Pileus Git - ~andy/linux/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 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 static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
 261                                    const char *buf, size_t count)
 262 {
 263         unsigned int input;
 264         int ret;
 265         ret = sscanf(buf, "%u", &input);
 266         if (ret != 1)
 267                 return -EINVAL;
 268         dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);
 269         return count;
 270 }
 271
 272 static ssize_t store_io_is_busy(struct kobject *a, struct attribute *b,
 273                                    const char *buf, size_t count)
 274 {
 275         unsigned int input;
 276         int ret;
 277
 278         ret = sscanf(buf, "%u", &input);
 279         if (ret != 1)
 280                 return -EINVAL;
 281         dbs_tuners_ins.io_is_busy = !!input;
 282         return count;
 283 }
 284
 285 static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
 286                                   const char *buf, size_t count)
 287 {
 288         unsigned int input;
 289         int ret;
 290         ret = sscanf(buf, "%u", &input);
 291
 292         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 293                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 294                 return -EINVAL;
 295         }
 296         dbs_tuners_ins.up_threshold = input;
 297         return count;
 298 }
 299
 300 static ssize_t store_sampling_down_factor(struct kobject *a,
 301                         struct attribute *b, const char *buf, size_t count)
 302 {
 303         unsigned int input, j;
 304         int ret;
 305         ret = sscanf(buf, "%u", &input);
 306
 307         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 308                 return -EINVAL;
 309         dbs_tuners_ins.sampling_down_factor = input;
 310
 311         /* Reset down sampling multiplier in case it was active */
 312         for_each_online_cpu(j) {
 313                 struct cpu_dbs_info_s *dbs_info;
 314                 dbs_info = &per_cpu(od_cpu_dbs_info, j);
 315                 dbs_info->rate_mult = 1;
 316         }
 317         return count;
 318 }
 319
 320 static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
 321                                       const char *buf, size_t count)
 322 {
 323         unsigned int input;
 324         int ret;
 325
 326         unsigned int j;
 327
 328         ret = sscanf(buf, "%u", &input);
 329         if (ret != 1)
 330                 return -EINVAL;
 331
 332         if (input > 1)
 333                 input = 1;
 334
 335         if (input == dbs_tuners_ins.ignore_nice) { /* nothing to do */
 336                 return count;
 337         }
 338         dbs_tuners_ins.ignore_nice = input;
 339
 340         /* we need to re-evaluate prev_cpu_idle */
 341         for_each_online_cpu(j) {
 342                 struct cpu_dbs_info_s *dbs_info;
 343                 dbs_info = &per_cpu(od_cpu_dbs_info, j);
 344                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 345                                                 &dbs_info->prev_cpu_wall);
 346                 if (dbs_tuners_ins.ignore_nice)
 347                         dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 348
 349         }
 350         return count;
 351 }
 352
 353 static ssize_t store_powersave_bias(struct kobject *a, struct attribute *b,
 354                                     const char *buf, size_t count)
 355 {
 356         unsigned int input;
 357         int ret;
 358         ret = sscanf(buf, "%u", &input);
 359
 360         if (ret != 1)
 361                 return -EINVAL;
 362
 363         if (input > 1000)
 364                 input = 1000;
 365
 366         dbs_tuners_ins.powersave_bias = input;
 367         ondemand_powersave_bias_init();
 368         return count;
 369 }
 370
 371 define_one_global_rw(sampling_rate);
 372 define_one_global_rw(io_is_busy);
 373 define_one_global_rw(up_threshold);
 374 define_one_global_rw(sampling_down_factor);
 375 define_one_global_rw(ignore_nice_load);
 376 define_one_global_rw(powersave_bias);
 377
 378 static struct attribute *dbs_attributes[] = {
 379         &sampling_rate_min.attr,
 380         &sampling_rate.attr,
 381         &up_threshold.attr,
 382         &sampling_down_factor.attr,
 383         &ignore_nice_load.attr,
 384         &powersave_bias.attr,
 385         &io_is_busy.attr,
 386         NULL
 387 };
 388
 389 static struct attribute_group dbs_attr_group = {
 390         .attrs = dbs_attributes,
 391         .name = "ondemand",
 392 };
 393
 394 /************************** sysfs end ************************/
 395
 396 static void dbs_freq_increase(struct cpufreq_policy *p, unsigned int freq)
 397 {
 398         if (dbs_tuners_ins.powersave_bias)
 399                 freq = powersave_bias_target(p, freq, CPUFREQ_RELATION_H);
 400         else if (p->cur == p->max)
 401                 return;
 402
 403         __cpufreq_driver_target(p, freq, dbs_tuners_ins.powersave_bias ?
 404                         CPUFREQ_RELATION_L : CPUFREQ_RELATION_H);
 405 }
 406
 407 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 408 {
 409         unsigned int max_load_freq;
 410
 411         struct cpufreq_policy *policy;
 412         unsigned int j;
 413
 414         this_dbs_info->freq_lo = 0;
 415         policy = this_dbs_info->cur_policy;
 416
 417         /*
 418          * Every sampling_rate, we check, if current idle time is less
 419          * than 20% (default), then we try to increase frequency
 420          * Every sampling_rate, we look for a the lowest
 421          * frequency which can sustain the load while keeping idle time over
 422          * 30%. If such a frequency exist, we try to decrease to this frequency.
 423          *
 424          * Any frequency increase takes it to the maximum frequency.
 425          * Frequency reduction happens at minimum steps of
 426          * 5% (default) of current frequency
 427          */
 428
 429         /* Get Absolute Load - in terms of freq */
 430         max_load_freq = 0;
 431
 432         for_each_cpu(j, policy->cpus) {
 433                 struct cpu_dbs_info_s *j_dbs_info;
 434                 cputime64_t cur_wall_time, cur_idle_time, cur_iowait_time;
 435                 unsigned int idle_time, wall_time, iowait_time;
 436                 unsigned int load, load_freq;
 437                 int freq_avg;
 438
 439                 j_dbs_info = &per_cpu(od_cpu_dbs_info, j);
 440
 441                 cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
 442                 cur_iowait_time = get_cpu_iowait_time(j, &cur_wall_time);
 443
 444                 wall_time = (unsigned int)
 445                         (cur_wall_time - j_dbs_info->prev_cpu_wall);
 446                 j_dbs_info->prev_cpu_wall = cur_wall_time;
 447
 448                 idle_time = (unsigned int)
 449                         (cur_idle_time - j_dbs_info->prev_cpu_idle);
 450                 j_dbs_info->prev_cpu_idle = cur_idle_time;
 451
 452                 iowait_time = (unsigned int)
 453                         (cur_iowait_time - j_dbs_info->prev_cpu_iowait);
 454                 j_dbs_info->prev_cpu_iowait = cur_iowait_time;
 455
 456                 if (dbs_tuners_ins.ignore_nice) {
 457                         u64 cur_nice;
 458                         unsigned long cur_nice_jiffies;
 459
 460                         cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE] -
 461                                          j_dbs_info->prev_cpu_nice;
 462                         /*
 463                          * Assumption: nice time between sampling periods will
 464                          * be less than 2^32 jiffies for 32 bit sys
 465                          */
 466                         cur_nice_jiffies = (unsigned long)
 467                                         cputime64_to_jiffies64(cur_nice);
 468
 469                         j_dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 470                         idle_time += jiffies_to_usecs(cur_nice_jiffies);
 471                 }
 472
 473                 /*
 474                  * For the purpose of ondemand, waiting for disk IO is an
 475                  * indication that you're performance critical, and not that
 476                  * the system is actually idle. So subtract the iowait time
 477                  * from the cpu idle time.
 478                  */
 479
 480                 if (dbs_tuners_ins.io_is_busy && idle_time >= iowait_time)
 481                         idle_time -= iowait_time;
 482
 483                 if (unlikely(!wall_time || wall_time < idle_time))
 484                         continue;
 485
 486                 load = 100 * (wall_time - idle_time) / wall_time;
 487
 488                 freq_avg = __cpufreq_driver_getavg(policy, j);
 489                 if (freq_avg <= 0)
 490                         freq_avg = policy->cur;
 491
 492                 load_freq = load * freq_avg;
 493                 if (load_freq > max_load_freq)
 494                         max_load_freq = load_freq;
 495         }
 496
 497         /* Check for frequency increase */
 498         if (max_load_freq > dbs_tuners_ins.up_threshold * policy->cur) {
 499                 /* If switching to max speed, apply sampling_down_factor */
 500                 if (policy->cur < policy->max)
 501                         this_dbs_info->rate_mult =
 502                                 dbs_tuners_ins.sampling_down_factor;
 503                 dbs_freq_increase(policy, policy->max);
 504                 return;
 505         }
 506
 507         /* Check for frequency decrease */
 508         /* if we cannot reduce the frequency anymore, break out early */
 509         if (policy->cur == policy->min)
 510                 return;
 511
 512         /*
 513          * The optimal frequency is the frequency that is the lowest that
 514          * can support the current CPU usage without triggering the up
 515          * policy. To be safe, we focus 10 points under the threshold.
 516          */
 517         if (max_load_freq <
 518             (dbs_tuners_ins.up_threshold - dbs_tuners_ins.down_differential) *
 519              policy->cur) {
 520                 unsigned int freq_next;
 521                 freq_next = max_load_freq /
 522                                 (dbs_tuners_ins.up_threshold -
 523                                  dbs_tuners_ins.down_differential);
 524
 525                 /* No longer fully busy, reset rate_mult */
 526                 this_dbs_info->rate_mult = 1;
 527
 528                 if (freq_next < policy->min)
 529                         freq_next = policy->min;
 530
 531                 if (!dbs_tuners_ins.powersave_bias) {
 532                         __cpufreq_driver_target(policy, freq_next,
 533                                         CPUFREQ_RELATION_L);
 534                 } else {
 535                         int freq = powersave_bias_target(policy, freq_next,
 536                                         CPUFREQ_RELATION_L);
 537                         __cpufreq_driver_target(policy, freq,
 538                                 CPUFREQ_RELATION_L);
 539                 }
 540         }
 541 }
 542
 543 static void do_dbs_timer(struct work_struct *work)
 544 {
 545         struct cpu_dbs_info_s *dbs_info =
 546                 container_of(work, struct cpu_dbs_info_s, work.work);
 547         unsigned int cpu = dbs_info->cpu;
 548         int sample_type = dbs_info->sample_type;
 549
 550         int delay;
 551
 552         mutex_lock(&dbs_info->timer_mutex);
 553
 554         /* Common NORMAL_SAMPLE setup */
 555         dbs_info->sample_type = DBS_NORMAL_SAMPLE;
 556         if (!dbs_tuners_ins.powersave_bias ||
 557             sample_type == DBS_NORMAL_SAMPLE) {
 558                 dbs_check_cpu(dbs_info);
 559                 if (dbs_info->freq_lo) {
 560                         /* Setup timer for SUB_SAMPLE */
 561                         dbs_info->sample_type = DBS_SUB_SAMPLE;
 562                         delay = dbs_info->freq_hi_jiffies;
 563                 } else {
 564                         /* We want all CPUs to do sampling nearly on
 565                          * same jiffy
 566                          */
 567                         delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate
 568                                 * dbs_info->rate_mult);
 569
 570                         if (num_online_cpus() > 1)
 571                                 delay -= jiffies % delay;
 572                 }
 573         } else {
 574                 __cpufreq_driver_target(dbs_info->cur_policy,
 575                         dbs_info->freq_lo, CPUFREQ_RELATION_H);
 576                 delay = dbs_info->freq_lo_jiffies;
 577         }
 578         schedule_delayed_work_on(cpu, &dbs_info->work, delay);
 579         mutex_unlock(&dbs_info->timer_mutex);
 580 }
 581
 582 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 583 {
 584         /* We want all CPUs to do sampling nearly on same jiffy */
 585         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 586
 587         if (num_online_cpus() > 1)
 588                 delay -= jiffies % delay;
 589
 590         dbs_info->sample_type = DBS_NORMAL_SAMPLE;
 591         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
 592         schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work, delay);
 593 }
 594
 595 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 596 {
 597         cancel_delayed_work_sync(&dbs_info->work);
 598 }
 599
 600 /*
 601  * Not all CPUs want IO time to be accounted as busy; this dependson how
 602  * efficient idling at a higher frequency/voltage is.
 603  * Pavel Machek says this is not so for various generations of AMD and old
 604  * Intel systems.
 605  * Mike Chan (androidlcom) calis this is also not true for ARM.
 606  * Because of this, whitelist specific known (series) of CPUs by default, and
 607  * leave all others up to the user.
 608  */
 609 static int should_io_be_busy(void)
 610 {
 611 #if defined(CONFIG_X86)
 612         /*
 613          * For Intel, Core 2 (model 15) andl later have an efficient idle.
 614          */
 615         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
 616             boot_cpu_data.x86 == 6 &&
 617             boot_cpu_data.x86_model >= 15)
 618                 return 1;
 619 #endif
 620         return 0;
 621 }
 622
 623 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 624                                    unsigned int event)
 625 {
 626         unsigned int cpu = policy->cpu;
 627         struct cpu_dbs_info_s *this_dbs_info;
 628         unsigned int j;
 629         int rc;
 630
 631         this_dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
 632
 633         switch (event) {
 634         case CPUFREQ_GOV_START:
 635                 if ((!cpu_online(cpu)) || (!policy->cur))
 636                         return -EINVAL;
 637
 638                 mutex_lock(&dbs_mutex);
 639
 640                 dbs_enable++;
 641                 for_each_cpu(j, policy->cpus) {
 642                         struct cpu_dbs_info_s *j_dbs_info;
 643                         j_dbs_info = &per_cpu(od_cpu_dbs_info, j);
 644                         j_dbs_info->cur_policy = policy;
 645
 646                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
 647                                                 &j_dbs_info->prev_cpu_wall);
 648                         if (dbs_tuners_ins.ignore_nice)
 649                                 j_dbs_info->prev_cpu_nice =
 650                                                 kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 651                 }
 652                 this_dbs_info->cpu = cpu;
 653                 this_dbs_info->rate_mult = 1;
 654                 ondemand_powersave_bias_init_cpu(cpu);
 655                 /*
 656                  * Start the timerschedule work, when this governor
 657                  * is used for first time
 658                  */
 659                 if (dbs_enable == 1) {
 660                         unsigned int latency;
 661
 662                         rc = sysfs_create_group(cpufreq_global_kobject,
 663                                                 &dbs_attr_group);
 664                         if (rc) {
 665                                 mutex_unlock(&dbs_mutex);
 666                                 return rc;
 667                         }
 668
 669                         /* policy latency is in nS. Convert it to uS first */
 670                         latency = policy->cpuinfo.transition_latency / 1000;
 671                         if (latency == 0)
 672                                 latency = 1;
 673                         /* Bring kernel and HW constraints together */
 674                         min_sampling_rate = max(min_sampling_rate,
 675                                         MIN_LATENCY_MULTIPLIER * latency);
 676                         dbs_tuners_ins.sampling_rate =
 677                                 max(min_sampling_rate,
 678                                     latency * LATENCY_MULTIPLIER);
 679                         dbs_tuners_ins.io_is_busy = should_io_be_busy();
 680                 }
 681                 mutex_unlock(&dbs_mutex);
 682
 683                 mutex_init(&this_dbs_info->timer_mutex);
 684                 dbs_timer_init(this_dbs_info);
 685                 break;
 686
 687         case CPUFREQ_GOV_STOP:
 688                 dbs_timer_exit(this_dbs_info);
 689
 690                 mutex_lock(&dbs_mutex);
 691                 mutex_destroy(&this_dbs_info->timer_mutex);
 692                 dbs_enable--;
 693                 mutex_unlock(&dbs_mutex);
 694                 if (!dbs_enable)
 695                         sysfs_remove_group(cpufreq_global_kobject,
 696                                            &dbs_attr_group);
 697
 698                 break;
 699
 700         case CPUFREQ_GOV_LIMITS:
 701                 mutex_lock(&this_dbs_info->timer_mutex);
 702                 if (policy->max < this_dbs_info->cur_policy->cur)
 703                         __cpufreq_driver_target(this_dbs_info->cur_policy,
 704                                 policy->max, CPUFREQ_RELATION_H);
 705                 else if (policy->min > this_dbs_info->cur_policy->cur)
 706                         __cpufreq_driver_target(this_dbs_info->cur_policy,
 707                                 policy->min, CPUFREQ_RELATION_L);
 708                 mutex_unlock(&this_dbs_info->timer_mutex);
 709                 break;
 710         }
 711         return 0;
 712 }
 713
 714 static int __init cpufreq_gov_dbs_init(void)
 715 {
 716         u64 idle_time;
 717         int cpu = get_cpu();
 718
 719         idle_time = get_cpu_idle_time_us(cpu, NULL);
 720         put_cpu();
 721         if (idle_time != -1ULL) {
 722                 /* Idle micro accounting is supported. Use finer thresholds */
 723                 dbs_tuners_ins.up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
 724                 dbs_tuners_ins.down_differential =
 725                                         MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
 726                 /*
 727                  * In nohz/micro accounting case we set the minimum frequency
 728                  * not depending on HZ, but fixed (very low). The deferred
 729                  * timer might skip some samples if idle/sleeping as needed.
 730                 */
 731                 min_sampling_rate = MICRO_FREQUENCY_MIN_SAMPLE_RATE;
 732         } else {
 733                 /* For correct statistics, we need 10 ticks for each measure */
 734                 min_sampling_rate =
 735                         MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
 736         }
 737
 738         return cpufreq_register_governor(&cpufreq_gov_ondemand);
 739 }
 740
 741 static void __exit cpufreq_gov_dbs_exit(void)
 742 {
 743         cpufreq_unregister_governor(&cpufreq_gov_ondemand);
 744 }
 745
 746
 747 MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 748 MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
 749 MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 750         "Low Latency Frequency Transition capable processors");
 751 MODULE_LICENSE("GPL");
 752
 753 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 754 fs_initcall(cpufreq_gov_dbs_init);
 755 #else
 756 module_init(cpufreq_gov_dbs_init);
 757 #endif
 758 module_exit(cpufreq_gov_dbs_exit);