linux/drivers/cpufreq/cpufreq_ondemand.c
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   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
  53static 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
  59static void do_dbs_timer(struct work_struct *work);
  60static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
  61                                unsigned int event);
  62
  63#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
  64static
  65#endif
  66struct 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 */
  74enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE};
  75
  76struct 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};
  97static DEFINE_PER_CPU(struct cpu_dbs_info_s, od_cpu_dbs_info);
  98
  99static unsigned int dbs_enable; /* number of CPUs using this policy */
 100
 101/*
 102 * dbs_mutex protects dbs_enable in governor start/stop.
 103 */
 104static DEFINE_MUTEX(dbs_mutex);
 105
 106static 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
 122static 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
 144static 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
 156static 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 */
 171static 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
 221static 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
 228static 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
 238static 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
 244define_one_global_ro(sampling_rate_min);
 245
 246/* cpufreq_ondemand Governor Tunables */
 247#define show_one(file_name, object)                                     \
 248static 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}
 253show_one(sampling_rate, sampling_rate);
 254show_one(io_is_busy, io_is_busy);
 255show_one(up_threshold, up_threshold);
 256show_one(sampling_down_factor, sampling_down_factor);
 257show_one(ignore_nice_load, ignore_nice);
 258show_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 */
 273static 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
 316static 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
 328static 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
 341static 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
 356static 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
 376static 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
 409static 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
 427define_one_global_rw(sampling_rate);
 428define_one_global_rw(io_is_busy);
 429define_one_global_rw(up_threshold);
 430define_one_global_rw(sampling_down_factor);
 431define_one_global_rw(ignore_nice_load);
 432define_one_global_rw(powersave_bias);
 433
 434static 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
 445static struct attribute_group dbs_attr_group = {
 446        .attrs = dbs_attributes,
 447        .name = "ondemand",
 448};
 449
 450/************************** sysfs end ************************/
 451
 452static 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
 463static 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
 599static 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
 638static 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
 651static 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 */
 665static 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
 679static 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
 770static 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
 797static void __exit cpufreq_gov_dbs_exit(void)
 798{
 799        cpufreq_unregister_governor(&cpufreq_gov_ondemand);
 800}
 801
 802
 803MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 804MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
 805MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 806        "Low Latency Frequency Transition capable processors");
 807MODULE_LICENSE("GPL");
 808
 809#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
 810fs_initcall(cpufreq_gov_dbs_init);
 811#else
 812module_init(cpufreq_gov_dbs_init);
 813#endif
 814module_exit(cpufreq_gov_dbs_exit);
 815
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