git.oblomov.eu Git - linux-2.6/blob - drivers/cpufreq/cpufreq_ondemand.c

   1 /*
   2  *  drivers/cpufreq/cpufreq_ondemand.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  *
   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
  25 /*
  26  * dbs is used in this file as a shortform for demandbased switching
  27  * It helps to keep variable names smaller, simpler
  28  */
  29
  30 #define DEF_FREQUENCY_DOWN_DIFFERENTIAL         (10)
  31 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
  32 #define MICRO_FREQUENCY_DOWN_DIFFERENTIAL       (3)
  33 #define MICRO_FREQUENCY_UP_THRESHOLD            (95)
  34 #define MIN_FREQUENCY_UP_THRESHOLD              (11)
  35 #define MAX_FREQUENCY_UP_THRESHOLD              (100)
  36
  37 /*
  38  * The polling frequency of this governor depends on the capability of
  39  * the processor. Default polling frequency is 1000 times the transition
  40  * latency of the processor. The governor will work on any processor with
  41  * transition latency <= 10mS, using appropriate sampling
  42  * rate.
  43  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
  44  * this governor will not work.
  45  * All times here are in uS.
  46  */
  47 static unsigned int def_sampling_rate;
  48 #define MIN_SAMPLING_RATE_RATIO                 (2)
  49 /* for correct statistics, we need at least 10 ticks between each measure */
  50 #define MIN_STAT_SAMPLING_RATE                  \
  51                         (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
  52 #define MIN_SAMPLING_RATE                       \
  53                         (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
  54 #define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
  55 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (1000)
  56 #define TRANSITION_LATENCY_LIMIT                (10 * 1000 * 1000)
  57
  58 static void do_dbs_timer(struct work_struct *work);
  59
  60 /* Sampling types */
  61 enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE};
  62
  63 struct cpu_dbs_info_s {
  64         cputime64_t prev_cpu_idle;
  65         cputime64_t prev_cpu_wall;
  66         cputime64_t prev_cpu_nice;
  67         struct cpufreq_policy *cur_policy;
  68         struct delayed_work work;
  69         struct cpufreq_frequency_table *freq_table;
  70         unsigned int freq_lo;
  71         unsigned int freq_lo_jiffies;
  72         unsigned int freq_hi_jiffies;
  73         int cpu;
  74         unsigned int enable:1,
  75                      sample_type:1;
  76 };
  77 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
  78
  79 static unsigned int dbs_enable; /* number of CPUs using this policy */
  80
  81 /*
  82  * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
  83  * lock and dbs_mutex. cpu_hotplug lock should always be held before
  84  * dbs_mutex. If any function that can potentially take cpu_hotplug lock
  85  * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
  86  * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
  87  * is recursive for the same process. -Venki
  88  */
  89 static DEFINE_MUTEX(dbs_mutex);
  90
  91 static struct workqueue_struct  *kondemand_wq;
  92
  93 static struct dbs_tuners {
  94         unsigned int sampling_rate;
  95         unsigned int up_threshold;
  96         unsigned int down_differential;
  97         unsigned int ignore_nice;
  98         unsigned int powersave_bias;
  99 } dbs_tuners_ins = {
 100         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
 101         .down_differential = DEF_FREQUENCY_DOWN_DIFFERENTIAL,
 102         .ignore_nice = 0,
 103         .powersave_bias = 0,
 104 };
 105
 106 static inline cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu,
 107                                                         cputime64_t *wall)
 108 {
 109         cputime64_t idle_time;
 110         cputime64_t cur_wall_time;
 111         cputime64_t busy_time;
 112
 113         cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
 114         busy_time = cputime64_add(kstat_cpu(cpu).cpustat.user,
 115                         kstat_cpu(cpu).cpustat.system);
 116
 117         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.irq);
 118         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.softirq);
 119         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.steal);
 120
 121         if (!dbs_tuners_ins.ignore_nice) {
 122                 busy_time = cputime64_add(busy_time,
 123                                 kstat_cpu(cpu).cpustat.nice);
 124         }
 125
 126         idle_time = cputime64_sub(cur_wall_time, busy_time);
 127         if (wall)
 128                 *wall = cur_wall_time;
 129
 130         return idle_time;
 131 }
 132
 133 static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
 134 {
 135         u64 idle_time = get_cpu_idle_time_us(cpu, wall);
 136
 137         if (idle_time == -1ULL)
 138                 return get_cpu_idle_time_jiffy(cpu, wall);
 139
 140         if (dbs_tuners_ins.ignore_nice) {
 141                 cputime64_t cur_nice;
 142                 unsigned long cur_nice_jiffies;
 143                 struct cpu_dbs_info_s *dbs_info;
 144
 145                 dbs_info = &per_cpu(cpu_dbs_info, cpu);
 146                 cur_nice = cputime64_sub(kstat_cpu(cpu).cpustat.nice,
 147                                          dbs_info->prev_cpu_nice);
 148                 /*
 149                  * Assumption: nice time between sampling periods will be
 150                  * less than 2^32 jiffies for 32 bit sys
 151                  */
 152                 cur_nice_jiffies = (unsigned long)
 153                                         cputime64_to_jiffies64(cur_nice);
 154                 dbs_info->prev_cpu_nice = kstat_cpu(cpu).cpustat.nice;
 155                 return idle_time + jiffies_to_usecs(cur_nice_jiffies);
 156         }
 157         return idle_time;
 158 }
 159
 160 /*
 161  * Find right freq to be set now with powersave_bias on.
 162  * Returns the freq_hi to be used right now and will set freq_hi_jiffies,
 163  * freq_lo, and freq_lo_jiffies in percpu area for averaging freqs.
 164  */
 165 static unsigned int powersave_bias_target(struct cpufreq_policy *policy,
 166                                           unsigned int freq_next,
 167                                           unsigned int relation)
 168 {
 169         unsigned int freq_req, freq_reduc, freq_avg;
 170         unsigned int freq_hi, freq_lo;
 171         unsigned int index = 0;
 172         unsigned int jiffies_total, jiffies_hi, jiffies_lo;
 173         struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, policy->cpu);
 174
 175         if (!dbs_info->freq_table) {
 176                 dbs_info->freq_lo = 0;
 177                 dbs_info->freq_lo_jiffies = 0;
 178                 return freq_next;
 179         }
 180
 181         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_next,
 182                         relation, &index);
 183         freq_req = dbs_info->freq_table[index].frequency;
 184         freq_reduc = freq_req * dbs_tuners_ins.powersave_bias / 1000;
 185         freq_avg = freq_req - freq_reduc;
 186
 187         /* Find freq bounds for freq_avg in freq_table */
 188         index = 0;
 189         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 190                         CPUFREQ_RELATION_H, &index);
 191         freq_lo = dbs_info->freq_table[index].frequency;
 192         index = 0;
 193         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 194                         CPUFREQ_RELATION_L, &index);
 195         freq_hi = dbs_info->freq_table[index].frequency;
 196
 197         /* Find out how long we have to be in hi and lo freqs */
 198         if (freq_hi == freq_lo) {
 199                 dbs_info->freq_lo = 0;
 200                 dbs_info->freq_lo_jiffies = 0;
 201                 return freq_lo;
 202         }
 203         jiffies_total = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 204         jiffies_hi = (freq_avg - freq_lo) * jiffies_total;
 205         jiffies_hi += ((freq_hi - freq_lo) / 2);
 206         jiffies_hi /= (freq_hi - freq_lo);
 207         jiffies_lo = jiffies_total - jiffies_hi;
 208         dbs_info->freq_lo = freq_lo;
 209         dbs_info->freq_lo_jiffies = jiffies_lo;
 210         dbs_info->freq_hi_jiffies = jiffies_hi;
 211         return freq_hi;
 212 }
 213
 214 static void ondemand_powersave_bias_init(void)
 215 {
 216         int i;
 217         for_each_online_cpu(i) {
 218                 struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, i);
 219                 dbs_info->freq_table = cpufreq_frequency_get_table(i);
 220                 dbs_info->freq_lo = 0;
 221         }
 222 }
 223
 224 /************************** sysfs interface ************************/
 225 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 226 {
 227         return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
 228 }
 229
 230 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 231 {
 232         return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 233 }
 234
 235 #define define_one_ro(_name)            \
 236 static struct freq_attr _name =         \
 237 __ATTR(_name, 0444, show_##_name, NULL)
 238
 239 define_one_ro(sampling_rate_max);
 240 define_one_ro(sampling_rate_min);
 241
 242 /* cpufreq_ondemand Governor Tunables */
 243 #define show_one(file_name, object)                                     \
 244 static ssize_t show_##file_name                                         \
 245 (struct cpufreq_policy *unused, char *buf)                              \
 246 {                                                                       \
 247         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 248 }
 249 show_one(sampling_rate, sampling_rate);
 250 show_one(up_threshold, up_threshold);
 251 show_one(ignore_nice_load, ignore_nice);
 252 show_one(powersave_bias, powersave_bias);
 253
 254 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 255                 const char *buf, size_t count)
 256 {
 257         unsigned int input;
 258         int ret;
 259         ret = sscanf(buf, "%u", &input);
 260
 261         mutex_lock(&dbs_mutex);
 262         if (ret != 1 || input > MAX_SAMPLING_RATE
 263                      || input < MIN_SAMPLING_RATE) {
 264                 mutex_unlock(&dbs_mutex);
 265                 return -EINVAL;
 266         }
 267
 268         dbs_tuners_ins.sampling_rate = input;
 269         mutex_unlock(&dbs_mutex);
 270
 271         return count;
 272 }
 273
 274 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 275                 const char *buf, size_t count)
 276 {
 277         unsigned int input;
 278         int ret;
 279         ret = sscanf(buf, "%u", &input);
 280
 281         mutex_lock(&dbs_mutex);
 282         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 283                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 284                 mutex_unlock(&dbs_mutex);
 285                 return -EINVAL;
 286         }
 287
 288         dbs_tuners_ins.up_threshold = input;
 289         mutex_unlock(&dbs_mutex);
 290
 291         return count;
 292 }
 293
 294 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 295                 const char *buf, size_t count)
 296 {
 297         unsigned int input;
 298         int ret;
 299
 300         unsigned int j;
 301
 302         ret = sscanf(buf, "%u", &input);
 303         if ( ret != 1 )
 304                 return -EINVAL;
 305
 306         if ( input > 1 )
 307                 input = 1;
 308
 309         mutex_lock(&dbs_mutex);
 310         if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
 311                 mutex_unlock(&dbs_mutex);
 312                 return count;
 313         }
 314         dbs_tuners_ins.ignore_nice = input;
 315
 316         /* we need to re-evaluate prev_cpu_idle */
 317         for_each_online_cpu(j) {
 318                 struct cpu_dbs_info_s *dbs_info;
 319                 dbs_info = &per_cpu(cpu_dbs_info, j);
 320                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 321                                                 &dbs_info->prev_cpu_wall);
 322         }
 323         mutex_unlock(&dbs_mutex);
 324
 325         return count;
 326 }
 327
 328 static ssize_t store_powersave_bias(struct cpufreq_policy *unused,
 329                 const char *buf, size_t count)
 330 {
 331         unsigned int input;
 332         int ret;
 333         ret = sscanf(buf, "%u", &input);
 334
 335         if (ret != 1)
 336                 return -EINVAL;
 337
 338         if (input > 1000)
 339                 input = 1000;
 340
 341         mutex_lock(&dbs_mutex);
 342         dbs_tuners_ins.powersave_bias = input;
 343         ondemand_powersave_bias_init();
 344         mutex_unlock(&dbs_mutex);
 345
 346         return count;
 347 }
 348
 349 #define define_one_rw(_name) \
 350 static struct freq_attr _name = \
 351 __ATTR(_name, 0644, show_##_name, store_##_name)
 352
 353 define_one_rw(sampling_rate);
 354 define_one_rw(up_threshold);
 355 define_one_rw(ignore_nice_load);
 356 define_one_rw(powersave_bias);
 357
 358 static struct attribute * dbs_attributes[] = {
 359         &sampling_rate_max.attr,
 360         &sampling_rate_min.attr,
 361         &sampling_rate.attr,
 362         &up_threshold.attr,
 363         &ignore_nice_load.attr,
 364         &powersave_bias.attr,
 365         NULL
 366 };
 367
 368 static struct attribute_group dbs_attr_group = {
 369         .attrs = dbs_attributes,
 370         .name = "ondemand",
 371 };
 372
 373 /************************** sysfs end ************************/
 374
 375 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 376 {
 377         unsigned int max_load_freq;
 378
 379         struct cpufreq_policy *policy;
 380         unsigned int j;
 381
 382         if (!this_dbs_info->enable)
 383                 return;
 384
 385         this_dbs_info->freq_lo = 0;
 386         policy = this_dbs_info->cur_policy;
 387
 388         /*
 389          * Every sampling_rate, we check, if current idle time is less
 390          * than 20% (default), then we try to increase frequency
 391          * Every sampling_rate, we look for a the lowest
 392          * frequency which can sustain the load while keeping idle time over
 393          * 30%. If such a frequency exist, we try to decrease to this frequency.
 394          *
 395          * Any frequency increase takes it to the maximum frequency.
 396          * Frequency reduction happens at minimum steps of
 397          * 5% (default) of current frequency
 398          */
 399
 400         /* Get Absolute Load - in terms of freq */
 401         max_load_freq = 0;
 402
 403         for_each_cpu(j, policy->cpus) {
 404                 struct cpu_dbs_info_s *j_dbs_info;
 405                 cputime64_t cur_wall_time, cur_idle_time;
 406                 unsigned int idle_time, wall_time;
 407                 unsigned int load, load_freq;
 408                 int freq_avg;
 409
 410                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 411
 412                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
 413
 414                 wall_time = (unsigned int) cputime64_sub(cur_wall_time,
 415                                 j_dbs_info->prev_cpu_wall);
 416                 j_dbs_info->prev_cpu_wall = cur_wall_time;
 417
 418                 idle_time = (unsigned int) cputime64_sub(cur_idle_time,
 419                                 j_dbs_info->prev_cpu_idle);
 420                 j_dbs_info->prev_cpu_idle = cur_idle_time;
 421
 422                 if (unlikely(!wall_time || wall_time < idle_time))
 423                         continue;
 424
 425                 load = 100 * (wall_time - idle_time) / wall_time;
 426
 427                 freq_avg = __cpufreq_driver_getavg(policy, j);
 428                 if (freq_avg <= 0)
 429                         freq_avg = policy->cur;
 430
 431                 load_freq = load * freq_avg;
 432                 if (load_freq > max_load_freq)
 433                         max_load_freq = load_freq;
 434         }
 435
 436         /* Check for frequency increase */
 437         if (max_load_freq > dbs_tuners_ins.up_threshold * policy->cur) {
 438                 /* if we are already at full speed then break out early */
 439                 if (!dbs_tuners_ins.powersave_bias) {
 440                         if (policy->cur == policy->max)
 441                                 return;
 442
 443                         __cpufreq_driver_target(policy, policy->max,
 444                                 CPUFREQ_RELATION_H);
 445                 } else {
 446                         int freq = powersave_bias_target(policy, policy->max,
 447                                         CPUFREQ_RELATION_H);
 448                         __cpufreq_driver_target(policy, freq,
 449                                 CPUFREQ_RELATION_L);
 450                 }
 451                 return;
 452         }
 453
 454         /* Check for frequency decrease */
 455         /* if we cannot reduce the frequency anymore, break out early */
 456         if (policy->cur == policy->min)
 457                 return;
 458
 459         /*
 460          * The optimal frequency is the frequency that is the lowest that
 461          * can support the current CPU usage without triggering the up
 462          * policy. To be safe, we focus 10 points under the threshold.
 463          */
 464         if (max_load_freq <
 465             (dbs_tuners_ins.up_threshold - dbs_tuners_ins.down_differential) *
 466              policy->cur) {
 467                 unsigned int freq_next;
 468                 freq_next = max_load_freq /
 469                                 (dbs_tuners_ins.up_threshold -
 470                                  dbs_tuners_ins.down_differential);
 471
 472                 if (!dbs_tuners_ins.powersave_bias) {
 473                         __cpufreq_driver_target(policy, freq_next,
 474                                         CPUFREQ_RELATION_L);
 475                 } else {
 476                         int freq = powersave_bias_target(policy, freq_next,
 477                                         CPUFREQ_RELATION_L);
 478                         __cpufreq_driver_target(policy, freq,
 479                                 CPUFREQ_RELATION_L);
 480                 }
 481         }
 482 }
 483
 484 static void do_dbs_timer(struct work_struct *work)
 485 {
 486         struct cpu_dbs_info_s *dbs_info =
 487                 container_of(work, struct cpu_dbs_info_s, work.work);
 488         unsigned int cpu = dbs_info->cpu;
 489         int sample_type = dbs_info->sample_type;
 490
 491         /* We want all CPUs to do sampling nearly on same jiffy */
 492         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 493
 494         delay -= jiffies % delay;
 495
 496         if (lock_policy_rwsem_write(cpu) < 0)
 497                 return;
 498
 499         if (!dbs_info->enable) {
 500                 unlock_policy_rwsem_write(cpu);
 501                 return;
 502         }
 503
 504         /* Common NORMAL_SAMPLE setup */
 505         dbs_info->sample_type = DBS_NORMAL_SAMPLE;
 506         if (!dbs_tuners_ins.powersave_bias ||
 507             sample_type == DBS_NORMAL_SAMPLE) {
 508                 dbs_check_cpu(dbs_info);
 509                 if (dbs_info->freq_lo) {
 510                         /* Setup timer for SUB_SAMPLE */
 511                         dbs_info->sample_type = DBS_SUB_SAMPLE;
 512                         delay = dbs_info->freq_hi_jiffies;
 513                 }
 514         } else {
 515                 __cpufreq_driver_target(dbs_info->cur_policy,
 516                                         dbs_info->freq_lo,
 517                                         CPUFREQ_RELATION_H);
 518         }
 519         queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
 520         unlock_policy_rwsem_write(cpu);
 521 }
 522
 523 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 524 {
 525         /* We want all CPUs to do sampling nearly on same jiffy */
 526         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 527         delay -= jiffies % delay;
 528
 529         dbs_info->enable = 1;
 530         ondemand_powersave_bias_init();
 531         dbs_info->sample_type = DBS_NORMAL_SAMPLE;
 532         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
 533         queue_delayed_work_on(dbs_info->cpu, kondemand_wq, &dbs_info->work,
 534                               delay);
 535 }
 536
 537 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 538 {
 539         dbs_info->enable = 0;
 540         cancel_delayed_work(&dbs_info->work);
 541 }
 542
 543 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 544                                    unsigned int event)
 545 {
 546         unsigned int cpu = policy->cpu;
 547         struct cpu_dbs_info_s *this_dbs_info;
 548         unsigned int j;
 549         int rc;
 550
 551         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 552
 553         switch (event) {
 554         case CPUFREQ_GOV_START:
 555                 if ((!cpu_online(cpu)) || (!policy->cur))
 556                         return -EINVAL;
 557
 558                 if (this_dbs_info->enable) /* Already enabled */
 559                         break;
 560
 561                 mutex_lock(&dbs_mutex);
 562                 dbs_enable++;
 563
 564                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
 565                 if (rc) {
 566                         dbs_enable--;
 567                         mutex_unlock(&dbs_mutex);
 568                         return rc;
 569                 }
 570
 571                 for_each_cpu(j, policy->cpus) {
 572                         struct cpu_dbs_info_s *j_dbs_info;
 573                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 574                         j_dbs_info->cur_policy = policy;
 575
 576                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 577                                                 &j_dbs_info->prev_cpu_wall);
 578                 }
 579                 this_dbs_info->cpu = cpu;
 580                 /*
 581                  * Start the timerschedule work, when this governor
 582                  * is used for first time
 583                  */
 584                 if (dbs_enable == 1) {
 585                         unsigned int latency;
 586                         /* policy latency is in nS. Convert it to uS first */
 587                         latency = policy->cpuinfo.transition_latency / 1000;
 588                         if (latency == 0)
 589                                 latency = 1;
 590
 591                         def_sampling_rate = latency *
 592                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 593
 594                         if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
 595                                 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 596
 597                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 598                 }
 599                 dbs_timer_init(this_dbs_info);
 600
 601                 mutex_unlock(&dbs_mutex);
 602                 break;
 603
 604         case CPUFREQ_GOV_STOP:
 605                 mutex_lock(&dbs_mutex);
 606                 dbs_timer_exit(this_dbs_info);
 607                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 608                 dbs_enable--;
 609                 mutex_unlock(&dbs_mutex);
 610
 611                 break;
 612
 613         case CPUFREQ_GOV_LIMITS:
 614                 mutex_lock(&dbs_mutex);
 615                 if (policy->max < this_dbs_info->cur_policy->cur)
 616                         __cpufreq_driver_target(this_dbs_info->cur_policy,
 617                                                 policy->max,
 618                                                 CPUFREQ_RELATION_H);
 619                 else if (policy->min > this_dbs_info->cur_policy->cur)
 620                         __cpufreq_driver_target(this_dbs_info->cur_policy,
 621                                                 policy->min,
 622                                                 CPUFREQ_RELATION_L);
 623                 mutex_unlock(&dbs_mutex);
 624                 break;
 625         }
 626         return 0;
 627 }
 628
 629 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 630 static
 631 #endif
 632 struct cpufreq_governor cpufreq_gov_ondemand = {
 633         .name                   = "ondemand",
 634         .governor               = cpufreq_governor_dbs,
 635         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 636         .owner                  = THIS_MODULE,
 637 };
 638
 639 static int __init cpufreq_gov_dbs_init(void)
 640 {
 641         int err;
 642         cputime64_t wall;
 643         u64 idle_time;
 644         int cpu = get_cpu();
 645
 646         idle_time = get_cpu_idle_time_us(cpu, &wall);
 647         put_cpu();
 648         if (idle_time != -1ULL) {
 649                 /* Idle micro accounting is supported. Use finer thresholds */
 650                 dbs_tuners_ins.up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
 651                 dbs_tuners_ins.down_differential =
 652                                         MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
 653         }
 654
 655         kondemand_wq = create_workqueue("kondemand");
 656         if (!kondemand_wq) {
 657                 printk(KERN_ERR "Creation of kondemand failed\n");
 658                 return -EFAULT;
 659         }
 660         err = cpufreq_register_governor(&cpufreq_gov_ondemand);
 661         if (err)
 662                 destroy_workqueue(kondemand_wq);
 663
 664         return err;
 665 }
 666
 667 static void __exit cpufreq_gov_dbs_exit(void)
 668 {
 669         cpufreq_unregister_governor(&cpufreq_gov_ondemand);
 670         destroy_workqueue(kondemand_wq);
 671 }
 672
 673
 674 MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 675 MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
 676 MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 677                    "Low Latency Frequency Transition capable processors");
 678 MODULE_LICENSE("GPL");
 679
 680 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 681 fs_initcall(cpufreq_gov_dbs_init);
 682 #else
 683 module_init(cpufreq_gov_dbs_init);
 684 #endif
 685 module_exit(cpufreq_gov_dbs_exit);