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 static unsigned int def_sampling_rate;
  46 #define MIN_SAMPLING_RATE_RATIO                 (2)
  47 /* for correct statistics, we need at least 10 ticks between each measure */
  48 #define MIN_STAT_SAMPLING_RATE                  \
  49                         (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
  50 #define MIN_SAMPLING_RATE                       \
  51                         (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
  52 /* Above MIN_SAMPLING_RATE will vanish with its sysfs file soon
  53  * Define the minimal settable sampling rate to the greater of:
  54  *   - "HW transition latency" * 100 (same as default sampling / 10)
  55  *   - MIN_STAT_SAMPLING_RATE
  56  * To avoid that userspace shoots itself.
  57 */
  58 static unsigned int minimum_sampling_rate(void)
  59 {
  60         return max(def_sampling_rate / 10, MIN_STAT_SAMPLING_RATE);
  61 }
  62
  63 /* This will also vanish soon with removing sampling_rate_max */
  64 #define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
  65 #define LATENCY_MULTIPLIER                      (1000)
  66 #define DEF_SAMPLING_DOWN_FACTOR                (1)
  67 #define MAX_SAMPLING_DOWN_FACTOR                (10)
  68 #define TRANSITION_LATENCY_LIMIT                (10 * 1000 * 1000)
  69
  70 static void do_dbs_timer(struct work_struct *work);
  71
  72 struct cpu_dbs_info_s {
  73         cputime64_t prev_cpu_idle;
  74         cputime64_t prev_cpu_wall;
  75         cputime64_t prev_cpu_nice;
  76         struct cpufreq_policy *cur_policy;
  77         struct delayed_work work;
  78         unsigned int down_skip;
  79         unsigned int requested_freq;
  80         int cpu;
  81         unsigned int enable:1;
  82 };
  83 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
  84
  85 static unsigned int dbs_enable; /* number of CPUs using this policy */
  86
  87 /*
  88  * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
  89  * lock and dbs_mutex. cpu_hotplug lock should always be held before
  90  * dbs_mutex. If any function that can potentially take cpu_hotplug lock
  91  * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
  92  * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
  93  * is recursive for the same process. -Venki
  94  */
  95 static DEFINE_MUTEX(dbs_mutex);
  96
  97 static struct workqueue_struct  *kconservative_wq;
  98
  99 static struct dbs_tuners {
 100         unsigned int sampling_rate;
 101         unsigned int sampling_down_factor;
 102         unsigned int up_threshold;
 103         unsigned int down_threshold;
 104         unsigned int ignore_nice;
 105         unsigned int freq_step;
 106 } dbs_tuners_ins = {
 107         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
 108         .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
 109         .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
 110         .ignore_nice = 0,
 111         .freq_step = 5,
 112 };
 113
 114 static inline cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu,
 115                                                         cputime64_t *wall)
 116 {
 117         cputime64_t idle_time;
 118         cputime64_t cur_wall_time;
 119         cputime64_t busy_time;
 120
 121         cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
 122         busy_time = cputime64_add(kstat_cpu(cpu).cpustat.user,
 123                         kstat_cpu(cpu).cpustat.system);
 124
 125         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.irq);
 126         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.softirq);
 127         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.steal);
 128         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.nice);
 129
 130         idle_time = cputime64_sub(cur_wall_time, busy_time);
 131         if (wall)
 132                 *wall = cur_wall_time;
 133
 134         return idle_time;
 135 }
 136
 137 static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
 138 {
 139         u64 idle_time = get_cpu_idle_time_us(cpu, wall);
 140
 141         if (idle_time == -1ULL)
 142                 return get_cpu_idle_time_jiffy(cpu, wall);
 143
 144         return idle_time;
 145 }
 146
 147 /* keep track of frequency transitions */
 148 static int
 149 dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
 150                      void *data)
 151 {
 152         struct cpufreq_freqs *freq = data;
 153         struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info,
 154                                                         freq->cpu);
 155
 156         struct cpufreq_policy *policy;
 157
 158         if (!this_dbs_info->enable)
 159                 return 0;
 160
 161         policy = this_dbs_info->cur_policy;
 162
 163         /*
 164          * we only care if our internally tracked freq moves outside
 165          * the 'valid' ranges of freqency available to us otherwise
 166          * we do not change it
 167         */
 168         if (this_dbs_info->requested_freq > policy->max
 169                         || this_dbs_info->requested_freq < policy->min)
 170                 this_dbs_info->requested_freq = freq->new;
 171
 172         return 0;
 173 }
 174
 175 static struct notifier_block dbs_cpufreq_notifier_block = {
 176         .notifier_call = dbs_cpufreq_notifier
 177 };
 178
 179 /************************** sysfs interface ************************/
 180 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 181 {
 182         static int print_once;
 183
 184         if (!print_once) {
 185                 printk(KERN_INFO "CPUFREQ: conservative sampling_rate_max "
 186                        "sysfs file is deprecated - used by: %s\n",
 187                        current->comm);
 188                 print_once = 1;
 189         }
 190         return sprintf(buf, "%u\n", MAX_SAMPLING_RATE);
 191 }
 192
 193 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 194 {
 195         static int print_once;
 196
 197         if (!print_once) {
 198                 printk(KERN_INFO "CPUFREQ: conservative sampling_rate_max "
 199                        "sysfs file is deprecated - used by: %s\n", current->comm);
 200                 print_once = 1;
 201         }
 202         return sprintf(buf, "%u\n", MIN_SAMPLING_RATE);
 203 }
 204
 205 #define define_one_ro(_name)            \
 206 static struct freq_attr _name =         \
 207 __ATTR(_name, 0444, show_##_name, NULL)
 208
 209 define_one_ro(sampling_rate_max);
 210 define_one_ro(sampling_rate_min);
 211
 212 /* cpufreq_conservative Governor Tunables */
 213 #define show_one(file_name, object)                                     \
 214 static ssize_t show_##file_name                                         \
 215 (struct cpufreq_policy *unused, char *buf)                              \
 216 {                                                                       \
 217         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 218 }
 219 show_one(sampling_rate, sampling_rate);
 220 show_one(sampling_down_factor, sampling_down_factor);
 221 show_one(up_threshold, up_threshold);
 222 show_one(down_threshold, down_threshold);
 223 show_one(ignore_nice_load, ignore_nice);
 224 show_one(freq_step, freq_step);
 225
 226 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
 227                 const char *buf, size_t count)
 228 {
 229         unsigned int input;
 230         int ret;
 231         ret = sscanf(buf, "%u", &input);
 232
 233         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 234                 return -EINVAL;
 235
 236         mutex_lock(&dbs_mutex);
 237         dbs_tuners_ins.sampling_down_factor = input;
 238         mutex_unlock(&dbs_mutex);
 239
 240         return count;
 241 }
 242
 243 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 244                 const char *buf, size_t count)
 245 {
 246         unsigned int input;
 247         int ret;
 248         ret = sscanf(buf, "%u", &input);
 249
 250         if (ret != 1)
 251                 return -EINVAL;
 252
 253         mutex_lock(&dbs_mutex);
 254         dbs_tuners_ins.sampling_rate = max(input, minimum_sampling_rate());
 255         mutex_unlock(&dbs_mutex);
 256
 257         return count;
 258 }
 259
 260 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 261                 const char *buf, size_t count)
 262 {
 263         unsigned int input;
 264         int ret;
 265         ret = sscanf(buf, "%u", &input);
 266
 267         mutex_lock(&dbs_mutex);
 268         if (ret != 1 || input > 100 ||
 269                         input <= dbs_tuners_ins.down_threshold) {
 270                 mutex_unlock(&dbs_mutex);
 271                 return -EINVAL;
 272         }
 273
 274         dbs_tuners_ins.up_threshold = input;
 275         mutex_unlock(&dbs_mutex);
 276
 277         return count;
 278 }
 279
 280 static ssize_t store_down_threshold(struct cpufreq_policy *unused,
 281                 const char *buf, size_t count)
 282 {
 283         unsigned int input;
 284         int ret;
 285         ret = sscanf(buf, "%u", &input);
 286
 287         mutex_lock(&dbs_mutex);
 288         /* cannot be lower than 11 otherwise freq will not fall */
 289         if (ret != 1 || input < 11 || input > 100 ||
 290                         input >= dbs_tuners_ins.up_threshold) {
 291                 mutex_unlock(&dbs_mutex);
 292                 return -EINVAL;
 293         }
 294
 295         dbs_tuners_ins.down_threshold = input;
 296         mutex_unlock(&dbs_mutex);
 297
 298         return count;
 299 }
 300
 301 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 302                 const char *buf, size_t count)
 303 {
 304         unsigned int input;
 305         int ret;
 306
 307         unsigned int j;
 308
 309         ret = sscanf(buf, "%u", &input);
 310         if (ret != 1)
 311                 return -EINVAL;
 312
 313         if (input > 1)
 314                 input = 1;
 315
 316         mutex_lock(&dbs_mutex);
 317         if (input == dbs_tuners_ins.ignore_nice) { /* nothing to do */
 318                 mutex_unlock(&dbs_mutex);
 319                 return count;
 320         }
 321         dbs_tuners_ins.ignore_nice = input;
 322
 323         /* we need to re-evaluate prev_cpu_idle */
 324         for_each_online_cpu(j) {
 325                 struct cpu_dbs_info_s *dbs_info;
 326                 dbs_info = &per_cpu(cpu_dbs_info, j);
 327                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 328                                                 &dbs_info->prev_cpu_wall);
 329                 if (dbs_tuners_ins.ignore_nice)
 330                         dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
 331         }
 332         mutex_unlock(&dbs_mutex);
 333
 334         return count;
 335 }
 336
 337 static ssize_t store_freq_step(struct cpufreq_policy *policy,
 338                 const char *buf, size_t count)
 339 {
 340         unsigned int input;
 341         int ret;
 342         ret = sscanf(buf, "%u", &input);
 343
 344         if (ret != 1)
 345                 return -EINVAL;
 346
 347         if (input > 100)
 348                 input = 100;
 349
 350         /* no need to test here if freq_step is zero as the user might actually
 351          * want this, they would be crazy though :) */
 352         mutex_lock(&dbs_mutex);
 353         dbs_tuners_ins.freq_step = input;
 354         mutex_unlock(&dbs_mutex);
 355
 356         return count;
 357 }
 358
 359 #define define_one_rw(_name) \
 360 static struct freq_attr _name = \
 361 __ATTR(_name, 0644, show_##_name, store_##_name)
 362
 363 define_one_rw(sampling_rate);
 364 define_one_rw(sampling_down_factor);
 365 define_one_rw(up_threshold);
 366 define_one_rw(down_threshold);
 367 define_one_rw(ignore_nice_load);
 368 define_one_rw(freq_step);
 369
 370 static struct attribute *dbs_attributes[] = {
 371         &sampling_rate_max.attr,
 372         &sampling_rate_min.attr,
 373         &sampling_rate.attr,
 374         &sampling_down_factor.attr,
 375         &up_threshold.attr,
 376         &down_threshold.attr,
 377         &ignore_nice_load.attr,
 378         &freq_step.attr,
 379         NULL
 380 };
 381
 382 static struct attribute_group dbs_attr_group = {
 383         .attrs = dbs_attributes,
 384         .name = "conservative",
 385 };
 386
 387 /************************** sysfs end ************************/
 388
 389 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 390 {
 391         unsigned int load = 0;
 392         unsigned int freq_target;
 393
 394         struct cpufreq_policy *policy;
 395         unsigned int j;
 396
 397         policy = this_dbs_info->cur_policy;
 398
 399         /*
 400          * Every sampling_rate, we check, if current idle time is less
 401          * than 20% (default), then we try to increase frequency
 402          * Every sampling_rate*sampling_down_factor, we check, if current
 403          * idle time is more than 80%, then we try to decrease frequency
 404          *
 405          * Any frequency increase takes it to the maximum frequency.
 406          * Frequency reduction happens at minimum steps of
 407          * 5% (default) of maximum frequency
 408          */
 409
 410         /* Get Absolute Load */
 411         for_each_cpu(j, policy->cpus) {
 412                 struct cpu_dbs_info_s *j_dbs_info;
 413                 cputime64_t cur_wall_time, cur_idle_time;
 414                 unsigned int idle_time, wall_time;
 415
 416                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 417
 418                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
 419
 420                 wall_time = (unsigned int) cputime64_sub(cur_wall_time,
 421                                 j_dbs_info->prev_cpu_wall);
 422                 j_dbs_info->prev_cpu_wall = cur_wall_time;
 423
 424                 idle_time = (unsigned int) cputime64_sub(cur_idle_time,
 425                                 j_dbs_info->prev_cpu_idle);
 426                 j_dbs_info->prev_cpu_idle = cur_idle_time;
 427
 428                 if (dbs_tuners_ins.ignore_nice) {
 429                         cputime64_t cur_nice;
 430                         unsigned long cur_nice_jiffies;
 431
 432                         cur_nice = cputime64_sub(kstat_cpu(j).cpustat.nice,
 433                                          j_dbs_info->prev_cpu_nice);
 434                         /*
 435                          * Assumption: nice time between sampling periods will
 436                          * be less than 2^32 jiffies for 32 bit sys
 437                          */
 438                         cur_nice_jiffies = (unsigned long)
 439                                         cputime64_to_jiffies64(cur_nice);
 440
 441                         j_dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
 442                         idle_time += jiffies_to_usecs(cur_nice_jiffies);
 443                 }
 444
 445                 if (unlikely(!wall_time || wall_time < idle_time))
 446                         continue;
 447
 448                 load = 100 * (wall_time - idle_time) / wall_time;
 449         }
 450
 451         /*
 452          * break out if we 'cannot' reduce the speed as the user might
 453          * want freq_step to be zero
 454          */
 455         if (dbs_tuners_ins.freq_step == 0)
 456                 return;
 457
 458         /* Check for frequency increase */
 459         if (load > dbs_tuners_ins.up_threshold) {
 460                 this_dbs_info->down_skip = 0;
 461
 462                 /* if we are already at full speed then break out early */
 463                 if (this_dbs_info->requested_freq == policy->max)
 464                         return;
 465
 466                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 467
 468                 /* max freq cannot be less than 100. But who knows.... */
 469                 if (unlikely(freq_target == 0))
 470                         freq_target = 5;
 471
 472                 this_dbs_info->requested_freq += freq_target;
 473                 if (this_dbs_info->requested_freq > policy->max)
 474                         this_dbs_info->requested_freq = policy->max;
 475
 476                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 477                         CPUFREQ_RELATION_H);
 478                 return;
 479         }
 480
 481         /*
 482          * The optimal frequency is the frequency that is the lowest that
 483          * can support the current CPU usage without triggering the up
 484          * policy. To be safe, we focus 10 points under the threshold.
 485          */
 486         if (load < (dbs_tuners_ins.down_threshold - 10)) {
 487                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 488
 489                 this_dbs_info->requested_freq -= freq_target;
 490                 if (this_dbs_info->requested_freq < policy->min)
 491                         this_dbs_info->requested_freq = policy->min;
 492
 493                 /*
 494                  * if we cannot reduce the frequency anymore, break out early
 495                  */
 496                 if (policy->cur == policy->min)
 497                         return;
 498
 499                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 500                                 CPUFREQ_RELATION_H);
 501                 return;
 502         }
 503 }
 504
 505 static void do_dbs_timer(struct work_struct *work)
 506 {
 507         struct cpu_dbs_info_s *dbs_info =
 508                 container_of(work, struct cpu_dbs_info_s, work.work);
 509         unsigned int cpu = dbs_info->cpu;
 510
 511         /* We want all CPUs to do sampling nearly on same jiffy */
 512         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 513
 514         delay -= jiffies % delay;
 515
 516         if (lock_policy_rwsem_write(cpu) < 0)
 517                 return;
 518
 519         if (!dbs_info->enable) {
 520                 unlock_policy_rwsem_write(cpu);
 521                 return;
 522         }
 523
 524         dbs_check_cpu(dbs_info);
 525
 526         queue_delayed_work_on(cpu, kconservative_wq, &dbs_info->work, delay);
 527         unlock_policy_rwsem_write(cpu);
 528 }
 529
 530 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 531 {
 532         /* We want all CPUs to do sampling nearly on same jiffy */
 533         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 534         delay -= jiffies % delay;
 535
 536         dbs_info->enable = 1;
 537         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
 538         queue_delayed_work_on(dbs_info->cpu, kconservative_wq, &dbs_info->work,
 539                                 delay);
 540 }
 541
 542 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 543 {
 544         dbs_info->enable = 0;
 545         cancel_delayed_work(&dbs_info->work);
 546 }
 547
 548 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 549                                    unsigned int event)
 550 {
 551         unsigned int cpu = policy->cpu;
 552         struct cpu_dbs_info_s *this_dbs_info;
 553         unsigned int j;
 554         int rc;
 555
 556         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 557
 558         switch (event) {
 559         case CPUFREQ_GOV_START:
 560                 if ((!cpu_online(cpu)) || (!policy->cur))
 561                         return -EINVAL;
 562
 563                 if (this_dbs_info->enable) /* Already enabled */
 564                         break;
 565
 566                 mutex_lock(&dbs_mutex);
 567
 568                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
 569                 if (rc) {
 570                         mutex_unlock(&dbs_mutex);
 571                         return rc;
 572                 }
 573
 574                 for_each_cpu(j, policy->cpus) {
 575                         struct cpu_dbs_info_s *j_dbs_info;
 576                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 577                         j_dbs_info->cur_policy = policy;
 578
 579                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 580                                                 &j_dbs_info->prev_cpu_wall);
 581                         if (dbs_tuners_ins.ignore_nice) {
 582                                 j_dbs_info->prev_cpu_nice =
 583                                                 kstat_cpu(j).cpustat.nice;
 584                         }
 585                 }
 586                 this_dbs_info->down_skip = 0;
 587                 this_dbs_info->requested_freq = policy->cur;
 588
 589                 dbs_enable++;
 590                 /*
 591                  * Start the timerschedule work, when this governor
 592                  * is used for first time
 593                  */
 594                 if (dbs_enable == 1) {
 595                         unsigned int latency;
 596                         /* policy latency is in nS. Convert it to uS first */
 597                         latency = policy->cpuinfo.transition_latency / 1000;
 598                         if (latency == 0)
 599                                 latency = 1;
 600
 601                         def_sampling_rate =
 602                                 max(latency * LATENCY_MULTIPLIER,
 603                                     MIN_STAT_SAMPLING_RATE);
 604
 605                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 606
 607                         cpufreq_register_notifier(
 608                                         &dbs_cpufreq_notifier_block,
 609                                         CPUFREQ_TRANSITION_NOTIFIER);
 610                 }
 611                 dbs_timer_init(this_dbs_info);
 612
 613                 mutex_unlock(&dbs_mutex);
 614
 615                 break;
 616
 617         case CPUFREQ_GOV_STOP:
 618                 mutex_lock(&dbs_mutex);
 619                 dbs_timer_exit(this_dbs_info);
 620                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 621                 dbs_enable--;
 622
 623                 /*
 624                  * Stop the timerschedule work, when this governor
 625                  * is used for first time
 626                  */
 627                 if (dbs_enable == 0)
 628                         cpufreq_unregister_notifier(
 629                                         &dbs_cpufreq_notifier_block,
 630                                         CPUFREQ_TRANSITION_NOTIFIER);
 631
 632                 mutex_unlock(&dbs_mutex);
 633
 634                 break;
 635
 636         case CPUFREQ_GOV_LIMITS:
 637                 mutex_lock(&dbs_mutex);
 638                 if (policy->max < this_dbs_info->cur_policy->cur)
 639                         __cpufreq_driver_target(
 640                                         this_dbs_info->cur_policy,
 641                                         policy->max, CPUFREQ_RELATION_H);
 642                 else if (policy->min > this_dbs_info->cur_policy->cur)
 643                         __cpufreq_driver_target(
 644                                         this_dbs_info->cur_policy,
 645                                         policy->min, CPUFREQ_RELATION_L);
 646                 mutex_unlock(&dbs_mutex);
 647
 648                 break;
 649         }
 650         return 0;
 651 }
 652
 653 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 654 static
 655 #endif
 656 struct cpufreq_governor cpufreq_gov_conservative = {
 657         .name                   = "conservative",
 658         .governor               = cpufreq_governor_dbs,
 659         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 660         .owner                  = THIS_MODULE,
 661 };
 662
 663 static int __init cpufreq_gov_dbs_init(void)
 664 {
 665         int err;
 666
 667         kconservative_wq = create_workqueue("kconservative");
 668         if (!kconservative_wq) {
 669                 printk(KERN_ERR "Creation of kconservative failed\n");
 670                 return -EFAULT;
 671         }
 672
 673         err = cpufreq_register_governor(&cpufreq_gov_conservative);
 674         if (err)
 675                 destroy_workqueue(kconservative_wq);
 676
 677         return err;
 678 }
 679
 680 static void __exit cpufreq_gov_dbs_exit(void)
 681 {
 682         cpufreq_unregister_governor(&cpufreq_gov_conservative);
 683         destroy_workqueue(kconservative_wq);
 684 }
 685
 686
 687 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
 688 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
 689                 "Low Latency Frequency Transition capable processors "
 690                 "optimised for use in a battery environment");
 691 MODULE_LICENSE("GPL");
 692
 693 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 694 fs_initcall(cpufreq_gov_dbs_init);
 695 #else
 696 module_init(cpufreq_gov_dbs_init);
 697 #endif
 698 module_exit(cpufreq_gov_dbs_exit);