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 static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs);
  26
  27 DEFINE_MUTEX(dbs_data_mutex);
  28 EXPORT_SYMBOL_GPL(dbs_data_mutex);
  29
  30 /* Common sysfs tunables */
  31 /**
  32  * store_sampling_rate - update sampling rate effective immediately if needed.
  33  *
  34  * If new rate is smaller than the old, simply updating
  35  * dbs.sampling_rate might not be appropriate. For example, if the
  36  * original sampling_rate was 1 second and the requested new sampling rate is 10
  37  * ms because the user needs immediate reaction from ondemand governor, but not
  38  * sure if higher frequency will be required or not, then, the governor may
  39  * change the sampling rate too late; up to 1 second later. Thus, if we are
  40  * reducing the sampling rate, we need to make the new value effective
  41  * immediately.
  42  *
  43  * This must be called with dbs_data->mutex held, otherwise traversing
  44  * policy_dbs_list isn't safe.
  45  */
  46 ssize_t store_sampling_rate(struct dbs_data *dbs_data, const char *buf,
  47                             size_t count)
  48 {
  49         struct policy_dbs_info *policy_dbs;
  50         unsigned int rate;
  51         int ret;
  52         ret = sscanf(buf, "%u", &rate);
  53         if (ret != 1)
  54                 return -EINVAL;
  55
  56         dbs_data->sampling_rate = max(rate, dbs_data->min_sampling_rate);
  57
  58         /*
  59          * We are operating under dbs_data->mutex and so the list and its
  60          * entries can't be freed concurrently.
  61          */
  62         list_for_each_entry(policy_dbs, &dbs_data->policy_dbs_list, list) {
  63                 mutex_lock(&policy_dbs->timer_mutex);
  64                 /*
  65                  * On 32-bit architectures this may race with the
  66                  * sample_delay_ns read in dbs_update_util_handler(), but that
  67                  * really doesn't matter.  If the read returns a value that's
  68                  * too big, the sample will be skipped, but the next invocation
  69                  * of dbs_update_util_handler() (when the update has been
  70                  * completed) will take a sample.
  71                  *
  72                  * If this runs in parallel with dbs_work_handler(), we may end
  73                  * up overwriting the sample_delay_ns value that it has just
  74                  * written, but it will be corrected next time a sample is
  75                  * taken, so it shouldn't be significant.
  76                  */
  77                 gov_update_sample_delay(policy_dbs, 0);
  78                 mutex_unlock(&policy_dbs->timer_mutex);
  79         }
  80
  81         return count;
  82 }
  83 EXPORT_SYMBOL_GPL(store_sampling_rate);
  84
  85 /**
  86  * gov_update_cpu_data - Update CPU load data.
  87  * @dbs_data: Top-level governor data pointer.
  88  *
  89  * Update CPU load data for all CPUs in the domain governed by @dbs_data
  90  * (that may be a single policy or a bunch of them if governor tunables are
  91  * system-wide).
  92  *
  93  * Call under the @dbs_data mutex.
  94  */
  95 void gov_update_cpu_data(struct dbs_data *dbs_data)
  96 {
  97         struct policy_dbs_info *policy_dbs;
  98
  99         list_for_each_entry(policy_dbs, &dbs_data->policy_dbs_list, list) {
 100                 unsigned int j;
 101
 102                 for_each_cpu(j, policy_dbs->policy->cpus) {
 103                         struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
 104
 105                         j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_cpu_wall,
 106                                                                   dbs_data->io_is_busy);
 107                         if (dbs_data->ignore_nice_load)
 108                                 j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 109                 }
 110         }
 111 }
 112 EXPORT_SYMBOL_GPL(gov_update_cpu_data);
 113
 114 static inline struct dbs_data *to_dbs_data(struct kobject *kobj)
 115 {
 116         return container_of(kobj, struct dbs_data, kobj);
 117 }
 118
 119 static inline struct governor_attr *to_gov_attr(struct attribute *attr)
 120 {
 121         return container_of(attr, struct governor_attr, attr);
 122 }
 123
 124 static ssize_t governor_show(struct kobject *kobj, struct attribute *attr,
 125                              char *buf)
 126 {
 127         struct dbs_data *dbs_data = to_dbs_data(kobj);
 128         struct governor_attr *gattr = to_gov_attr(attr);
 129         int ret = -EIO;
 130
 131         if (gattr->show)
 132                 ret = gattr->show(dbs_data, buf);
 133
 134         return ret;
 135 }
 136
 137 static ssize_t governor_store(struct kobject *kobj, struct attribute *attr,
 138                               const char *buf, size_t count)
 139 {
 140         struct dbs_data *dbs_data = to_dbs_data(kobj);
 141         struct governor_attr *gattr = to_gov_attr(attr);
 142         int ret = -EIO;
 143
 144         mutex_lock(&dbs_data->mutex);
 145
 146         if (dbs_data->usage_count && gattr->store)
 147                 ret = gattr->store(dbs_data, buf, count);
 148
 149         mutex_unlock(&dbs_data->mutex);
 150
 151         return ret;
 152 }
 153
 154 /*
 155  * Sysfs Ops for accessing governor attributes.
 156  *
 157  * All show/store invocations for governor specific sysfs attributes, will first
 158  * call the below show/store callbacks and the attribute specific callback will
 159  * be called from within it.
 160  */
 161 static const struct sysfs_ops governor_sysfs_ops = {
 162         .show   = governor_show,
 163         .store  = governor_store,
 164 };
 165
 166 unsigned int dbs_update(struct cpufreq_policy *policy)
 167 {
 168         struct policy_dbs_info *policy_dbs = policy->governor_data;
 169         struct dbs_data *dbs_data = policy_dbs->dbs_data;
 170         unsigned int ignore_nice = dbs_data->ignore_nice_load;
 171         unsigned int max_load = 0;
 172         unsigned int sampling_rate, io_busy, j;
 173
 174         /*
 175          * Sometimes governors may use an additional multiplier to increase
 176          * sample delays temporarily.  Apply that multiplier to sampling_rate
 177          * so as to keep the wake-up-from-idle detection logic a bit
 178          * conservative.
 179          */
 180         sampling_rate = dbs_data->sampling_rate * policy_dbs->rate_mult;
 181         /*
 182          * For the purpose of ondemand, waiting for disk IO is an indication
 183          * that you're performance critical, and not that the system is actually
 184          * idle, so do not add the iowait time to the CPU idle time then.
 185          */
 186         io_busy = dbs_data->io_is_busy;
 187
 188         /* Get Absolute Load */
 189         for_each_cpu(j, policy->cpus) {
 190                 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
 191                 u64 cur_wall_time, cur_idle_time;
 192                 unsigned int idle_time, wall_time;
 193                 unsigned int load;
 194
 195                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time, io_busy);
 196
 197                 wall_time = cur_wall_time - j_cdbs->prev_cpu_wall;
 198                 j_cdbs->prev_cpu_wall = cur_wall_time;
 199
 200                 if (cur_idle_time <= j_cdbs->prev_cpu_idle) {
 201                         idle_time = 0;
 202                 } else {
 203                         idle_time = cur_idle_time - j_cdbs->prev_cpu_idle;
 204                         j_cdbs->prev_cpu_idle = cur_idle_time;
 205                 }
 206
 207                 if (ignore_nice) {
 208                         u64 cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 209
 210                         idle_time += cputime_to_usecs(cur_nice - j_cdbs->prev_cpu_nice);
 211                         j_cdbs->prev_cpu_nice = cur_nice;
 212                 }
 213
 214                 if (unlikely(!wall_time || wall_time < idle_time))
 215                         continue;
 216
 217                 /*
 218                  * If the CPU had gone completely idle, and a task just woke up
 219                  * on this CPU now, it would be unfair to calculate 'load' the
 220                  * usual way for this elapsed time-window, because it will show
 221                  * near-zero load, irrespective of how CPU intensive that task
 222                  * actually is. This is undesirable for latency-sensitive bursty
 223                  * workloads.
 224                  *
 225                  * To avoid this, we reuse the 'load' from the previous
 226                  * time-window and give this task a chance to start with a
 227                  * reasonably high CPU frequency. (However, we shouldn't over-do
 228                  * this copy, lest we get stuck at a high load (high frequency)
 229                  * for too long, even when the current system load has actually
 230                  * dropped down. So we perform the copy only once, upon the
 231                  * first wake-up from idle.)
 232                  *
 233                  * Detecting this situation is easy: the governor's utilization
 234                  * update handler would not have run during CPU-idle periods.
 235                  * Hence, an unusually large 'wall_time' (as compared to the
 236                  * sampling rate) indicates this scenario.
 237                  *
 238                  * prev_load can be zero in two cases and we must recalculate it
 239                  * for both cases:
 240                  * - during long idle intervals
 241                  * - explicitly set to zero
 242                  */
 243                 if (unlikely(wall_time > (2 * sampling_rate) &&
 244                              j_cdbs->prev_load)) {
 245                         load = j_cdbs->prev_load;
 246
 247                         /*
 248                          * Perform a destructive copy, to ensure that we copy
 249                          * the previous load only once, upon the first wake-up
 250                          * from idle.
 251                          */
 252                         j_cdbs->prev_load = 0;
 253                 } else {
 254                         load = 100 * (wall_time - idle_time) / wall_time;
 255                         j_cdbs->prev_load = load;
 256                 }
 257
 258                 if (load > max_load)
 259                         max_load = load;
 260         }
 261         return max_load;
 262 }
 263 EXPORT_SYMBOL_GPL(dbs_update);
 264
 265 void gov_set_update_util(struct policy_dbs_info *policy_dbs,
 266                          unsigned int delay_us)
 267 {
 268         struct cpufreq_policy *policy = policy_dbs->policy;
 269         int cpu;
 270
 271         gov_update_sample_delay(policy_dbs, delay_us);
 272         policy_dbs->last_sample_time = 0;
 273
 274         for_each_cpu(cpu, policy->cpus) {
 275                 struct cpu_dbs_info *cdbs = &per_cpu(cpu_dbs, cpu);
 276
 277                 cpufreq_set_update_util_data(cpu, &cdbs->update_util);
 278         }
 279 }
 280 EXPORT_SYMBOL_GPL(gov_set_update_util);
 281
 282 static inline void gov_clear_update_util(struct cpufreq_policy *policy)
 283 {
 284         int i;
 285
 286         for_each_cpu(i, policy->cpus)
 287                 cpufreq_set_update_util_data(i, NULL);
 288
 289         synchronize_rcu();
 290 }
 291
 292 static void gov_cancel_work(struct cpufreq_policy *policy)
 293 {
 294         struct policy_dbs_info *policy_dbs = policy->governor_data;
 295
 296         gov_clear_update_util(policy_dbs->policy);
 297         irq_work_sync(&policy_dbs->irq_work);
 298         cancel_work_sync(&policy_dbs->work);
 299         atomic_set(&policy_dbs->work_count, 0);
 300         policy_dbs->work_in_progress = false;
 301 }
 302
 303 static void dbs_work_handler(struct work_struct *work)
 304 {
 305         struct policy_dbs_info *policy_dbs;
 306         struct cpufreq_policy *policy;
 307         struct dbs_governor *gov;
 308
 309         policy_dbs = container_of(work, struct policy_dbs_info, work);
 310         policy = policy_dbs->policy;
 311         gov = dbs_governor_of(policy);
 312
 313         /*
 314          * Make sure cpufreq_governor_limits() isn't evaluating load or the
 315          * ondemand governor isn't updating the sampling rate in parallel.
 316          */
 317         mutex_lock(&policy_dbs->timer_mutex);
 318         gov_update_sample_delay(policy_dbs, gov->gov_dbs_timer(policy));
 319         mutex_unlock(&policy_dbs->timer_mutex);
 320
 321         /* Allow the utilization update handler to queue up more work. */
 322         atomic_set(&policy_dbs->work_count, 0);
 323         /*
 324          * If the update below is reordered with respect to the sample delay
 325          * modification, the utilization update handler may end up using a stale
 326          * sample delay value.
 327          */
 328         smp_wmb();
 329         policy_dbs->work_in_progress = false;
 330 }
 331
 332 static void dbs_irq_work(struct irq_work *irq_work)
 333 {
 334         struct policy_dbs_info *policy_dbs;
 335
 336         policy_dbs = container_of(irq_work, struct policy_dbs_info, irq_work);
 337         schedule_work(&policy_dbs->work);
 338 }
 339
 340 static void dbs_update_util_handler(struct update_util_data *data, u64 time,
 341                                     unsigned long util, unsigned long max)
 342 {
 343         struct cpu_dbs_info *cdbs = container_of(data, struct cpu_dbs_info, update_util);
 344         struct policy_dbs_info *policy_dbs = cdbs->policy_dbs;
 345         u64 delta_ns;
 346
 347         /*
 348          * The work may not be allowed to be queued up right now.
 349          * Possible reasons:
 350          * - Work has already been queued up or is in progress.
 351          * - It is too early (too little time from the previous sample).
 352          */
 353         if (policy_dbs->work_in_progress)
 354                 return;
 355
 356         /*
 357          * If the reads below are reordered before the check above, the value
 358          * of sample_delay_ns used in the computation may be stale.
 359          */
 360         smp_rmb();
 361         delta_ns = time - policy_dbs->last_sample_time;
 362         if ((s64)delta_ns < policy_dbs->sample_delay_ns)
 363                 return;
 364
 365         /*
 366          * If the policy is not shared, the irq_work may be queued up right away
 367          * at this point.  Otherwise, we need to ensure that only one of the
 368          * CPUs sharing the policy will do that.
 369          */
 370         if (policy_dbs->is_shared &&
 371             !atomic_add_unless(&policy_dbs->work_count, 1, 1))
 372                 return;
 373
 374         policy_dbs->last_sample_time = time;
 375         policy_dbs->work_in_progress = true;
 376         irq_work_queue(&policy_dbs->irq_work);
 377 }
 378
 379 static struct policy_dbs_info *alloc_policy_dbs_info(struct cpufreq_policy *policy,
 380                                                      struct dbs_governor *gov)
 381 {
 382         struct policy_dbs_info *policy_dbs;
 383         int j;
 384
 385         /* Allocate memory for per-policy governor data. */
 386         policy_dbs = gov->alloc();
 387         if (!policy_dbs)
 388                 return NULL;
 389
 390         policy_dbs->policy = policy;
 391         mutex_init(&policy_dbs->timer_mutex);
 392         atomic_set(&policy_dbs->work_count, 0);
 393         init_irq_work(&policy_dbs->irq_work, dbs_irq_work);
 394         INIT_WORK(&policy_dbs->work, dbs_work_handler);
 395
 396         /* Set policy_dbs for all CPUs, online+offline */
 397         for_each_cpu(j, policy->related_cpus) {
 398                 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
 399
 400                 j_cdbs->policy_dbs = policy_dbs;
 401                 j_cdbs->update_util.func = dbs_update_util_handler;
 402         }
 403         return policy_dbs;
 404 }
 405
 406 static void free_policy_dbs_info(struct policy_dbs_info *policy_dbs,
 407                                  struct dbs_governor *gov)
 408 {
 409         int j;
 410
 411         mutex_destroy(&policy_dbs->timer_mutex);
 412
 413         for_each_cpu(j, policy_dbs->policy->related_cpus) {
 414                 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
 415
 416                 j_cdbs->policy_dbs = NULL;
 417                 j_cdbs->update_util.func = NULL;
 418         }
 419         gov->free(policy_dbs);
 420 }
 421
 422 static int cpufreq_governor_init(struct cpufreq_policy *policy)
 423 {
 424         struct dbs_governor *gov = dbs_governor_of(policy);
 425         struct dbs_data *dbs_data = gov->gdbs_data;
 426         struct policy_dbs_info *policy_dbs;
 427         unsigned int latency;
 428         int ret;
 429
 430         /* State should be equivalent to EXIT */
 431         if (policy->governor_data)
 432                 return -EBUSY;
 433
 434         policy_dbs = alloc_policy_dbs_info(policy, gov);
 435         if (!policy_dbs)
 436                 return -ENOMEM;
 437
 438         if (dbs_data) {
 439                 if (WARN_ON(have_governor_per_policy())) {
 440                         ret = -EINVAL;
 441                         goto free_policy_dbs_info;
 442                 }
 443                 policy_dbs->dbs_data = dbs_data;
 444                 policy->governor_data = policy_dbs;
 445
 446                 mutex_lock(&dbs_data->mutex);
 447                 dbs_data->usage_count++;
 448                 list_add(&policy_dbs->list, &dbs_data->policy_dbs_list);
 449                 mutex_unlock(&dbs_data->mutex);
 450
 451                 return 0;
 452         }
 453
 454         dbs_data = kzalloc(sizeof(*dbs_data), GFP_KERNEL);
 455         if (!dbs_data) {
 456                 ret = -ENOMEM;
 457                 goto free_policy_dbs_info;
 458         }
 459
 460         INIT_LIST_HEAD(&dbs_data->policy_dbs_list);
 461         mutex_init(&dbs_data->mutex);
 462
 463         ret = gov->init(dbs_data, !policy->governor->initialized);
 464         if (ret)
 465                 goto free_policy_dbs_info;
 466
 467         /* policy latency is in ns. Convert it to us first */
 468         latency = policy->cpuinfo.transition_latency / 1000;
 469         if (latency == 0)
 470                 latency = 1;
 471
 472         /* Bring kernel and HW constraints together */
 473         dbs_data->min_sampling_rate = max(dbs_data->min_sampling_rate,
 474                                           MIN_LATENCY_MULTIPLIER * latency);
 475         dbs_data->sampling_rate = max(dbs_data->min_sampling_rate,
 476                                       LATENCY_MULTIPLIER * latency);
 477
 478         if (!have_governor_per_policy())
 479                 gov->gdbs_data = dbs_data;
 480
 481         policy->governor_data = policy_dbs;
 482
 483         policy_dbs->dbs_data = dbs_data;
 484         dbs_data->usage_count = 1;
 485         list_add(&policy_dbs->list, &dbs_data->policy_dbs_list);
 486
 487         gov->kobj_type.sysfs_ops = &governor_sysfs_ops;
 488         ret = kobject_init_and_add(&dbs_data->kobj, &gov->kobj_type,
 489                                    get_governor_parent_kobj(policy),
 490                                    "%s", gov->gov.name);
 491         if (!ret)
 492                 return 0;
 493
 494         /* Failure, so roll back. */
 495         pr_err("cpufreq: Governor initialization failed (dbs_data kobject init error %d)\n", ret);
 496
 497         policy->governor_data = NULL;
 498
 499         if (!have_governor_per_policy())
 500                 gov->gdbs_data = NULL;
 501         gov->exit(dbs_data, !policy->governor->initialized);
 502         kfree(dbs_data);
 503
 504 free_policy_dbs_info:
 505         free_policy_dbs_info(policy_dbs, gov);
 506         return ret;
 507 }
 508
 509 static int cpufreq_governor_exit(struct cpufreq_policy *policy)
 510 {
 511         struct dbs_governor *gov = dbs_governor_of(policy);
 512         struct policy_dbs_info *policy_dbs = policy->governor_data;
 513         struct dbs_data *dbs_data = policy_dbs->dbs_data;
 514         int count;
 515
 516         mutex_lock(&dbs_data->mutex);
 517         list_del(&policy_dbs->list);
 518         count = --dbs_data->usage_count;
 519         mutex_unlock(&dbs_data->mutex);
 520
 521         if (!count) {
 522                 kobject_put(&dbs_data->kobj);
 523
 524                 policy->governor_data = NULL;
 525
 526                 if (!have_governor_per_policy())
 527                         gov->gdbs_data = NULL;
 528
 529                 gov->exit(dbs_data, policy->governor->initialized == 1);
 530                 mutex_destroy(&dbs_data->mutex);
 531                 kfree(dbs_data);
 532         } else {
 533                 policy->governor_data = NULL;
 534         }
 535
 536         free_policy_dbs_info(policy_dbs, gov);
 537         return 0;
 538 }
 539
 540 static int cpufreq_governor_start(struct cpufreq_policy *policy)
 541 {
 542         struct dbs_governor *gov = dbs_governor_of(policy);
 543         struct policy_dbs_info *policy_dbs = policy->governor_data;
 544         struct dbs_data *dbs_data = policy_dbs->dbs_data;
 545         unsigned int sampling_rate, ignore_nice, j;
 546         unsigned int io_busy;
 547
 548         if (!policy->cur)
 549                 return -EINVAL;
 550
 551         policy_dbs->is_shared = policy_is_shared(policy);
 552         policy_dbs->rate_mult = 1;
 553
 554         sampling_rate = dbs_data->sampling_rate;
 555         ignore_nice = dbs_data->ignore_nice_load;
 556         io_busy = dbs_data->io_is_busy;
 557
 558         for_each_cpu(j, policy->cpus) {
 559                 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
 560                 unsigned int prev_load;
 561
 562                 j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_cpu_wall, io_busy);
 563
 564                 prev_load = j_cdbs->prev_cpu_wall - j_cdbs->prev_cpu_idle;
 565                 j_cdbs->prev_load = 100 * prev_load / (unsigned int)j_cdbs->prev_cpu_wall;
 566
 567                 if (ignore_nice)
 568                         j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 569         }
 570
 571         gov->start(policy);
 572
 573         gov_set_update_util(policy_dbs, sampling_rate);
 574         return 0;
 575 }
 576
 577 static int cpufreq_governor_stop(struct cpufreq_policy *policy)
 578 {
 579         gov_cancel_work(policy);
 580         return 0;
 581 }
 582
 583 static int cpufreq_governor_limits(struct cpufreq_policy *policy)
 584 {
 585         struct policy_dbs_info *policy_dbs = policy->governor_data;
 586
 587         mutex_lock(&policy_dbs->timer_mutex);
 588
 589         if (policy->max < policy->cur)
 590                 __cpufreq_driver_target(policy, policy->max, CPUFREQ_RELATION_H);
 591         else if (policy->min > policy->cur)
 592                 __cpufreq_driver_target(policy, policy->min, CPUFREQ_RELATION_L);
 593
 594         gov_update_sample_delay(policy_dbs, 0);
 595
 596         mutex_unlock(&policy_dbs->timer_mutex);
 597
 598         return 0;
 599 }
 600
 601 int cpufreq_governor_dbs(struct cpufreq_policy *policy, unsigned int event)
 602 {
 603         int ret = -EINVAL;
 604
 605         /* Lock governor to block concurrent initialization of governor */
 606         mutex_lock(&dbs_data_mutex);
 607
 608         if (event == CPUFREQ_GOV_POLICY_INIT) {
 609                 ret = cpufreq_governor_init(policy);
 610         } else if (policy->governor_data) {
 611                 switch (event) {
 612                 case CPUFREQ_GOV_POLICY_EXIT:
 613                         ret = cpufreq_governor_exit(policy);
 614                         break;
 615                 case CPUFREQ_GOV_START:
 616                         ret = cpufreq_governor_start(policy);
 617                         break;
 618                 case CPUFREQ_GOV_STOP:
 619                         ret = cpufreq_governor_stop(policy);
 620                         break;
 621                 case CPUFREQ_GOV_LIMITS:
 622                         ret = cpufreq_governor_limits(policy);
 623                         break;
 624                 }
 625         }
 626
 627         mutex_unlock(&dbs_data_mutex);
 628         return ret;
 629 }
 630 EXPORT_SYMBOL_GPL(cpufreq_governor_dbs);