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/cpufreq.h>
  16 #include <linux/init.h>
  17 #include <linux/kernel.h>
  18 #include <linux/kernel_stat.h>
  19 #include <linux/kobject.h>
  20 #include <linux/module.h>
  21 #include <linux/mutex.h>
  22 #include <linux/percpu-defs.h>
  23 #include <linux/slab.h>
  24 #include <linux/sysfs.h>
  25 #include <linux/tick.h>
  26 #include <linux/types.h>
  27
  28 #include "cpufreq_governor.h"
  29
  30 /* On-demand governor macros */
  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 static DEFINE_PER_CPU(struct od_cpu_dbs_info_s, od_cpu_dbs_info);
  42
  43 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
  44 static struct cpufreq_governor cpufreq_gov_ondemand;
  45 #endif
  46
  47 static void ondemand_powersave_bias_init_cpu(int cpu)
  48 {
  49         struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
  50
  51         dbs_info->freq_table = cpufreq_frequency_get_table(cpu);
  52         dbs_info->freq_lo = 0;
  53 }
  54
  55 /*
  56  * Not all CPUs want IO time to be accounted as busy; this depends on how
  57  * efficient idling at a higher frequency/voltage is.
  58  * Pavel Machek says this is not so for various generations of AMD and old
  59  * Intel systems.
  60  * Mike Chan (android.com) claims this is also not true for ARM.
  61  * Because of this, whitelist specific known (series) of CPUs by default, and
  62  * leave all others up to the user.
  63  */
  64 static int should_io_be_busy(void)
  65 {
  66 #if defined(CONFIG_X86)
  67         /*
  68          * For Intel, Core 2 (model 15) and later have an efficient idle.
  69          */
  70         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
  71                         boot_cpu_data.x86 == 6 &&
  72                         boot_cpu_data.x86_model >= 15)
  73                 return 1;
  74 #endif
  75         return 0;
  76 }
  77
  78 /*
  79  * Find right freq to be set now with powersave_bias on.
  80  * Returns the freq_hi to be used right now and will set freq_hi_jiffies,
  81  * freq_lo, and freq_lo_jiffies in percpu area for averaging freqs.
  82  */
  83 static unsigned int powersave_bias_target(struct cpufreq_policy *policy,
  84                 unsigned int freq_next, unsigned int relation)
  85 {
  86         unsigned int freq_req, freq_reduc, freq_avg;
  87         unsigned int freq_hi, freq_lo;
  88         unsigned int index = 0;
  89         unsigned int jiffies_total, jiffies_hi, jiffies_lo;
  90         struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
  91                                                    policy->cpu);
  92         struct dbs_data *dbs_data = policy->governor_data;
  93         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
  94
  95         if (!dbs_info->freq_table) {
  96                 dbs_info->freq_lo = 0;
  97                 dbs_info->freq_lo_jiffies = 0;
  98                 return freq_next;
  99         }
 100
 101         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_next,
 102                         relation, &index);
 103         freq_req = dbs_info->freq_table[index].frequency;
 104         freq_reduc = freq_req * od_tuners->powersave_bias / 1000;
 105         freq_avg = freq_req - freq_reduc;
 106
 107         /* Find freq bounds for freq_avg in freq_table */
 108         index = 0;
 109         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 110                         CPUFREQ_RELATION_H, &index);
 111         freq_lo = dbs_info->freq_table[index].frequency;
 112         index = 0;
 113         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 114                         CPUFREQ_RELATION_L, &index);
 115         freq_hi = dbs_info->freq_table[index].frequency;
 116
 117         /* Find out how long we have to be in hi and lo freqs */
 118         if (freq_hi == freq_lo) {
 119                 dbs_info->freq_lo = 0;
 120                 dbs_info->freq_lo_jiffies = 0;
 121                 return freq_lo;
 122         }
 123         jiffies_total = usecs_to_jiffies(od_tuners->sampling_rate);
 124         jiffies_hi = (freq_avg - freq_lo) * jiffies_total;
 125         jiffies_hi += ((freq_hi - freq_lo) / 2);
 126         jiffies_hi /= (freq_hi - freq_lo);
 127         jiffies_lo = jiffies_total - jiffies_hi;
 128         dbs_info->freq_lo = freq_lo;
 129         dbs_info->freq_lo_jiffies = jiffies_lo;
 130         dbs_info->freq_hi_jiffies = jiffies_hi;
 131         return freq_hi;
 132 }
 133
 134 static void ondemand_powersave_bias_init(void)
 135 {
 136         int i;
 137         for_each_online_cpu(i) {
 138                 ondemand_powersave_bias_init_cpu(i);
 139         }
 140 }
 141
 142 static void dbs_freq_increase(struct cpufreq_policy *p, unsigned int freq)
 143 {
 144         struct dbs_data *dbs_data = p->governor_data;
 145         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 146
 147         if (od_tuners->powersave_bias)
 148                 freq = powersave_bias_target(p, freq, CPUFREQ_RELATION_H);
 149         else if (p->cur == p->max)
 150                 return;
 151
 152         __cpufreq_driver_target(p, freq, od_tuners->powersave_bias ?
 153                         CPUFREQ_RELATION_L : CPUFREQ_RELATION_H);
 154 }
 155
 156 /*
 157  * Every sampling_rate, we check, if current idle time is less than 20%
 158  * (default), then we try to increase frequency. Every sampling_rate, we look
 159  * for the lowest frequency which can sustain the load while keeping idle time
 160  * over 30%. If such a frequency exist, we try to decrease to this frequency.
 161  *
 162  * Any frequency increase takes it to the maximum frequency. Frequency reduction
 163  * happens at minimum steps of 5% (default) of current frequency
 164  */
 165 static void od_check_cpu(int cpu, unsigned int load_freq)
 166 {
 167         struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
 168         struct cpufreq_policy *policy = dbs_info->cdbs.cur_policy;
 169         struct dbs_data *dbs_data = policy->governor_data;
 170         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 171
 172         dbs_info->freq_lo = 0;
 173
 174         /* Check for frequency increase */
 175         if (load_freq > od_tuners->up_threshold * policy->cur) {
 176                 /* If switching to max speed, apply sampling_down_factor */
 177                 if (policy->cur < policy->max)
 178                         dbs_info->rate_mult =
 179                                 od_tuners->sampling_down_factor;
 180                 dbs_freq_increase(policy, policy->max);
 181                 return;
 182         }
 183
 184         /* Check for frequency decrease */
 185         /* if we cannot reduce the frequency anymore, break out early */
 186         if (policy->cur == policy->min)
 187                 return;
 188
 189         /*
 190          * The optimal frequency is the frequency that is the lowest that can
 191          * support the current CPU usage without triggering the up policy. To be
 192          * safe, we focus 10 points under the threshold.
 193          */
 194         if (load_freq < od_tuners->adj_up_threshold
 195                         * policy->cur) {
 196                 unsigned int freq_next;
 197                 freq_next = load_freq / od_tuners->adj_up_threshold;
 198
 199                 /* No longer fully busy, reset rate_mult */
 200                 dbs_info->rate_mult = 1;
 201
 202                 if (freq_next < policy->min)
 203                         freq_next = policy->min;
 204
 205                 if (!od_tuners->powersave_bias) {
 206                         __cpufreq_driver_target(policy, freq_next,
 207                                         CPUFREQ_RELATION_L);
 208                 } else {
 209                         int freq = powersave_bias_target(policy, freq_next,
 210                                         CPUFREQ_RELATION_L);
 211                         __cpufreq_driver_target(policy, freq,
 212                                         CPUFREQ_RELATION_L);
 213                 }
 214         }
 215 }
 216
 217 static void od_dbs_timer(struct work_struct *work)
 218 {
 219         struct delayed_work *dw = to_delayed_work(work);
 220         struct od_cpu_dbs_info_s *dbs_info =
 221                 container_of(work, struct od_cpu_dbs_info_s, cdbs.work.work);
 222         unsigned int cpu = dbs_info->cdbs.cur_policy->cpu;
 223         struct od_cpu_dbs_info_s *core_dbs_info = &per_cpu(od_cpu_dbs_info,
 224                         cpu);
 225         struct dbs_data *dbs_data = dbs_info->cdbs.cur_policy->governor_data;
 226         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 227         int delay = 0, sample_type = core_dbs_info->sample_type;
 228
 229         mutex_lock(&core_dbs_info->cdbs.timer_mutex);
 230         if (!need_load_eval(&core_dbs_info->cdbs, od_tuners->sampling_rate))
 231                 goto max_delay;
 232
 233         /* Common NORMAL_SAMPLE setup */
 234         core_dbs_info->sample_type = OD_NORMAL_SAMPLE;
 235         if (sample_type == OD_SUB_SAMPLE) {
 236                 delay = core_dbs_info->freq_lo_jiffies;
 237                 __cpufreq_driver_target(core_dbs_info->cdbs.cur_policy,
 238                                 core_dbs_info->freq_lo, CPUFREQ_RELATION_H);
 239         } else {
 240                 dbs_check_cpu(dbs_data, cpu);
 241                 if (core_dbs_info->freq_lo) {
 242                         /* Setup timer for SUB_SAMPLE */
 243                         core_dbs_info->sample_type = OD_SUB_SAMPLE;
 244                         delay = core_dbs_info->freq_hi_jiffies;
 245                 }
 246         }
 247
 248 max_delay:
 249         if (!delay)
 250                 delay = delay_for_sampling_rate(od_tuners->sampling_rate
 251                                 * core_dbs_info->rate_mult);
 252
 253         schedule_delayed_work_on(smp_processor_id(), dw, delay);
 254         mutex_unlock(&core_dbs_info->cdbs.timer_mutex);
 255 }
 256
 257 /************************** sysfs interface ************************/
 258 static struct common_dbs_data od_dbs_cdata;
 259
 260 /**
 261  * update_sampling_rate - update sampling rate effective immediately if needed.
 262  * @new_rate: new sampling rate
 263  *
 264  * If new rate is smaller than the old, simply updating
 265  * dbs_tuners_int.sampling_rate might not be appropriate. For example, if the
 266  * original sampling_rate was 1 second and the requested new sampling rate is 10
 267  * ms because the user needs immediate reaction from ondemand governor, but not
 268  * sure if higher frequency will be required or not, then, the governor may
 269  * change the sampling rate too late; up to 1 second later. Thus, if we are
 270  * reducing the sampling rate, we need to make the new value effective
 271  * immediately.
 272  */
 273 static void update_sampling_rate(struct dbs_data *dbs_data,
 274                 unsigned int new_rate)
 275 {
 276         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 277         int cpu;
 278
 279         od_tuners->sampling_rate = new_rate = max(new_rate,
 280                         dbs_data->min_sampling_rate);
 281
 282         for_each_online_cpu(cpu) {
 283                 struct cpufreq_policy *policy;
 284                 struct od_cpu_dbs_info_s *dbs_info;
 285                 unsigned long next_sampling, appointed_at;
 286
 287                 policy = cpufreq_cpu_get(cpu);
 288                 if (!policy)
 289                         continue;
 290                 if (policy->governor != &cpufreq_gov_ondemand) {
 291                         cpufreq_cpu_put(policy);
 292                         continue;
 293                 }
 294                 dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
 295                 cpufreq_cpu_put(policy);
 296
 297                 mutex_lock(&dbs_info->cdbs.timer_mutex);
 298
 299                 if (!delayed_work_pending(&dbs_info->cdbs.work)) {
 300                         mutex_unlock(&dbs_info->cdbs.timer_mutex);
 301                         continue;
 302                 }
 303
 304                 next_sampling = jiffies + usecs_to_jiffies(new_rate);
 305                 appointed_at = dbs_info->cdbs.work.timer.expires;
 306
 307                 if (time_before(next_sampling, appointed_at)) {
 308
 309                         mutex_unlock(&dbs_info->cdbs.timer_mutex);
 310                         cancel_delayed_work_sync(&dbs_info->cdbs.work);
 311                         mutex_lock(&dbs_info->cdbs.timer_mutex);
 312
 313                         schedule_delayed_work_on(cpu, &dbs_info->cdbs.work,
 314                                         usecs_to_jiffies(new_rate));
 315
 316                 }
 317                 mutex_unlock(&dbs_info->cdbs.timer_mutex);
 318         }
 319 }
 320
 321 static ssize_t store_sampling_rate(struct dbs_data *dbs_data, const char *buf,
 322                 size_t count)
 323 {
 324         unsigned int input;
 325         int ret;
 326         ret = sscanf(buf, "%u", &input);
 327         if (ret != 1)
 328                 return -EINVAL;
 329
 330         update_sampling_rate(dbs_data, input);
 331         return count;
 332 }
 333
 334 static ssize_t store_io_is_busy(struct dbs_data *dbs_data, const char *buf,
 335                 size_t count)
 336 {
 337         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 338         unsigned int input;
 339         int ret;
 340
 341         ret = sscanf(buf, "%u", &input);
 342         if (ret != 1)
 343                 return -EINVAL;
 344         od_tuners->io_is_busy = !!input;
 345         return count;
 346 }
 347
 348 static ssize_t store_up_threshold(struct dbs_data *dbs_data, const char *buf,
 349                 size_t count)
 350 {
 351         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 352         unsigned int input;
 353         int ret;
 354         ret = sscanf(buf, "%u", &input);
 355
 356         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 357                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 358                 return -EINVAL;
 359         }
 360         /* Calculate the new adj_up_threshold */
 361         od_tuners->adj_up_threshold += input;
 362         od_tuners->adj_up_threshold -= od_tuners->up_threshold;
 363
 364         od_tuners->up_threshold = input;
 365         return count;
 366 }
 367
 368 static ssize_t store_sampling_down_factor(struct dbs_data *dbs_data,
 369                 const char *buf, size_t count)
 370 {
 371         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 372         unsigned int input, j;
 373         int ret;
 374         ret = sscanf(buf, "%u", &input);
 375
 376         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 377                 return -EINVAL;
 378         od_tuners->sampling_down_factor = input;
 379
 380         /* Reset down sampling multiplier in case it was active */
 381         for_each_online_cpu(j) {
 382                 struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
 383                                 j);
 384                 dbs_info->rate_mult = 1;
 385         }
 386         return count;
 387 }
 388
 389 static ssize_t store_ignore_nice(struct dbs_data *dbs_data, const char *buf,
 390                 size_t count)
 391 {
 392         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 393         unsigned int input;
 394         int ret;
 395
 396         unsigned int j;
 397
 398         ret = sscanf(buf, "%u", &input);
 399         if (ret != 1)
 400                 return -EINVAL;
 401
 402         if (input > 1)
 403                 input = 1;
 404
 405         if (input == od_tuners->ignore_nice) { /* nothing to do */
 406                 return count;
 407         }
 408         od_tuners->ignore_nice = input;
 409
 410         /* we need to re-evaluate prev_cpu_idle */
 411         for_each_online_cpu(j) {
 412                 struct od_cpu_dbs_info_s *dbs_info;
 413                 dbs_info = &per_cpu(od_cpu_dbs_info, j);
 414                 dbs_info->cdbs.prev_cpu_idle = get_cpu_idle_time(j,
 415                                                 &dbs_info->cdbs.prev_cpu_wall);
 416                 if (od_tuners->ignore_nice)
 417                         dbs_info->cdbs.prev_cpu_nice =
 418                                 kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 419
 420         }
 421         return count;
 422 }
 423
 424 static ssize_t store_powersave_bias(struct dbs_data *dbs_data, const char *buf,
 425                 size_t count)
 426 {
 427         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 428         unsigned int input;
 429         int ret;
 430         ret = sscanf(buf, "%u", &input);
 431
 432         if (ret != 1)
 433                 return -EINVAL;
 434
 435         if (input > 1000)
 436                 input = 1000;
 437
 438         od_tuners->powersave_bias = input;
 439         ondemand_powersave_bias_init();
 440         return count;
 441 }
 442
 443 show_store_one(od, sampling_rate);
 444 show_store_one(od, io_is_busy);
 445 show_store_one(od, up_threshold);
 446 show_store_one(od, sampling_down_factor);
 447 show_store_one(od, ignore_nice);
 448 show_store_one(od, powersave_bias);
 449 declare_show_sampling_rate_min(od);
 450
 451 gov_sys_pol_attr_rw(sampling_rate);
 452 gov_sys_pol_attr_rw(io_is_busy);
 453 gov_sys_pol_attr_rw(up_threshold);
 454 gov_sys_pol_attr_rw(sampling_down_factor);
 455 gov_sys_pol_attr_rw(ignore_nice);
 456 gov_sys_pol_attr_rw(powersave_bias);
 457 gov_sys_pol_attr_ro(sampling_rate_min);
 458
 459 static struct attribute *dbs_attributes_gov_sys[] = {
 460         &sampling_rate_min_gov_sys.attr,
 461         &sampling_rate_gov_sys.attr,
 462         &up_threshold_gov_sys.attr,
 463         &sampling_down_factor_gov_sys.attr,
 464         &ignore_nice_gov_sys.attr,
 465         &powersave_bias_gov_sys.attr,
 466         &io_is_busy_gov_sys.attr,
 467         NULL
 468 };
 469
 470 static struct attribute_group od_attr_group_gov_sys = {
 471         .attrs = dbs_attributes_gov_sys,
 472         .name = "ondemand",
 473 };
 474
 475 static struct attribute *dbs_attributes_gov_pol[] = {
 476         &sampling_rate_min_gov_pol.attr,
 477         &sampling_rate_gov_pol.attr,
 478         &up_threshold_gov_pol.attr,
 479         &sampling_down_factor_gov_pol.attr,
 480         &ignore_nice_gov_pol.attr,
 481         &powersave_bias_gov_pol.attr,
 482         &io_is_busy_gov_pol.attr,
 483         NULL
 484 };
 485
 486 static struct attribute_group od_attr_group_gov_pol = {
 487         .attrs = dbs_attributes_gov_pol,
 488         .name = "ondemand",
 489 };
 490
 491 /************************** sysfs end ************************/
 492
 493 static int od_init(struct dbs_data *dbs_data)
 494 {
 495         struct od_dbs_tuners *tuners;
 496         u64 idle_time;
 497         int cpu;
 498
 499         tuners = kzalloc(sizeof(struct od_dbs_tuners), GFP_KERNEL);
 500         if (!tuners) {
 501                 pr_err("%s: kzalloc failed\n", __func__);
 502                 return -ENOMEM;
 503         }
 504
 505         cpu = get_cpu();
 506         idle_time = get_cpu_idle_time_us(cpu, NULL);
 507         put_cpu();
 508         if (idle_time != -1ULL) {
 509                 /* Idle micro accounting is supported. Use finer thresholds */
 510                 tuners->up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
 511                 tuners->adj_up_threshold = MICRO_FREQUENCY_UP_THRESHOLD -
 512                         MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
 513                 /*
 514                  * In nohz/micro accounting case we set the minimum frequency
 515                  * not depending on HZ, but fixed (very low). The deferred
 516                  * timer might skip some samples if idle/sleeping as needed.
 517                 */
 518                 dbs_data->min_sampling_rate = MICRO_FREQUENCY_MIN_SAMPLE_RATE;
 519         } else {
 520                 tuners->up_threshold = DEF_FREQUENCY_UP_THRESHOLD;
 521                 tuners->adj_up_threshold = DEF_FREQUENCY_UP_THRESHOLD -
 522                         DEF_FREQUENCY_DOWN_DIFFERENTIAL;
 523
 524                 /* For correct statistics, we need 10 ticks for each measure */
 525                 dbs_data->min_sampling_rate = MIN_SAMPLING_RATE_RATIO *
 526                         jiffies_to_usecs(10);
 527         }
 528
 529         tuners->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
 530         tuners->ignore_nice = 0;
 531         tuners->powersave_bias = 0;
 532         tuners->io_is_busy = should_io_be_busy();
 533
 534         dbs_data->tuners = tuners;
 535         pr_info("%s: tuners %p\n", __func__, tuners);
 536         mutex_init(&dbs_data->mutex);
 537         return 0;
 538 }
 539
 540 static void od_exit(struct dbs_data *dbs_data)
 541 {
 542         kfree(dbs_data->tuners);
 543 }
 544
 545 define_get_cpu_dbs_routines(od_cpu_dbs_info);
 546
 547 static struct od_ops od_ops = {
 548         .powersave_bias_init_cpu = ondemand_powersave_bias_init_cpu,
 549         .powersave_bias_target = powersave_bias_target,
 550         .freq_increase = dbs_freq_increase,
 551 };
 552
 553 static struct common_dbs_data od_dbs_cdata = {
 554         .governor = GOV_ONDEMAND,
 555         .attr_group_gov_sys = &od_attr_group_gov_sys,
 556         .attr_group_gov_pol = &od_attr_group_gov_pol,
 557         .get_cpu_cdbs = get_cpu_cdbs,
 558         .get_cpu_dbs_info_s = get_cpu_dbs_info_s,
 559         .gov_dbs_timer = od_dbs_timer,
 560         .gov_check_cpu = od_check_cpu,
 561         .gov_ops = &od_ops,
 562         .init = od_init,
 563         .exit = od_exit,
 564 };
 565
 566 static int od_cpufreq_governor_dbs(struct cpufreq_policy *policy,
 567                 unsigned int event)
 568 {
 569         return cpufreq_governor_dbs(policy, &od_dbs_cdata, event);
 570 }
 571
 572 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 573 static
 574 #endif
 575 struct cpufreq_governor cpufreq_gov_ondemand = {
 576         .name                   = "ondemand",
 577         .governor               = od_cpufreq_governor_dbs,
 578         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 579         .owner                  = THIS_MODULE,
 580 };
 581
 582 static int __init cpufreq_gov_dbs_init(void)
 583 {
 584         return cpufreq_register_governor(&cpufreq_gov_ondemand);
 585 }
 586
 587 static void __exit cpufreq_gov_dbs_exit(void)
 588 {
 589         cpufreq_unregister_governor(&cpufreq_gov_ondemand);
 590 }
 591
 592 MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 593 MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
 594 MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 595         "Low Latency Frequency Transition capable processors");
 596 MODULE_LICENSE("GPL");
 597
 598 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 599 fs_initcall(cpufreq_gov_dbs_init);
 600 #else
 601 module_init(cpufreq_gov_dbs_init);
 602 #endif
 603 module_exit(cpufreq_gov_dbs_exit);