freq_target == 0))
529                         freq_target = 5;
530
531                 this_dbs_info->requested_freq += freq_target;
532                 if (this_dbs_info->requested_freq > policy->max)
533                         this_dbs_info->requested_freq = policy->max;
534
535                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
536                         CPUFREQ_RELATION_H);
537                 return;
538         }
539
540         /*
541          * The optimal frequency is the frequency that is the lowest that
542          * can support the current CPU usage without triggering the up
543          * policy. To be safe, we focus 10 points under the threshold.
544          */
545         if (max_load < (dbs_tuners_ins.down_threshold - 10)) {
546                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
547
548                 this_dbs_info->requested_freq -= freq_target;
549                 if (this_dbs_info->requested_freq < policy->min)
550                         this_dbs_info->requested_freq = policy->min;
551
552                 /*
553                  * if we cannot reduce the frequency anymore, break out early
554                  */
555                 if (policy->cur == policy->min)
556                         return;
557
558                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
559                                 CPUFREQ_RELATION_H);
560                 return;
561         }
562 }
563
564 static void do_dbs_timer(struct work_struct *work)
565 {
566         struct cpu_dbs_info_s *dbs_info =
567                 container_of(work, struct cpu_dbs_info_s, work.work);
568         unsigned int cpu = dbs_info->cpu;
569
570         /* We want all CPUs to do sampling nearly on same jiffy */
571         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
572
573         delay -= jiffies % delay;
574
575         mutex_lock(&dbs_info->timer_mutex);
576
577         dbs_check_cpu(dbs_info);
578
579         queue_delayed_work_on(cpu, kconservative_wq, &dbs_info->work, delay);
580         mutex_unlock(&dbs_info->timer_mutex);
581 }
582
583 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
584 {
585         /* We want all CPUs to do sampling nearly on same jiffy */
586         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
587         delay -= jiffies % delay;
588
589         dbs_info->enable = 1;
590         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
591         queue_delayed_work_on(dbs_info->cpu, kconservative_wq, &dbs_info->work,
592                                 delay);
593 }
594
595 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
596 {
597         dbs_info->enable = 0;
598         cancel_delayed_work_sync(&dbs_info->work);
599 }
600
601 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
602                                    unsigned int event)
603 {
604         unsigned int cpu = policy->cpu;
605         struct cpu_dbs_info_s *this_dbs_info;
606         unsigned int j;
607         int rc;
608
609         this_dbs_info = &per_cpu(cs_cpu_dbs_info, cpu);
610
611         switch (event) {
612         case CPUFREQ_GOV_START:
613                 if ((!cpu_online(cpu)) || (!policy->cur))
614                         return -EINVAL;
615
616                 mutex_lock(&dbs_mutex);
617
618                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group_old);
619                 if (rc) {
620                         mutex_unlock(&dbs_mutex);
621                         return rc;
622                 }
623
624                 for_each_cpu(j, policy->cpus) {
625                         struct cpu_dbs_info_s *j_dbs_info;
626                         j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
627                         j_dbs_info->cur_policy = policy;
628
629                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
630                                                 &j_dbs_info->prev_cpu_wall);
631                         if (dbs_tuners_ins.ignore_nice) {
632                                 j_dbs_info->prev_cpu_nice =
633                                                 kstat_cpu(j).cpustat.nice;
634                         }
635                 }
636                 this_dbs_info->down_skip = 0;
637                 this_dbs_info->requested_freq = policy->cur;
638
639                 mutex_init(&this_dbs_info->timer_mutex);
640                 dbs_enable++;
641                 /*
642                  * Start the timerschedule work, when this governor
643                  * is used for first time
644                  */
645                 if (dbs_enable == 1) {
646                         unsigned int latency;
647                         /* policy latency is in nS. Convert it to uS first */
648                         latency = policy->cpuinfo.transition_latency / 1000;
649                         if (latency == 0)
650                                 latency = 1;
651
652                         rc = sysfs_create_group(cpufreq_global_kobject,
653                                                 &dbs_attr_group);
654                         if (rc) {
655                                 mutex_unlock(&dbs_mutex);
656                                 return rc;
657                         }
658
659                         /*
660                          * conservative does not implement micro like ondemand
661                          * governor, thus we are bound to jiffes/HZ
662                          */
663                         min_sampling_rate =
664                                 MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
665                         /* Bring kernel and HW constraints together */
666                         min_sampling_rate = max(min_sampling_rate,
667                                         MIN_LATENCY_MULTIPLIER * latency);
668                         dbs_tuners_ins.sampling_rate =
669                                 max(min_sampling_rate,
670                                     latency * LATENCY_MULTIPLIER);
671
672                         cpufreq_register_notifier(
673                                         &dbs_cpufreq_notifier_block,
674                                         CPUFREQ_TRANSITION_NOTIFIER);
675                 }
676                 mutex_unlock(&dbs_mutex);
677
678                 dbs_timer_init(this_dbs_info);
679
680                 break;
681
682         case CPUFREQ_GOV_STOP:
683                 dbs_timer_exit(this_dbs_info);
684
685                 mutex_lock(&dbs_mutex);
686                 sysfs_remove_group(&policy->kobj, &dbs_attr_group_old);
687                 dbs_enable--;
688                 mutex_destroy(&this_dbs_info->timer_mutex);
689
690                 /*
691                  * Stop the timerschedule work, when this governor
692                  * is used for first time
693                  */
694                 if (dbs_enable == 0)
695                         cpufreq_unregister_notifier(
696                                         &dbs_cpufreq_notifier_block,
697                                         CPUFREQ_TRANSITION_NOTIFIER);
698
699                 mutex_unlock(&dbs_mutex);
700                 if (!dbs_enable)
701                         sysfs_remove_group(cpufreq_global_kobject,
702                                            &dbs_attr_group);
703
704                 break;
705
706         case CPUFREQ_GOV_LIMITS:
707                 mutex_lock(&this_dbs_info->timer_mutex);
708                 if (policy->max < this_dbs_info->cur_policy->cur)
709                         __cpufreq_driver_target(
710                                         this_dbs_info->cur_policy,
711                                         policy->max, CPUFREQ_RELATION_H);
712                 else if (policy->min > this_dbs_info->cur_policy->cur)
713                         __cpufreq_driver_target(
714                                         this_dbs_info->cur_policy,
715                                         policy->min, CPUFREQ_RELATION_L);
716                 mutex_unlock(&this_dbs_info->timer_mutex);
717
718                 break;
719         }
720         return 0;
721 }
722
723 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
724 static
725 #endif
726 struct cpufreq_governor cpufreq_gov_conservative = {
727         .name                   = "conservative",
728         .governor               = cpufreq_governor_dbs,
729         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
730         .owner                  = THIS_MODULE,
731 };
732
733 static int __init cpufreq_gov_dbs_init(void)
734 {
735         int err;
736
737         kconservative_wq = create_workqueue("kconservative");
738         if (!kconservative_wq) {
739                 printk(KERN_ERR "Creation of kconservative failed\n");
740                 return -EFAULT;
741         }
742
743         err = cpufreq_register_governor(&cpufreq_gov_conservative);
744         if (err)
745                 destroy_workqueue(kconservative_wq);
746
747         return err;
748 }
749
750 static void __exit cpufreq_gov_dbs_exit(void)
751 {
752         cpufreq_unregister_governor(&cpufreq_gov_conservative);
753         destroy_workqueue(kconservative_wq);
754 }
755
756
757 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
758 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
759                 "Low Latency Frequency Transition capable processors "
760                 "optimised for use in a battery environment");
761 MODULE_LICENSE("GPL");
762
763 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
764 fs_initcall(cpufreq_gov_dbs_init);
765 #else
766 module_init(cpufreq_gov_dbs_init);
767 #endif
768 module_exit(cpufreq_gov_dbs_exit);