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
  22 /*
  23  * dbs is used in this file as a shortform for demandbased switching
  24  * It helps to keep variable names smaller, simpler
  25  */
  26
  27 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
  28 #define MIN_FREQUENCY_UP_THRESHOLD              (11)
  29 #define MAX_FREQUENCY_UP_THRESHOLD              (100)
  30
  31 /*
  32  * The polling frequency of this governor depends on the capability of
  33  * the processor. Default polling frequency is 1000 times the transition
  34  * latency of the processor. The governor will work on any processor with
  35  * transition latency <= 10mS, using appropriate sampling
  36  * rate.
  37  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
  38  * this governor will not work.
  39  * All times here are in uS.
  40  */
  41 static unsigned int def_sampling_rate;
  42 #define MIN_SAMPLING_RATE_RATIO                 (2)
  43 /* for correct statistics, we need at least 10 ticks between each measure */
  44 #define MIN_STAT_SAMPLING_RATE                  \
  45                         (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
  46 #define MIN_SAMPLING_RATE                       \
  47                         (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
  48 #define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
  49 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (1000)
  50 #define TRANSITION_LATENCY_LIMIT                (10 * 1000 * 1000)
  51
  52 static void do_dbs_timer(struct work_struct *work);
  53
  54 /* Sampling types */
  55 enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE};
  56
  57 struct cpu_dbs_info_s {
  58         cputime64_t prev_cpu_idle;
  59         cputime64_t prev_cpu_wall;
  60         struct cpufreq_policy *cur_policy;
  61         struct delayed_work work;
  62         struct cpufreq_frequency_table *freq_table;
  63         unsigned int freq_lo;
  64         unsigned int freq_lo_jiffies;
  65         unsigned int freq_hi_jiffies;
  66         int cpu;
  67         unsigned int enable:1,
  68                      sample_type:1;
  69 };
  70 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
  71
  72 static unsigned int dbs_enable; /* number of CPUs using this policy */
  73
  74 /*
  75  * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
  76  * lock and dbs_mutex. cpu_hotplug lock should always be held before
  77  * dbs_mutex. If any function that can potentially take cpu_hotplug lock
  78  * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
  79  * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
  80  * is recursive for the same process. -Venki
  81  */
  82 static DEFINE_MUTEX(dbs_mutex);
  83
  84 static struct workqueue_struct  *kondemand_wq;
  85
  86 static struct dbs_tuners {
  87         unsigned int sampling_rate;
  88         unsigned int up_threshold;
  89         unsigned int ignore_nice;
  90         unsigned int powersave_bias;
  91 } dbs_tuners_ins = {
  92         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
  93         .ignore_nice = 0,
  94         .powersave_bias = 0,
  95 };
  96
  97 static inline cputime64_t get_cpu_idle_time(unsigned int cpu)
  98 {
  99         cputime64_t idle_time;
 100         cputime64_t cur_jiffies;
 101         cputime64_t busy_time;
 102
 103         cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());
 104         busy_time = cputime64_add(kstat_cpu(cpu).cpustat.user,
 105                         kstat_cpu(cpu).cpustat.system);
 106
 107         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.irq);
 108         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.softirq);
 109         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.steal);
 110
 111         if (!dbs_tuners_ins.ignore_nice) {
 112                 busy_time = cputime64_add(busy_time,
 113                                 kstat_cpu(cpu).cpustat.nice);
 114         }
 115
 116         idle_time = cputime64_sub(cur_jiffies, busy_time);
 117         return idle_time;
 118 }
 119
 120 /*
 121  * Find right freq to be set now with powersave_bias on.
 122  * Returns the freq_hi to be used right now and will set freq_hi_jiffies,
 123  * freq_lo, and freq_lo_jiffies in percpu area for averaging freqs.
 124  */
 125 static unsigned int powersave_bias_target(struct cpufreq_policy *policy,
 126                                           unsigned int freq_next,
 127                                           unsigned int relation)
 128 {
 129         unsigned int freq_req, freq_reduc, freq_avg;
 130         unsigned int freq_hi, freq_lo;
 131         unsigned int index = 0;
 132         unsigned int jiffies_total, jiffies_hi, jiffies_lo;
 133         struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, policy->cpu);
 134
 135         if (!dbs_info->freq_table) {
 136                 dbs_info->freq_lo = 0;
 137                 dbs_info->freq_lo_jiffies = 0;
 138                 return freq_next;
 139         }
 140
 141         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_next,
 142                         relation, &index);
 143         freq_req = dbs_info->freq_table[index].frequency;
 144         freq_reduc = freq_req * dbs_tuners_ins.powersave_bias / 1000;
 145         freq_avg = freq_req - freq_reduc;
 146
 147         /* Find freq bounds for freq_avg in freq_table */
 148         index = 0;
 149         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 150                         CPUFREQ_RELATION_H, &index);
 151         freq_lo = dbs_info->freq_table[index].frequency;
 152         index = 0;
 153         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 154                         CPUFREQ_RELATION_L, &index);
 155         freq_hi = dbs_info->freq_table[index].frequency;
 156
 157         /* Find out how long we have to be in hi and lo freqs */
 158         if (freq_hi == freq_lo) {
 159                 dbs_info->freq_lo = 0;
 160                 dbs_info->freq_lo_jiffies = 0;
 161                 return freq_lo;
 162         }
 163         jiffies_total = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 164         jiffies_hi = (freq_avg - freq_lo) * jiffies_total;
 165         jiffies_hi += ((freq_hi - freq_lo) / 2);
 166         jiffies_hi /= (freq_hi - freq_lo);
 167         jiffies_lo = jiffies_total - jiffies_hi;
 168         dbs_info->freq_lo = freq_lo;
 169         dbs_info->freq_lo_jiffies = jiffies_lo;
 170         dbs_info->freq_hi_jiffies = jiffies_hi;
 171         return freq_hi;
 172 }
 173
 174 static void ondemand_powersave_bias_init(void)
 175 {
 176         int i;
 177         for_each_online_cpu(i) {
 178                 struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, i);
 179                 dbs_info->freq_table = cpufreq_frequency_get_table(i);
 180                 dbs_info->freq_lo = 0;
 181         }
 182 }
 183
 184 /************************** sysfs interface ************************/
 185 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 186 {
 187         return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
 188 }
 189
 190 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 191 {
 192         return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 193 }
 194
 195 #define define_one_ro(_name)            \
 196 static struct freq_attr _name =         \
 197 __ATTR(_name, 0444, show_##_name, NULL)
 198
 199 define_one_ro(sampling_rate_max);
 200 define_one_ro(sampling_rate_min);
 201
 202 /* cpufreq_ondemand Governor Tunables */
 203 #define show_one(file_name, object)                                     \
 204 static ssize_t show_##file_name                                         \
 205 (struct cpufreq_policy *unused, char *buf)                              \
 206 {                                                                       \
 207         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 208 }
 209 show_one(sampling_rate, sampling_rate);
 210 show_one(up_threshold, up_threshold);
 211 show_one(ignore_nice_load, ignore_nice);
 212 show_one(powersave_bias, powersave_bias);
 213
 214 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 215                 const char *buf, size_t count)
 216 {
 217         unsigned int input;
 218         int ret;
 219         ret = sscanf(buf, "%u", &input);
 220
 221         mutex_lock(&dbs_mutex);
 222         if (ret != 1 || input > MAX_SAMPLING_RATE
 223                      || input < MIN_SAMPLING_RATE) {
 224                 mutex_unlock(&dbs_mutex);
 225                 return -EINVAL;
 226         }
 227
 228         dbs_tuners_ins.sampling_rate = input;
 229         mutex_unlock(&dbs_mutex);
 230
 231         return count;
 232 }
 233
 234 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 235                 const char *buf, size_t count)
 236 {
 237         unsigned int input;
 238         int ret;
 239         ret = sscanf(buf, "%u", &input);
 240
 241         mutex_lock(&dbs_mutex);
 242         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 243                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 244                 mutex_unlock(&dbs_mutex);
 245                 return -EINVAL;
 246         }
 247
 248         dbs_tuners_ins.up_threshold = input;
 249         mutex_unlock(&dbs_mutex);
 250
 251         return count;
 252 }
 253
 254 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 255                 const char *buf, size_t count)
 256 {
 257         unsigned int input;
 258         int ret;
 259
 260         unsigned int j;
 261
 262         ret = sscanf(buf, "%u", &input);
 263         if ( ret != 1 )
 264                 return -EINVAL;
 265
 266         if ( input > 1 )
 267                 input = 1;
 268
 269         mutex_lock(&dbs_mutex);
 270         if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
 271                 mutex_unlock(&dbs_mutex);
 272                 return count;
 273         }
 274         dbs_tuners_ins.ignore_nice = input;
 275
 276         /* we need to re-evaluate prev_cpu_idle */
 277         for_each_online_cpu(j) {
 278                 struct cpu_dbs_info_s *dbs_info;
 279                 dbs_info = &per_cpu(cpu_dbs_info, j);
 280                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
 281                 dbs_info->prev_cpu_wall = get_jiffies_64();
 282         }
 283         mutex_unlock(&dbs_mutex);
 284
 285         return count;
 286 }
 287
 288 static ssize_t store_powersave_bias(struct cpufreq_policy *unused,
 289                 const char *buf, size_t count)
 290 {
 291         unsigned int input;
 292         int ret;
 293         ret = sscanf(buf, "%u", &input);
 294
 295         if (ret != 1)
 296                 return -EINVAL;
 297
 298         if (input > 1000)
 299                 input = 1000;
 300
 301         mutex_lock(&dbs_mutex);
 302         dbs_tuners_ins.powersave_bias = input;
 303         ondemand_powersave_bias_init();
 304         mutex_unlock(&dbs_mutex);
 305
 306         return count;
 307 }
 308
 309 #define define_one_rw(_name) \
 310 static struct freq_attr _name = \
 311 __ATTR(_name, 0644, show_##_name, store_##_name)
 312
 313 define_one_rw(sampling_rate);
 314 define_one_rw(up_threshold);
 315 define_one_rw(ignore_nice_load);
 316 define_one_rw(powersave_bias);
 317
 318 static struct attribute * dbs_attributes[] = {
 319         &sampling_rate_max.attr,
 320         &sampling_rate_min.attr,
 321         &sampling_rate.attr,
 322         &up_threshold.attr,
 323         &ignore_nice_load.attr,
 324         &powersave_bias.attr,
 325         NULL
 326 };
 327
 328 static struct attribute_group dbs_attr_group = {
 329         .attrs = dbs_attributes,
 330         .name = "ondemand",
 331 };
 332
 333 /************************** sysfs end ************************/
 334
 335 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 336 {
 337         unsigned int max_load_freq;
 338
 339         struct cpufreq_policy *policy;
 340         unsigned int j;
 341
 342         if (!this_dbs_info->enable)
 343                 return;
 344
 345         this_dbs_info->freq_lo = 0;
 346         policy = this_dbs_info->cur_policy;
 347
 348         /*
 349          * Every sampling_rate, we check, if current idle time is less
 350          * than 20% (default), then we try to increase frequency
 351          * Every sampling_rate, we look for a the lowest
 352          * frequency which can sustain the load while keeping idle time over
 353          * 30%. If such a frequency exist, we try to decrease to this frequency.
 354          *
 355          * Any frequency increase takes it to the maximum frequency.
 356          * Frequency reduction happens at minimum steps of
 357          * 5% (default) of current frequency
 358          */
 359
 360         /* Get Absolute Load - in terms of freq */
 361         max_load_freq = 0;
 362
 363         for_each_cpu_mask_nr(j, policy->cpus) {
 364                 struct cpu_dbs_info_s *j_dbs_info;
 365                 cputime64_t cur_wall_time, cur_idle_time;
 366                 unsigned int idle_time, wall_time;
 367                 unsigned int load, load_freq;
 368                 int freq_avg;
 369
 370                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 371                 cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
 372                 wall_time = (unsigned int) cputime64_sub(cur_wall_time,
 373                                 j_dbs_info->prev_cpu_wall);
 374                 j_dbs_info->prev_cpu_wall = cur_wall_time;
 375
 376                 cur_idle_time = get_cpu_idle_time(j);
 377                 idle_time = (unsigned int) cputime64_sub(cur_idle_time,
 378                                 j_dbs_info->prev_cpu_idle);
 379                 j_dbs_info->prev_cpu_idle = cur_idle_time;
 380
 381                 if (unlikely(wall_time <= idle_time ||
 382                              (cputime_to_msecs(wall_time) <
 383                               dbs_tuners_ins.sampling_rate / (2 * 1000)))) {
 384                         continue;
 385                 }
 386
 387                 load = 100 * (wall_time - idle_time) / wall_time;
 388
 389                 freq_avg = __cpufreq_driver_getavg(policy, j);
 390                 if (freq_avg <= 0)
 391                         freq_avg = policy->cur;
 392
 393                 load_freq = load * freq_avg;
 394                 if (load_freq > max_load_freq)
 395                         max_load_freq = load_freq;
 396         }
 397
 398         /* Check for frequency increase */
 399         if (max_load_freq > dbs_tuners_ins.up_threshold * policy->cur) {
 400                 /* if we are already at full speed then break out early */
 401                 if (!dbs_tuners_ins.powersave_bias) {
 402                         if (policy->cur == policy->max)
 403                                 return;
 404
 405                         __cpufreq_driver_target(policy, policy->max,
 406                                 CPUFREQ_RELATION_H);
 407                 } else {
 408                         int freq = powersave_bias_target(policy, policy->max,
 409                                         CPUFREQ_RELATION_H);
 410                         __cpufreq_driver_target(policy, freq,
 411                                 CPUFREQ_RELATION_L);
 412                 }
 413                 return;
 414         }
 415
 416         /* Check for frequency decrease */
 417         /* if we cannot reduce the frequency anymore, break out early */
 418         if (policy->cur == policy->min)
 419                 return;
 420
 421         /*
 422          * The optimal frequency is the frequency that is the lowest that
 423          * can support the current CPU usage without triggering the up
 424          * policy. To be safe, we focus 10 points under the threshold.
 425          */
 426         if (max_load_freq < (dbs_tuners_ins.up_threshold - 10) * policy->cur) {
 427                 unsigned int freq_next;
 428                 freq_next = max_load_freq / (dbs_tuners_ins.up_threshold - 10);
 429
 430                 if (!dbs_tuners_ins.powersave_bias) {
 431                         __cpufreq_driver_target(policy, freq_next,
 432                                         CPUFREQ_RELATION_L);
 433                 } else {
 434                         int freq = powersave_bias_target(policy, freq_next,
 435                                         CPUFREQ_RELATION_L);
 436                         __cpufreq_driver_target(policy, freq,
 437                                 CPUFREQ_RELATION_L);
 438                 }
 439         }
 440 }
 441
 442 static void do_dbs_timer(struct work_struct *work)
 443 {
 444         struct cpu_dbs_info_s *dbs_info =
 445                 container_of(work, struct cpu_dbs_info_s, work.work);
 446         unsigned int cpu = dbs_info->cpu;
 447         int sample_type = dbs_info->sample_type;
 448
 449         /* We want all CPUs to do sampling nearly on same jiffy */
 450         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 451
 452         delay -= jiffies % delay;
 453
 454         if (lock_policy_rwsem_write(cpu) < 0)
 455                 return;
 456
 457         if (!dbs_info->enable) {
 458                 unlock_policy_rwsem_write(cpu);
 459                 return;
 460         }
 461
 462         /* Common NORMAL_SAMPLE setup */
 463         dbs_info->sample_type = DBS_NORMAL_SAMPLE;
 464         if (!dbs_tuners_ins.powersave_bias ||
 465             sample_type == DBS_NORMAL_SAMPLE) {
 466                 dbs_check_cpu(dbs_info);
 467                 if (dbs_info->freq_lo) {
 468                         /* Setup timer for SUB_SAMPLE */
 469                         dbs_info->sample_type = DBS_SUB_SAMPLE;
 470                         delay = dbs_info->freq_hi_jiffies;
 471                 }
 472         } else {
 473                 __cpufreq_driver_target(dbs_info->cur_policy,
 474                                         dbs_info->freq_lo,
 475                                         CPUFREQ_RELATION_H);
 476         }
 477         queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
 478         unlock_policy_rwsem_write(cpu);
 479 }
 480
 481 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 482 {
 483         /* We want all CPUs to do sampling nearly on same jiffy */
 484         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 485         delay -= jiffies % delay;
 486
 487         dbs_info->enable = 1;
 488         ondemand_powersave_bias_init();
 489         dbs_info->sample_type = DBS_NORMAL_SAMPLE;
 490         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
 491         queue_delayed_work_on(dbs_info->cpu, kondemand_wq, &dbs_info->work,
 492                               delay);
 493 }
 494
 495 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 496 {
 497         dbs_info->enable = 0;
 498         cancel_delayed_work(&dbs_info->work);
 499 }
 500
 501 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 502                                    unsigned int event)
 503 {
 504         unsigned int cpu = policy->cpu;
 505         struct cpu_dbs_info_s *this_dbs_info;
 506         unsigned int j;
 507         int rc;
 508
 509         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 510
 511         switch (event) {
 512         case CPUFREQ_GOV_START:
 513                 if ((!cpu_online(cpu)) || (!policy->cur))
 514                         return -EINVAL;
 515
 516                 if (this_dbs_info->enable) /* Already enabled */
 517                         break;
 518
 519                 mutex_lock(&dbs_mutex);
 520                 dbs_enable++;
 521
 522                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
 523                 if (rc) {
 524                         dbs_enable--;
 525                         mutex_unlock(&dbs_mutex);
 526                         return rc;
 527                 }
 528
 529                 for_each_cpu_mask_nr(j, policy->cpus) {
 530                         struct cpu_dbs_info_s *j_dbs_info;
 531                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 532                         j_dbs_info->cur_policy = policy;
 533
 534                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
 535                         j_dbs_info->prev_cpu_wall = get_jiffies_64();
 536                 }
 537                 this_dbs_info->cpu = cpu;
 538                 /*
 539                  * Start the timerschedule work, when this governor
 540                  * is used for first time
 541                  */
 542                 if (dbs_enable == 1) {
 543                         unsigned int latency;
 544                         /* policy latency is in nS. Convert it to uS first */
 545                         latency = policy->cpuinfo.transition_latency / 1000;
 546                         if (latency == 0)
 547                                 latency = 1;
 548
 549                         def_sampling_rate = latency *
 550                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 551
 552                         if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
 553                                 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 554
 555                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 556                 }
 557                 dbs_timer_init(this_dbs_info);
 558
 559                 mutex_unlock(&dbs_mutex);
 560                 break;
 561
 562         case CPUFREQ_GOV_STOP:
 563                 mutex_lock(&dbs_mutex);
 564                 dbs_timer_exit(this_dbs_info);
 565                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 566                 dbs_enable--;
 567                 mutex_unlock(&dbs_mutex);
 568
 569                 break;
 570
 571         case CPUFREQ_GOV_LIMITS:
 572                 mutex_lock(&dbs_mutex);
 573                 if (policy->max < this_dbs_info->cur_policy->cur)
 574                         __cpufreq_driver_target(this_dbs_info->cur_policy,
 575                                                 policy->max,
 576                                                 CPUFREQ_RELATION_H);
 577                 else if (policy->min > this_dbs_info->cur_policy->cur)
 578                         __cpufreq_driver_target(this_dbs_info->cur_policy,
 579                                                 policy->min,
 580                                                 CPUFREQ_RELATION_L);
 581                 mutex_unlock(&dbs_mutex);
 582                 break;
 583         }
 584         return 0;
 585 }
 586
 587 struct cpufreq_governor cpufreq_gov_ondemand = {
 588         .name                   = "ondemand",
 589         .governor               = cpufreq_governor_dbs,
 590         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 591         .owner                  = THIS_MODULE,
 592 };
 593 EXPORT_SYMBOL(cpufreq_gov_ondemand);
 594
 595 static int __init cpufreq_gov_dbs_init(void)
 596 {
 597         int err;
 598
 599         kondemand_wq = create_workqueue("kondemand");
 600         if (!kondemand_wq) {
 601                 printk(KERN_ERR "Creation of kondemand failed\n");
 602                 return -EFAULT;
 603         }
 604         err = cpufreq_register_governor(&cpufreq_gov_ondemand);
 605         if (err)
 606                 destroy_workqueue(kondemand_wq);
 607
 608         return err;
 609 }
 610
 611 static void __exit cpufreq_gov_dbs_exit(void)
 612 {
 613         cpufreq_unregister_governor(&cpufreq_gov_ondemand);
 614         destroy_workqueue(kondemand_wq);
 615 }
 616
 617
 618 MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 619 MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
 620 MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 621                    "Low Latency Frequency Transition capable processors");
 622 MODULE_LICENSE("GPL");
 623
 624 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 625 fs_initcall(cpufreq_gov_dbs_init);
 626 #else
 627 module_init(cpufreq_gov_dbs_init);
 628 #endif
 629 module_exit(cpufreq_gov_dbs_exit);