drivers/cpufreq/cpufreq_governor.c

   1 /*
   2  * drivers/cpufreq/cpufreq_governor.c
   3  *
   4  * CPUFREQ governors common code
   5  *
   6  * Copyright    (C) 2001 Russell King
   7  *              (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
   8  *              (C) 2003 Jun Nakajima <jun.nakajima@intel.com>
   9  *              (C) 2009 Alexander Clouter <alex@digriz.org.uk>
  10  *              (c) 2012 Viresh Kumar <viresh.kumar@linaro.org>
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License version 2 as
  14  * published by the Free Software Foundation.
  15  */
  16
  17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  18
  19 #include <linux/export.h>
  20 #include <linux/kernel_stat.h>
  21 #include <linux/slab.h>
  22
  23 #include "cpufreq_governor.h"
  24
  25 DEFINE_MUTEX(dbs_data_mutex);
  26 EXPORT_SYMBOL_GPL(dbs_data_mutex);
  27
  28 /* Common sysfs tunables */
  29 /**
  30  * store_sampling_rate - update sampling rate effective immediately if needed.
  31  *
  32  * If new rate is smaller than the old, simply updating
  33  * dbs.sampling_rate might not be appropriate. For example, if the
  34  * original sampling_rate was 1 second and the requested new sampling rate is 10
  35  * ms because the user needs immediate reaction from ondemand governor, but not
  36  * sure if higher frequency will be required or not, then, the governor may
  37  * change the sampling rate too late; up to 1 second later. Thus, if we are
  38  * reducing the sampling rate, we need to make the new value effective
  39  * immediately.
  40  *
  41  * This must be called with dbs_data->mutex held, otherwise traversing
  42  * policy_dbs_list isn't safe.
  43  */
  44 ssize_t store_sampling_rate(struct dbs_data *dbs_data, const char *buf,
  45                             size_t count)
  46 {
  47         struct policy_dbs_info *policy_dbs;
  48         unsigned int rate;
  49         int ret;
  50         ret = sscanf(buf, "%u", &rate);
  51         if (ret != 1)
  52                 return -EINVAL;
  53
  54         dbs_data->sampling_rate = max(rate, dbs_data->min_sampling_rate);
  55
  56         /*
  57          * We are operating under dbs_data->mutex and so the list and its
  58          * entries can't be freed concurrently.
  59          */
  60         list_for_each_entry(policy_dbs, &dbs_data->policy_dbs_list, list) {
  61                 mutex_lock(&policy_dbs->timer_mutex);
  62                 /*
  63                  * On 32-bit architectures this may race with the
  64                  * sample_delay_ns read in dbs_update_util_handler(), but that
  65                  * really doesn't matter.  If the read returns a value that's
  66                  * too big, the sample will be skipped, but the next invocation
  67                  * of dbs_update_util_handler() (when the update has been
  68                  * completed) will take a sample.
  69                  *
  70                  * If this runs in parallel with dbs_work_handler(), we may end
  71                  * up overwriting the sample_delay_ns value that it has just
  72                  * written, but it will be corrected next time a sample is
  73                  * taken, so it shouldn't be significant.
  74                  */
  75                 gov_update_sample_delay(policy_dbs, 0);
  76                 mutex_unlock(&policy_dbs->timer_mutex);
  77         }
  78
  79         return count;
  80 }
  81 EXPORT_SYMBOL_GPL(store_sampling_rate);
  82
  83 static inline struct dbs_data *to_dbs_data(struct kobject *kobj)
  84 {
  85         return container_of(kobj, struct dbs_data, kobj);
  86 }
  87
  88 static inline struct governor_attr *to_gov_attr(struct attribute *attr)
  89 {
  90         return container_of(attr, struct governor_attr, attr);
  91 }
  92
  93 static ssize_t governor_show(struct kobject *kobj, struct attribute *attr,
  94                              char *buf)
  95 {
  96         struct dbs_data *dbs_data = to_dbs_data(kobj);
  97         struct governor_attr *gattr = to_gov_attr(attr);
  98         int ret = -EIO;
  99
 100         if (gattr->show)
 101                 ret = gattr->show(dbs_data, buf);
 102
 103         return ret;
 104 }
 105
 106 static ssize_t governor_store(struct kobject *kobj, struct attribute *attr,
 107                               const char *buf, size_t count)
 108 {
 109         struct dbs_data *dbs_data = to_dbs_data(kobj);
 110         struct governor_attr *gattr = to_gov_attr(attr);
 111         int ret = -EIO;
 112
 113         mutex_lock(&dbs_data->mutex);
 114
 115         if (dbs_data->usage_count && gattr->store)
 116                 ret = gattr->store(dbs_data, buf, count);
 117
 118         mutex_unlock(&dbs_data->mutex);
 119
 120         return ret;
 121 }
 122
 123 /*
 124  * Sysfs Ops for accessing governor attributes.
 125  *
 126  * All show/store invocations for governor specific sysfs attributes, will first
 127  * call the below show/store callbacks and the attribute specific callback will
 128  * be called from within it.
 129  */
 130 static const struct sysfs_ops governor_sysfs_ops = {
 131         .show   = governor_show,
 132         .store  = governor_store,
 133 };
 134
 135 unsigned int dbs_update(struct cpufreq_policy *policy)
 136 {
 137         struct dbs_governor *gov = dbs_governor_of(policy);
 138         struct policy_dbs_info *policy_dbs = policy->governor_data;
 139         struct dbs_data *dbs_data = policy_dbs->dbs_data;
 140         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 141         unsigned int ignore_nice = dbs_data->ignore_nice_load;
 142         unsigned int max_load = 0;
 143         unsigned int sampling_rate, j;
 144
 145         /*
 146          * Sometimes governors may use an additional multiplier to increase
 147          * sample delays temporarily.  Apply that multiplier to sampling_rate
 148          * so as to keep the wake-up-from-idle detection logic a bit
 149          * conservative.
 150          */
 151         sampling_rate = dbs_data->sampling_rate * policy_dbs->rate_mult;
 152
 153         /* Get Absolute Load */
 154         for_each_cpu(j, policy->cpus) {
 155                 struct cpu_dbs_info *j_cdbs;
 156                 u64 cur_wall_time, cur_idle_time;
 157                 unsigned int idle_time, wall_time;
 158                 unsigned int load;
 159                 int io_busy = 0;
 160
 161                 j_cdbs = gov->get_cpu_cdbs(j);
 162
 163                 /*
 164                  * For the purpose of ondemand, waiting for disk IO is
 165                  * an indication that you're performance critical, and
 166                  * not that the system is actually idle. So do not add
 167                  * the iowait time to the cpu idle time.
 168                  */
 169                 if (gov->governor == GOV_ONDEMAND)
 170                         io_busy = od_tuners->io_is_busy;
 171                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time, io_busy);
 172
 173                 wall_time = cur_wall_time - j_cdbs->prev_cpu_wall;
 174                 j_cdbs->prev_cpu_wall = cur_wall_time;
 175
 176                 if (cur_idle_time <= j_cdbs->prev_cpu_idle) {
 177                         idle_time = 0;
 178                 } else {
 179                         idle_time = cur_idle_time - j_cdbs->prev_cpu_idle;
 180                         j_cdbs->prev_cpu_idle = cur_idle_time;
 181                 }
 182
 183                 if (ignore_nice) {
 184                         u64 cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 185
 186                         idle_time += cputime_to_usecs(cur_nice - j_cdbs->prev_cpu_nice);
 187                         j_cdbs->prev_cpu_nice = cur_nice;
 188                 }
 189
 190                 if (unlikely(!wall_time || wall_time < idle_time))
 191                         continue;
 192
 193                 /*
 194                  * If the CPU had gone completely idle, and a task just woke up
 195                  * on this CPU now, it would be unfair to calculate 'load' the
 196                  * usual way for this elapsed time-window, because it will show
 197                  * near-zero load, irrespective of how CPU intensive that task
 198                  * actually is. This is undesirable for latency-sensitive bursty
 199                  * workloads.
 200                  *
 201                  * To avoid this, we reuse the 'load' from the previous
 202                  * time-window and give this task a chance to start with a
 203                  * reasonably high CPU frequency. (However, we shouldn't over-do
 204                  * this copy, lest we get stuck at a high load (high frequency)
 205                  * for too long, even when the current system load has actually
 206                  * dropped down. So we perform the copy only once, upon the
 207                  * first wake-up from idle.)
 208                  *
 209                  * Detecting this situation is easy: the governor's utilization
 210                  * update handler would not have run during CPU-idle periods.
 211                  * Hence, an unusually large 'wall_time' (as compared to the
 212                  * sampling rate) indicates this scenario.
 213                  *
 214                  * prev_load can be zero in two cases and we must recalculate it
 215                  * for both cases:
 216                  * - during long idle intervals
 217                  * - explicitly set to zero
 218                  */
 219                 if (unlikely(wall_time > (2 * sampling_rate) &&
 220                              j_cdbs->prev_load)) {
 221                         load = j_cdbs->prev_load;
 222
 223                         /*
 224                          * Perform a destructive copy, to ensure that we copy
 225                          * the previous load only once, upon the first wake-up
 226                          * from idle.
 227                          */
 228                         j_cdbs->prev_load = 0;
 229                 } else {
 230                         load = 100 * (wall_time - idle_time) / wall_time;
 231                         j_cdbs->prev_load = load;
 232                 }
 233
 234                 if (load > max_load)
 235                         max_load = load;
 236         }
 237         return max_load;
 238 }
 239 EXPORT_SYMBOL_GPL(dbs_update);
 240
 241 void gov_set_update_util(struct policy_dbs_info *policy_dbs,
 242                          unsigned int delay_us)
 243 {
 244         struct cpufreq_policy *policy = policy_dbs->policy;
 245         struct dbs_governor *gov = dbs_governor_of(policy);
 246         int cpu;
 247
 248         gov_update_sample_delay(policy_dbs, delay_us);
 249         policy_dbs->last_sample_time = 0;
 250
 251         for_each_cpu(cpu, policy->cpus) {
 252                 struct cpu_dbs_info *cdbs = gov->get_cpu_cdbs(cpu);
 253
 254                 cpufreq_set_update_util_data(cpu, &cdbs->update_util);
 255         }
 256 }
 257 EXPORT_SYMBOL_GPL(gov_set_update_util);
 258
 259 static inline void gov_clear_update_util(struct cpufreq_policy *policy)
 260 {
 261         int i;
 262
 263         for_each_cpu(i, policy->cpus)
 264                 cpufreq_set_update_util_data(i, NULL);
 265
 266         synchronize_rcu();
 267 }
 268
 269 static void gov_cancel_work(struct cpufreq_policy *policy)
 270 {
 271         struct policy_dbs_info *policy_dbs = policy->governor_data;
 272
 273         gov_clear_update_util(policy_dbs->policy);
 274         irq_work_sync(&policy_dbs->irq_work);
 275         cancel_work_sync(&policy_dbs->work);
 276         atomic_set(&policy_dbs->work_count, 0);
 277         policy_dbs->work_in_progress = false;
 278 }
 279
 280 static void dbs_work_handler(struct work_struct *work)
 281 {
 282         struct policy_dbs_info *policy_dbs;
 283         struct cpufreq_policy *policy;
 284         struct dbs_governor *gov;
 285
 286         policy_dbs = container_of(work, struct policy_dbs_info, work);
 287         policy = policy_dbs->policy;
 288         gov = dbs_governor_of(policy);
 289
 290         /*
 291          * Make sure cpufreq_governor_limits() isn't evaluating load or the
 292          * ondemand governor isn't updating the sampling rate in parallel.
 293          */
 294         mutex_lock(&policy_dbs->timer_mutex);
 295         gov_update_sample_delay(policy_dbs, gov->gov_dbs_timer(policy));
 296         mutex_unlock(&policy_dbs->timer_mutex);
 297
 298         /* Allow the utilization update handler to queue up more work. */
 299         atomic_set(&policy_dbs->work_count, 0);
 300         /*
 301          * If the update below is reordered with respect to the sample delay
 302          * modification, the utilization update handler may end up using a stale
 303          * sample delay value.
 304          */
 305         smp_wmb();
 306         policy_dbs->work_in_progress = false;
 307 }
 308
 309 static void dbs_irq_work(struct irq_work *irq_work)
 310 {
 311         struct policy_dbs_info *policy_dbs;
 312
 313         policy_dbs = container_of(irq_work, struct policy_dbs_info, irq_work);
 314         schedule_work(&policy_dbs->work);
 315 }
 316
 317 static void dbs_update_util_handler(struct update_util_data *data, u64 time,
 318                                     unsigned long util, unsigned long max)
 319 {
 320         struct cpu_dbs_info *cdbs = container_of(data, struct cpu_dbs_info, update_util);
 321         struct policy_dbs_info *policy_dbs = cdbs->policy_dbs;
 322         u64 delta_ns;
 323
 324         /*
 325          * The work may not be allowed to be queued up right now.
 326          * Possible reasons:
 327          * - Work has already been queued up or is in progress.
 328          * - It is too early (too little time from the previous sample).
 329          */
 330         if (policy_dbs->work_in_progress)
 331                 return;
 332
 333         /*
 334          * If the reads below are reordered before the check above, the value
 335          * of sample_delay_ns used in the computation may be stale.
 336          */
 337         smp_rmb();
 338         delta_ns = time - policy_dbs->last_sample_time;
 339         if ((s64)delta_ns < policy_dbs->sample_delay_ns)
 340                 return;
 341
 342         /*
 343          * If the policy is not shared, the irq_work may be queued up right away
 344          * at this point.  Otherwise, we need to ensure that only one of the
 345          * CPUs sharing the policy will do that.
 346          */
 347         if (policy_dbs->is_shared &&
 348             !atomic_add_unless(&policy_dbs->work_count, 1, 1))
 349                 return;
 350
 351         policy_dbs->last_sample_time = time;
 352         policy_dbs->work_in_progress = true;
 353         irq_work_queue(&policy_dbs->irq_work);
 354 }
 355
 356 static struct policy_dbs_info *alloc_policy_dbs_info(struct cpufreq_policy *policy,
 357                                                      struct dbs_governor *gov)
 358 {
 359         struct policy_dbs_info *policy_dbs;
 360         int j;
 361
 362         /* Allocate memory for the common information for policy->cpus */
 363         policy_dbs = kzalloc(sizeof(*policy_dbs), GFP_KERNEL);
 364         if (!policy_dbs)
 365                 return NULL;
 366
 367         policy_dbs->policy = policy;
 368         mutex_init(&policy_dbs->timer_mutex);
 369         atomic_set(&policy_dbs->work_count, 0);
 370         init_irq_work(&policy_dbs->irq_work, dbs_irq_work);
 371         INIT_WORK(&policy_dbs->work, dbs_work_handler);
 372
 373         /* Set policy_dbs for all CPUs, online+offline */
 374         for_each_cpu(j, policy->related_cpus) {
 375                 struct cpu_dbs_info *j_cdbs = gov->get_cpu_cdbs(j);
 376
 377                 j_cdbs->policy_dbs = policy_dbs;
 378                 j_cdbs->update_util.func = dbs_update_util_handler;
 379         }
 380         return policy_dbs;
 381 }
 382
 383 static void free_policy_dbs_info(struct cpufreq_policy *policy,
 384                                  struct dbs_governor *gov)
 385 {
 386         struct cpu_dbs_info *cdbs = gov->get_cpu_cdbs(policy->cpu);
 387         struct policy_dbs_info *policy_dbs = cdbs->policy_dbs;
 388         int j;
 389
 390         mutex_destroy(&policy_dbs->timer_mutex);
 391
 392         for_each_cpu(j, policy->related_cpus) {
 393                 struct cpu_dbs_info *j_cdbs = gov->get_cpu_cdbs(j);
 394
 395                 j_cdbs->policy_dbs = NULL;
 396                 j_cdbs->update_util.func = NULL;
 397         }
 398         kfree(policy_dbs);
 399 }
 400
 401 static int cpufreq_governor_init(struct cpufreq_policy *policy)
 402 {
 403         struct dbs_governor *gov = dbs_governor_of(policy);
 404         struct dbs_data *dbs_data = gov->gdbs_data;
 405         struct policy_dbs_info *policy_dbs;
 406         unsigned int latency;
 407         int ret;
 408
 409         /* State should be equivalent to EXIT */
 410         if (policy->governor_data)
 411                 return -EBUSY;
 412
 413         policy_dbs = alloc_policy_dbs_info(policy, gov);
 414         if (!policy_dbs)
 415                 return -ENOMEM;
 416
 417         if (dbs_data) {
 418                 if (WARN_ON(have_governor_per_policy())) {
 419                         ret = -EINVAL;
 420                         goto free_policy_dbs_info;
 421                 }
 422                 policy_dbs->dbs_data = dbs_data;
 423                 policy->governor_data = policy_dbs;
 424
 425                 mutex_lock(&dbs_data->mutex);
 426                 dbs_data->usage_count++;
 427                 list_add(&policy_dbs->list, &dbs_data->policy_dbs_list);
 428                 mutex_unlock(&dbs_data->mutex);
 429
 430                 return 0;
 431         }
 432
 433         dbs_data = kzalloc(sizeof(*dbs_data), GFP_KERNEL);
 434         if (!dbs_data) {
 435                 ret = -ENOMEM;
 436                 goto free_policy_dbs_info;
 437         }
 438
 439         INIT_LIST_HEAD(&dbs_data->policy_dbs_list);
 440         mutex_init(&dbs_data->mutex);
 441
 442         ret = gov->init(dbs_data, !policy->governor->initialized);
 443         if (ret)
 444                 goto free_policy_dbs_info;
 445
 446         /* policy latency is in ns. Convert it to us first */
 447         latency = policy->cpuinfo.transition_latency / 1000;
 448         if (latency == 0)
 449                 latency = 1;
 450
 451         /* Bring kernel and HW constraints together */
 452         dbs_data->min_sampling_rate = max(dbs_data->min_sampling_rate,
 453                                           MIN_LATENCY_MULTIPLIER * latency);
 454         dbs_data->sampling_rate = max(dbs_data->min_sampling_rate,
 455                                       LATENCY_MULTIPLIER * latency);
 456
 457         if (!have_governor_per_policy())
 458                 gov->gdbs_data = dbs_data;
 459
 460         policy->governor_data = policy_dbs;
 461
 462         policy_dbs->dbs_data = dbs_data;
 463         dbs_data->usage_count = 1;
 464         list_add(&policy_dbs->list, &dbs_data->policy_dbs_list);
 465
 466         gov->kobj_type.sysfs_ops = &governor_sysfs_ops;
 467         ret = kobject_init_and_add(&dbs_data->kobj, &gov->kobj_type,
 468                                    get_governor_parent_kobj(policy),
 469                                    "%s", gov->gov.name);
 470         if (!ret)
 471                 return 0;
 472
 473         /* Failure, so roll back. */
 474         pr_err("cpufreq: Governor initialization failed (dbs_data kobject init error %d)\n", ret);
 475
 476         policy->governor_data = NULL;
 477
 478         if (!have_governor_per_policy())
 479                 gov->gdbs_data = NULL;
 480         gov->exit(dbs_data, !policy->governor->initialized);
 481         kfree(dbs_data);
 482
 483 free_policy_dbs_info:
 484         free_policy_dbs_info(policy, gov);
 485         return ret;
 486 }
 487
 488 static int cpufreq_governor_exit(struct cpufreq_policy *policy)
 489 {
 490         struct dbs_governor *gov = dbs_governor_of(policy);
 491         struct policy_dbs_info *policy_dbs = policy->governor_data;
 492         struct dbs_data *dbs_data = policy_dbs->dbs_data;
 493         int count;
 494
 495         mutex_lock(&dbs_data->mutex);
 496         list_del(&policy_dbs->list);
 497         count = --dbs_data->usage_count;
 498         mutex_unlock(&dbs_data->mutex);
 499
 500         if (!count) {
 501                 kobject_put(&dbs_data->kobj);
 502
 503                 policy->governor_data = NULL;
 504
 505                 if (!have_governor_per_policy())
 506                         gov->gdbs_data = NULL;
 507
 508                 gov->exit(dbs_data, policy->governor->initialized == 1);
 509                 mutex_destroy(&dbs_data->mutex);
 510                 kfree(dbs_data);
 511         } else {
 512                 policy->governor_data = NULL;
 513         }
 514
 515         free_policy_dbs_info(policy, gov);
 516         return 0;
 517 }
 518
 519 static int cpufreq_governor_start(struct cpufreq_policy *policy)
 520 {
 521         struct dbs_governor *gov = dbs_governor_of(policy);
 522         struct policy_dbs_info *policy_dbs = policy->governor_data;
 523         struct dbs_data *dbs_data = policy_dbs->dbs_data;
 524         unsigned int sampling_rate, ignore_nice, j, cpu = policy->cpu;
 525         int io_busy = 0;
 526
 527         if (!policy->cur)
 528                 return -EINVAL;
 529
 530         policy_dbs->is_shared = policy_is_shared(policy);
 531         policy_dbs->rate_mult = 1;
 532
 533         sampling_rate = dbs_data->sampling_rate;
 534         ignore_nice = dbs_data->ignore_nice_load;
 535
 536         if (gov->governor == GOV_ONDEMAND) {
 537                 struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 538
 539                 io_busy = od_tuners->io_is_busy;
 540         }
 541
 542         for_each_cpu(j, policy->cpus) {
 543                 struct cpu_dbs_info *j_cdbs = gov->get_cpu_cdbs(j);
 544                 unsigned int prev_load;
 545
 546                 j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_cpu_wall, io_busy);
 547
 548                 prev_load = j_cdbs->prev_cpu_wall - j_cdbs->prev_cpu_idle;
 549                 j_cdbs->prev_load = 100 * prev_load / (unsigned int)j_cdbs->prev_cpu_wall;
 550
 551                 if (ignore_nice)
 552                         j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 553         }
 554
 555         if (gov->governor == GOV_CONSERVATIVE) {
 556                 struct cs_cpu_dbs_info_s *cs_dbs_info =
 557                         gov->get_cpu_dbs_info_s(cpu);
 558
 559                 cs_dbs_info->down_skip = 0;
 560                 cs_dbs_info->requested_freq = policy->cur;
 561         } else {
 562                 struct od_ops *od_ops = gov->gov_ops;
 563                 struct od_cpu_dbs_info_s *od_dbs_info = gov->get_cpu_dbs_info_s(cpu);
 564
 565                 od_dbs_info->sample_type = OD_NORMAL_SAMPLE;
 566                 od_ops->powersave_bias_init_cpu(cpu);
 567         }
 568
 569         gov_set_update_util(policy_dbs, sampling_rate);
 570         return 0;
 571 }
 572
 573 static int cpufreq_governor_stop(struct cpufreq_policy *policy)
 574 {
 575         gov_cancel_work(policy);
 576
 577         return 0;
 578 }
 579
 580 static int cpufreq_governor_limits(struct cpufreq_policy *policy)
 581 {
 582         struct policy_dbs_info *policy_dbs = policy->governor_data;
 583
 584         mutex_lock(&policy_dbs->timer_mutex);
 585
 586         if (policy->max < policy->cur)
 587                 __cpufreq_driver_target(policy, policy->max, CPUFREQ_RELATION_H);
 588         else if (policy->min > policy->cur)
 589                 __cpufreq_driver_target(policy, policy->min, CPUFREQ_RELATION_L);
 590
 591         gov_update_sample_delay(policy_dbs, 0);
 592
 593         mutex_unlock(&policy_dbs->timer_mutex);
 594
 595         return 0;
 596 }
 597
 598 int cpufreq_governor_dbs(struct cpufreq_policy *policy, unsigned int event)
 599 {
 600         int ret = -EINVAL;
 601
 602         /* Lock governor to block concurrent initialization of governor */
 603         mutex_lock(&dbs_data_mutex);
 604
 605         if (event == CPUFREQ_GOV_POLICY_INIT) {
 606                 ret = cpufreq_governor_init(policy);
 607         } else if (policy->governor_data) {
 608                 switch (event) {
 609                 case CPUFREQ_GOV_POLICY_EXIT:
 610                         ret = cpufreq_governor_exit(policy);
 611                         break;
 612                 case CPUFREQ_GOV_START:
 613                         ret = cpufreq_governor_start(policy);
 614                         break;
 615                 case CPUFREQ_GOV_STOP:
 616                         ret = cpufreq_governor_stop(policy);
 617                         break;
 618                 case CPUFREQ_GOV_LIMITS:
 619                         ret = cpufreq_governor_limits(policy);
 620                         break;
 621                 }
 622         }
 623
 624         mutex_unlock(&dbs_data_mutex);
 625         return ret;
 626 }
 627 EXPORT_SYMBOL_GPL(cpufreq_governor_dbs);