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 DEF_SAMPLING_DOWN_FACTOR                (1)
  34 #define MAX_SAMPLING_DOWN_FACTOR                (100000)
  35 #define MICRO_FREQUENCY_DOWN_DIFFERENTIAL       (3)
  36 #define MICRO_FREQUENCY_UP_THRESHOLD            (95)
  37 #define MICRO_FREQUENCY_MIN_SAMPLE_RATE         (10000)
  38 #define MIN_FREQUENCY_UP_THRESHOLD              (11)
  39 #define MAX_FREQUENCY_UP_THRESHOLD              (100)
  40
  41 /*
  42  * The polling frequency of this governor depends on the capability of
  43  * the processor. Default polling frequency is 1000 times the transition
  44  * latency of the processor. The governor will work on any processor with
  45  * transition latency <= 10mS, using appropriate sampling
  46  * rate.
  47  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
  48  * this governor will not work.
  49  * All times here are in uS.
  50  */
  51 #define MIN_SAMPLING_RATE_RATIO                 (2)
  52
  53 static unsigned int min_sampling_rate;
  54
  55 #define LATENCY_MULTIPLIER                      (1000)
  56 #define MIN_LATENCY_MULTIPLIER                  (100)
  57 #define TRANSITION_LATENCY_LIMIT                (10 * 1000 * 1000)
  58
  59 static void do_dbs_timer(struct work_struct *work);
  60 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
  61                                 unsigned int event);
  62
  63 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
  64 static
  65 #endif
  66 struct cpufreq_governor cpufreq_gov_ondemand = {
  67        .name                   = "ondemand",
  68        .governor               = cpufreq_governor_dbs,
  69        .max_transition_latency = TRANSITION_LATENCY_LIMIT,
  70        .owner                  = THIS_MODULE,
  71 };
  72
  73 /* Sampling types */
  74 enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE};
  75
  76 struct cpu_dbs_info_s {
  77         cputime64_t prev_cpu_idle;
  78         cputime64_t prev_cpu_iowait;
  79         cputime64_t prev_cpu_wall;
  80         cputime64_t prev_cpu_nice;
  81         struct cpufreq_policy *cur_policy;
  82         struct delayed_work work;
  83         struct cpufreq_frequency_table *freq_table;
  84         unsigned int freq_lo;
  85         unsigned int freq_lo_jiffies;
  86         unsigned int freq_hi_jiffies;
  87         unsigned int rate_mult;
  88         int cpu;
  89         unsigned int sample_type:1;
  90         /*
  91          * percpu mutex that serializes governor limit change with
  92          * do_dbs_timer invocation. We do not want do_dbs_timer to run
  93          * when user is changing the governor or limits.
  94          */
  95         struct mutex timer_mutex;
  96 };
  97 static DEFINE_PER_CPU(struct cpu_dbs_info_s, od_cpu_dbs_info);
  98
  99 static unsigned int dbs_enable; /* number of CPUs using this policy */
 100
 101 /*
 102  * dbs_mutex protects dbs_enable in governor start/stop.
 103  */
 104 static DEFINE_MUTEX(dbs_mutex);
 105
 106 static struct dbs_tuners {
 107         unsigned int sampling_rate;
 108         unsigned int up_threshold;
 109         unsigned int down_differential;
 110         unsigned int ignore_nice;
 111         unsigned int sampling_down_factor;
 112         unsigned int powersave_bias;
 113         unsigned int io_is_busy;
 114 } dbs_tuners_ins = {
 115         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
 116         .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
 117         .down_differential = DEF_FREQUENCY_DOWN_DIFFERENTIAL,
 118         .ignore_nice = 0,
 119         .powersave_bias = 0,
 120 };
 121
 122 static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)
 123 {
 124         u64 idle_time;
 125         u64 cur_wall_time;
 126         u64 busy_time;
 127
 128         cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
 129
 130         busy_time  = kcpustat_cpu(cpu).cpustat[CPUTIME_USER];
 131         busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SYSTEM];
 132         busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_IRQ];
 133         busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SOFTIRQ];
 134         busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_STEAL];
 135         busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_NICE];
 136
 137         idle_time = cur_wall_time - busy_time;
 138         if (wall)
 139                 *wall = jiffies_to_usecs(cur_wall_time);
 140
 141         return jiffies_to_usecs(idle_time);
 142 }
 143
 144 static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
 145 {
 146         u64 idle_time = get_cpu_idle_time_us(cpu, NULL);
 147
 148         if (idle_time == -1ULL)
 149                 return get_cpu_idle_time_jiffy(cpu, wall);
 150         else
 151                 idle_time += get_cpu_iowait_time_us(cpu, wall);
 152
 153         return idle_time;
 154 }
 155
 156 static inline cputime64_t get_cpu_iowait_time(unsigned int cpu, cputime64_t *wall)
 157 {
 158         u64 iowait_time = get_cpu_iowait_time_us(cpu, wall);
 159
 160         if (iowait_time == -1ULL)
 161                 return 0;
 162
 163         return iowait_time;
 164 }
 165
 166 /*
 167  * Find right freq to be set now with powersave_bias on.
 168  * Returns the freq_hi to be used right now and will set freq_hi_jiffies,
 169  * freq_lo, and freq_lo_jiffies in percpu area for averaging freqs.
 170  */
 171 static unsigned int powersave_bias_target(struct cpufreq_policy *policy,
 172                                           unsigned int freq_next,
 173                                           unsigned int relation)
 174 {
 175         unsigned int freq_req, freq_reduc, freq_avg;
 176         unsigned int freq_hi, freq_lo;
 177         unsigned int index = 0;
 178         unsigned int jiffies_total, jiffies_hi, jiffies_lo;
 179         struct cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
 180                                                    policy->cpu);
 181
 182         if (!dbs_info->freq_table) {
 183                 dbs_info->freq_lo = 0;
 184                 dbs_info->freq_lo_jiffies = 0;
 185                 return freq_next;
 186         }
 187
 188         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_next,
 189                         relation, &index);
 190         freq_req = dbs_info->freq_table[index].frequency;
 191         freq_reduc = freq_req * dbs_tuners_ins.powersave_bias / 1000;
 192         freq_avg = freq_req - freq_reduc;
 193
 194         /* Find freq bounds for freq_avg in freq_table */
 195         index = 0;
 196         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 197                         CPUFREQ_RELATION_H, &index);
 198         freq_lo = dbs_info->freq_table[index].frequency;
 199         index = 0;
 200         cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
 201                         CPUFREQ_RELATION_L, &index);
 202         freq_hi = dbs_info->freq_table[index].frequency;
 203
 204         /* Find out how long we have to be in hi and lo freqs */
 205         if (freq_hi == freq_lo) {
 206                 dbs_info->freq_lo = 0;
 207                 dbs_info->freq_lo_jiffies = 0;
 208                 return freq_lo;
 209         }
 210         jiffies_total = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 211         jiffies_hi = (freq_avg - freq_lo) * jiffies_total;
 212         jiffies_hi += ((freq_hi - freq_lo) / 2);
 213         jiffies_hi /= (freq_hi - freq_lo);
 214         jiffies_lo = jiffies_total - jiffies_hi;
 215         dbs_info->freq_lo = freq_lo;
 216         dbs_info->freq_lo_jiffies = jiffies_lo;
 217         dbs_info->freq_hi_jiffies = jiffies_hi;
 218         return freq_hi;
 219 }
 220
 221 static void ondemand_powersave_bias_init_cpu(int cpu)
 222 {
 223         struct cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
 224         dbs_info->freq_table = cpufreq_frequency_get_table(cpu);
 225         dbs_info->freq_lo = 0;
 226 }
 227
 228 static void ondemand_powersave_bias_init(void)
 229 {
 230         int i;
 231         for_each_online_cpu(i) {
 232                 ondemand_powersave_bias_init_cpu(i);
 233         }
 234 }
 235
 236 /************************** sysfs interface ************************/
 237
 238 static ssize_t show_sampling_rate_min(struct kobject *kobj,
 239                                       struct attribute *attr, char *buf)
 240 {
 241         return sprintf(buf, "%u\n", min_sampling_rate);
 242 }
 243
 244 define_one_global_ro(sampling_rate_min);
 245
 246 /* cpufreq_ondemand Governor Tunables */
 247 #define show_one(file_name, object)                                     \
 248 static ssize_t show_##file_name                                         \
 249 (struct kobject *kobj, struct attribute *attr, char *buf)              \
 250 {                                                                       \
 251         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 252 }
 253 show_one(sampling_rate, sampling_rate);
 254 show_one(io_is_busy, io_is_busy);
 255 show_one(up_threshold, up_threshold);
 256 show_one(sampling_down_factor, sampling_down_factor);
 257 show_one(ignore_nice_load, ignore_nice);
 258 show_one(powersave_bias, powersave_bias);
 259
 260 /**
 261  * update_sampling_rate - update sampling rate effective immediately if needed.
 262  * @new_rate: new sampling rate
 263  *
 264  * If new rate is smaller than the old, simply updaing
 265  * dbs_tuners_int.sampling_rate might not be appropriate. For example,
 266  * if the original sampling_rate was 1 second and the requested new sampling
 267  * rate is 10 ms because the user needs immediate reaction from ondemand
 268  * governor, but not sure if higher frequency will be required or not,
 269  * then, the governor may change the sampling rate too late; up to 1 second
 270  * later. Thus, if we are reducing the sampling rate, we need to make the
 271  * new value effective immediately.
 272  */
 273 static void update_sampling_rate(unsigned int new_rate)
 274 {
 275         int cpu;
 276
 277         dbs_tuners_ins.sampling_rate = new_rate
 278                                      = max(new_rate, min_sampling_rate);
 279
 280         for_each_online_cpu(cpu) {
 281                 struct cpufreq_policy *policy;
 282                 struct cpu_dbs_info_s *dbs_info;
 283                 unsigned long next_sampling, appointed_at;
 284
 285                 policy = cpufreq_cpu_get(cpu);
 286                 if (!policy)
 287                         continue;
 288                 dbs_info = &per_cpu(od_cpu_dbs_info, policy->cpu);
 289                 cpufreq_cpu_put(policy);
 290
 291                 mutex_lock(&dbs_info->timer_mutex);
 292
 293                 if (!delayed_work_pending(&dbs_info->work)) {
 294                         mutex_unlock(&dbs_info->timer_mutex);
 295                         continue;
 296                 }
 297
 298                 next_sampling  = jiffies + usecs_to_jiffies(new_rate);
 299                 appointed_at = dbs_info->work.timer.expires;
 300
 301
 302                 if (time_before(next_sampling, appointed_at)) {
 303
 304                         mutex_unlock(&dbs_info->timer_mutex);
 305                         cancel_delayed_work_sync(&dbs_info->work);
 306                         mutex_lock(&dbs_info->timer_mutex);
 307
 308                         schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work,
 309                                                  usecs_to_jiffies(new_rate));
 310
 311                 }
 312                 mutex_unlock(&dbs_info->timer_mutex);
 313         }
 314 }
 315
 316 static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
 317                                    const char *buf, size_t count)
 318 {
 319         unsigned int input;
 320         int ret;
 321         ret = sscanf(buf, "%u", &input);
 322         if (ret != 1)
 323                 return -EINVAL;
 324         update_sampling_rate(input);
 325         return count;
 326 }
 327
 328 static ssize_t store_io_is_busy(struct kobject *a, struct attribute *b,
 329                                    const char *buf, size_t count)
 330 {
 331         unsigned int input;
 332         int ret;
 333
 334         ret = sscanf(buf, "%u", &input);
 335         if (ret != 1)
 336                 return -EINVAL;
 337         dbs_tuners_ins.io_is_busy = !!input;
 338         return count;
 339 }
 340
 341 static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
 342                                   const char *buf, size_t count)
 343 {
 344         unsigned int input;
 345         int ret;
 346         ret = sscanf(buf, "%u", &input);
 347
 348         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 349                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 350                 return -EINVAL;
 351         }
 352         dbs_tuners_ins.up_threshold = input;
 353         return count;
 354 }
 355
 356 static ssize_t store_sampling_down_factor(struct kobject *a,
 357                         struct attribute *b, const char *buf, size_t count)
 358 {
 359         unsigned int input, j;
 360         int ret;
 361         ret = sscanf(buf, "%u", &input);
 362
 363         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 364                 return -EINVAL;
 365         dbs_tuners_ins.sampling_down_factor = input;
 366
 367         /* Reset down sampling multiplier in case it was active */
 368         for_each_online_cpu(j) {
 369                 struct cpu_dbs_info_s *dbs_info;
 370                 dbs_info = &per_cpu(od_cpu_dbs_info, j);
 371                 dbs_info->rate_mult = 1;
 372         }
 373         return count;
 374 }
 375
 376 static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
 377                                       const char *buf, size_t count)
 378 {
 379         unsigned int input;
 380         int ret;
 381
 382         unsigned int j;
 383
 384         ret = sscanf(buf, "%u", &input);
 385         if (ret != 1)
 386                 return -EINVAL;
 387
 388         if (input > 1)
 389                 input = 1;
 390
 391         if (input == dbs_tuners_ins.ignore_nice) { /* nothing to do */
 392                 return count;
 393         }
 394         dbs_tuners_ins.ignore_nice = input;
 395
 396         /* we need to re-evaluate prev_cpu_idle */
 397         for_each_online_cpu(j) {
 398                 struct cpu_dbs_info_s *dbs_info;
 399                 dbs_info = &per_cpu(od_cpu_dbs_info, j);
 400                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 401                                                 &dbs_info->prev_cpu_wall);
 402                 if (dbs_tuners_ins.ignore_nice)
 403                         dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 404
 405         }
 406         return count;
 407 }
 408
 409 static ssize_t store_powersave_bias(struct kobject *a, struct attribute *b,
 410                                     const char *buf, size_t count)
 411 {
 412         unsigned int input;
 413         int ret;
 414         ret = sscanf(buf, "%u", &input);
 415
 416         if (ret != 1)
 417                 return -EINVAL;
 418
 419         if (input > 1000)
 420                 input = 1000;
 421
 422         dbs_tuners_ins.powersave_bias = input;
 423         ondemand_powersave_bias_init();
 424         return count;
 425 }
 426
 427 define_one_global_rw(sampling_rate);
 428 define_one_global_rw(io_is_busy);
 429 define_one_global_rw(up_threshold);
 430 define_one_global_rw(sampling_down_factor);
 431 define_one_global_rw(ignore_nice_load);
 432 define_one_global_rw(powersave_bias);
 433
 434 static struct attribute *dbs_attributes[] = {
 435         &sampling_rate_min.attr,
 436         &sampling_rate.attr,
 437         &up_threshold.attr,
 438         &sampling_down_factor.attr,
 439         &ignore_nice_load.attr,
 440         &powersave_bias.attr,
 441         &io_is_busy.attr,
 442         NULL
 443 };
 444
 445 static struct attribute_group dbs_attr_group = {
 446         .attrs = dbs_attributes,
 447         .name = "ondemand",
 448 };
 449
 450 /************************** sysfs end ************************/
 451
 452 static void dbs_freq_increase(struct cpufreq_policy *p, unsigned int freq)
 453 {
 454         if (dbs_tuners_ins.powersave_bias)
 455                 freq = powersave_bias_target(p, freq, CPUFREQ_RELATION_H);
 456         else if (p->cur == p->max)
 457                 return;
 458
 459         __cpufreq_driver_target(p, freq, dbs_tuners_ins.powersave_bias ?
 460                         CPUFREQ_RELATION_L : CPUFREQ_RELATION_H);
 461 }
 462
 463 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 464 {
 465         unsigned int max_load_freq;
 466
 467         struct cpufreq_policy *policy;
 468         unsigned int j;
 469
 470         this_dbs_info->freq_lo = 0;
 471         policy = this_dbs_info->cur_policy;
 472
 473         /*
 474          * Every sampling_rate, we check, if current idle time is less
 475          * than 20% (default), then we try to increase frequency
 476          * Every sampling_rate, we look for a the lowest
 477          * frequency which can sustain the load while keeping idle time over
 478          * 30%. If such a frequency exist, we try to decrease to this frequency.
 479          *
 480          * Any frequency increase takes it to the maximum frequency.
 481          * Frequency reduction happens at minimum steps of
 482          * 5% (default) of current frequency
 483          */
 484
 485         /* Get Absolute Load - in terms of freq */
 486         max_load_freq = 0;
 487
 488         for_each_cpu(j, policy->cpus) {
 489                 struct cpu_dbs_info_s *j_dbs_info;
 490                 cputime64_t cur_wall_time, cur_idle_time, cur_iowait_time;
 491                 unsigned int idle_time, wall_time, iowait_time;
 492                 unsigned int load, load_freq;
 493                 int freq_avg;
 494
 495                 j_dbs_info = &per_cpu(od_cpu_dbs_info, j);
 496
 497                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
 498                 cur_iowait_time = get_cpu_iowait_time(j, &cur_wall_time);
 499
 500                 wall_time = (unsigned int)
 501                         (cur_wall_time - j_dbs_info->prev_cpu_wall);
 502                 j_dbs_info->prev_cpu_wall = cur_wall_time;
 503
 504                 idle_time = (unsigned int)
 505                         (cur_idle_time - j_dbs_info->prev_cpu_idle);
 506                 j_dbs_info->prev_cpu_idle = cur_idle_time;
 507
 508                 iowait_time = (unsigned int)
 509                         (cur_iowait_time - j_dbs_info->prev_cpu_iowait);
 510                 j_dbs_info->prev_cpu_iowait = cur_iowait_time;
 511
 512                 if (dbs_tuners_ins.ignore_nice) {
 513                         u64 cur_nice;
 514                         unsigned long cur_nice_jiffies;
 515
 516                         cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE] -
 517                                          j_dbs_info->prev_cpu_nice;
 518                         /*
 519                          * Assumption: nice time between sampling periods will
 520                          * be less than 2^32 jiffies for 32 bit sys
 521                          */
 522                         cur_nice_jiffies = (unsigned long)
 523                                         cputime64_to_jiffies64(cur_nice);
 524
 525                         j_dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 526                         idle_time += jiffies_to_usecs(cur_nice_jiffies);
 527                 }
 528
 529                 /*
 530                  * For the purpose of ondemand, waiting for disk IO is an
 531                  * indication that you're performance critical, and not that
 532                  * the system is actually idle. So subtract the iowait time
 533                  * from the cpu idle time.
 534                  */
 535
 536                 if (dbs_tuners_ins.io_is_busy && idle_time >= iowait_time)
 537                         idle_time -= iowait_time;
 538
 539                 if (unlikely(!wall_time || wall_time < idle_time))
 540                         continue;
 541
 542                 load = 100 * (wall_time - idle_time) / wall_time;
 543
 544                 freq_avg = __cpufreq_driver_getavg(policy, j);
 545                 if (freq_avg <= 0)
 546                         freq_avg = policy->cur;
 547
 548                 load_freq = load * freq_avg;
 549                 if (load_freq > max_load_freq)
 550                         max_load_freq = load_freq;
 551         }
 552
 553         /* Check for frequency increase */
 554         if (max_load_freq > dbs_tuners_ins.up_threshold * policy->cur) {
 555                 /* If switching to max speed, apply sampling_down_factor */
 556                 if (policy->cur < policy->max)
 557                         this_dbs_info->rate_mult =
 558                                 dbs_tuners_ins.sampling_down_factor;
 559                 dbs_freq_increase(policy, policy->max);
 560                 return;
 561         }
 562
 563         /* Check for frequency decrease */
 564         /* if we cannot reduce the frequency anymore, break out early */
 565         if (policy->cur == policy->min)
 566                 return;
 567
 568         /*
 569          * The optimal frequency is the frequency that is the lowest that
 570          * can support the current CPU usage without triggering the up
 571          * policy. To be safe, we focus 10 points under the threshold.
 572          */
 573         if (max_load_freq <
 574             (dbs_tuners_ins.up_threshold - dbs_tuners_ins.down_differential) *
 575              policy->cur) {
 576                 unsigned int freq_next;
 577                 freq_next = max_load_freq /
 578                                 (dbs_tuners_ins.up_threshold -
 579                                  dbs_tuners_ins.down_differential);
 580
 581                 /* No longer fully busy, reset rate_mult */
 582                 this_dbs_info->rate_mult = 1;
 583
 584                 if (freq_next < policy->min)
 585                         freq_next = policy->min;
 586
 587                 if (!dbs_tuners_ins.powersave_bias) {
 588                         __cpufreq_driver_target(policy, freq_next,
 589                                         CPUFREQ_RELATION_L);
 590                 } else {
 591                         int freq = powersave_bias_target(policy, freq_next,
 592                                         CPUFREQ_RELATION_L);
 593                         __cpufreq_driver_target(policy, freq,
 594                                 CPUFREQ_RELATION_L);
 595                 }
 596         }
 597 }
 598
 599 static void do_dbs_timer(struct work_struct *work)
 600 {
 601         struct cpu_dbs_info_s *dbs_info =
 602                 container_of(work, struct cpu_dbs_info_s, work.work);
 603         unsigned int cpu = dbs_info->cpu;
 604         int sample_type = dbs_info->sample_type;
 605
 606         int delay;
 607
 608         mutex_lock(&dbs_info->timer_mutex);
 609
 610         /* Common NORMAL_SAMPLE setup */
 611         dbs_info->sample_type = DBS_NORMAL_SAMPLE;
 612         if (!dbs_tuners_ins.powersave_bias ||
 613             sample_type == DBS_NORMAL_SAMPLE) {
 614                 dbs_check_cpu(dbs_info);
 615                 if (dbs_info->freq_lo) {
 616                         /* Setup timer for SUB_SAMPLE */
 617                         dbs_info->sample_type = DBS_SUB_SAMPLE;
 618                         delay = dbs_info->freq_hi_jiffies;
 619                 } else {
 620                         /* We want all CPUs to do sampling nearly on
 621                          * same jiffy
 622                          */
 623                         delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate
 624                                 * dbs_info->rate_mult);
 625
 626                         if (num_online_cpus() > 1)
 627                                 delay -= jiffies % delay;
 628                 }
 629         } else {
 630                 __cpufreq_driver_target(dbs_info->cur_policy,
 631                         dbs_info->freq_lo, CPUFREQ_RELATION_H);
 632                 delay = dbs_info->freq_lo_jiffies;
 633         }
 634         schedule_delayed_work_on(cpu, &dbs_info->work, delay);
 635         mutex_unlock(&dbs_info->timer_mutex);
 636 }
 637
 638 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 639 {
 640         /* We want all CPUs to do sampling nearly on same jiffy */
 641         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 642
 643         if (num_online_cpus() > 1)
 644                 delay -= jiffies % delay;
 645
 646         dbs_info->sample_type = DBS_NORMAL_SAMPLE;
 647         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
 648         schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work, delay);
 649 }
 650
 651 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 652 {
 653         cancel_delayed_work_sync(&dbs_info->work);
 654 }
 655
 656 /*
 657  * Not all CPUs want IO time to be accounted as busy; this dependson how
 658  * efficient idling at a higher frequency/voltage is.
 659  * Pavel Machek says this is not so for various generations of AMD and old
 660  * Intel systems.
 661  * Mike Chan (androidlcom) calis this is also not true for ARM.
 662  * Because of this, whitelist specific known (series) of CPUs by default, and
 663  * leave all others up to the user.
 664  */
 665 static int should_io_be_busy(void)
 666 {
 667 #if defined(CONFIG_X86)
 668         /*
 669          * For Intel, Core 2 (model 15) andl later have an efficient idle.
 670          */
 671         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
 672             boot_cpu_data.x86 == 6 &&
 673             boot_cpu_data.x86_model >= 15)
 674                 return 1;
 675 #endif
 676         return 0;
 677 }
 678
 679 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 680                                    unsigned int event)
 681 {
 682         unsigned int cpu = policy->cpu;
 683         struct cpu_dbs_info_s *this_dbs_info;
 684         unsigned int j;
 685         int rc;
 686
 687         this_dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
 688
 689         switch (event) {
 690         case CPUFREQ_GOV_START:
 691                 if ((!cpu_online(cpu)) || (!policy->cur))
 692                         return -EINVAL;
 693
 694                 mutex_lock(&dbs_mutex);
 695
 696                 dbs_enable++;
 697                 for_each_cpu(j, policy->cpus) {
 698                         struct cpu_dbs_info_s *j_dbs_info;
 699                         j_dbs_info = &per_cpu(od_cpu_dbs_info, j);
 700                         j_dbs_info->cur_policy = policy;
 701
 702                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 703                                                 &j_dbs_info->prev_cpu_wall);
 704                         if (dbs_tuners_ins.ignore_nice)
 705                                 j_dbs_info->prev_cpu_nice =
 706                                                 kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 707                 }
 708                 this_dbs_info->cpu = cpu;
 709                 this_dbs_info->rate_mult = 1;
 710                 ondemand_powersave_bias_init_cpu(cpu);
 711                 /*
 712                  * Start the timerschedule work, when this governor
 713                  * is used for first time
 714                  */
 715                 if (dbs_enable == 1) {
 716                         unsigned int latency;
 717
 718                         rc = sysfs_create_group(cpufreq_global_kobject,
 719                                                 &dbs_attr_group);
 720                         if (rc) {
 721                                 mutex_unlock(&dbs_mutex);
 722                                 return rc;
 723                         }
 724
 725                         /* policy latency is in nS. Convert it to uS first */
 726                         latency = policy->cpuinfo.transition_latency / 1000;
 727                         if (latency == 0)
 728                                 latency = 1;
 729                         /* Bring kernel and HW constraints together */
 730                         min_sampling_rate = max(min_sampling_rate,
 731                                         MIN_LATENCY_MULTIPLIER * latency);
 732                         dbs_tuners_ins.sampling_rate =
 733                                 max(min_sampling_rate,
 734                                     latency * LATENCY_MULTIPLIER);
 735                         dbs_tuners_ins.io_is_busy = should_io_be_busy();
 736                 }
 737                 mutex_unlock(&dbs_mutex);
 738
 739                 mutex_init(&this_dbs_info->timer_mutex);
 740                 dbs_timer_init(this_dbs_info);
 741                 break;
 742
 743         case CPUFREQ_GOV_STOP:
 744                 dbs_timer_exit(this_dbs_info);
 745
 746                 mutex_lock(&dbs_mutex);
 747                 mutex_destroy(&this_dbs_info->timer_mutex);
 748                 dbs_enable--;
 749                 mutex_unlock(&dbs_mutex);
 750                 if (!dbs_enable)
 751                         sysfs_remove_group(cpufreq_global_kobject,
 752                                            &dbs_attr_group);
 753
 754                 break;
 755
 756         case CPUFREQ_GOV_LIMITS:
 757                 mutex_lock(&this_dbs_info->timer_mutex);
 758                 if (policy->max < this_dbs_info->cur_policy->cur)
 759                         __cpufreq_driver_target(this_dbs_info->cur_policy,
 760                                 policy->max, CPUFREQ_RELATION_H);
 761                 else if (policy->min > this_dbs_info->cur_policy->cur)
 762                         __cpufreq_driver_target(this_dbs_info->cur_policy,
 763                                 policy->min, CPUFREQ_RELATION_L);
 764                 mutex_unlock(&this_dbs_info->timer_mutex);
 765                 break;
 766         }
 767         return 0;
 768 }
 769
 770 static int __init cpufreq_gov_dbs_init(void)
 771 {
 772         u64 idle_time;
 773         int cpu = get_cpu();
 774
 775         idle_time = get_cpu_idle_time_us(cpu, NULL);
 776         put_cpu();
 777         if (idle_time != -1ULL) {
 778                 /* Idle micro accounting is supported. Use finer thresholds */
 779                 dbs_tuners_ins.up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
 780                 dbs_tuners_ins.down_differential =
 781                                         MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
 782                 /*
 783                  * In nohz/micro accounting case we set the minimum frequency
 784                  * not depending on HZ, but fixed (very low). The deferred
 785                  * timer might skip some samples if idle/sleeping as needed.
 786                 */
 787                 min_sampling_rate = MICRO_FREQUENCY_MIN_SAMPLE_RATE;
 788         } else {
 789                 /* For correct statistics, we need 10 ticks for each measure */
 790                 min_sampling_rate =
 791                         MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
 792         }
 793
 794         return cpufreq_register_governor(&cpufreq_gov_ondemand);
 795 }
 796
 797 static void __exit cpufreq_gov_dbs_exit(void)
 798 {
 799         cpufreq_unregister_governor(&cpufreq_gov_ondemand);
 800 }
 801
 802
 803 MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 804 MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
 805 MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 806         "Low Latency Frequency Transition capable processors");
 807 MODULE_LICENSE("GPL");
 808
 809 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 810 fs_initcall(cpufreq_gov_dbs_init);
 811 #else
 812 module_init(cpufreq_gov_dbs_init);
 813 #endif
 814 module_exit(cpufreq_gov_dbs_exit);