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, sample_type = core_dbs_info->sample_type;
 228         bool eval_load;
 229
 230         mutex_lock(&core_dbs_info->cdbs.timer_mutex);
 231         eval_load = need_load_eval(&core_dbs_info->cdbs,
 232                         od_tuners->sampling_rate);
 233
 234         /* Common NORMAL_SAMPLE setup */
 235         core_dbs_info->sample_type = OD_NORMAL_SAMPLE;
 236         if (sample_type == OD_SUB_SAMPLE) {
 237                 delay = core_dbs_info->freq_lo_jiffies;
 238                 if (eval_load)
 239                         __cpufreq_driver_target(core_dbs_info->cdbs.cur_policy,
 240                                                 core_dbs_info->freq_lo,
 241                                                 CPUFREQ_RELATION_H);
 242         } else {
 243                 if (eval_load)
 244                         dbs_check_cpu(dbs_data, cpu);
 245                 if (core_dbs_info->freq_lo) {
 246                         /* Setup timer for SUB_SAMPLE */
 247                         core_dbs_info->sample_type = OD_SUB_SAMPLE;
 248                         delay = core_dbs_info->freq_hi_jiffies;
 249                 } else {
 250                         delay = delay_for_sampling_rate(od_tuners->sampling_rate
 251                                                 * core_dbs_info->rate_mult);
 252                 }
 253         }
 254
 255         schedule_delayed_work_on(smp_processor_id(), dw, delay);
 256         mutex_unlock(&core_dbs_info->cdbs.timer_mutex);
 257 }
 258
 259 /************************** sysfs interface ************************/
 260 static struct common_dbs_data od_dbs_cdata;
 261
 262 /**
 263  * update_sampling_rate - update sampling rate effective immediately if needed.
 264  * @new_rate: new sampling rate
 265  *
 266  * If new rate is smaller than the old, simply updating
 267  * dbs_tuners_int.sampling_rate might not be appropriate. For example, if the
 268  * original sampling_rate was 1 second and the requested new sampling rate is 10
 269  * ms because the user needs immediate reaction from ondemand governor, but not
 270  * sure if higher frequency will be required or not, then, the governor may
 271  * change the sampling rate too late; up to 1 second later. Thus, if we are
 272  * reducing the sampling rate, we need to make the new value effective
 273  * immediately.
 274  */
 275 static void update_sampling_rate(struct dbs_data *dbs_data,
 276                 unsigned int new_rate)
 277 {
 278         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 279         int cpu;
 280
 281         od_tuners->sampling_rate = new_rate = max(new_rate,
 282                         dbs_data->min_sampling_rate);
 283
 284         for_each_online_cpu(cpu) {
 285                 struct cpufreq_policy *policy;
 286                 struct od_cpu_dbs_info_s *dbs_info;
 287                 unsigned long next_sampling, appointed_at;
 288
 289                 policy = cpufreq_cpu_get(cpu);
 290                 if (!policy)
 291                         continue;
 292                 if (policy->governor != &cpufreq_gov_ondemand) {
 293                         cpufreq_cpu_put(policy);
 294                         continue;
 295                 }
 296                 dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
 297                 cpufreq_cpu_put(policy);
 298
 299                 mutex_lock(&dbs_info->cdbs.timer_mutex);
 300
 301                 if (!delayed_work_pending(&dbs_info->cdbs.work)) {
 302                         mutex_unlock(&dbs_info->cdbs.timer_mutex);
 303                         continue;
 304                 }
 305
 306                 next_sampling = jiffies + usecs_to_jiffies(new_rate);
 307                 appointed_at = dbs_info->cdbs.work.timer.expires;
 308
 309                 if (time_before(next_sampling, appointed_at)) {
 310
 311                         mutex_unlock(&dbs_info->cdbs.timer_mutex);
 312                         cancel_delayed_work_sync(&dbs_info->cdbs.work);
 313                         mutex_lock(&dbs_info->cdbs.timer_mutex);
 314
 315                         schedule_delayed_work_on(cpu, &dbs_info->cdbs.work,
 316                                         usecs_to_jiffies(new_rate));
 317
 318                 }
 319                 mutex_unlock(&dbs_info->cdbs.timer_mutex);
 320         }
 321 }
 322
 323 static ssize_t store_sampling_rate(struct dbs_data *dbs_data, const char *buf,
 324                 size_t count)
 325 {
 326         unsigned int input;
 327         int ret;
 328         ret = sscanf(buf, "%u", &input);
 329         if (ret != 1)
 330                 return -EINVAL;
 331
 332         update_sampling_rate(dbs_data, input);
 333         return count;
 334 }
 335
 336 static ssize_t store_io_is_busy(struct dbs_data *dbs_data, const char *buf,
 337                 size_t count)
 338 {
 339         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 340         unsigned int input;
 341         int ret;
 342
 343         ret = sscanf(buf, "%u", &input);
 344         if (ret != 1)
 345                 return -EINVAL;
 346         od_tuners->io_is_busy = !!input;
 347         return count;
 348 }
 349
 350 static ssize_t store_up_threshold(struct dbs_data *dbs_data, const char *buf,
 351                 size_t count)
 352 {
 353         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 354         unsigned int input;
 355         int ret;
 356         ret = sscanf(buf, "%u", &input);
 357
 358         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 359                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 360                 return -EINVAL;
 361         }
 362         /* Calculate the new adj_up_threshold */
 363         od_tuners->adj_up_threshold += input;
 364         od_tuners->adj_up_threshold -= od_tuners->up_threshold;
 365
 366         od_tuners->up_threshold = input;
 367         return count;
 368 }
 369
 370 static ssize_t store_sampling_down_factor(struct dbs_data *dbs_data,
 371                 const char *buf, size_t count)
 372 {
 373         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 374         unsigned int input, j;
 375         int ret;
 376         ret = sscanf(buf, "%u", &input);
 377
 378         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 379                 return -EINVAL;
 380         od_tuners->sampling_down_factor = input;
 381
 382         /* Reset down sampling multiplier in case it was active */
 383         for_each_online_cpu(j) {
 384                 struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
 385                                 j);
 386                 dbs_info->rate_mult = 1;
 387         }
 388         return count;
 389 }
 390
 391 static ssize_t store_ignore_nice(struct dbs_data *dbs_data, const char *buf,
 392                 size_t count)
 393 {
 394         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 395         unsigned int input;
 396         int ret;
 397
 398         unsigned int j;
 399
 400         ret = sscanf(buf, "%u", &input);
 401         if (ret != 1)
 402                 return -EINVAL;
 403
 404         if (input > 1)
 405                 input = 1;
 406
 407         if (input == od_tuners->ignore_nice) { /* nothing to do */
 408                 return count;
 409         }
 410         od_tuners->ignore_nice = input;
 411
 412         /* we need to re-evaluate prev_cpu_idle */
 413         for_each_online_cpu(j) {
 414                 struct od_cpu_dbs_info_s *dbs_info;
 415                 dbs_info = &per_cpu(od_cpu_dbs_info, j);
 416                 dbs_info->cdbs.prev_cpu_idle = get_cpu_idle_time(j,
 417                                                 &dbs_info->cdbs.prev_cpu_wall);
 418                 if (od_tuners->ignore_nice)
 419                         dbs_info->cdbs.prev_cpu_nice =
 420                                 kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 421
 422         }
 423         return count;
 424 }
 425
 426 static ssize_t store_powersave_bias(struct dbs_data *dbs_data, const char *buf,
 427                 size_t count)
 428 {
 429         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 430         unsigned int input;
 431         int ret;
 432         ret = sscanf(buf, "%u", &input);
 433
 434         if (ret != 1)
 435                 return -EINVAL;
 436
 437         if (input > 1000)
 438                 input = 1000;
 439
 440         od_tuners->powersave_bias = input;
 441         ondemand_powersave_bias_init();
 442         return count;
 443 }
 444
 445 show_store_one(od, sampling_rate);
 446 show_store_one(od, io_is_busy);
 447 show_store_one(od, up_threshold);
 448 show_store_one(od, sampling_down_factor);
 449 show_store_one(od, ignore_nice);
 450 show_store_one(od, powersave_bias);
 451 declare_show_sampling_rate_min(od);
 452
 453 gov_sys_pol_attr_rw(sampling_rate);
 454 gov_sys_pol_attr_rw(io_is_busy);
 455 gov_sys_pol_attr_rw(up_threshold);
 456 gov_sys_pol_attr_rw(sampling_down_factor);
 457 gov_sys_pol_attr_rw(ignore_nice);
 458 gov_sys_pol_attr_rw(powersave_bias);
 459 gov_sys_pol_attr_ro(sampling_rate_min);
 460
 461 static struct attribute *dbs_attributes_gov_sys[] = {
 462         &sampling_rate_min_gov_sys.attr,
 463         &sampling_rate_gov_sys.attr,
 464         &up_threshold_gov_sys.attr,
 465         &sampling_down_factor_gov_sys.attr,
 466         &ignore_nice_gov_sys.attr,
 467         &powersave_bias_gov_sys.attr,
 468         &io_is_busy_gov_sys.attr,
 469         NULL
 470 };
 471
 472 static struct attribute_group od_attr_group_gov_sys = {
 473         .attrs = dbs_attributes_gov_sys,
 474         .name = "ondemand",
 475 };
 476
 477 static struct attribute *dbs_attributes_gov_pol[] = {
 478         &sampling_rate_min_gov_pol.attr,
 479         &sampling_rate_gov_pol.attr,
 480         &up_threshold_gov_pol.attr,
 481         &sampling_down_factor_gov_pol.attr,
 482         &ignore_nice_gov_pol.attr,
 483         &powersave_bias_gov_pol.attr,
 484         &io_is_busy_gov_pol.attr,
 485         NULL
 486 };
 487
 488 static struct attribute_group od_attr_group_gov_pol = {
 489         .attrs = dbs_attributes_gov_pol,
 490         .name = "ondemand",
 491 };
 492
 493 /************************** sysfs end ************************/
 494
 495 static int od_init(struct dbs_data *dbs_data)
 496 {
 497         struct od_dbs_tuners *tuners;
 498         u64 idle_time;
 499         int cpu;
 500
 501         tuners = kzalloc(sizeof(struct od_dbs_tuners), GFP_KERNEL);
 502         if (!tuners) {
 503                 pr_err("%s: kzalloc failed\n", __func__);
 504                 return -ENOMEM;
 505         }
 506
 507         cpu = get_cpu();
 508         idle_time = get_cpu_idle_time_us(cpu, NULL);
 509         put_cpu();
 510         if (idle_time != -1ULL) {
 511                 /* Idle micro accounting is supported. Use finer thresholds */
 512                 tuners->up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
 513                 tuners->adj_up_threshold = MICRO_FREQUENCY_UP_THRESHOLD -
 514                         MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
 515                 /*
 516                  * In nohz/micro accounting case we set the minimum frequency
 517                  * not depending on HZ, but fixed (very low). The deferred
 518                  * timer might skip some samples if idle/sleeping as needed.
 519                 */
 520                 dbs_data->min_sampling_rate = MICRO_FREQUENCY_MIN_SAMPLE_RATE;
 521         } else {
 522                 tuners->up_threshold = DEF_FREQUENCY_UP_THRESHOLD;
 523                 tuners->adj_up_threshold = DEF_FREQUENCY_UP_THRESHOLD -
 524                         DEF_FREQUENCY_DOWN_DIFFERENTIAL;
 525
 526                 /* For correct statistics, we need 10 ticks for each measure */
 527                 dbs_data->min_sampling_rate = MIN_SAMPLING_RATE_RATIO *
 528                         jiffies_to_usecs(10);
 529         }
 530
 531         tuners->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
 532         tuners->ignore_nice = 0;
 533         tuners->powersave_bias = 0;
 534         tuners->io_is_busy = should_io_be_busy();
 535
 536         dbs_data->tuners = tuners;
 537         pr_info("%s: tuners %p\n", __func__, tuners);
 538         mutex_init(&dbs_data->mutex);
 539         return 0;
 540 }
 541
 542 static void od_exit(struct dbs_data *dbs_data)
 543 {
 544         kfree(dbs_data->tuners);
 545 }
 546
 547 define_get_cpu_dbs_routines(od_cpu_dbs_info);
 548
 549 static struct od_ops od_ops = {
 550         .powersave_bias_init_cpu = ondemand_powersave_bias_init_cpu,
 551         .powersave_bias_target = powersave_bias_target,
 552         .freq_increase = dbs_freq_increase,
 553 };
 554
 555 static struct common_dbs_data od_dbs_cdata = {
 556         .governor = GOV_ONDEMAND,
 557         .attr_group_gov_sys = &od_attr_group_gov_sys,
 558         .attr_group_gov_pol = &od_attr_group_gov_pol,
 559         .get_cpu_cdbs = get_cpu_cdbs,
 560         .get_cpu_dbs_info_s = get_cpu_dbs_info_s,
 561         .gov_dbs_timer = od_dbs_timer,
 562         .gov_check_cpu = od_check_cpu,
 563         .gov_ops = &od_ops,
 564         .init = od_init,
 565         .exit = od_exit,
 566 };
 567
 568 static int od_cpufreq_governor_dbs(struct cpufreq_policy *policy,
 569                 unsigned int event)
 570 {
 571         return cpufreq_governor_dbs(policy, &od_dbs_cdata, event);
 572 }
 573
 574 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 575 static
 576 #endif
 577 struct cpufreq_governor cpufreq_gov_ondemand = {
 578         .name                   = "ondemand",
 579         .governor               = od_cpufreq_governor_dbs,
 580         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 581         .owner                  = THIS_MODULE,
 582 };
 583
 584 static int __init cpufreq_gov_dbs_init(void)
 585 {
 586         return cpufreq_register_governor(&cpufreq_gov_ondemand);
 587 }
 588
 589 static void __exit cpufreq_gov_dbs_exit(void)
 590 {
 591         cpufreq_unregister_governor(&cpufreq_gov_ondemand);
 592 }
 593
 594 MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 595 MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
 596 MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 597         "Low Latency Frequency Transition capable processors");
 598 MODULE_LICENSE("GPL");
 599
 600 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 601 fs_initcall(cpufreq_gov_dbs_init);
 602 #else
 603 module_init(cpufreq_gov_dbs_init);
 604 #endif
 605 module_exit(cpufreq_gov_dbs_exit);