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, cs_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 dbs_tuners {
  85         unsigned int sampling_rate;
  86         unsigned int sampling_down_factor;
  87         unsigned int up_threshold;
  88         unsigned int down_threshold;
  89         unsigned int ignore_nice;
  90         unsigned int freq_step;
  91 } dbs_tuners_ins = {
  92         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
  93         .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
  94         .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
  95         .ignore_nice = 0,
  96         .freq_step = 5,
  97 };
  98
  99 static inline cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu,
 100                                                         cputime64_t *wall)
 101 {
 102         cputime64_t idle_time;
 103         cputime64_t cur_wall_time;
 104         cputime64_t busy_time;
 105
 106         cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
 107         busy_time = cputime64_add(kstat_cpu(cpu).cpustat.user,
 108                         kstat_cpu(cpu).cpustat.system);
 109
 110         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.irq);
 111         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.softirq);
 112         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.steal);
 113         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.nice);
 114
 115         idle_time = cputime64_sub(cur_wall_time, busy_time);
 116         if (wall)
 117                 *wall = (cputime64_t)jiffies_to_usecs(cur_wall_time);
 118
 119         return (cputime64_t)jiffies_to_usecs(idle_time);
 120 }
 121
 122 static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
 123 {
 124         u64 idle_time = get_cpu_idle_time_us(cpu, wall);
 125
 126         if (idle_time == -1ULL)
 127                 return get_cpu_idle_time_jiffy(cpu, wall);
 128
 129         return idle_time;
 130 }
 131
 132 /* keep track of frequency transitions */
 133 static int
 134 dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
 135                      void *data)
 136 {
 137         struct cpufreq_freqs *freq = data;
 138         struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cs_cpu_dbs_info,
 139                                                         freq->cpu);
 140
 141         struct cpufreq_policy *policy;
 142
 143         if (!this_dbs_info->enable)
 144                 return 0;
 145
 146         policy = this_dbs_info->cur_policy;
 147
 148         /*
 149          * we only care if our internally tracked freq moves outside
 150          * the 'valid' ranges of freqency available to us otherwise
 151          * we do not change it
 152         */
 153         if (this_dbs_info->requested_freq > policy->max
 154                         || this_dbs_info->requested_freq < policy->min)
 155                 this_dbs_info->requested_freq = freq->new;
 156
 157         return 0;
 158 }
 159
 160 static struct notifier_block dbs_cpufreq_notifier_block = {
 161         .notifier_call = dbs_cpufreq_notifier
 162 };
 163
 164 /************************** sysfs interface ************************/
 165 static ssize_t show_sampling_rate_max(struct kobject *kobj,
 166                                       struct attribute *attr, char *buf)
 167 {
 168         printk_once(KERN_INFO "CPUFREQ: conservative sampling_rate_max "
 169                     "sysfs file is deprecated - used by: %s\n", current->comm);
 170         return sprintf(buf, "%u\n", -1U);
 171 }
 172
 173 static ssize_t show_sampling_rate_min(struct kobject *kobj,
 174                                       struct attribute *attr, char *buf)
 175 {
 176         return sprintf(buf, "%u\n", min_sampling_rate);
 177 }
 178
 179 define_one_global_ro(sampling_rate_max);
 180 define_one_global_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 kobject *kobj, struct attribute *attr, 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 /*** delete after deprecation time ***/
 197 #define DEPRECATION_MSG(file_name)                                      \
 198         printk_once(KERN_INFO "CPUFREQ: Per core conservative sysfs "   \
 199                 "interface is deprecated - " #file_name "\n");
 200
 201 #define show_one_old(file_name)                                         \
 202 static ssize_t show_##file_name##_old                                   \
 203 (struct cpufreq_policy *unused, char *buf)                              \
 204 {                                                                       \
 205         printk_once(KERN_INFO "CPUFREQ: Per core conservative sysfs "   \
 206                 "interface is deprecated - " #file_name "\n");          \
 207         return show_##file_name(NULL, NULL, buf);                       \
 208 }
 209 show_one_old(sampling_rate);
 210 show_one_old(sampling_down_factor);
 211 show_one_old(up_threshold);
 212 show_one_old(down_threshold);
 213 show_one_old(ignore_nice_load);
 214 show_one_old(freq_step);
 215 show_one_old(sampling_rate_min);
 216 show_one_old(sampling_rate_max);
 217
 218 cpufreq_freq_attr_ro_old(sampling_rate_min);
 219 cpufreq_freq_attr_ro_old(sampling_rate_max);
 220
 221 /*** delete after deprecation time ***/
 222
 223 static ssize_t store_sampling_down_factor(struct kobject *a,
 224                                           struct attribute *b,
 225                                           const char *buf, size_t count)
 226 {
 227         unsigned int input;
 228         int ret;
 229         ret = sscanf(buf, "%u", &input);
 230
 231         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 232                 return -EINVAL;
 233
 234         mutex_lock(&dbs_mutex);
 235         dbs_tuners_ins.sampling_down_factor = input;
 236         mutex_unlock(&dbs_mutex);
 237
 238         return count;
 239 }
 240
 241 static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
 242                                    const char *buf, size_t count)
 243 {
 244         unsigned int input;
 245         int ret;
 246         ret = sscanf(buf, "%u", &input);
 247
 248         if (ret != 1)
 249                 return -EINVAL;
 250
 251         mutex_lock(&dbs_mutex);
 252         dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);
 253         mutex_unlock(&dbs_mutex);
 254
 255         return count;
 256 }
 257
 258 static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
 259                                   const char *buf, size_t count)
 260 {
 261         unsigned int input;
 262         int ret;
 263         ret = sscanf(buf, "%u", &input);
 264
 265         mutex_lock(&dbs_mutex);
 266         if (ret != 1 || input > 100 ||
 267                         input <= dbs_tuners_ins.down_threshold) {
 268                 mutex_unlock(&dbs_mutex);
 269                 return -EINVAL;
 270         }
 271
 272         dbs_tuners_ins.up_threshold = input;
 273         mutex_unlock(&dbs_mutex);
 274
 275         return count;
 276 }
 277
 278 static ssize_t store_down_threshold(struct kobject *a, struct attribute *b,
 279                                     const char *buf, size_t count)
 280 {
 281         unsigned int input;
 282         int ret;
 283         ret = sscanf(buf, "%u", &input);
 284
 285         mutex_lock(&dbs_mutex);
 286         /* cannot be lower than 11 otherwise freq will not fall */
 287         if (ret != 1 || input < 11 || input > 100 ||
 288                         input >= dbs_tuners_ins.up_threshold) {
 289                 mutex_unlock(&dbs_mutex);
 290                 return -EINVAL;
 291         }
 292
 293         dbs_tuners_ins.down_threshold = input;
 294         mutex_unlock(&dbs_mutex);
 295
 296         return count;
 297 }
 298
 299 static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
 300                                       const char *buf, size_t count)
 301 {
 302         unsigned int input;
 303         int ret;
 304
 305         unsigned int j;
 306
 307         ret = sscanf(buf, "%u", &input);
 308         if (ret != 1)
 309                 return -EINVAL;
 310
 311         if (input > 1)
 312                 input = 1;
 313
 314         mutex_lock(&dbs_mutex);
 315         if (input == dbs_tuners_ins.ignore_nice) { /* nothing to do */
 316                 mutex_unlock(&dbs_mutex);
 317                 return count;
 318         }
 319         dbs_tuners_ins.ignore_nice = input;
 320
 321         /* we need to re-evaluate prev_cpu_idle */
 322         for_each_online_cpu(j) {
 323                 struct cpu_dbs_info_s *dbs_info;
 324                 dbs_info = &per_cpu(cs_cpu_dbs_info, j);
 325                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 326                                                 &dbs_info->prev_cpu_wall);
 327                 if (dbs_tuners_ins.ignore_nice)
 328                         dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
 329         }
 330         mutex_unlock(&dbs_mutex);
 331
 332         return count;
 333 }
 334
 335 static ssize_t store_freq_step(struct kobject *a, struct attribute *b,
 336                                const char *buf, size_t count)
 337 {
 338         unsigned int input;
 339         int ret;
 340         ret = sscanf(buf, "%u", &input);
 341
 342         if (ret != 1)
 343                 return -EINVAL;
 344
 345         if (input > 100)
 346                 input = 100;
 347
 348         /* no need to test here if freq_step is zero as the user might actually
 349          * want this, they would be crazy though :) */
 350         mutex_lock(&dbs_mutex);
 351         dbs_tuners_ins.freq_step = input;
 352         mutex_unlock(&dbs_mutex);
 353
 354         return count;
 355 }
 356
 357 define_one_global_rw(sampling_rate);
 358 define_one_global_rw(sampling_down_factor);
 359 define_one_global_rw(up_threshold);
 360 define_one_global_rw(down_threshold);
 361 define_one_global_rw(ignore_nice_load);
 362 define_one_global_rw(freq_step);
 363
 364 static struct attribute *dbs_attributes[] = {
 365         &sampling_rate_max.attr,
 366         &sampling_rate_min.attr,
 367         &sampling_rate.attr,
 368         &sampling_down_factor.attr,
 369         &up_threshold.attr,
 370         &down_threshold.attr,
 371         &ignore_nice_load.attr,
 372         &freq_step.attr,
 373         NULL
 374 };
 375
 376 static struct attribute_group dbs_attr_group = {
 377         .attrs = dbs_attributes,
 378         .name = "conservative",
 379 };
 380
 381 /*** delete after deprecation time ***/
 382
 383 #define write_one_old(file_name)                                        \
 384 static ssize_t store_##file_name##_old                                  \
 385 (struct cpufreq_policy *unused, const char *buf, size_t count)          \
 386 {                                                                       \
 387         printk_once(KERN_INFO "CPUFREQ: Per core conservative sysfs "   \
 388                 "interface is deprecated - " #file_name "\n");  \
 389         return store_##file_name(NULL, NULL, buf, count);               \
 390 }
 391 write_one_old(sampling_rate);
 392 write_one_old(sampling_down_factor);
 393 write_one_old(up_threshold);
 394 write_one_old(down_threshold);
 395 write_one_old(ignore_nice_load);
 396 write_one_old(freq_step);
 397
 398 cpufreq_freq_attr_rw_old(sampling_rate);
 399 cpufreq_freq_attr_rw_old(sampling_down_factor);
 400 cpufreq_freq_attr_rw_old(up_threshold);
 401 cpufreq_freq_attr_rw_old(down_threshold);
 402 cpufreq_freq_attr_rw_old(ignore_nice_load);
 403 cpufreq_freq_attr_rw_old(freq_step);
 404
 405 static struct attribute *dbs_attributes_old[] = {
 406         &sampling_rate_max_old.attr,
 407         &sampling_rate_min_old.attr,
 408         &sampling_rate_old.attr,
 409         &sampling_down_factor_old.attr,
 410         &up_threshold_old.attr,
 411         &down_threshold_old.attr,
 412         &ignore_nice_load_old.attr,
 413         &freq_step_old.attr,
 414         NULL
 415 };
 416
 417 static struct attribute_group dbs_attr_group_old = {
 418         .attrs = dbs_attributes_old,
 419         .name = "conservative",
 420 };
 421
 422 /*** delete after deprecation time ***/
 423
 424 /************************** sysfs end ************************/
 425
 426 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 427 {
 428         unsigned int load = 0;
 429         unsigned int max_load = 0;
 430         unsigned int freq_target;
 431
 432         struct cpufreq_policy *policy;
 433         unsigned int j;
 434
 435         policy = this_dbs_info->cur_policy;
 436
 437         /*
 438          * Every sampling_rate, we check, if current idle time is less
 439          * than 20% (default), then we try to increase frequency
 440          * Every sampling_rate*sampling_down_factor, we check, if current
 441          * idle time is more than 80%, then we try to decrease frequency
 442          *
 443          * Any frequency increase takes it to the maximum frequency.
 444          * Frequency reduction happens at minimum steps of
 445          * 5% (default) of maximum frequency
 446          */
 447
 448         /* Get Absolute Load */
 449         for_each_cpu(j, policy->cpus) {
 450                 struct cpu_dbs_info_s *j_dbs_info;
 451                 cputime64_t cur_wall_time, cur_idle_time;
 452                 unsigned int idle_time, wall_time;
 453
 454                 j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
 455
 456                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
 457
 458                 wall_time = (unsigned int) cputime64_sub(cur_wall_time,
 459                                 j_dbs_info->prev_cpu_wall);
 460                 j_dbs_info->prev_cpu_wall = cur_wall_time;
 461
 462                 idle_time = (unsigned int) cputime64_sub(cur_idle_time,
 463                                 j_dbs_info->prev_cpu_idle);
 464                 j_dbs_info->prev_cpu_idle = cur_idle_time;
 465
 466                 if (dbs_tuners_ins.ignore_nice) {
 467                         cputime64_t cur_nice;
 468                         unsigned long cur_nice_jiffies;
 469
 470                         cur_nice = cputime64_sub(kstat_cpu(j).cpustat.nice,
 471                                          j_dbs_info->prev_cpu_nice);
 472                         /*
 473                          * Assumption: nice time between sampling periods will
 474                          * be less than 2^32 jiffies for 32 bit sys
 475                          */
 476                         cur_nice_jiffies = (unsigned long)
 477                                         cputime64_to_jiffies64(cur_nice);
 478
 479                         j_dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
 480                         idle_time += jiffies_to_usecs(cur_nice_jiffies);
 481                 }
 482
 483                 if (unlikely(!wall_time || wall_time < idle_time))
 484                         continue;
 485
 486                 load = 100 * (wall_time - idle_time) / wall_time;
 487
 488                 if (load > max_load)
 489                         max_load = load;
 490         }
 491
 492         /*
 493          * break out if we 'cannot' reduce the speed as the user might
 494          * want freq_step to be zero
 495          */
 496         if (dbs_tuners_ins.freq_step == 0)
 497                 return;
 498
 499         /* Check for frequency increase */
 500         if (max_load > dbs_tuners_ins.up_threshold) {
 501                 this_dbs_info->down_skip = 0;
 502
 503                 /* if we are already at full speed then break out early */
 504                 if (this_dbs_info->requested_freq == policy->max)
 505                         return;
 506
 507                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 508
 509                 /* max freq cannot be less than 100. But who knows.... */
 510                 if (unlikely(freq_target == 0))
 511                         freq_target = 5;
 512
 513                 this_dbs_info->requested_freq += freq_target;
 514                 if (this_dbs_info->requested_freq > policy->max)
 515                         this_dbs_info->requested_freq = policy->max;
 516
 517                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 518                         CPUFREQ_RELATION_H);
 519                 return;
 520         }
 521
 522         /*
 523          * The optimal frequency is the frequency that is the lowest that
 524          * can support the current CPU usage without triggering the up
 525          * policy. To be safe, we focus 10 points under the threshold.
 526          */
 527         if (max_load < (dbs_tuners_ins.down_threshold - 10)) {
 528                 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;
 529
 530                 this_dbs_info->requested_freq -= freq_target;
 531                 if (this_dbs_info->requested_freq < policy->min)
 532                         this_dbs_info->requested_freq = policy->min;
 533
 534                 /*
 535                  * if we cannot reduce the frequency anymore, break out early
 536                  */
 537                 if (policy->cur == policy->min)
 538                         return;
 539
 540                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 541                                 CPUFREQ_RELATION_H);
 542                 return;
 543         }
 544 }
 545
 546 static void do_dbs_timer(struct work_struct *work)
 547 {
 548         struct cpu_dbs_info_s *dbs_info =
 549                 container_of(work, struct cpu_dbs_info_s, work.work);
 550         unsigned int cpu = dbs_info->cpu;
 551
 552         /* We want all CPUs to do sampling nearly on same jiffy */
 553         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 554
 555         delay -= jiffies % delay;
 556
 557         mutex_lock(&dbs_info->timer_mutex);
 558
 559         dbs_check_cpu(dbs_info);
 560
 561         schedule_delayed_work_on(cpu, &dbs_info->work, delay);
 562         mutex_unlock(&dbs_info->timer_mutex);
 563 }
 564
 565 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 566 {
 567         /* We want all CPUs to do sampling nearly on same jiffy */
 568         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 569         delay -= jiffies % delay;
 570
 571         dbs_info->enable = 1;
 572         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
 573         schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work, delay);
 574 }
 575
 576 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 577 {
 578         dbs_info->enable = 0;
 579         cancel_delayed_work_sync(&dbs_info->work);
 580 }
 581
 582 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 583                                    unsigned int event)
 584 {
 585         unsigned int cpu = policy->cpu;
 586         struct cpu_dbs_info_s *this_dbs_info;
 587         unsigned int j;
 588         int rc;
 589
 590         this_dbs_info = &per_cpu(cs_cpu_dbs_info, cpu);
 591
 592         switch (event) {
 593         case CPUFREQ_GOV_START:
 594                 if ((!cpu_online(cpu)) || (!policy->cur))
 595                         return -EINVAL;
 596
 597                 mutex_lock(&dbs_mutex);
 598
 599                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group_old);
 600                 if (rc) {
 601                         mutex_unlock(&dbs_mutex);
 602                         return rc;
 603                 }
 604
 605                 for_each_cpu(j, policy->cpus) {
 606                         struct cpu_dbs_info_s *j_dbs_info;
 607                         j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);
 608                         j_dbs_info->cur_policy = policy;
 609
 610                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 611                                                 &j_dbs_info->prev_cpu_wall);
 612                         if (dbs_tuners_ins.ignore_nice) {
 613                                 j_dbs_info->prev_cpu_nice =
 614                                                 kstat_cpu(j).cpustat.nice;
 615                         }
 616                 }
 617                 this_dbs_info->down_skip = 0;
 618                 this_dbs_info->requested_freq = policy->cur;
 619
 620                 mutex_init(&this_dbs_info->timer_mutex);
 621                 dbs_enable++;
 622                 /*
 623                  * Start the timerschedule work, when this governor
 624                  * is used for first time
 625                  */
 626                 if (dbs_enable == 1) {
 627                         unsigned int latency;
 628                         /* policy latency is in nS. Convert it to uS first */
 629                         latency = policy->cpuinfo.transition_latency / 1000;
 630                         if (latency == 0)
 631                                 latency = 1;
 632
 633                         rc = sysfs_create_group(cpufreq_global_kobject,
 634                                                 &dbs_attr_group);
 635                         if (rc) {
 636                                 mutex_unlock(&dbs_mutex);
 637                                 return rc;
 638                         }
 639
 640                         /*
 641                          * conservative does not implement micro like ondemand
 642                          * governor, thus we are bound to jiffes/HZ
 643                          */
 644                         min_sampling_rate =
 645                                 MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
 646                         /* Bring kernel and HW constraints together */
 647                         min_sampling_rate = max(min_sampling_rate,
 648                                         MIN_LATENCY_MULTIPLIER * latency);
 649                         dbs_tuners_ins.sampling_rate =
 650                                 max(min_sampling_rate,
 651                                     latency * LATENCY_MULTIPLIER);
 652
 653                         cpufreq_register_notifier(
 654                                         &dbs_cpufreq_notifier_block,
 655                                         CPUFREQ_TRANSITION_NOTIFIER);
 656                 }
 657                 mutex_unlock(&dbs_mutex);
 658
 659                 dbs_timer_init(this_dbs_info);
 660
 661                 break;
 662
 663         case CPUFREQ_GOV_STOP:
 664                 dbs_timer_exit(this_dbs_info);
 665
 666                 mutex_lock(&dbs_mutex);
 667                 sysfs_remove_group(&policy->kobj, &dbs_attr_group_old);
 668                 dbs_enable--;
 669                 mutex_destroy(&this_dbs_info->timer_mutex);
 670
 671                 /*
 672                  * Stop the timerschedule work, when this governor
 673                  * is used for first time
 674                  */
 675                 if (dbs_enable == 0)
 676                         cpufreq_unregister_notifier(
 677                                         &dbs_cpufreq_notifier_block,
 678                                         CPUFREQ_TRANSITION_NOTIFIER);
 679
 680                 mutex_unlock(&dbs_mutex);
 681                 if (!dbs_enable)
 682                         sysfs_remove_group(cpufreq_global_kobject,
 683                                            &dbs_attr_group);
 684
 685                 break;
 686
 687         case CPUFREQ_GOV_LIMITS:
 688                 mutex_lock(&this_dbs_info->timer_mutex);
 689                 if (policy->max < this_dbs_info->cur_policy->cur)
 690                         __cpufreq_driver_target(
 691                                         this_dbs_info->cur_policy,
 692                                         policy->max, CPUFREQ_RELATION_H);
 693                 else if (policy->min > this_dbs_info->cur_policy->cur)
 694                         __cpufreq_driver_target(
 695                                         this_dbs_info->cur_policy,
 696                                         policy->min, CPUFREQ_RELATION_L);
 697                 mutex_unlock(&this_dbs_info->timer_mutex);
 698
 699                 break;
 700         }
 701         return 0;
 702 }
 703
 704 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 705 static
 706 #endif
 707 struct cpufreq_governor cpufreq_gov_conservative = {
 708         .name                   = "conservative",
 709         .governor               = cpufreq_governor_dbs,
 710         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 711         .owner                  = THIS_MODULE,
 712 };
 713
 714 static int __init cpufreq_gov_dbs_init(void)
 715 {
 716         return cpufreq_register_governor(&cpufreq_gov_conservative);
 717 }
 718
 719 static void __exit cpufreq_gov_dbs_exit(void)
 720 {
 721         cpufreq_unregister_governor(&cpufreq_gov_conservative);
 722 }
 723
 724
 725 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
 726 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
 727                 "Low Latency Frequency Transition capable processors "
 728                 "optimised for use in a battery environment");
 729 MODULE_LICENSE("GPL");
 730
 731 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 732 fs_initcall(cpufreq_gov_dbs_init);
 733 #else
 734 module_init(cpufreq_gov_dbs_init);
 735 #endif
 736 module_exit(cpufreq_gov_dbs_exit);