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/sched.h>
  22 #include <linux/slab.h>
  23
  24 #include "cpufreq_governor.h"
  25
  26 static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs);
  27
  28 static DEFINE_MUTEX(gov_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
 130         return gattr->show(dbs_data, buf);
 131 }
 132
 133 static ssize_t governor_store(struct kobject *kobj, struct attribute *attr,
 134                               const char *buf, size_t count)
 135 {
 136         struct dbs_data *dbs_data = to_dbs_data(kobj);
 137         struct governor_attr *gattr = to_gov_attr(attr);
 138         int ret = -EBUSY;
 139
 140         mutex_lock(&dbs_data->mutex);
 141
 142         if (dbs_data->usage_count)
 143                 ret = gattr->store(dbs_data, buf, count);
 144
 145         mutex_unlock(&dbs_data->mutex);
 146
 147         return ret;
 148 }
 149
 150 /*
 151  * Sysfs Ops for accessing governor attributes.
 152  *
 153  * All show/store invocations for governor specific sysfs attributes, will first
 154  * call the below show/store callbacks and the attribute specific callback will
 155  * be called from within it.
 156  */
 157 static const struct sysfs_ops governor_sysfs_ops = {
 158         .show   = governor_show,
 159         .store  = governor_store,
 160 };
 161
 162 unsigned int dbs_update(struct cpufreq_policy *policy)
 163 {
 164         struct policy_dbs_info *policy_dbs = policy->governor_data;
 165         struct dbs_data *dbs_data = policy_dbs->dbs_data;
 166         unsigned int ignore_nice = dbs_data->ignore_nice_load;
 167         unsigned int max_load = 0;
 168         unsigned int sampling_rate, io_busy, j;
 169
 170         /*
 171          * Sometimes governors may use an additional multiplier to increase
 172          * sample delays temporarily.  Apply that multiplier to sampling_rate
 173          * so as to keep the wake-up-from-idle detection logic a bit
 174          * conservative.
 175          */
 176         sampling_rate = dbs_data->sampling_rate * policy_dbs->rate_mult;
 177         /*
 178          * For the purpose of ondemand, waiting for disk IO is an indication
 179          * that you're performance critical, and not that the system is actually
 180          * idle, so do not add the iowait time to the CPU idle time then.
 181          */
 182         io_busy = dbs_data->io_is_busy;
 183
 184         /* Get Absolute Load */
 185         for_each_cpu(j, policy->cpus) {
 186                 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
 187                 u64 cur_wall_time, cur_idle_time;
 188                 unsigned int idle_time, wall_time;
 189                 unsigned int load;
 190
 191                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time, io_busy);
 192
 193                 wall_time = cur_wall_time - j_cdbs->prev_cpu_wall;
 194                 j_cdbs->prev_cpu_wall = cur_wall_time;
 195
 196                 idle_time = cur_idle_time - j_cdbs->prev_cpu_idle;
 197                 j_cdbs->prev_cpu_idle = cur_idle_time;
 198
 199                 if (ignore_nice) {
 200                         u64 cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 201
 202                         idle_time += cputime_to_usecs(cur_nice - j_cdbs->prev_cpu_nice);
 203                         j_cdbs->prev_cpu_nice = cur_nice;
 204                 }
 205
 206                 if (unlikely(!wall_time || wall_time < idle_time))
 207                         continue;
 208
 209                 /*
 210                  * If the CPU had gone completely idle, and a task just woke up
 211                  * on this CPU now, it would be unfair to calculate 'load' the
 212                  * usual way for this elapsed time-window, because it will show
 213                  * near-zero load, irrespective of how CPU intensive that task
 214                  * actually is. This is undesirable for latency-sensitive bursty
 215                  * workloads.
 216                  *
 217                  * To avoid this, we reuse the 'load' from the previous
 218                  * time-window and give this task a chance to start with a
 219                  * reasonably high CPU frequency. (However, we shouldn't over-do
 220                  * this copy, lest we get stuck at a high load (high frequency)
 221                  * for too long, even when the current system load has actually
 222                  * dropped down. So we perform the copy only once, upon the
 223                  * first wake-up from idle.)
 224                  *
 225                  * Detecting this situation is easy: the governor's utilization
 226                  * update handler would not have run during CPU-idle periods.
 227                  * Hence, an unusually large 'wall_time' (as compared to the
 228                  * sampling rate) indicates this scenario.
 229                  *
 230                  * prev_load can be zero in two cases and we must recalculate it
 231                  * for both cases:
 232                  * - during long idle intervals
 233                  * - explicitly set to zero
 234                  */
 235                 if (unlikely(wall_time > (2 * sampling_rate) &&
 236                              j_cdbs->prev_load)) {
 237                         load = j_cdbs->prev_load;
 238
 239                         /*
 240                          * Perform a destructive copy, to ensure that we copy
 241                          * the previous load only once, upon the first wake-up
 242                          * from idle.
 243                          */
 244                         j_cdbs->prev_load = 0;
 245                 } else {
 246                         load = 100 * (wall_time - idle_time) / wall_time;
 247                         j_cdbs->prev_load = load;
 248                 }
 249
 250                 if (load > max_load)
 251                         max_load = load;
 252         }
 253         return max_load;
 254 }
 255 EXPORT_SYMBOL_GPL(dbs_update);
 256
 257 static void gov_set_update_util(struct policy_dbs_info *policy_dbs,
 258                                 unsigned int delay_us)
 259 {
 260         struct cpufreq_policy *policy = policy_dbs->policy;
 261         int cpu;
 262
 263         gov_update_sample_delay(policy_dbs, delay_us);
 264         policy_dbs->last_sample_time = 0;
 265
 266         for_each_cpu(cpu, policy->cpus) {
 267                 struct cpu_dbs_info *cdbs = &per_cpu(cpu_dbs, cpu);
 268
 269                 cpufreq_set_update_util_data(cpu, &cdbs->update_util);
 270         }
 271 }
 272
 273 static inline void gov_clear_update_util(struct cpufreq_policy *policy)
 274 {
 275         int i;
 276
 277         for_each_cpu(i, policy->cpus)
 278                 cpufreq_set_update_util_data(i, NULL);
 279
 280         synchronize_sched();
 281 }
 282
 283 static void gov_cancel_work(struct cpufreq_policy *policy)
 284 {
 285         struct policy_dbs_info *policy_dbs = policy->governor_data;
 286
 287         gov_clear_update_util(policy_dbs->policy);
 288         irq_work_sync(&policy_dbs->irq_work);
 289         cancel_work_sync(&policy_dbs->work);
 290         atomic_set(&policy_dbs->work_count, 0);
 291         policy_dbs->work_in_progress = false;
 292 }
 293
 294 static void dbs_work_handler(struct work_struct *work)
 295 {
 296         struct policy_dbs_info *policy_dbs;
 297         struct cpufreq_policy *policy;
 298         struct dbs_governor *gov;
 299
 300         policy_dbs = container_of(work, struct policy_dbs_info, work);
 301         policy = policy_dbs->policy;
 302         gov = dbs_governor_of(policy);
 303
 304         /*
 305          * Make sure cpufreq_governor_limits() isn't evaluating load or the
 306          * ondemand governor isn't updating the sampling rate in parallel.
 307          */
 308         mutex_lock(&policy_dbs->timer_mutex);
 309         gov_update_sample_delay(policy_dbs, gov->gov_dbs_timer(policy));
 310         mutex_unlock(&policy_dbs->timer_mutex);
 311
 312         /* Allow the utilization update handler to queue up more work. */
 313         atomic_set(&policy_dbs->work_count, 0);
 314         /*
 315          * If the update below is reordered with respect to the sample delay
 316          * modification, the utilization update handler may end up using a stale
 317          * sample delay value.
 318          */
 319         smp_wmb();
 320         policy_dbs->work_in_progress = false;
 321 }
 322
 323 static void dbs_irq_work(struct irq_work *irq_work)
 324 {
 325         struct policy_dbs_info *policy_dbs;
 326
 327         policy_dbs = container_of(irq_work, struct policy_dbs_info, irq_work);
 328         schedule_work_on(smp_processor_id(), &policy_dbs->work);
 329 }
 330
 331 static void dbs_update_util_handler(struct update_util_data *data, u64 time,
 332                                     unsigned long util, unsigned long max)
 333 {
 334         struct cpu_dbs_info *cdbs = container_of(data, struct cpu_dbs_info, update_util);
 335         struct policy_dbs_info *policy_dbs = cdbs->policy_dbs;
 336         u64 delta_ns, lst;
 337
 338         /*
 339          * The work may not be allowed to be queued up right now.
 340          * Possible reasons:
 341          * - Work has already been queued up or is in progress.
 342          * - It is too early (too little time from the previous sample).
 343          */
 344         if (policy_dbs->work_in_progress)
 345                 return;
 346
 347         /*
 348          * If the reads below are reordered before the check above, the value
 349          * of sample_delay_ns used in the computation may be stale.
 350          */
 351         smp_rmb();
 352         lst = READ_ONCE(policy_dbs->last_sample_time);
 353         delta_ns = time - lst;
 354         if ((s64)delta_ns < policy_dbs->sample_delay_ns)
 355                 return;
 356
 357         /*
 358          * If the policy is not shared, the irq_work may be queued up right away
 359          * at this point.  Otherwise, we need to ensure that only one of the
 360          * CPUs sharing the policy will do that.
 361          */
 362         if (policy_dbs->is_shared) {
 363                 if (!atomic_add_unless(&policy_dbs->work_count, 1, 1))
 364                         return;
 365
 366                 /*
 367                  * If another CPU updated last_sample_time in the meantime, we
 368                  * shouldn't be here, so clear the work counter and bail out.
 369                  */
 370                 if (unlikely(lst != READ_ONCE(policy_dbs->last_sample_time))) {
 371                         atomic_set(&policy_dbs->work_count, 0);
 372                         return;
 373                 }
 374         }
 375
 376         policy_dbs->last_sample_time = time;
 377         policy_dbs->work_in_progress = true;
 378         irq_work_queue(&policy_dbs->irq_work);
 379 }
 380
 381 static struct policy_dbs_info *alloc_policy_dbs_info(struct cpufreq_policy *policy,
 382                                                      struct dbs_governor *gov)
 383 {
 384         struct policy_dbs_info *policy_dbs;
 385         int j;
 386
 387         /* Allocate memory for per-policy governor data. */
 388         policy_dbs = gov->alloc();
 389         if (!policy_dbs)
 390                 return NULL;
 391
 392         policy_dbs->policy = policy;
 393         mutex_init(&policy_dbs->timer_mutex);
 394         atomic_set(&policy_dbs->work_count, 0);
 395         init_irq_work(&policy_dbs->irq_work, dbs_irq_work);
 396         INIT_WORK(&policy_dbs->work, dbs_work_handler);
 397
 398         /* Set policy_dbs for all CPUs, online+offline */
 399         for_each_cpu(j, policy->related_cpus) {
 400                 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
 401
 402                 j_cdbs->policy_dbs = policy_dbs;
 403                 j_cdbs->update_util.func = dbs_update_util_handler;
 404         }
 405         return policy_dbs;
 406 }
 407
 408 static void free_policy_dbs_info(struct policy_dbs_info *policy_dbs,
 409                                  struct dbs_governor *gov)
 410 {
 411         int j;
 412
 413         mutex_destroy(&policy_dbs->timer_mutex);
 414
 415         for_each_cpu(j, policy_dbs->policy->related_cpus) {
 416                 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
 417
 418                 j_cdbs->policy_dbs = NULL;
 419                 j_cdbs->update_util.func = NULL;
 420         }
 421         gov->free(policy_dbs);
 422 }
 423
 424 static int cpufreq_governor_init(struct cpufreq_policy *policy)
 425 {
 426         struct dbs_governor *gov = dbs_governor_of(policy);
 427         struct dbs_data *dbs_data;
 428         struct policy_dbs_info *policy_dbs;
 429         unsigned int latency;
 430         int ret = 0;
 431
 432         /* State should be equivalent to EXIT */
 433         if (policy->governor_data)
 434                 return -EBUSY;
 435
 436         policy_dbs = alloc_policy_dbs_info(policy, gov);
 437         if (!policy_dbs)
 438                 return -ENOMEM;
 439
 440         /* Protect gov->gdbs_data against concurrent updates. */
 441         mutex_lock(&gov_dbs_data_mutex);
 442
 443         dbs_data = gov->gdbs_data;
 444         if (dbs_data) {
 445                 if (WARN_ON(have_governor_per_policy())) {
 446                         ret = -EINVAL;
 447                         goto free_policy_dbs_info;
 448                 }
 449                 policy_dbs->dbs_data = dbs_data;
 450                 policy->governor_data = policy_dbs;
 451
 452                 mutex_lock(&dbs_data->mutex);
 453                 dbs_data->usage_count++;
 454                 list_add(&policy_dbs->list, &dbs_data->policy_dbs_list);
 455                 mutex_unlock(&dbs_data->mutex);
 456                 goto out;
 457         }
 458
 459         dbs_data = kzalloc(sizeof(*dbs_data), GFP_KERNEL);
 460         if (!dbs_data) {
 461                 ret = -ENOMEM;
 462                 goto free_policy_dbs_info;
 463         }
 464
 465         INIT_LIST_HEAD(&dbs_data->policy_dbs_list);
 466         mutex_init(&dbs_data->mutex);
 467
 468         ret = gov->init(dbs_data, !policy->governor->initialized);
 469         if (ret)
 470                 goto free_policy_dbs_info;
 471
 472         /* policy latency is in ns. Convert it to us first */
 473         latency = policy->cpuinfo.transition_latency / 1000;
 474         if (latency == 0)
 475                 latency = 1;
 476
 477         /* Bring kernel and HW constraints together */
 478         dbs_data->min_sampling_rate = max(dbs_data->min_sampling_rate,
 479                                           MIN_LATENCY_MULTIPLIER * latency);
 480         dbs_data->sampling_rate = max(dbs_data->min_sampling_rate,
 481                                       LATENCY_MULTIPLIER * latency);
 482
 483         if (!have_governor_per_policy())
 484                 gov->gdbs_data = dbs_data;
 485
 486         policy->governor_data = policy_dbs;
 487
 488         policy_dbs->dbs_data = dbs_data;
 489         dbs_data->usage_count = 1;
 490         list_add(&policy_dbs->list, &dbs_data->policy_dbs_list);
 491
 492         gov->kobj_type.sysfs_ops = &governor_sysfs_ops;
 493         ret = kobject_init_and_add(&dbs_data->kobj, &gov->kobj_type,
 494                                    get_governor_parent_kobj(policy),
 495                                    "%s", gov->gov.name);
 496         if (!ret)
 497                 goto out;
 498
 499         /* Failure, so roll back. */
 500         pr_err("cpufreq: Governor initialization failed (dbs_data kobject init error %d)\n", ret);
 501
 502         policy->governor_data = NULL;
 503
 504         if (!have_governor_per_policy())
 505                 gov->gdbs_data = NULL;
 506         gov->exit(dbs_data, !policy->governor->initialized);
 507         kfree(dbs_data);
 508
 509 free_policy_dbs_info:
 510         free_policy_dbs_info(policy_dbs, gov);
 511
 512 out:
 513         mutex_unlock(&gov_dbs_data_mutex);
 514         return ret;
 515 }
 516
 517 static int cpufreq_governor_exit(struct cpufreq_policy *policy)
 518 {
 519         struct dbs_governor *gov = dbs_governor_of(policy);
 520         struct policy_dbs_info *policy_dbs = policy->governor_data;
 521         struct dbs_data *dbs_data = policy_dbs->dbs_data;
 522         int count;
 523
 524         /* Protect gov->gdbs_data against concurrent updates. */
 525         mutex_lock(&gov_dbs_data_mutex);
 526
 527         mutex_lock(&dbs_data->mutex);
 528         list_del(&policy_dbs->list);
 529         count = --dbs_data->usage_count;
 530         mutex_unlock(&dbs_data->mutex);
 531
 532         if (!count) {
 533                 kobject_put(&dbs_data->kobj);
 534
 535                 policy->governor_data = NULL;
 536
 537                 if (!have_governor_per_policy())
 538                         gov->gdbs_data = NULL;
 539
 540                 gov->exit(dbs_data, policy->governor->initialized == 1);
 541                 mutex_destroy(&dbs_data->mutex);
 542                 kfree(dbs_data);
 543         } else {
 544                 policy->governor_data = NULL;
 545         }
 546
 547         free_policy_dbs_info(policy_dbs, gov);
 548
 549         mutex_unlock(&gov_dbs_data_mutex);
 550         return 0;
 551 }
 552
 553 static int cpufreq_governor_start(struct cpufreq_policy *policy)
 554 {
 555         struct dbs_governor *gov = dbs_governor_of(policy);
 556         struct policy_dbs_info *policy_dbs = policy->governor_data;
 557         struct dbs_data *dbs_data = policy_dbs->dbs_data;
 558         unsigned int sampling_rate, ignore_nice, j;
 559         unsigned int io_busy;
 560
 561         if (!policy->cur)
 562                 return -EINVAL;
 563
 564         policy_dbs->is_shared = policy_is_shared(policy);
 565         policy_dbs->rate_mult = 1;
 566
 567         sampling_rate = dbs_data->sampling_rate;
 568         ignore_nice = dbs_data->ignore_nice_load;
 569         io_busy = dbs_data->io_is_busy;
 570
 571         for_each_cpu(j, policy->cpus) {
 572                 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
 573                 unsigned int prev_load;
 574
 575                 j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_cpu_wall, io_busy);
 576
 577                 prev_load = j_cdbs->prev_cpu_wall - j_cdbs->prev_cpu_idle;
 578                 j_cdbs->prev_load = 100 * prev_load / (unsigned int)j_cdbs->prev_cpu_wall;
 579
 580                 if (ignore_nice)
 581                         j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 582         }
 583
 584         gov->start(policy);
 585
 586         gov_set_update_util(policy_dbs, sampling_rate);
 587         return 0;
 588 }
 589
 590 static int cpufreq_governor_stop(struct cpufreq_policy *policy)
 591 {
 592         gov_cancel_work(policy);
 593         return 0;
 594 }
 595
 596 static int cpufreq_governor_limits(struct cpufreq_policy *policy)
 597 {
 598         struct policy_dbs_info *policy_dbs = policy->governor_data;
 599
 600         mutex_lock(&policy_dbs->timer_mutex);
 601
 602         if (policy->max < policy->cur)
 603                 __cpufreq_driver_target(policy, policy->max, CPUFREQ_RELATION_H);
 604         else if (policy->min > policy->cur)
 605                 __cpufreq_driver_target(policy, policy->min, CPUFREQ_RELATION_L);
 606
 607         gov_update_sample_delay(policy_dbs, 0);
 608
 609         mutex_unlock(&policy_dbs->timer_mutex);
 610
 611         return 0;
 612 }
 613
 614 int cpufreq_governor_dbs(struct cpufreq_policy *policy, unsigned int event)
 615 {
 616         if (event == CPUFREQ_GOV_POLICY_INIT) {
 617                 return cpufreq_governor_init(policy);
 618         } else if (policy->governor_data) {
 619                 switch (event) {
 620                 case CPUFREQ_GOV_POLICY_EXIT:
 621                         return cpufreq_governor_exit(policy);
 622                 case CPUFREQ_GOV_START:
 623                         return cpufreq_governor_start(policy);
 624                 case CPUFREQ_GOV_STOP:
 625                         return cpufreq_governor_stop(policy);
 626                 case CPUFREQ_GOV_LIMITS:
 627                         return cpufreq_governor_limits(policy);
 628                 }
 629         }
 630         return -EINVAL;
 631 }
 632 EXPORT_SYMBOL_GPL(cpufreq_governor_dbs);