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cpufreq_ondemand.c
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1 /*
2  * drivers/cpufreq/cpufreq_ondemand.c
3  *
4  * Copyright (C) 2001 Russell King
5  * (C) 2003 Venkatesh Pallipadi <[email protected]>.
6  * Jun Nakajima <[email protected]>
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License version 2 as
10  * published by the Free Software Foundation.
11  */
12 
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/init.h>
16 #include <linux/cpufreq.h>
17 #include <linux/cpu.h>
18 #include <linux/jiffies.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/mutex.h>
21 #include <linux/hrtimer.h>
22 #include <linux/tick.h>
23 #include <linux/ktime.h>
24 #include <linux/sched.h>
25 
26 /*
27  * dbs is used in this file as a shortform for demandbased switching
28  * It helps to keep variable names smaller, simpler
29  */
30 
31 #define DEF_FREQUENCY_DOWN_DIFFERENTIAL (10)
32 #define DEF_FREQUENCY_UP_THRESHOLD (80)
33 #define DEF_SAMPLING_DOWN_FACTOR (1)
34 #define MAX_SAMPLING_DOWN_FACTOR (100000)
35 #define MICRO_FREQUENCY_DOWN_DIFFERENTIAL (3)
36 #define MICRO_FREQUENCY_UP_THRESHOLD (95)
37 #define MICRO_FREQUENCY_MIN_SAMPLE_RATE (10000)
38 #define MIN_FREQUENCY_UP_THRESHOLD (11)
39 #define MAX_FREQUENCY_UP_THRESHOLD (100)
40 
41 /*
42  * The polling frequency of this governor depends on the capability of
43  * the processor. Default polling frequency is 1000 times the transition
44  * latency of the processor. The governor will work on any processor with
45  * transition latency <= 10mS, using appropriate sampling
46  * rate.
47  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
48  * this governor will not work.
49  * All times here are in uS.
50  */
51 #define MIN_SAMPLING_RATE_RATIO (2)
52 
53 static unsigned int min_sampling_rate;
54 
55 #define LATENCY_MULTIPLIER (1000)
56 #define MIN_LATENCY_MULTIPLIER (100)
57 #define TRANSITION_LATENCY_LIMIT (10 * 1000 * 1000)
58 
59 static void do_dbs_timer(struct work_struct *work);
60 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
61  unsigned int event);
62 
63 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
64 static
65 #endif
66 struct cpufreq_governor cpufreq_gov_ondemand = {
67  .name = "ondemand",
68  .governor = cpufreq_governor_dbs,
69  .max_transition_latency = TRANSITION_LATENCY_LIMIT,
70  .owner = THIS_MODULE,
71 };
72 
73 /* Sampling types */
74 enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE};
75 
76 struct cpu_dbs_info_s {
77  cputime64_t prev_cpu_idle;
78  cputime64_t prev_cpu_iowait;
79  cputime64_t prev_cpu_wall;
80  cputime64_t prev_cpu_nice;
81  struct cpufreq_policy *cur_policy;
82  struct delayed_work work;
83  struct cpufreq_frequency_table *freq_table;
84  unsigned int freq_lo;
85  unsigned int freq_lo_jiffies;
86  unsigned int freq_hi_jiffies;
87  unsigned int rate_mult;
88  int cpu;
89  unsigned int sample_type:1;
90  /*
91  * percpu mutex that serializes governor limit change with
92  * do_dbs_timer invocation. We do not want do_dbs_timer to run
93  * when user is changing the governor or limits.
94  */
95  struct mutex timer_mutex;
96 };
97 static DEFINE_PER_CPU(struct cpu_dbs_info_s, od_cpu_dbs_info);
98 
99 static unsigned int dbs_enable; /* number of CPUs using this policy */
100 
101 /*
102  * dbs_mutex protects dbs_enable in governor start/stop.
103  */
104 static DEFINE_MUTEX(dbs_mutex);
105 
106 static struct dbs_tuners {
107  unsigned int sampling_rate;
108  unsigned int up_threshold;
109  unsigned int down_differential;
110  unsigned int ignore_nice;
111  unsigned int sampling_down_factor;
112  unsigned int powersave_bias;
113  unsigned int io_is_busy;
114 } dbs_tuners_ins = {
115  .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
116  .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
117  .down_differential = DEF_FREQUENCY_DOWN_DIFFERENTIAL,
118  .ignore_nice = 0,
119  .powersave_bias = 0,
120 };
121 
122 static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)
123 {
124  u64 idle_time;
125  u64 cur_wall_time;
126  u64 busy_time;
127 
128  cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
129 
130  busy_time = kcpustat_cpu(cpu).cpustat[CPUTIME_USER];
131  busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SYSTEM];
132  busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_IRQ];
133  busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SOFTIRQ];
134  busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_STEAL];
135  busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_NICE];
136 
137  idle_time = cur_wall_time - busy_time;
138  if (wall)
139  *wall = jiffies_to_usecs(cur_wall_time);
140 
141  return jiffies_to_usecs(idle_time);
142 }
143 
144 static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
145 {
146  u64 idle_time = get_cpu_idle_time_us(cpu, NULL);
147 
148  if (idle_time == -1ULL)
149  return get_cpu_idle_time_jiffy(cpu, wall);
150  else
151  idle_time += get_cpu_iowait_time_us(cpu, wall);
152 
153  return idle_time;
154 }
155 
156 static inline cputime64_t get_cpu_iowait_time(unsigned int cpu, cputime64_t *wall)
157 {
158  u64 iowait_time = get_cpu_iowait_time_us(cpu, wall);
159 
160  if (iowait_time == -1ULL)
161  return 0;
162 
163  return iowait_time;
164 }
165 
166 /*
167  * Find right freq to be set now with powersave_bias on.
168  * Returns the freq_hi to be used right now and will set freq_hi_jiffies,
169  * freq_lo, and freq_lo_jiffies in percpu area for averaging freqs.
170  */
171 static unsigned int powersave_bias_target(struct cpufreq_policy *policy,
172  unsigned int freq_next,
173  unsigned int relation)
174 {
175  unsigned int freq_req, freq_reduc, freq_avg;
176  unsigned int freq_hi, freq_lo;
177  unsigned int index = 0;
178  unsigned int jiffies_total, jiffies_hi, jiffies_lo;
179  struct cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
180  policy->cpu);
181 
182  if (!dbs_info->freq_table) {
183  dbs_info->freq_lo = 0;
184  dbs_info->freq_lo_jiffies = 0;
185  return freq_next;
186  }
187 
188  cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_next,
189  relation, &index);
190  freq_req = dbs_info->freq_table[index].frequency;
191  freq_reduc = freq_req * dbs_tuners_ins.powersave_bias / 1000;
192  freq_avg = freq_req - freq_reduc;
193 
194  /* Find freq bounds for freq_avg in freq_table */
195  index = 0;
196  cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
197  CPUFREQ_RELATION_H, &index);
198  freq_lo = dbs_info->freq_table[index].frequency;
199  index = 0;
200  cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
201  CPUFREQ_RELATION_L, &index);
202  freq_hi = dbs_info->freq_table[index].frequency;
203 
204  /* Find out how long we have to be in hi and lo freqs */
205  if (freq_hi == freq_lo) {
206  dbs_info->freq_lo = 0;
207  dbs_info->freq_lo_jiffies = 0;
208  return freq_lo;
209  }
210  jiffies_total = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
211  jiffies_hi = (freq_avg - freq_lo) * jiffies_total;
212  jiffies_hi += ((freq_hi - freq_lo) / 2);
213  jiffies_hi /= (freq_hi - freq_lo);
214  jiffies_lo = jiffies_total - jiffies_hi;
215  dbs_info->freq_lo = freq_lo;
216  dbs_info->freq_lo_jiffies = jiffies_lo;
217  dbs_info->freq_hi_jiffies = jiffies_hi;
218  return freq_hi;
219 }
220 
221 static void ondemand_powersave_bias_init_cpu(int cpu)
222 {
223  struct cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
224  dbs_info->freq_table = cpufreq_frequency_get_table(cpu);
225  dbs_info->freq_lo = 0;
226 }
227 
228 static void ondemand_powersave_bias_init(void)
229 {
230  int i;
231  for_each_online_cpu(i) {
232  ondemand_powersave_bias_init_cpu(i);
233  }
234 }
235 
236 /************************** sysfs interface ************************/
237 
238 static ssize_t show_sampling_rate_min(struct kobject *kobj,
239  struct attribute *attr, char *buf)
240 {
241  return sprintf(buf, "%u\n", min_sampling_rate);
242 }
243 
244 define_one_global_ro(sampling_rate_min);
245 
246 /* cpufreq_ondemand Governor Tunables */
247 #define show_one(file_name, object) \
248 static ssize_t show_##file_name \
249 (struct kobject *kobj, struct attribute *attr, char *buf) \
250 { \
251  return sprintf(buf, "%u\n", dbs_tuners_ins.object); \
252 }
253 show_one(sampling_rate, sampling_rate);
254 show_one(io_is_busy, io_is_busy);
255 show_one(up_threshold, up_threshold);
256 show_one(sampling_down_factor, sampling_down_factor);
257 show_one(ignore_nice_load, ignore_nice);
258 show_one(powersave_bias, powersave_bias);
259 
273 static void update_sampling_rate(unsigned int new_rate)
274 {
275  int cpu;
276 
277  dbs_tuners_ins.sampling_rate = new_rate
278  = max(new_rate, min_sampling_rate);
279 
280  for_each_online_cpu(cpu) {
281  struct cpufreq_policy *policy;
282  struct cpu_dbs_info_s *dbs_info;
283  unsigned long next_sampling, appointed_at;
284 
285  policy = cpufreq_cpu_get(cpu);
286  if (!policy)
287  continue;
288  dbs_info = &per_cpu(od_cpu_dbs_info, policy->cpu);
289  cpufreq_cpu_put(policy);
290 
291  mutex_lock(&dbs_info->timer_mutex);
292 
293  if (!delayed_work_pending(&dbs_info->work)) {
294  mutex_unlock(&dbs_info->timer_mutex);
295  continue;
296  }
297 
298  next_sampling = jiffies + usecs_to_jiffies(new_rate);
299  appointed_at = dbs_info->work.timer.expires;
300 
301 
302  if (time_before(next_sampling, appointed_at)) {
303 
304  mutex_unlock(&dbs_info->timer_mutex);
305  cancel_delayed_work_sync(&dbs_info->work);
306  mutex_lock(&dbs_info->timer_mutex);
307 
308  schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work,
309  usecs_to_jiffies(new_rate));
310 
311  }
312  mutex_unlock(&dbs_info->timer_mutex);
313  }
314 }
315 
316 static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
317  const char *buf, size_t count)
318 {
319  unsigned int input;
320  int ret;
321  ret = sscanf(buf, "%u", &input);
322  if (ret != 1)
323  return -EINVAL;
324  update_sampling_rate(input);
325  return count;
326 }
327 
328 static ssize_t store_io_is_busy(struct kobject *a, struct attribute *b,
329  const char *buf, size_t count)
330 {
331  unsigned int input;
332  int ret;
333 
334  ret = sscanf(buf, "%u", &input);
335  if (ret != 1)
336  return -EINVAL;
337  dbs_tuners_ins.io_is_busy = !!input;
338  return count;
339 }
340 
341 static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
342  const char *buf, size_t count)
343 {
344  unsigned int input;
345  int ret;
346  ret = sscanf(buf, "%u", &input);
347 
348  if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
349  input < MIN_FREQUENCY_UP_THRESHOLD) {
350  return -EINVAL;
351  }
352  dbs_tuners_ins.up_threshold = input;
353  return count;
354 }
355 
356 static ssize_t store_sampling_down_factor(struct kobject *a,
357  struct attribute *b, const char *buf, size_t count)
358 {
359  unsigned int input, j;
360  int ret;
361  ret = sscanf(buf, "%u", &input);
362 
363  if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
364  return -EINVAL;
365  dbs_tuners_ins.sampling_down_factor = input;
366 
367  /* Reset down sampling multiplier in case it was active */
368  for_each_online_cpu(j) {
369  struct cpu_dbs_info_s *dbs_info;
370  dbs_info = &per_cpu(od_cpu_dbs_info, j);
371  dbs_info->rate_mult = 1;
372  }
373  return count;
374 }
375 
376 static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
377  const char *buf, size_t count)
378 {
379  unsigned int input;
380  int ret;
381 
382  unsigned int j;
383 
384  ret = sscanf(buf, "%u", &input);
385  if (ret != 1)
386  return -EINVAL;
387 
388  if (input > 1)
389  input = 1;
390 
391  if (input == dbs_tuners_ins.ignore_nice) { /* nothing to do */
392  return count;
393  }
394  dbs_tuners_ins.ignore_nice = input;
395 
396  /* we need to re-evaluate prev_cpu_idle */
397  for_each_online_cpu(j) {
398  struct cpu_dbs_info_s *dbs_info;
399  dbs_info = &per_cpu(od_cpu_dbs_info, j);
400  dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
401  &dbs_info->prev_cpu_wall);
402  if (dbs_tuners_ins.ignore_nice)
403  dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
404 
405  }
406  return count;
407 }
408 
409 static ssize_t store_powersave_bias(struct kobject *a, struct attribute *b,
410  const char *buf, size_t count)
411 {
412  unsigned int input;
413  int ret;
414  ret = sscanf(buf, "%u", &input);
415 
416  if (ret != 1)
417  return -EINVAL;
418 
419  if (input > 1000)
420  input = 1000;
421 
422  dbs_tuners_ins.powersave_bias = input;
423  ondemand_powersave_bias_init();
424  return count;
425 }
426 
427 define_one_global_rw(sampling_rate);
428 define_one_global_rw(io_is_busy);
429 define_one_global_rw(up_threshold);
430 define_one_global_rw(sampling_down_factor);
431 define_one_global_rw(ignore_nice_load);
432 define_one_global_rw(powersave_bias);
433 
434 static struct attribute *dbs_attributes[] = {
435  &sampling_rate_min.attr,
436  &sampling_rate.attr,
437  &up_threshold.attr,
438  &sampling_down_factor.attr,
439  &ignore_nice_load.attr,
440  &powersave_bias.attr,
441  &io_is_busy.attr,
442  NULL
443 };
444 
445 static struct attribute_group dbs_attr_group = {
446  .attrs = dbs_attributes,
447  .name = "ondemand",
448 };
449 
450 /************************** sysfs end ************************/
451 
452 static void dbs_freq_increase(struct cpufreq_policy *p, unsigned int freq)
453 {
454  if (dbs_tuners_ins.powersave_bias)
455  freq = powersave_bias_target(p, freq, CPUFREQ_RELATION_H);
456  else if (p->cur == p->max)
457  return;
458 
459  __cpufreq_driver_target(p, freq, dbs_tuners_ins.powersave_bias ?
460  CPUFREQ_RELATION_L : CPUFREQ_RELATION_H);
461 }
462 
463 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
464 {
465  unsigned int max_load_freq;
466 
467  struct cpufreq_policy *policy;
468  unsigned int j;
469 
470  this_dbs_info->freq_lo = 0;
471  policy = this_dbs_info->cur_policy;
472 
473  /*
474  * Every sampling_rate, we check, if current idle time is less
475  * than 20% (default), then we try to increase frequency
476  * Every sampling_rate, we look for a the lowest
477  * frequency which can sustain the load while keeping idle time over
478  * 30%. If such a frequency exist, we try to decrease to this frequency.
479  *
480  * Any frequency increase takes it to the maximum frequency.
481  * Frequency reduction happens at minimum steps of
482  * 5% (default) of current frequency
483  */
484 
485  /* Get Absolute Load - in terms of freq */
486  max_load_freq = 0;
487 
488  for_each_cpu(j, policy->cpus) {
489  struct cpu_dbs_info_s *j_dbs_info;
490  cputime64_t cur_wall_time, cur_idle_time, cur_iowait_time;
491  unsigned int idle_time, wall_time, iowait_time;
492  unsigned int load, load_freq;
493  int freq_avg;
494 
495  j_dbs_info = &per_cpu(od_cpu_dbs_info, j);
496 
497  cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
498  cur_iowait_time = get_cpu_iowait_time(j, &cur_wall_time);
499 
500  wall_time = (unsigned int)
501  (cur_wall_time - j_dbs_info->prev_cpu_wall);
502  j_dbs_info->prev_cpu_wall = cur_wall_time;
503 
504  idle_time = (unsigned int)
505  (cur_idle_time - j_dbs_info->prev_cpu_idle);
506  j_dbs_info->prev_cpu_idle = cur_idle_time;
507 
508  iowait_time = (unsigned int)
509  (cur_iowait_time - j_dbs_info->prev_cpu_iowait);
510  j_dbs_info->prev_cpu_iowait = cur_iowait_time;
511 
512  if (dbs_tuners_ins.ignore_nice) {
513  u64 cur_nice;
514  unsigned long cur_nice_jiffies;
515 
516  cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE] -
517  j_dbs_info->prev_cpu_nice;
518  /*
519  * Assumption: nice time between sampling periods will
520  * be less than 2^32 jiffies for 32 bit sys
521  */
522  cur_nice_jiffies = (unsigned long)
523  cputime64_to_jiffies64(cur_nice);
524 
525  j_dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
526  idle_time += jiffies_to_usecs(cur_nice_jiffies);
527  }
528 
529  /*
530  * For the purpose of ondemand, waiting for disk IO is an
531  * indication that you're performance critical, and not that
532  * the system is actually idle. So subtract the iowait time
533  * from the cpu idle time.
534  */
535 
536  if (dbs_tuners_ins.io_is_busy && idle_time >= iowait_time)
537  idle_time -= iowait_time;
538 
539  if (unlikely(!wall_time || wall_time < idle_time))
540  continue;
541 
542  load = 100 * (wall_time - idle_time) / wall_time;
543 
544  freq_avg = __cpufreq_driver_getavg(policy, j);
545  if (freq_avg <= 0)
546  freq_avg = policy->cur;
547 
548  load_freq = load * freq_avg;
549  if (load_freq > max_load_freq)
550  max_load_freq = load_freq;
551  }
552 
553  /* Check for frequency increase */
554  if (max_load_freq > dbs_tuners_ins.up_threshold * policy->cur) {
555  /* If switching to max speed, apply sampling_down_factor */
556  if (policy->cur < policy->max)
557  this_dbs_info->rate_mult =
558  dbs_tuners_ins.sampling_down_factor;
559  dbs_freq_increase(policy, policy->max);
560  return;
561  }
562 
563  /* Check for frequency decrease */
564  /* if we cannot reduce the frequency anymore, break out early */
565  if (policy->cur == policy->min)
566  return;
567 
568  /*
569  * The optimal frequency is the frequency that is the lowest that
570  * can support the current CPU usage without triggering the up
571  * policy. To be safe, we focus 10 points under the threshold.
572  */
573  if (max_load_freq <
574  (dbs_tuners_ins.up_threshold - dbs_tuners_ins.down_differential) *
575  policy->cur) {
576  unsigned int freq_next;
577  freq_next = max_load_freq /
578  (dbs_tuners_ins.up_threshold -
579  dbs_tuners_ins.down_differential);
580 
581  /* No longer fully busy, reset rate_mult */
582  this_dbs_info->rate_mult = 1;
583 
584  if (freq_next < policy->min)
585  freq_next = policy->min;
586 
587  if (!dbs_tuners_ins.powersave_bias) {
588  __cpufreq_driver_target(policy, freq_next,
589  CPUFREQ_RELATION_L);
590  } else {
591  int freq = powersave_bias_target(policy, freq_next,
592  CPUFREQ_RELATION_L);
593  __cpufreq_driver_target(policy, freq,
594  CPUFREQ_RELATION_L);
595  }
596  }
597 }
598 
599 static void do_dbs_timer(struct work_struct *work)
600 {
601  struct cpu_dbs_info_s *dbs_info =
602  container_of(work, struct cpu_dbs_info_s, work.work);
603  unsigned int cpu = dbs_info->cpu;
604  int sample_type = dbs_info->sample_type;
605 
606  int delay;
607 
608  mutex_lock(&dbs_info->timer_mutex);
609 
610  /* Common NORMAL_SAMPLE setup */
611  dbs_info->sample_type = DBS_NORMAL_SAMPLE;
612  if (!dbs_tuners_ins.powersave_bias ||
613  sample_type == DBS_NORMAL_SAMPLE) {
614  dbs_check_cpu(dbs_info);
615  if (dbs_info->freq_lo) {
616  /* Setup timer for SUB_SAMPLE */
617  dbs_info->sample_type = DBS_SUB_SAMPLE;
618  delay = dbs_info->freq_hi_jiffies;
619  } else {
620  /* We want all CPUs to do sampling nearly on
621  * same jiffy
622  */
623  delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate
624  * dbs_info->rate_mult);
625 
626  if (num_online_cpus() > 1)
627  delay -= jiffies % delay;
628  }
629  } else {
630  __cpufreq_driver_target(dbs_info->cur_policy,
631  dbs_info->freq_lo, CPUFREQ_RELATION_H);
632  delay = dbs_info->freq_lo_jiffies;
633  }
634  schedule_delayed_work_on(cpu, &dbs_info->work, delay);
635  mutex_unlock(&dbs_info->timer_mutex);
636 }
637 
638 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
639 {
640  /* We want all CPUs to do sampling nearly on same jiffy */
641  int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
642 
643  if (num_online_cpus() > 1)
644  delay -= jiffies % delay;
645 
646  dbs_info->sample_type = DBS_NORMAL_SAMPLE;
647  INIT_DEFERRABLE_WORK(&dbs_info->work, do_dbs_timer);
648  schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work, delay);
649 }
650 
651 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
652 {
653  cancel_delayed_work_sync(&dbs_info->work);
654 }
655 
656 /*
657  * Not all CPUs want IO time to be accounted as busy; this dependson how
658  * efficient idling at a higher frequency/voltage is.
659  * Pavel Machek says this is not so for various generations of AMD and old
660  * Intel systems.
661  * Mike Chan (androidlcom) calis this is also not true for ARM.
662  * Because of this, whitelist specific known (series) of CPUs by default, and
663  * leave all others up to the user.
664  */
665 static int should_io_be_busy(void)
666 {
667 #if defined(CONFIG_X86)
668  /*
669  * For Intel, Core 2 (model 15) andl later have an efficient idle.
670  */
671  if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
672  boot_cpu_data.x86 == 6 &&
673  boot_cpu_data.x86_model >= 15)
674  return 1;
675 #endif
676  return 0;
677 }
678 
679 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
680  unsigned int event)
681 {
682  unsigned int cpu = policy->cpu;
683  struct cpu_dbs_info_s *this_dbs_info;
684  unsigned int j;
685  int rc;
686 
687  this_dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
688 
689  switch (event) {
690  case CPUFREQ_GOV_START:
691  if ((!cpu_online(cpu)) || (!policy->cur))
692  return -EINVAL;
693 
694  mutex_lock(&dbs_mutex);
695 
696  dbs_enable++;
697  for_each_cpu(j, policy->cpus) {
698  struct cpu_dbs_info_s *j_dbs_info;
699  j_dbs_info = &per_cpu(od_cpu_dbs_info, j);
700  j_dbs_info->cur_policy = policy;
701 
702  j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
703  &j_dbs_info->prev_cpu_wall);
704  if (dbs_tuners_ins.ignore_nice)
705  j_dbs_info->prev_cpu_nice =
706  kcpustat_cpu(j).cpustat[CPUTIME_NICE];
707  }
708  this_dbs_info->cpu = cpu;
709  this_dbs_info->rate_mult = 1;
710  ondemand_powersave_bias_init_cpu(cpu);
711  /*
712  * Start the timerschedule work, when this governor
713  * is used for first time
714  */
715  if (dbs_enable == 1) {
716  unsigned int latency;
717 
718  rc = sysfs_create_group(cpufreq_global_kobject,
719  &dbs_attr_group);
720  if (rc) {
721  mutex_unlock(&dbs_mutex);
722  return rc;
723  }
724 
725  /* policy latency is in nS. Convert it to uS first */
726  latency = policy->cpuinfo.transition_latency / 1000;
727  if (latency == 0)
728  latency = 1;
729  /* Bring kernel and HW constraints together */
730  min_sampling_rate = max(min_sampling_rate,
731  MIN_LATENCY_MULTIPLIER * latency);
732  dbs_tuners_ins.sampling_rate =
733  max(min_sampling_rate,
734  latency * LATENCY_MULTIPLIER);
735  dbs_tuners_ins.io_is_busy = should_io_be_busy();
736  }
737  mutex_unlock(&dbs_mutex);
738 
739  mutex_init(&this_dbs_info->timer_mutex);
740  dbs_timer_init(this_dbs_info);
741  break;
742 
743  case CPUFREQ_GOV_STOP:
744  dbs_timer_exit(this_dbs_info);
745 
746  mutex_lock(&dbs_mutex);
747  mutex_destroy(&this_dbs_info->timer_mutex);
748  dbs_enable--;
749  mutex_unlock(&dbs_mutex);
750  if (!dbs_enable)
751  sysfs_remove_group(cpufreq_global_kobject,
752  &dbs_attr_group);
753 
754  break;
755 
756  case CPUFREQ_GOV_LIMITS:
757  mutex_lock(&this_dbs_info->timer_mutex);
758  if (policy->max < this_dbs_info->cur_policy->cur)
759  __cpufreq_driver_target(this_dbs_info->cur_policy,
760  policy->max, CPUFREQ_RELATION_H);
761  else if (policy->min > this_dbs_info->cur_policy->cur)
762  __cpufreq_driver_target(this_dbs_info->cur_policy,
763  policy->min, CPUFREQ_RELATION_L);
764  dbs_check_cpu(this_dbs_info);
765  mutex_unlock(&this_dbs_info->timer_mutex);
766  break;
767  }
768  return 0;
769 }
770 
771 static int __init cpufreq_gov_dbs_init(void)
772 {
773  u64 idle_time;
774  int cpu = get_cpu();
775 
776  idle_time = get_cpu_idle_time_us(cpu, NULL);
777  put_cpu();
778  if (idle_time != -1ULL) {
779  /* Idle micro accounting is supported. Use finer thresholds */
780  dbs_tuners_ins.up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
781  dbs_tuners_ins.down_differential =
782  MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
783  /*
784  * In nohz/micro accounting case we set the minimum frequency
785  * not depending on HZ, but fixed (very low). The deferred
786  * timer might skip some samples if idle/sleeping as needed.
787  */
788  min_sampling_rate = MICRO_FREQUENCY_MIN_SAMPLE_RATE;
789  } else {
790  /* For correct statistics, we need 10 ticks for each measure */
791  min_sampling_rate =
792  MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
793  }
794 
795  return cpufreq_register_governor(&cpufreq_gov_ondemand);
796 }
797 
798 static void __exit cpufreq_gov_dbs_exit(void)
799 {
800  cpufreq_unregister_governor(&cpufreq_gov_ondemand);
801 }
802 
803 
804 MODULE_AUTHOR("Venkatesh Pallipadi <[email protected]>");
805 MODULE_AUTHOR("Alexey Starikovskiy <[email protected]>");
806 MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
807  "Low Latency Frequency Transition capable processors");
808 MODULE_LICENSE("GPL");
809 
810 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
811 fs_initcall(cpufreq_gov_dbs_init);
812 #else
813 module_init(cpufreq_gov_dbs_init);
814 #endif
815 module_exit(cpufreq_gov_dbs_exit);
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