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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  14
  15 #include <linux/cpu.h>
  16 #include <linux/percpu-defs.h>
  17 #include <linux/slab.h>
  18 #include <linux/tick.h>
  19 #include "cpufreq_governor.h"
  20
  21 /* On-demand governor macros */
  22 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
  23 #define DEF_SAMPLING_DOWN_FACTOR                (1)
  24 #define MAX_SAMPLING_DOWN_FACTOR                (100000)
  25 #define MICRO_FREQUENCY_UP_THRESHOLD            (95)
  26 #define MICRO_FREQUENCY_MIN_SAMPLE_RATE         (10000)
  27 #define MIN_FREQUENCY_UP_THRESHOLD              (11)
  28 #define MAX_FREQUENCY_UP_THRESHOLD              (100)
  29
  30 static DEFINE_PER_CPU(struct od_cpu_dbs_info_s, od_cpu_dbs_info);
  31
  32 static struct od_ops od_ops;
  33
  34 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
  35 static struct cpufreq_governor cpufreq_gov_ondemand;
  36 #endif
  37
  38 static unsigned int default_powersave_bias;
  39
  40 static void ondemand_powersave_bias_init_cpu(int cpu)
  41 {
  42         struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
  43
  44         dbs_info->freq_table = cpufreq_frequency_get_table(cpu);
  45         dbs_info->freq_lo = 0;
  46 }
  47
  48 /*
  49  * Not all CPUs want IO time to be accounted as busy; this depends on how
  50  * efficient idling at a higher frequency/voltage is.
  51  * Pavel Machek says this is not so for various generations of AMD and old
  52  * Intel systems.
  53  * Mike Chan (android.com) claims this is also not true for ARM.
  54  * Because of this, whitelist specific known (series) of CPUs by default, and
  55  * leave all others up to the user.
  56  */
  57 static int should_io_be_busy(void)
  58 {
  59 #if defined(CONFIG_X86)
  60         /*
  61          * For Intel, Core 2 (model 15) and later have an efficient idle.
  62          */
  63         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
  64                         boot_cpu_data.x86 == 6 &&
  65                         boot_cpu_data.x86_model >= 15)
  66                 return 1;
  67 #endif
  68         return 0;
  69 }
  70
  71 /*
  72  * Find right freq to be set now with powersave_bias on.
  73  * Returns the freq_hi to be used right now and will set freq_hi_jiffies,
  74  * freq_lo, and freq_lo_jiffies in percpu area for averaging freqs.
  75  */
  76 static unsigned int generic_powersave_bias_target(struct cpufreq_policy *policy,
  77                 unsigned int freq_next, unsigned int relation)
  78 {
  79         unsigned int freq_req, freq_reduc, freq_avg;
  80         unsigned int freq_hi, freq_lo;
  81         unsigned int index = 0;
  82         unsigned int jiffies_total, jiffies_hi, jiffies_lo;
  83         struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
  84                                                    policy->cpu);
  85         struct dbs_data *dbs_data = policy->governor_data;
  86         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
  87
  88         if (!dbs_info->freq_table) {
  89                 dbs_info->freq_lo = 0;
  90                 dbs_info->freq_lo_jiffies = 0;
  91                 return freq_next;
  92         }
  93
  94         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_next,
  95                         relation, &index);
  96         freq_req = dbs_info->freq_table[index].frequency;
  97         freq_reduc = freq_req * od_tuners->powersave_bias / 1000;
  98         freq_avg = freq_req - freq_reduc;
  99
 100         /* Find freq bounds for freq_avg in freq_table */
 101         index = 0;
 102         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 103                         CPUFREQ_RELATION_H, &index);
 104         freq_lo = dbs_info->freq_table[index].frequency;
 105         index = 0;
 106         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 107                         CPUFREQ_RELATION_L, &index);
 108         freq_hi = dbs_info->freq_table[index].frequency;
 109
 110         /* Find out how long we have to be in hi and lo freqs */
 111         if (freq_hi == freq_lo) {
 112                 dbs_info->freq_lo = 0;
 113                 dbs_info->freq_lo_jiffies = 0;
 114                 return freq_lo;
 115         }
 116         jiffies_total = usecs_to_jiffies(od_tuners->sampling_rate);
 117         jiffies_hi = (freq_avg - freq_lo) * jiffies_total;
 118         jiffies_hi += ((freq_hi - freq_lo) / 2);
 119         jiffies_hi /= (freq_hi - freq_lo);
 120         jiffies_lo = jiffies_total - jiffies_hi;
 121         dbs_info->freq_lo = freq_lo;
 122         dbs_info->freq_lo_jiffies = jiffies_lo;
 123         dbs_info->freq_hi_jiffies = jiffies_hi;
 124         return freq_hi;
 125 }
 126
 127 static void ondemand_powersave_bias_init(void)
 128 {
 129         int i;
 130         for_each_online_cpu(i) {
 131                 ondemand_powersave_bias_init_cpu(i);
 132         }
 133 }
 134
 135 static void dbs_freq_increase(struct cpufreq_policy *policy, unsigned int freq)
 136 {
 137         struct dbs_data *dbs_data = policy->governor_data;
 138         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 139
 140         if (od_tuners->powersave_bias)
 141                 freq = od_ops.powersave_bias_target(policy, freq,
 142                                 CPUFREQ_RELATION_H);
 143         else if (policy->cur == policy->max)
 144                 return;
 145
 146         __cpufreq_driver_target(policy, freq, od_tuners->powersave_bias ?
 147                         CPUFREQ_RELATION_L : CPUFREQ_RELATION_H);
 148 }
 149
 150 /*
 151  * Every sampling_rate, we check, if current idle time is less than 20%
 152  * (default), then we try to increase frequency. Else, we adjust the frequency
 153  * proportional to load.
 154  */
 155 static void od_check_cpu(int cpu, unsigned int load)
 156 {
 157         struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
 158         struct cpufreq_policy *policy = dbs_info->cdbs.shared->policy;
 159         struct dbs_data *dbs_data = policy->governor_data;
 160         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 161
 162         dbs_info->freq_lo = 0;
 163
 164         /* Check for frequency increase */
 165         if (load > od_tuners->up_threshold) {
 166                 /* If switching to max speed, apply sampling_down_factor */
 167                 if (policy->cur < policy->max)
 168                         dbs_info->rate_mult =
 169                                 od_tuners->sampling_down_factor;
 170                 dbs_freq_increase(policy, policy->max);
 171         } else {
 172                 /* Calculate the next frequency proportional to load */
 173                 unsigned int freq_next, min_f, max_f;
 174
 175                 min_f = policy->cpuinfo.min_freq;
 176                 max_f = policy->cpuinfo.max_freq;
 177                 freq_next = min_f + load * (max_f - min_f) / 100;
 178
 179                 /* No longer fully busy, reset rate_mult */
 180                 dbs_info->rate_mult = 1;
 181
 182                 if (!od_tuners->powersave_bias) {
 183                         __cpufreq_driver_target(policy, freq_next,
 184                                         CPUFREQ_RELATION_C);
 185                         return;
 186                 }
 187
 188                 freq_next = od_ops.powersave_bias_target(policy, freq_next,
 189                                         CPUFREQ_RELATION_L);
 190                 __cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_C);
 191         }
 192 }
 193
 194 static unsigned int od_dbs_timer(struct cpu_dbs_info *cdbs,
 195                                  struct dbs_data *dbs_data, bool modify_all)
 196 {
 197         struct cpufreq_policy *policy = cdbs->shared->policy;
 198         unsigned int cpu = policy->cpu;
 199         struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
 200                         cpu);
 201         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 202         int delay = 0, sample_type = dbs_info->sample_type;
 203
 204         if (!modify_all)
 205                 goto max_delay;
 206
 207         /* Common NORMAL_SAMPLE setup */
 208         dbs_info->sample_type = OD_NORMAL_SAMPLE;
 209         if (sample_type == OD_SUB_SAMPLE) {
 210                 delay = dbs_info->freq_lo_jiffies;
 211                 __cpufreq_driver_target(policy, dbs_info->freq_lo,
 212                                         CPUFREQ_RELATION_H);
 213         } else {
 214                 dbs_check_cpu(dbs_data, cpu);
 215                 if (dbs_info->freq_lo) {
 216                         /* Setup timer for SUB_SAMPLE */
 217                         dbs_info->sample_type = OD_SUB_SAMPLE;
 218                         delay = dbs_info->freq_hi_jiffies;
 219                 }
 220         }
 221
 222 max_delay:
 223         if (!delay)
 224                 delay = delay_for_sampling_rate(od_tuners->sampling_rate
 225                                 * dbs_info->rate_mult);
 226
 227         return delay;
 228 }
 229
 230 /************************** sysfs interface ************************/
 231 static struct common_dbs_data od_dbs_cdata;
 232
 233 /**
 234  * update_sampling_rate - update sampling rate effective immediately if needed.
 235  * @new_rate: new sampling rate
 236  *
 237  * If new rate is smaller than the old, simply updating
 238  * dbs_tuners_int.sampling_rate might not be appropriate. For example, if the
 239  * original sampling_rate was 1 second and the requested new sampling rate is 10
 240  * ms because the user needs immediate reaction from ondemand governor, but not
 241  * sure if higher frequency will be required or not, then, the governor may
 242  * change the sampling rate too late; up to 1 second later. Thus, if we are
 243  * reducing the sampling rate, we need to make the new value effective
 244  * immediately.
 245  */
 246 static void update_sampling_rate(struct dbs_data *dbs_data,
 247                 unsigned int new_rate)
 248 {
 249         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 250         int cpu;
 251
 252         od_tuners->sampling_rate = new_rate = max(new_rate,
 253                         dbs_data->min_sampling_rate);
 254
 255         for_each_online_cpu(cpu) {
 256                 struct cpufreq_policy *policy;
 257                 struct od_cpu_dbs_info_s *dbs_info;
 258                 unsigned long next_sampling, appointed_at;
 259
 260                 policy = cpufreq_cpu_get(cpu);
 261                 if (!policy)
 262                         continue;
 263                 if (policy->governor != &cpufreq_gov_ondemand) {
 264                         cpufreq_cpu_put(policy);
 265                         continue;
 266                 }
 267                 dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
 268                 cpufreq_cpu_put(policy);
 269
 270                 if (!delayed_work_pending(&dbs_info->cdbs.dwork))
 271                         continue;
 272
 273                 next_sampling = jiffies + usecs_to_jiffies(new_rate);
 274                 appointed_at = dbs_info->cdbs.dwork.timer.expires;
 275
 276                 if (time_before(next_sampling, appointed_at)) {
 277                         cancel_delayed_work_sync(&dbs_info->cdbs.dwork);
 278
 279                         gov_queue_work(dbs_data, policy,
 280                                        usecs_to_jiffies(new_rate), true);
 281
 282                 }
 283         }
 284 }
 285
 286 static ssize_t store_sampling_rate(struct dbs_data *dbs_data, const char *buf,
 287                 size_t count)
 288 {
 289         unsigned int input;
 290         int ret;
 291         ret = sscanf(buf, "%u", &input);
 292         if (ret != 1)
 293                 return -EINVAL;
 294
 295         update_sampling_rate(dbs_data, input);
 296         return count;
 297 }
 298
 299 static ssize_t store_io_is_busy(struct dbs_data *dbs_data, const char *buf,
 300                 size_t count)
 301 {
 302         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 303         unsigned int input;
 304         int ret;
 305         unsigned int j;
 306
 307         ret = sscanf(buf, "%u", &input);
 308         if (ret != 1)
 309                 return -EINVAL;
 310         od_tuners->io_is_busy = !!input;
 311
 312         /* we need to re-evaluate prev_cpu_idle */
 313         for_each_online_cpu(j) {
 314                 struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
 315                                                                         j);
 316                 dbs_info->cdbs.prev_cpu_idle = get_cpu_idle_time(j,
 317                         &dbs_info->cdbs.prev_cpu_wall, od_tuners->io_is_busy);
 318         }
 319         return count;
 320 }
 321
 322 static ssize_t store_up_threshold(struct dbs_data *dbs_data, const char *buf,
 323                 size_t count)
 324 {
 325         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 326         unsigned int input;
 327         int ret;
 328         ret = sscanf(buf, "%u", &input);
 329
 330         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 331                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 332                 return -EINVAL;
 333         }
 334
 335         od_tuners->up_threshold = input;
 336         return count;
 337 }
 338
 339 static ssize_t store_sampling_down_factor(struct dbs_data *dbs_data,
 340                 const char *buf, size_t count)
 341 {
 342         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 343         unsigned int input, j;
 344         int ret;
 345         ret = sscanf(buf, "%u", &input);
 346
 347         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 348                 return -EINVAL;
 349         od_tuners->sampling_down_factor = input;
 350
 351         /* Reset down sampling multiplier in case it was active */
 352         for_each_online_cpu(j) {
 353                 struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
 354                                 j);
 355                 dbs_info->rate_mult = 1;
 356         }
 357         return count;
 358 }
 359
 360 static ssize_t store_ignore_nice_load(struct dbs_data *dbs_data,
 361                 const char *buf, size_t count)
 362 {
 363         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 364         unsigned int input;
 365         int ret;
 366
 367         unsigned int j;
 368
 369         ret = sscanf(buf, "%u", &input);
 370         if (ret != 1)
 371                 return -EINVAL;
 372
 373         if (input > 1)
 374                 input = 1;
 375
 376         if (input == od_tuners->ignore_nice_load) { /* nothing to do */
 377                 return count;
 378         }
 379         od_tuners->ignore_nice_load = input;
 380
 381         /* we need to re-evaluate prev_cpu_idle */
 382         for_each_online_cpu(j) {
 383                 struct od_cpu_dbs_info_s *dbs_info;
 384                 dbs_info = &per_cpu(od_cpu_dbs_info, j);
 385                 dbs_info->cdbs.prev_cpu_idle = get_cpu_idle_time(j,
 386                         &dbs_info->cdbs.prev_cpu_wall, od_tuners->io_is_busy);
 387                 if (od_tuners->ignore_nice_load)
 388                         dbs_info->cdbs.prev_cpu_nice =
 389                                 kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 390
 391         }
 392         return count;
 393 }
 394
 395 static ssize_t store_powersave_bias(struct dbs_data *dbs_data, const char *buf,
 396                 size_t count)
 397 {
 398         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 399         unsigned int input;
 400         int ret;
 401         ret = sscanf(buf, "%u", &input);
 402
 403         if (ret != 1)
 404                 return -EINVAL;
 405
 406         if (input > 1000)
 407                 input = 1000;
 408
 409         od_tuners->powersave_bias = input;
 410         ondemand_powersave_bias_init();
 411         return count;
 412 }
 413
 414 show_store_one(od, sampling_rate);
 415 show_store_one(od, io_is_busy);
 416 show_store_one(od, up_threshold);
 417 show_store_one(od, sampling_down_factor);
 418 show_store_one(od, ignore_nice_load);
 419 show_store_one(od, powersave_bias);
 420 declare_show_sampling_rate_min(od);
 421
 422 gov_sys_pol_attr_rw(sampling_rate);
 423 gov_sys_pol_attr_rw(io_is_busy);
 424 gov_sys_pol_attr_rw(up_threshold);
 425 gov_sys_pol_attr_rw(sampling_down_factor);
 426 gov_sys_pol_attr_rw(ignore_nice_load);
 427 gov_sys_pol_attr_rw(powersave_bias);
 428 gov_sys_pol_attr_ro(sampling_rate_min);
 429
 430 static struct attribute *dbs_attributes_gov_sys[] = {
 431         &sampling_rate_min_gov_sys.attr,
 432         &sampling_rate_gov_sys.attr,
 433         &up_threshold_gov_sys.attr,
 434         &sampling_down_factor_gov_sys.attr,
 435         &ignore_nice_load_gov_sys.attr,
 436         &powersave_bias_gov_sys.attr,
 437         &io_is_busy_gov_sys.attr,
 438         NULL
 439 };
 440
 441 static struct attribute_group od_attr_group_gov_sys = {
 442         .attrs = dbs_attributes_gov_sys,
 443         .name = "ondemand",
 444 };
 445
 446 static struct attribute *dbs_attributes_gov_pol[] = {
 447         &sampling_rate_min_gov_pol.attr,
 448         &sampling_rate_gov_pol.attr,
 449         &up_threshold_gov_pol.attr,
 450         &sampling_down_factor_gov_pol.attr,
 451         &ignore_nice_load_gov_pol.attr,
 452         &powersave_bias_gov_pol.attr,
 453         &io_is_busy_gov_pol.attr,
 454         NULL
 455 };
 456
 457 static struct attribute_group od_attr_group_gov_pol = {
 458         .attrs = dbs_attributes_gov_pol,
 459         .name = "ondemand",
 460 };
 461
 462 /************************** sysfs end ************************/
 463
 464 static int od_init(struct dbs_data *dbs_data, bool notify)
 465 {
 466         struct od_dbs_tuners *tuners;
 467         u64 idle_time;
 468         int cpu;
 469
 470         tuners = kzalloc(sizeof(*tuners), GFP_KERNEL);
 471         if (!tuners) {
 472                 pr_err("%s: kzalloc failed\n", __func__);
 473                 return -ENOMEM;
 474         }
 475
 476         cpu = get_cpu();
 477         idle_time = get_cpu_idle_time_us(cpu, NULL);
 478         put_cpu();
 479         if (idle_time != -1ULL) {
 480                 /* Idle micro accounting is supported. Use finer thresholds */
 481                 tuners->up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
 482                 /*
 483                  * In nohz/micro accounting case we set the minimum frequency
 484                  * not depending on HZ, but fixed (very low). The deferred
 485                  * timer might skip some samples if idle/sleeping as needed.
 486                 */
 487                 dbs_data->min_sampling_rate = MICRO_FREQUENCY_MIN_SAMPLE_RATE;
 488         } else {
 489                 tuners->up_threshold = DEF_FREQUENCY_UP_THRESHOLD;
 490
 491                 /* For correct statistics, we need 10 ticks for each measure */
 492                 dbs_data->min_sampling_rate = MIN_SAMPLING_RATE_RATIO *
 493                         jiffies_to_usecs(10);
 494         }
 495
 496         tuners->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
 497         tuners->ignore_nice_load = 0;
 498         tuners->powersave_bias = default_powersave_bias;
 499         tuners->io_is_busy = should_io_be_busy();
 500
 501         dbs_data->tuners = tuners;
 502         return 0;
 503 }
 504
 505 static void od_exit(struct dbs_data *dbs_data, bool notify)
 506 {
 507         kfree(dbs_data->tuners);
 508 }
 509
 510 define_get_cpu_dbs_routines(od_cpu_dbs_info);
 511
 512 static struct od_ops od_ops = {
 513         .powersave_bias_init_cpu = ondemand_powersave_bias_init_cpu,
 514         .powersave_bias_target = generic_powersave_bias_target,
 515         .freq_increase = dbs_freq_increase,
 516 };
 517
 518 static struct common_dbs_data od_dbs_cdata = {
 519         .governor = GOV_ONDEMAND,
 520         .attr_group_gov_sys = &od_attr_group_gov_sys,
 521         .attr_group_gov_pol = &od_attr_group_gov_pol,
 522         .get_cpu_cdbs = get_cpu_cdbs,
 523         .get_cpu_dbs_info_s = get_cpu_dbs_info_s,
 524         .gov_dbs_timer = od_dbs_timer,
 525         .gov_check_cpu = od_check_cpu,
 526         .gov_ops = &od_ops,
 527         .init = od_init,
 528         .exit = od_exit,
 529         .mutex = __MUTEX_INITIALIZER(od_dbs_cdata.mutex),
 530 };
 531
 532 static void od_set_powersave_bias(unsigned int powersave_bias)
 533 {
 534         struct cpufreq_policy *policy;
 535         struct dbs_data *dbs_data;
 536         struct od_dbs_tuners *od_tuners;
 537         unsigned int cpu;
 538         cpumask_t done;
 539
 540         default_powersave_bias = powersave_bias;
 541         cpumask_clear(&done);
 542
 543         get_online_cpus();
 544         for_each_online_cpu(cpu) {
 545                 struct cpu_common_dbs_info *shared;
 546
 547                 if (cpumask_test_cpu(cpu, &done))
 548                         continue;
 549
 550                 shared = per_cpu(od_cpu_dbs_info, cpu).cdbs.shared;
 551                 if (!shared)
 552                         continue;
 553
 554                 policy = shared->policy;
 555                 cpumask_or(&done, &done, policy->cpus);
 556
 557                 if (policy->governor != &cpufreq_gov_ondemand)
 558                         continue;
 559
 560                 dbs_data = policy->governor_data;
 561                 od_tuners = dbs_data->tuners;
 562                 od_tuners->powersave_bias = default_powersave_bias;
 563         }
 564         put_online_cpus();
 565 }
 566
 567 void od_register_powersave_bias_handler(unsigned int (*f)
 568                 (struct cpufreq_policy *, unsigned int, unsigned int),
 569                 unsigned int powersave_bias)
 570 {
 571         od_ops.powersave_bias_target = f;
 572         od_set_powersave_bias(powersave_bias);
 573 }
 574 EXPORT_SYMBOL_GPL(od_register_powersave_bias_handler);
 575
 576 void od_unregister_powersave_bias_handler(void)
 577 {
 578         od_ops.powersave_bias_target = generic_powersave_bias_target;
 579         od_set_powersave_bias(0);
 580 }
 581 EXPORT_SYMBOL_GPL(od_unregister_powersave_bias_handler);
 582
 583 static int od_cpufreq_governor_dbs(struct cpufreq_policy *policy,
 584                 unsigned int event)
 585 {
 586         return cpufreq_governor_dbs(policy, &od_dbs_cdata, event);
 587 }
 588
 589 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 590 static
 591 #endif
 592 struct cpufreq_governor cpufreq_gov_ondemand = {
 593         .name                   = "ondemand",
 594         .governor               = od_cpufreq_governor_dbs,
 595         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 596         .owner                  = THIS_MODULE,
 597 };
 598
 599 static int __init cpufreq_gov_dbs_init(void)
 600 {
 601         return cpufreq_register_governor(&cpufreq_gov_ondemand);
 602 }
 603
 604 static void __exit cpufreq_gov_dbs_exit(void)
 605 {
 606         cpufreq_unregister_governor(&cpufreq_gov_ondemand);
 607 }
 608
 609 MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 610 MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
 611 MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 612         "Low Latency Frequency Transition capable processors");
 613 MODULE_LICENSE("GPL");
 614
 615 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 616 fs_initcall(cpufreq_gov_dbs_init);
 617 #else
 618 module_init(cpufreq_gov_dbs_init);
 619 #endif
 620 module_exit(cpufreq_gov_dbs_exit);