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