git.oblomov.eu Git - linux-2.6/blob - drivers/cpufreq/cpufreq_conservative.c

   1 /*
   2  *  drivers/cpufreq/cpufreq_conservative.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  *            (C)  2009 Alexander Clouter <alex@digriz.org.uk>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  */
  13
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/init.h>
  17 #include <linux/cpufreq.h>
  18 #include <linux/cpu.h>
  19 #include <linux/jiffies.h>
  20 #include <linux/kernel_stat.h>
  21 #include <linux/mutex.h>
  22 #include <linux/hrtimer.h>
  23 #include <linux/tick.h>
  24 #include <linux/ktime.h>
  25 #include <linux/sched.h>
  26
  27 /*
  28  * dbs is used in this file as a shortform for demandbased switching
  29  * It helps to keep variable names smaller, simpler
  30  */
  31
  32 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
  33 #define DEF_FREQUENCY_DOWN_THRESHOLD            (20)
  34
  35 /*
  36  * The polling frequency of this governor depends on the capability of
  37  * the processor. Default polling frequency is 1000 times the transition
  38  * latency of the processor. The governor will work on any processor with
  39  * transition latency <= 10mS, using appropriate sampling
  40  * rate.
  41  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
  42  * this governor will not work.
  43  * All times here are in uS.
  44  */
  45 #define MIN_SAMPLING_RATE_RATIO                 (2)
  46
  47 static unsigned int min_sampling_rate;
  48
  49 #define LATENCY_MULTIPLIER                      (1000)
  50 #define MIN_LATENCY_MULTIPLIER                  (100)
  51 #define DEF_SAMPLING_DOWN_FACTOR                (1)
  52 #define MAX_SAMPLING_DOWN_FACTOR                (10)
  53 #define TRANSITION_LATENCY_LIMIT                (10 * 1000 * 1000)
  54
  55 static void do_dbs_timer(struct work_struct *work);
  56
  57 struct cpu_dbs_info_s {
  58         cputime64_t prev_cpu_idle;
  59         cputime64_t prev_cpu_wall;
  60         cputime64_t prev_cpu_nice;
  61         struct cpufreq_policy *cur_policy;
  62         struct delayed_work work;
  63         unsigned int down_skip;
  64         unsigned int requested_freq;
  65         int cpu;
  66         /*
  67          * percpu mutex that serializes governor limit change with
  68          * do_dbs_timer invocation. We do not want do_dbs_timer to run
  69          * when user is changing the governor or limits.
  70          */
  71         struct mutex timer_mutex;
  72 };
  73 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
  74
  75 static unsigned int dbs_enable; /* number of CPUs using this policy */
  76
  77 /*
  78  * dbs_mutex protects data in dbs_tuners_ins from concurrent changes on
  79  * different CPUs. It protects dbs_enable in governor start/stop.
  80  */
  81 static DEFINE_MUTEX(dbs_mutex);
  82
  83 static struct workqueue_struct  *kconservative_wq;
  84
  85 static struct dbs_tuners {
  86         unsigned int sampling_rate;
  87         unsigned int sampling_down_factor;
  88         unsigned int up_threshold;
  89         unsigned int down_threshold;
  90         unsigned int ignore_nice;
  91         unsigned int freq_step;
  92 } dbs_tuners_ins = {
  93         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
  94         .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
  95         .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
  96         .ignore_nice = 0,
  97         .freq_step = 5,
  98 };
  99
 100 static inline cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu,
 101                                                         cputime64_t *wall)
 102 {
 103         cputime64_t idle_time;
 104         cputime64_t cur_wall_time;
 105         cputime64_t busy_time;
 106
 107         cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
 108         busy_time = cputime64_add(kstat_cpu(cpu).cpustat.user,
 109                         kstat_cpu(cpu).cpustat.system);
 110
 111         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.irq);
 112         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.softirq);
 113         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.steal);
 114         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.nice);
 115
 116         idle_time = cputime64_sub(cur_wall_time, busy_time);
 117         if (wall)
 118                 *wall = cur_wall_time;
 119
 120         return idle_time;
 121 }
 122
 123 static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
 124 {
 125         u64 idle_time = get_cpu_idle_time_us(cpu, wall);
 126
 127         if (idle_time == -1ULL)
 128                 return get_cpu_idle_time_jiffy(cpu, wall);
 129
 130         return idle_time;
 131 }
 132
 133 /* keep track of frequency transitions */
 134 static int
 135 dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
 136                      void *data)
 137 {
 138         struct cpufreq_freqs *freq = data;
 139         struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info,
 140                                                         freq->cpu);
 141
 142         struct cpufreq_policy *policy;
 143
 144         policy = this_dbs_info->cur_policy;
 145
 146         /*
 147          * we only care if our internally tracked freq moves outside
 148          * the 'valid' ranges of freqency available to us otherwise
 149          * we do not change it
 150         */
 151         if (this_dbs_info->requested_freq > policy->max
 152                         || this_dbs_info->requested_freq < policy->min)
 153                 this_dbs_info->requested_freq = freq->new;
 154
 155         return 0;
 156 }
 157
 158 static struct notifier_block dbs_cpufreq_notifier_block = {
 159         .notifier_call = dbs_cpufreq_notifier
 160 };
 161
 162 /************************** sysfs interface ************************/
 163 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 164 {
 165         printk_once(KERN_INFO "CPUFREQ: conservative sampling_rate_max "
 166                     "sysfs file is deprecated - used by: %s\n", current->comm);
 167         return sprintf(buf, "%u\n", -1U);
 168 }
 169
 170 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 171 {
 172         return sprintf(buf, "%u\n", min_sampling_rate);
 173 }
 174
 175 #define define_one_ro(_name)            \
 176 static struct freq_attr _name =         \
 177 __ATTR(_name, 0444, show_##_name, NULL)
 178
 179 define_one_ro(sampling_rate_max);
 180 define_one_ro(sampling_rate_min);
 181
 182 /* cpufreq_conservative Governor Tunables */
 183 #define show_one(file_name, object)                                     \
 184 static ssize_t show_##file_name                                         \
 185 (struct cpufreq_policy *unused, char *buf)                              \
 186 {                                                                       \
 187         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 188 }
 189 show_one(sampling_rate, sampling_rate);
 190 show_one(sampling_down_factor, sampling_down_factor);
 191 show_one(up_threshold, up_threshold);
 192 show_one(down_threshold, down_threshold);
 193 show_one(ignore_nice_load, ignore_nice);
 194 show_one(freq_step, freq_step);
 195
 196 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
 197                 const char *buf, size_t count)
 198 {
 199         unsigned int input;
 200         int ret;
 201         ret = sscanf(buf, "%u", &input);
 202
 203         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 204                 return -EINVAL;
 205
 206         mutex_lock(&dbs_mutex);
 207         dbs_tuners_ins.sampling_down_factor = input;
 208         mutex_unlock(&dbs_mutex);
 209
 210         return count;
 211 }
 212
 213 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 214                 const char *buf, size_t count)
 215 {
 216         unsigned int input;
 217         int ret;
 218         ret = sscanf(buf, "%u", &input);
 219
 220         if (ret != 1)
 221                 return -EINVAL;
 222
 223         mutex_lock(&dbs_mutex);
 224         dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);
 225         mutex_unlock(&dbs_mutex);
 226
 227         return count;
 228 }
 229
 230 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 231                 const char *buf, size_t count)
 232 {
 233         unsigned int input;
 234         int ret;
 235         ret = sscanf(buf, "%u", &input);
 236
 237         mutex_lock(&dbs_mutex);
 238         if (ret != 1 || input > 100 ||
 239                         input <= dbs_tuners_ins.down_threshold) {
 240                 mutex_unlock(&dbs_mutex);
 241                 return -EINVAL;
 242         }
 243
 244         dbs_tuners_ins.up_threshold = input;
 245         mutex_unlock(&dbs_mutex);
 246
 247         return count;
 248 }
 249
 250 static ssize_t store_down_threshold(struct cpufreq_policy *unused,
 251                 const char *buf, size_t count)
 252 {
 253         unsigned int input;
 254         int ret;
 255         ret = sscanf(buf, "%u", &input);
 256
 257         mutex_lock(&dbs_mutex);
 258         /* cannot be lower than 11 otherwise freq will not fall */
 259         if (ret != 1 || input < 11 || input > 100 ||
 260                         input >= dbs_tuners_ins.up_threshold) {
 261                 mutex_unlock(&dbs_mutex);
 262                 return -EINVAL;
 263         }
 264
 265         dbs_tuners_ins.down_threshold = input;
 266         mutex_unlock(&dbs_mutex);
 267
 268         return count;
 269 }
 270
 271 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 272                 const char *buf, size_t count)
 273 {
 274         unsigned int input;
 275         int ret;
 276
 277         unsigned int j;
 278
 279         ret = sscanf(buf, "%u", &input);
 280         if (ret != 1)
 281                 return -EINVAL;
 282
 283         if (input > 1)
 284                 input = 1;
 285
 286         mutex_lock(&dbs_mutex);
 287         if (input == dbs_tuners_ins.ignore_nice) { /* nothing to do */
 288                 mutex_unlock(&dbs_mutex);
 289                 return count;
 290         }
 291         dbs_tuners_ins.ignore_nice = input;
 292
 293         /* we need to re-evaluate prev_cpu_idle */
 294         for_each_online_cpu(j) {
 295                 struct cpu_dbs_info_s *dbs_info;
 296                 dbs_info = &per_cpu(cpu_dbs_info, j);
 297                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 298                                                 &dbs_info->prev_cpu_wall);
 299                 if (dbs_tuners_ins.ignore_nice)
 300                         dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
 301         }
 302         mutex_unlock(&dbs_mutex);
 303
 304         return count;
 305 }
 306
 307 static ssize_t store_freq_step(struct cpufreq_policy *policy,
 308                 const char *buf, size_t count)
 309 {
 310         unsigned int input;
 311         int ret;
 312         ret = sscanf(buf, "%u", &input);
 313
 314         if (ret != 1)
 315                 return -EINVAL;
 316
 317         if (input > 100)
 318                 input = 100;
 319
 320         /* no need to test here if freq_step is zero as the user might actually
 321          * want this, they would be crazy though :) */
 322         mutex_lock(&dbs_mutex);
 323         dbs_tuners_ins.freq_step = input;
 324         mutex_unlock(&dbs_mutex);
 325
 326         return count;
 327 }
 328
 329 #define define_one_rw(_name) \
 330 static struct freq_attr _name = \
 331 __ATTR(_name, 0644, show_##_name, store_##_name)
 332
 333 define_one_rw(sampling_rate);
 334 define_one_rw(sampling_down_factor);
 335 define_one_rw(up_threshold);
 336 define_one_rw(down_threshold);
 337 define_one_rw(ignore_nice_load);
 338 define_one_rw(freq_step);
 339
 340 static struct attribute *dbs_attributes[] = {
 341         &sampling_rate_max.attr,
 342         &sampling_rate_min.attr,
 343         &sampling_rate.attr,
 344         &sampling_down_factor.attr,
 345         &up_threshold.attr,
 346         &down_threshold.attr,
 347         &ignore_nice_load.attr,
 348         &freq_step.attr,
 349         NULL
 350 };
 351
 352 static struct attribute_group dbs_attr_group = {
 353         .attrs = dbs_attributes,
 354         .name = "conservative",
 355 };
 356
 357 /************************** sysfs end ************************/
 358
 359 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 360 {
 361         unsigned int load = 0;
 362         unsigned int freq_target;
 363
 364         struct cpufreq_policy *policy;
 365         unsigned int j;
 366
 367         policy = this_dbs_info->cur_policy;
 368
 369         /*
 370          * Every sampling_rate, we check, if current idle time is less
 371          * than 20% (default), then we try to increase frequency
 372          * Every sampling_rate*sampling_down_factor, we check, if current
 373          * idle time is more than 80%, then we try to decrease frequency
 374          *
 375          * Any frequency increase takes it to the maximum frequency.
 376          * Frequency reduction happens at minimum steps of
 377          * 5% (default) of maximum frequency
 378          */
 379
 380         /* Get Absolute Load */
 381         for_each_cpu(j, policy->cpus) {
 382                 struct cpu_dbs_info_s *j_dbs_info;
 383                 cputime64_t cur_wall_time, cur_idle_time;
 384                 unsigned int idle_time, wall_time;
 385
 386                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 387
 388                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
 389
 390                 wall_time = (unsigned int) cputime64_sub(cur_wall_time,
 391                                 j_dbs_info->prev_cpu_wall);
 392                 j_dbs_info->prev_cpu_wall = cur_wall_time;
 393
 394                 idle_time = (unsigned int) cputime64_sub(cur_idle_time,
 395                                 j_dbs_info->prev_cpu_idle);
 396                 j_dbs_info->prev_cpu_idle = cur_idle_time;
 397
 398                 if (dbs_tuners_ins.ignore_nice) {
 399                         cputime64_t cur_nice;
 400                         unsigned long cur_nice_jiffies;
 401
 402                         cur_nice = cputime64_sub(kstat_cpu(j).cpustat.nice,
 403                                          j_dbs_info->prev_cpu_nice);
 404                         /*
 405                          * Assumption: nice time between sampling periods will
 406                          * be less than 2^32 jiffies for 32 bit sys
 407                          */
 408                         cur_nice_jiffies = (unsigned long)
 409                                         cputime64_to_jiffies64(cur_nice);
 410
 411                         j_dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
 412                         idle_time += jiffies_to_usecs(cur_nice_jiffies);
 413                 }
 414
 415                 if (unlikely(!wall_time || wall_time < idle_time))
 416                         continue;
 417
 418                 load = 100 * (wall_time - idle_time) / wall_time;
 419         }
 420
 421         /*
 422          * break out if we 'cannot' reduce the speed as the user might
 423          * want freq_step to be zero
 424          */
 425         if (dbs_tuners_ins.freq_step == 0)
 426                 return;
 427
 428         /* Check for frequency increase */
 429         if (load > dbs_tuners_ins.up_threshold) {
 430                 this_dbs_info->down_skip = 0;
 431
 432                 /* if we are already at full speed then break out early */
 433                 if (this_dbs_info->requested_freq == policy->max)
 434                         return;
 435
 436                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 437
 438                 /* max freq cannot be less than 100. But who knows.... */
 439                 if (unlikely(freq_target == 0))
 440                         freq_target = 5;
 441
 442                 this_dbs_info->requested_freq += freq_target;
 443                 if (this_dbs_info->requested_freq > policy->max)
 444                         this_dbs_info->requested_freq = policy->max;
 445
 446                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 447                         CPUFREQ_RELATION_H);
 448                 return;
 449         }
 450
 451         /*
 452          * The optimal frequency is the frequency that is the lowest that
 453          * can support the current CPU usage without triggering the up
 454          * policy. To be safe, we focus 10 points under the threshold.
 455          */
 456         if (load < (dbs_tuners_ins.down_threshold - 10)) {
 457                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 458
 459                 this_dbs_info->requested_freq -= freq_target;
 460                 if (this_dbs_info->requested_freq < policy->min)
 461                         this_dbs_info->requested_freq = policy->min;
 462
 463                 /*
 464                  * if we cannot reduce the frequency anymore, break out early
 465                  */
 466                 if (policy->cur == policy->min)
 467                         return;
 468
 469                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 470                                 CPUFREQ_RELATION_H);
 471                 return;
 472         }
 473 }
 474
 475 static void do_dbs_timer(struct work_struct *work)
 476 {
 477         struct cpu_dbs_info_s *dbs_info =
 478                 container_of(work, struct cpu_dbs_info_s, work.work);
 479         unsigned int cpu = dbs_info->cpu;
 480
 481         /* We want all CPUs to do sampling nearly on same jiffy */
 482         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 483
 484         delay -= jiffies % delay;
 485
 486         mutex_lock(&dbs_info->timer_mutex);
 487
 488         dbs_check_cpu(dbs_info);
 489
 490         queue_delayed_work_on(cpu, kconservative_wq, &dbs_info->work, delay);
 491         mutex_unlock(&dbs_info->timer_mutex);
 492 }
 493
 494 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 495 {
 496         /* We want all CPUs to do sampling nearly on same jiffy */
 497         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 498         delay -= jiffies % delay;
 499
 500         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
 501         queue_delayed_work_on(dbs_info->cpu, kconservative_wq, &dbs_info->work,
 502                                 delay);
 503 }
 504
 505 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 506 {
 507         cancel_delayed_work_sync(&dbs_info->work);
 508 }
 509
 510 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 511                                    unsigned int event)
 512 {
 513         unsigned int cpu = policy->cpu;
 514         struct cpu_dbs_info_s *this_dbs_info;
 515         unsigned int j;
 516         int rc;
 517
 518         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 519
 520         switch (event) {
 521         case CPUFREQ_GOV_START:
 522                 if ((!cpu_online(cpu)) || (!policy->cur))
 523                         return -EINVAL;
 524
 525                 mutex_lock(&dbs_mutex);
 526
 527                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
 528                 if (rc) {
 529                         mutex_unlock(&dbs_mutex);
 530                         return rc;
 531                 }
 532
 533                 for_each_cpu(j, policy->cpus) {
 534                         struct cpu_dbs_info_s *j_dbs_info;
 535                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 536                         j_dbs_info->cur_policy = policy;
 537
 538                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 539                                                 &j_dbs_info->prev_cpu_wall);
 540                         if (dbs_tuners_ins.ignore_nice) {
 541                                 j_dbs_info->prev_cpu_nice =
 542                                                 kstat_cpu(j).cpustat.nice;
 543                         }
 544                 }
 545                 this_dbs_info->down_skip = 0;
 546                 this_dbs_info->requested_freq = policy->cur;
 547
 548                 mutex_init(&this_dbs_info->timer_mutex);
 549                 dbs_enable++;
 550                 /*
 551                  * Start the timerschedule work, when this governor
 552                  * is used for first time
 553                  */
 554                 if (dbs_enable == 1) {
 555                         unsigned int latency;
 556                         /* policy latency is in nS. Convert it to uS first */
 557                         latency = policy->cpuinfo.transition_latency / 1000;
 558                         if (latency == 0)
 559                                 latency = 1;
 560
 561                         /*
 562                          * conservative does not implement micro like ondemand
 563                          * governor, thus we are bound to jiffes/HZ
 564                          */
 565                         min_sampling_rate =
 566                                 MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
 567                         /* Bring kernel and HW constraints together */
 568                         min_sampling_rate = max(min_sampling_rate,
 569                                         MIN_LATENCY_MULTIPLIER * latency);
 570                         dbs_tuners_ins.sampling_rate =
 571                                 max(min_sampling_rate,
 572                                     latency * LATENCY_MULTIPLIER);
 573
 574                         cpufreq_register_notifier(
 575                                         &dbs_cpufreq_notifier_block,
 576                                         CPUFREQ_TRANSITION_NOTIFIER);
 577                 }
 578                 mutex_unlock(&dbs_mutex);
 579
 580                 dbs_timer_init(this_dbs_info);
 581
 582                 break;
 583
 584         case CPUFREQ_GOV_STOP:
 585                 dbs_timer_exit(this_dbs_info);
 586
 587                 mutex_lock(&dbs_mutex);
 588                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 589                 dbs_enable--;
 590                 mutex_destroy(&this_dbs_info->timer_mutex);
 591
 592                 /*
 593                  * Stop the timerschedule work, when this governor
 594                  * is used for first time
 595                  */
 596                 if (dbs_enable == 0)
 597                         cpufreq_unregister_notifier(
 598                                         &dbs_cpufreq_notifier_block,
 599                                         CPUFREQ_TRANSITION_NOTIFIER);
 600
 601                 mutex_unlock(&dbs_mutex);
 602
 603                 break;
 604
 605         case CPUFREQ_GOV_LIMITS:
 606                 mutex_lock(&this_dbs_info->timer_mutex);
 607                 if (policy->max < this_dbs_info->cur_policy->cur)
 608                         __cpufreq_driver_target(
 609                                         this_dbs_info->cur_policy,
 610                                         policy->max, CPUFREQ_RELATION_H);
 611                 else if (policy->min > this_dbs_info->cur_policy->cur)
 612                         __cpufreq_driver_target(
 613                                         this_dbs_info->cur_policy,
 614                                         policy->min, CPUFREQ_RELATION_L);
 615                 mutex_unlock(&this_dbs_info->timer_mutex);
 616
 617                 break;
 618         }
 619         return 0;
 620 }
 621
 622 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 623 static
 624 #endif
 625 struct cpufreq_governor cpufreq_gov_conservative = {
 626         .name                   = "conservative",
 627         .governor               = cpufreq_governor_dbs,
 628         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 629         .owner                  = THIS_MODULE,
 630 };
 631
 632 static int __init cpufreq_gov_dbs_init(void)
 633 {
 634         int err;
 635
 636         kconservative_wq = create_workqueue("kconservative");
 637         if (!kconservative_wq) {
 638                 printk(KERN_ERR "Creation of kconservative failed\n");
 639                 return -EFAULT;
 640         }
 641
 642         err = cpufreq_register_governor(&cpufreq_gov_conservative);
 643         if (err)
 644                 destroy_workqueue(kconservative_wq);
 645
 646         return err;
 647 }
 648
 649 static void __exit cpufreq_gov_dbs_exit(void)
 650 {
 651         cpufreq_unregister_governor(&cpufreq_gov_conservative);
 652         destroy_workqueue(kconservative_wq);
 653 }
 654
 655
 656 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
 657 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
 658                 "Low Latency Frequency Transition capable processors "
 659                 "optimised for use in a battery environment");
 660 MODULE_LICENSE("GPL");
 661
 662 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 663 fs_initcall(cpufreq_gov_dbs_init);
 664 #else
 665 module_init(cpufreq_gov_dbs_init);
 666 #endif
 667 module_exit(cpufreq_gov_dbs_exit);