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

   1 /*
   2  *  drivers/cpufreq/cpufreq_ondemand.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  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/kernel.h>
  14 #include <linux/module.h>
  15 #include <linux/init.h>
  16 #include <linux/cpufreq.h>
  17 #include <linux/cpu.h>
  18 #include <linux/jiffies.h>
  19 #include <linux/kernel_stat.h>
  20 #include <linux/mutex.h>
  21 #include <linux/hrtimer.h>
  22 #include <linux/tick.h>
  23 #include <linux/ktime.h>
  24 #include <linux/sched.h>
  25
  26 /*
  27  * dbs is used in this file as a shortform for demandbased switching
  28  * It helps to keep variable names smaller, simpler
  29  */
  30
  31 #define DEF_FREQUENCY_DOWN_DIFFERENTIAL         (10)
  32 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
  33 #define MICRO_FREQUENCY_DOWN_DIFFERENTIAL       (3)
  34 #define MICRO_FREQUENCY_UP_THRESHOLD            (95)
  35 #define MICRO_FREQUENCY_MIN_SAMPLE_RATE         (10000)
  36 #define MIN_FREQUENCY_UP_THRESHOLD              (11)
  37 #define MAX_FREQUENCY_UP_THRESHOLD              (100)
  38
  39 /*
  40  * The polling frequency of this governor depends on the capability of
  41  * the processor. Default polling frequency is 1000 times the transition
  42  * latency of the processor. The governor will work on any processor with
  43  * transition latency <= 10mS, using appropriate sampling
  44  * rate.
  45  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
  46  * this governor will not work.
  47  * All times here are in uS.
  48  */
  49 #define MIN_SAMPLING_RATE_RATIO                 (2)
  50
  51 static unsigned int min_sampling_rate;
  52
  53 #define LATENCY_MULTIPLIER                      (1000)
  54 #define MIN_LATENCY_MULTIPLIER                  (100)
  55 #define TRANSITION_LATENCY_LIMIT                (10 * 1000 * 1000)
  56
  57 static void do_dbs_timer(struct work_struct *work);
  58
  59 /* Sampling types */
  60 enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE};
  61
  62 struct cpu_dbs_info_s {
  63         cputime64_t prev_cpu_idle;
  64         cputime64_t prev_cpu_wall;
  65         cputime64_t prev_cpu_nice;
  66         struct cpufreq_policy *cur_policy;
  67         struct delayed_work work;
  68         struct cpufreq_frequency_table *freq_table;
  69         unsigned int freq_lo;
  70         unsigned int freq_lo_jiffies;
  71         unsigned int freq_hi_jiffies;
  72         int cpu;
  73         unsigned int enable:1,
  74                 sample_type:1;
  75 };
  76 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
  77
  78 static unsigned int dbs_enable; /* number of CPUs using this policy */
  79
  80 /*
  81  * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
  82  * lock and dbs_mutex. cpu_hotplug lock should always be held before
  83  * dbs_mutex. If any function that can potentially take cpu_hotplug lock
  84  * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
  85  * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
  86  * is recursive for the same process. -Venki
  87  * DEADLOCK ALERT! (2) : do_dbs_timer() must not take the dbs_mutex, because it
  88  * would deadlock with cancel_delayed_work_sync(), which is needed for proper
  89  * raceless workqueue teardown.
  90  */
  91 static DEFINE_MUTEX(dbs_mutex);
  92
  93 static struct workqueue_struct  *kondemand_wq;
  94
  95 static struct dbs_tuners {
  96         unsigned int sampling_rate;
  97         unsigned int up_threshold;
  98         unsigned int down_differential;
  99         unsigned int ignore_nice;
 100         unsigned int powersave_bias;
 101 } dbs_tuners_ins = {
 102         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
 103         .down_differential = DEF_FREQUENCY_DOWN_DIFFERENTIAL,
 104         .ignore_nice = 0,
 105         .powersave_bias = 0,
 106 };
 107
 108 static inline cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu,
 109                                                         cputime64_t *wall)
 110 {
 111         cputime64_t idle_time;
 112         cputime64_t cur_wall_time;
 113         cputime64_t busy_time;
 114
 115         cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
 116         busy_time = cputime64_add(kstat_cpu(cpu).cpustat.user,
 117                         kstat_cpu(cpu).cpustat.system);
 118
 119         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.irq);
 120         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.softirq);
 121         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.steal);
 122         busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.nice);
 123
 124         idle_time = cputime64_sub(cur_wall_time, busy_time);
 125         if (wall)
 126                 *wall = cur_wall_time;
 127
 128         return idle_time;
 129 }
 130
 131 static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
 132 {
 133         u64 idle_time = get_cpu_idle_time_us(cpu, wall);
 134
 135         if (idle_time == -1ULL)
 136                 return get_cpu_idle_time_jiffy(cpu, wall);
 137
 138         return idle_time;
 139 }
 140
 141 /*
 142  * Find right freq to be set now with powersave_bias on.
 143  * Returns the freq_hi to be used right now and will set freq_hi_jiffies,
 144  * freq_lo, and freq_lo_jiffies in percpu area for averaging freqs.
 145  */
 146 static unsigned int powersave_bias_target(struct cpufreq_policy *policy,
 147                                           unsigned int freq_next,
 148                                           unsigned int relation)
 149 {
 150         unsigned int freq_req, freq_reduc, freq_avg;
 151         unsigned int freq_hi, freq_lo;
 152         unsigned int index = 0;
 153         unsigned int jiffies_total, jiffies_hi, jiffies_lo;
 154         struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, policy->cpu);
 155
 156         if (!dbs_info->freq_table) {
 157                 dbs_info->freq_lo = 0;
 158                 dbs_info->freq_lo_jiffies = 0;
 159                 return freq_next;
 160         }
 161
 162         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_next,
 163                         relation, &index);
 164         freq_req = dbs_info->freq_table[index].frequency;
 165         freq_reduc = freq_req * dbs_tuners_ins.powersave_bias / 1000;
 166         freq_avg = freq_req - freq_reduc;
 167
 168         /* Find freq bounds for freq_avg in freq_table */
 169         index = 0;
 170         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 171                         CPUFREQ_RELATION_H, &index);
 172         freq_lo = dbs_info->freq_table[index].frequency;
 173         index = 0;
 174         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 175                         CPUFREQ_RELATION_L, &index);
 176         freq_hi = dbs_info->freq_table[index].frequency;
 177
 178         /* Find out how long we have to be in hi and lo freqs */
 179         if (freq_hi == freq_lo) {
 180                 dbs_info->freq_lo = 0;
 181                 dbs_info->freq_lo_jiffies = 0;
 182                 return freq_lo;
 183         }
 184         jiffies_total = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 185         jiffies_hi = (freq_avg - freq_lo) * jiffies_total;
 186         jiffies_hi += ((freq_hi - freq_lo) / 2);
 187         jiffies_hi /= (freq_hi - freq_lo);
 188         jiffies_lo = jiffies_total - jiffies_hi;
 189         dbs_info->freq_lo = freq_lo;
 190         dbs_info->freq_lo_jiffies = jiffies_lo;
 191         dbs_info->freq_hi_jiffies = jiffies_hi;
 192         return freq_hi;
 193 }
 194
 195 static void ondemand_powersave_bias_init(void)
 196 {
 197         int i;
 198         for_each_online_cpu(i) {
 199                 struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, i);
 200                 dbs_info->freq_table = cpufreq_frequency_get_table(i);
 201                 dbs_info->freq_lo = 0;
 202         }
 203 }
 204
 205 /************************** sysfs interface ************************/
 206 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 207 {
 208         printk_once(KERN_INFO "CPUFREQ: ondemand sampling_rate_max "
 209                "sysfs file is deprecated - used by: %s\n", current->comm);
 210         return sprintf(buf, "%u\n", -1U);
 211 }
 212
 213 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 214 {
 215         return sprintf(buf, "%u\n", min_sampling_rate);
 216 }
 217
 218 #define define_one_ro(_name)            \
 219 static struct freq_attr _name =         \
 220 __ATTR(_name, 0444, show_##_name, NULL)
 221
 222 define_one_ro(sampling_rate_max);
 223 define_one_ro(sampling_rate_min);
 224
 225 /* cpufreq_ondemand Governor Tunables */
 226 #define show_one(file_name, object)                                     \
 227 static ssize_t show_##file_name                                         \
 228 (struct cpufreq_policy *unused, char *buf)                              \
 229 {                                                                       \
 230         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 231 }
 232 show_one(sampling_rate, sampling_rate);
 233 show_one(up_threshold, up_threshold);
 234 show_one(ignore_nice_load, ignore_nice);
 235 show_one(powersave_bias, powersave_bias);
 236
 237 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 238                 const char *buf, size_t count)
 239 {
 240         unsigned int input;
 241         int ret;
 242         ret = sscanf(buf, "%u", &input);
 243
 244         mutex_lock(&dbs_mutex);
 245         if (ret != 1) {
 246                 mutex_unlock(&dbs_mutex);
 247                 return -EINVAL;
 248         }
 249         dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);
 250         mutex_unlock(&dbs_mutex);
 251
 252         return count;
 253 }
 254
 255 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 256                 const char *buf, size_t count)
 257 {
 258         unsigned int input;
 259         int ret;
 260         ret = sscanf(buf, "%u", &input);
 261
 262         mutex_lock(&dbs_mutex);
 263         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 264                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 265                 mutex_unlock(&dbs_mutex);
 266                 return -EINVAL;
 267         }
 268
 269         dbs_tuners_ins.up_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         }
 307         mutex_unlock(&dbs_mutex);
 308
 309         return count;
 310 }
 311
 312 static ssize_t store_powersave_bias(struct cpufreq_policy *unused,
 313                 const char *buf, size_t count)
 314 {
 315         unsigned int input;
 316         int ret;
 317         ret = sscanf(buf, "%u", &input);
 318
 319         if (ret != 1)
 320                 return -EINVAL;
 321
 322         if (input > 1000)
 323                 input = 1000;
 324
 325         mutex_lock(&dbs_mutex);
 326         dbs_tuners_ins.powersave_bias = input;
 327         ondemand_powersave_bias_init();
 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(up_threshold);
 339 define_one_rw(ignore_nice_load);
 340 define_one_rw(powersave_bias);
 341
 342 static struct attribute *dbs_attributes[] = {
 343         &sampling_rate_max.attr,
 344         &sampling_rate_min.attr,
 345         &sampling_rate.attr,
 346         &up_threshold.attr,
 347         &ignore_nice_load.attr,
 348         &powersave_bias.attr,
 349         NULL
 350 };
 351
 352 static struct attribute_group dbs_attr_group = {
 353         .attrs = dbs_attributes,
 354         .name = "ondemand",
 355 };
 356
 357 /************************** sysfs end ************************/
 358
 359 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 360 {
 361         unsigned int max_load_freq;
 362
 363         struct cpufreq_policy *policy;
 364         unsigned int j;
 365
 366         if (!this_dbs_info->enable)
 367                 return;
 368
 369         this_dbs_info->freq_lo = 0;
 370         policy = this_dbs_info->cur_policy;
 371
 372         /*
 373          * Every sampling_rate, we check, if current idle time is less
 374          * than 20% (default), then we try to increase frequency
 375          * Every sampling_rate, we look for a the lowest
 376          * frequency which can sustain the load while keeping idle time over
 377          * 30%. If such a frequency exist, we try to decrease to this frequency.
 378          *
 379          * Any frequency increase takes it to the maximum frequency.
 380          * Frequency reduction happens at minimum steps of
 381          * 5% (default) of current frequency
 382          */
 383
 384         /* Get Absolute Load - in terms of freq */
 385         max_load_freq = 0;
 386
 387         for_each_cpu(j, policy->cpus) {
 388                 struct cpu_dbs_info_s *j_dbs_info;
 389                 cputime64_t cur_wall_time, cur_idle_time;
 390                 unsigned int idle_time, wall_time;
 391                 unsigned int load, load_freq;
 392                 int freq_avg;
 393
 394                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 395
 396                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
 397
 398                 wall_time = (unsigned int) cputime64_sub(cur_wall_time,
 399                                 j_dbs_info->prev_cpu_wall);
 400                 j_dbs_info->prev_cpu_wall = cur_wall_time;
 401
 402                 idle_time = (unsigned int) cputime64_sub(cur_idle_time,
 403                                 j_dbs_info->prev_cpu_idle);
 404                 j_dbs_info->prev_cpu_idle = cur_idle_time;
 405
 406                 if (dbs_tuners_ins.ignore_nice) {
 407                         cputime64_t cur_nice;
 408                         unsigned long cur_nice_jiffies;
 409
 410                         cur_nice = cputime64_sub(kstat_cpu(j).cpustat.nice,
 411                                          j_dbs_info->prev_cpu_nice);
 412                         /*
 413                          * Assumption: nice time between sampling periods will
 414                          * be less than 2^32 jiffies for 32 bit sys
 415                          */
 416                         cur_nice_jiffies = (unsigned long)
 417                                         cputime64_to_jiffies64(cur_nice);
 418
 419                         j_dbs_info->prev_cpu_nice = kstat_cpu(j).cpustat.nice;
 420                         idle_time += jiffies_to_usecs(cur_nice_jiffies);
 421                 }
 422
 423                 if (unlikely(!wall_time || wall_time < idle_time))
 424                         continue;
 425
 426                 load = 100 * (wall_time - idle_time) / wall_time;
 427
 428                 freq_avg = __cpufreq_driver_getavg(policy, j);
 429                 if (freq_avg <= 0)
 430                         freq_avg = policy->cur;
 431
 432                 load_freq = load * freq_avg;
 433                 if (load_freq > max_load_freq)
 434                         max_load_freq = load_freq;
 435         }
 436
 437         /* Check for frequency increase */
 438         if (max_load_freq > dbs_tuners_ins.up_threshold * policy->cur) {
 439                 /* if we are already at full speed then break out early */
 440                 if (!dbs_tuners_ins.powersave_bias) {
 441                         if (policy->cur == policy->max)
 442                                 return;
 443
 444                         __cpufreq_driver_target(policy, policy->max,
 445                                 CPUFREQ_RELATION_H);
 446                 } else {
 447                         int freq = powersave_bias_target(policy, policy->max,
 448                                         CPUFREQ_RELATION_H);
 449                         __cpufreq_driver_target(policy, freq,
 450                                 CPUFREQ_RELATION_L);
 451                 }
 452                 return;
 453         }
 454
 455         /* Check for frequency decrease */
 456         /* if we cannot reduce the frequency anymore, break out early */
 457         if (policy->cur == policy->min)
 458                 return;
 459
 460         /*
 461          * The optimal frequency is the frequency that is the lowest that
 462          * can support the current CPU usage without triggering the up
 463          * policy. To be safe, we focus 10 points under the threshold.
 464          */
 465         if (max_load_freq <
 466             (dbs_tuners_ins.up_threshold - dbs_tuners_ins.down_differential) *
 467              policy->cur) {
 468                 unsigned int freq_next;
 469                 freq_next = max_load_freq /
 470                                 (dbs_tuners_ins.up_threshold -
 471                                  dbs_tuners_ins.down_differential);
 472
 473                 if (!dbs_tuners_ins.powersave_bias) {
 474                         __cpufreq_driver_target(policy, freq_next,
 475                                         CPUFREQ_RELATION_L);
 476                 } else {
 477                         int freq = powersave_bias_target(policy, freq_next,
 478                                         CPUFREQ_RELATION_L);
 479                         __cpufreq_driver_target(policy, freq,
 480                                 CPUFREQ_RELATION_L);
 481                 }
 482         }
 483 }
 484
 485 static void do_dbs_timer(struct work_struct *work)
 486 {
 487         struct cpu_dbs_info_s *dbs_info =
 488                 container_of(work, struct cpu_dbs_info_s, work.work);
 489         unsigned int cpu = dbs_info->cpu;
 490         int sample_type = dbs_info->sample_type;
 491
 492         /* We want all CPUs to do sampling nearly on same jiffy */
 493         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 494
 495         delay -= jiffies % delay;
 496
 497         if (lock_policy_rwsem_write(cpu) < 0)
 498                 return;
 499
 500         if (!dbs_info->enable) {
 501                 unlock_policy_rwsem_write(cpu);
 502                 return;
 503         }
 504
 505         /* Common NORMAL_SAMPLE setup */
 506         dbs_info->sample_type = DBS_NORMAL_SAMPLE;
 507         if (!dbs_tuners_ins.powersave_bias ||
 508             sample_type == DBS_NORMAL_SAMPLE) {
 509                 dbs_check_cpu(dbs_info);
 510                 if (dbs_info->freq_lo) {
 511                         /* Setup timer for SUB_SAMPLE */
 512                         dbs_info->sample_type = DBS_SUB_SAMPLE;
 513                         delay = dbs_info->freq_hi_jiffies;
 514                 }
 515         } else {
 516                 __cpufreq_driver_target(dbs_info->cur_policy,
 517                         dbs_info->freq_lo, CPUFREQ_RELATION_H);
 518         }
 519         queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
 520         unlock_policy_rwsem_write(cpu);
 521 }
 522
 523 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 524 {
 525         /* We want all CPUs to do sampling nearly on same jiffy */
 526         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 527         delay -= jiffies % delay;
 528
 529         dbs_info->enable = 1;
 530         ondemand_powersave_bias_init();
 531         dbs_info->sample_type = DBS_NORMAL_SAMPLE;
 532         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
 533         queue_delayed_work_on(dbs_info->cpu, kondemand_wq, &dbs_info->work,
 534                 delay);
 535 }
 536
 537 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 538 {
 539         dbs_info->enable = 0;
 540         cancel_delayed_work_sync(&dbs_info->work);
 541 }
 542
 543 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 544                                    unsigned int event)
 545 {
 546         unsigned int cpu = policy->cpu;
 547         struct cpu_dbs_info_s *this_dbs_info;
 548         unsigned int j;
 549         int rc;
 550
 551         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 552
 553         switch (event) {
 554         case CPUFREQ_GOV_START:
 555                 if ((!cpu_online(cpu)) || (!policy->cur))
 556                         return -EINVAL;
 557
 558                 if (this_dbs_info->enable) /* Already enabled */
 559                         break;
 560
 561                 mutex_lock(&dbs_mutex);
 562                 dbs_enable++;
 563
 564                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
 565                 if (rc) {
 566                         dbs_enable--;
 567                         mutex_unlock(&dbs_mutex);
 568                         return rc;
 569                 }
 570
 571                 for_each_cpu(j, policy->cpus) {
 572                         struct cpu_dbs_info_s *j_dbs_info;
 573                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 574                         j_dbs_info->cur_policy = policy;
 575
 576                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 577                                                 &j_dbs_info->prev_cpu_wall);
 578                         if (dbs_tuners_ins.ignore_nice) {
 579                                 j_dbs_info->prev_cpu_nice =
 580                                                 kstat_cpu(j).cpustat.nice;
 581                         }
 582                 }
 583                 this_dbs_info->cpu = cpu;
 584                 /*
 585                  * Start the timerschedule work, when this governor
 586                  * is used for first time
 587                  */
 588                 if (dbs_enable == 1) {
 589                         unsigned int latency;
 590                         /* policy latency is in nS. Convert it to uS first */
 591                         latency = policy->cpuinfo.transition_latency / 1000;
 592                         if (latency == 0)
 593                                 latency = 1;
 594                         /* Bring kernel and HW constraints together */
 595                         min_sampling_rate = max(min_sampling_rate,
 596                                         MIN_LATENCY_MULTIPLIER * latency);
 597                         dbs_tuners_ins.sampling_rate =
 598                                 max(min_sampling_rate,
 599                                     latency * LATENCY_MULTIPLIER);
 600                 }
 601                 dbs_timer_init(this_dbs_info);
 602
 603                 mutex_unlock(&dbs_mutex);
 604                 break;
 605
 606         case CPUFREQ_GOV_STOP:
 607                 mutex_lock(&dbs_mutex);
 608                 dbs_timer_exit(this_dbs_info);
 609                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 610                 dbs_enable--;
 611                 mutex_unlock(&dbs_mutex);
 612
 613                 break;
 614
 615         case CPUFREQ_GOV_LIMITS:
 616                 mutex_lock(&dbs_mutex);
 617                 if (policy->max < this_dbs_info->cur_policy->cur)
 618                         __cpufreq_driver_target(this_dbs_info->cur_policy,
 619                                 policy->max, CPUFREQ_RELATION_H);
 620                 else if (policy->min > this_dbs_info->cur_policy->cur)
 621                         __cpufreq_driver_target(this_dbs_info->cur_policy,
 622                                 policy->min, CPUFREQ_RELATION_L);
 623                 mutex_unlock(&dbs_mutex);
 624                 break;
 625         }
 626         return 0;
 627 }
 628
 629 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 630 static
 631 #endif
 632 struct cpufreq_governor cpufreq_gov_ondemand = {
 633         .name                   = "ondemand",
 634         .governor               = cpufreq_governor_dbs,
 635         .max_transition_latency = TRANSITION_LATENCY_LIMIT,
 636         .owner                  = THIS_MODULE,
 637 };
 638
 639 static int __init cpufreq_gov_dbs_init(void)
 640 {
 641         int err;
 642         cputime64_t wall;
 643         u64 idle_time;
 644         int cpu = get_cpu();
 645
 646         idle_time = get_cpu_idle_time_us(cpu, &wall);
 647         put_cpu();
 648         if (idle_time != -1ULL) {
 649                 /* Idle micro accounting is supported. Use finer thresholds */
 650                 dbs_tuners_ins.up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
 651                 dbs_tuners_ins.down_differential =
 652                                         MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
 653                 /*
 654                  * In no_hz/micro accounting case we set the minimum frequency
 655                  * not depending on HZ, but fixed (very low). The deferred
 656                  * timer might skip some samples if idle/sleeping as needed.
 657                 */
 658                 min_sampling_rate = MICRO_FREQUENCY_MIN_SAMPLE_RATE;
 659         } else {
 660                 /* For correct statistics, we need 10 ticks for each measure */
 661                 min_sampling_rate =
 662                         MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
 663         }
 664
 665         kondemand_wq = create_workqueue("kondemand");
 666         if (!kondemand_wq) {
 667                 printk(KERN_ERR "Creation of kondemand failed\n");
 668                 return -EFAULT;
 669         }
 670         err = cpufreq_register_governor(&cpufreq_gov_ondemand);
 671         if (err)
 672                 destroy_workqueue(kondemand_wq);
 673
 674         return err;
 675 }
 676
 677 static void __exit cpufreq_gov_dbs_exit(void)
 678 {
 679         cpufreq_unregister_governor(&cpufreq_gov_ondemand);
 680         destroy_workqueue(kondemand_wq);
 681 }
 682
 683
 684 MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 685 MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
 686 MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 687         "Low Latency Frequency Transition capable processors");
 688 MODULE_LICENSE("GPL");
 689
 690 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 691 fs_initcall(cpufreq_gov_dbs_init);
 692 #else
 693 module_init(cpufreq_gov_dbs_init);
 694 #endif
 695 module_exit(cpufreq_gov_dbs_exit);