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/smp.h>
  16 #include <linux/init.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/ctype.h>
  19 #include <linux/cpufreq.h>
  20 #include <linux/sysctl.h>
  21 #include <linux/types.h>
  22 #include <linux/fs.h>
  23 #include <linux/sysfs.h>
  24 #include <linux/sched.h>
  25 #include <linux/kmod.h>
  26 #include <linux/workqueue.h>
  27 #include <linux/jiffies.h>
  28 #include <linux/kernel_stat.h>
  29 #include <linux/percpu.h>
  30
  31 /*
  32  * dbs is used in this file as a shortform for demandbased switching
  33  * It helps to keep variable names smaller, simpler
  34  */
  35
  36 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
  37 #define MIN_FREQUENCY_UP_THRESHOLD              (0)
  38 #define MAX_FREQUENCY_UP_THRESHOLD              (100)
  39
  40 #define DEF_FREQUENCY_DOWN_THRESHOLD            (20)
  41 #define MIN_FREQUENCY_DOWN_THRESHOLD            (0)
  42 #define MAX_FREQUENCY_DOWN_THRESHOLD            (100)
  43
  44 /*
  45  * The polling frequency of this governor depends on the capability of
  46  * the processor. Default polling frequency is 1000 times the transition
  47  * latency of the processor. The governor will work on any processor with
  48  * transition latency <= 10mS, using appropriate sampling
  49  * rate.
  50  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
  51  * this governor will not work.
  52  * All times here are in uS.
  53  */
  54 static unsigned int                             def_sampling_rate;
  55 #define MIN_SAMPLING_RATE                       (def_sampling_rate / 2)
  56 #define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
  57 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (1000)
  58 #define DEF_SAMPLING_DOWN_FACTOR                (10)
  59 #define TRANSITION_LATENCY_LIMIT                (10 * 1000)
  60
  61 static void do_dbs_timer(void *data);
  62
  63 struct cpu_dbs_info_s {
  64         struct cpufreq_policy   *cur_policy;
  65         unsigned int            prev_cpu_idle_up;
  66         unsigned int            prev_cpu_idle_down;
  67         unsigned int            enable;
  68 };
  69 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
  70
  71 static unsigned int dbs_enable; /* number of CPUs using this policy */
  72
  73 static DECLARE_MUTEX    (dbs_sem);
  74 static DECLARE_WORK     (dbs_work, do_dbs_timer, NULL);
  75
  76 struct dbs_tuners {
  77         unsigned int            sampling_rate;
  78         unsigned int            sampling_down_factor;
  79         unsigned int            up_threshold;
  80         unsigned int            down_threshold;
  81         unsigned int            ignore_nice;
  82         unsigned int            freq_step;
  83 };
  84
  85 static struct dbs_tuners dbs_tuners_ins = {
  86         .up_threshold           = DEF_FREQUENCY_UP_THRESHOLD,
  87         .down_threshold         = DEF_FREQUENCY_DOWN_THRESHOLD,
  88         .sampling_down_factor   = DEF_SAMPLING_DOWN_FACTOR,
  89 };
  90
  91 static inline unsigned int get_cpu_idle_time(unsigned int cpu)
  92 {
  93         return  kstat_cpu(cpu).cpustat.idle +
  94                 kstat_cpu(cpu).cpustat.iowait +
  95                 ( !dbs_tuners_ins.ignore_nice ?
  96                   kstat_cpu(cpu).cpustat.nice :
  97                   0);
  98 }
  99
 100 /************************** sysfs interface ************************/
 101 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 102 {
 103         return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
 104 }
 105
 106 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 107 {
 108         return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 109 }
 110
 111 #define define_one_ro(_name)                                    \
 112 static struct freq_attr _name =                                 \
 113 __ATTR(_name, 0444, show_##_name, NULL)
 114
 115 define_one_ro(sampling_rate_max);
 116 define_one_ro(sampling_rate_min);
 117
 118 /* cpufreq_ondemand Governor Tunables */
 119 #define show_one(file_name, object)                                     \
 120 static ssize_t show_##file_name                                         \
 121 (struct cpufreq_policy *unused, char *buf)                              \
 122 {                                                                       \
 123         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 124 }
 125 show_one(sampling_rate, sampling_rate);
 126 show_one(sampling_down_factor, sampling_down_factor);
 127 show_one(up_threshold, up_threshold);
 128 show_one(down_threshold, down_threshold);
 129 show_one(ignore_nice, ignore_nice);
 130 show_one(freq_step, freq_step);
 131
 132 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
 133                 const char *buf, size_t count)
 134 {
 135         unsigned int input;
 136         int ret;
 137         ret = sscanf (buf, "%u", &input);
 138         if (ret != 1 )
 139                 return -EINVAL;
 140
 141         down(&dbs_sem);
 142         dbs_tuners_ins.sampling_down_factor = input;
 143         up(&dbs_sem);
 144
 145         return count;
 146 }
 147
 148 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 149                 const char *buf, size_t count)
 150 {
 151         unsigned int input;
 152         int ret;
 153         ret = sscanf (buf, "%u", &input);
 154
 155         down(&dbs_sem);
 156         if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
 157                 up(&dbs_sem);
 158                 return -EINVAL;
 159         }
 160
 161         dbs_tuners_ins.sampling_rate = input;
 162         up(&dbs_sem);
 163
 164         return count;
 165 }
 166
 167 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 168                 const char *buf, size_t count)
 169 {
 170         unsigned int input;
 171         int ret;
 172         ret = sscanf (buf, "%u", &input);
 173
 174         down(&dbs_sem);
 175         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 176                         input < MIN_FREQUENCY_UP_THRESHOLD ||
 177                         input <= dbs_tuners_ins.down_threshold) {
 178                 up(&dbs_sem);
 179                 return -EINVAL;
 180         }
 181
 182         dbs_tuners_ins.up_threshold = input;
 183         up(&dbs_sem);
 184
 185         return count;
 186 }
 187
 188 static ssize_t store_down_threshold(struct cpufreq_policy *unused,
 189                 const char *buf, size_t count)
 190 {
 191         unsigned int input;
 192         int ret;
 193         ret = sscanf (buf, "%u", &input);
 194
 195         down(&dbs_sem);
 196         if (ret != 1 || input > MAX_FREQUENCY_DOWN_THRESHOLD ||
 197                         input < MIN_FREQUENCY_DOWN_THRESHOLD ||
 198                         input >= dbs_tuners_ins.up_threshold) {
 199                 up(&dbs_sem);
 200                 return -EINVAL;
 201         }
 202
 203         dbs_tuners_ins.down_threshold = input;
 204         up(&dbs_sem);
 205
 206         return count;
 207 }
 208
 209 static ssize_t store_ignore_nice(struct cpufreq_policy *policy,
 210                 const char *buf, size_t count)
 211 {
 212         unsigned int input;
 213         int ret;
 214
 215         unsigned int j;
 216
 217         ret = sscanf (buf, "%u", &input);
 218         if ( ret != 1 )
 219                 return -EINVAL;
 220
 221         if ( input > 1 )
 222                 input = 1;
 223
 224         down(&dbs_sem);
 225         if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
 226                 up(&dbs_sem);
 227                 return count;
 228         }
 229         dbs_tuners_ins.ignore_nice = input;
 230
 231         /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
 232         for_each_online_cpu(j) {
 233                 struct cpu_dbs_info_s *j_dbs_info;
 234                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 235                 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 236                 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
 237         }
 238         up(&dbs_sem);
 239
 240         return count;
 241 }
 242
 243 static ssize_t store_freq_step(struct cpufreq_policy *policy,
 244                 const char *buf, size_t count)
 245 {
 246         unsigned int input;
 247         int ret;
 248
 249         ret = sscanf (buf, "%u", &input);
 250
 251         if ( ret != 1 )
 252                 return -EINVAL;
 253
 254         if ( input > 100 )
 255                 input = 100;
 256
 257         /* no need to test here if freq_step is zero as the user might actually
 258          * want this, they would be crazy though :) */
 259         down(&dbs_sem);
 260         dbs_tuners_ins.freq_step = input;
 261         up(&dbs_sem);
 262
 263         return count;
 264 }
 265
 266 #define define_one_rw(_name) \
 267 static struct freq_attr _name = \
 268 __ATTR(_name, 0644, show_##_name, store_##_name)
 269
 270 define_one_rw(sampling_rate);
 271 define_one_rw(sampling_down_factor);
 272 define_one_rw(up_threshold);
 273 define_one_rw(down_threshold);
 274 define_one_rw(ignore_nice);
 275 define_one_rw(freq_step);
 276
 277 static struct attribute * dbs_attributes[] = {
 278         &sampling_rate_max.attr,
 279         &sampling_rate_min.attr,
 280         &sampling_rate.attr,
 281         &sampling_down_factor.attr,
 282         &up_threshold.attr,
 283         &down_threshold.attr,
 284         &ignore_nice.attr,
 285         &freq_step.attr,
 286         NULL
 287 };
 288
 289 static struct attribute_group dbs_attr_group = {
 290         .attrs = dbs_attributes,
 291         .name = "ondemand",
 292 };
 293
 294 /************************** sysfs end ************************/
 295
 296 static void dbs_check_cpu(int cpu)
 297 {
 298         unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;
 299         unsigned int total_idle_ticks;
 300         unsigned int freq_down_step;
 301         unsigned int freq_down_sampling_rate;
 302         static int down_skip[NR_CPUS];
 303         struct cpu_dbs_info_s *this_dbs_info;
 304
 305         struct cpufreq_policy *policy;
 306         unsigned int j;
 307
 308         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 309         if (!this_dbs_info->enable)
 310                 return;
 311
 312         policy = this_dbs_info->cur_policy;
 313         /*
 314          * The default safe range is 20% to 80%
 315          * Every sampling_rate, we check
 316          *      - If current idle time is less than 20%, then we try to
 317          *        increase frequency
 318          * Every sampling_rate*sampling_down_factor, we check
 319          *      - If current idle time is more than 80%, then we try to
 320          *        decrease frequency
 321          *
 322          * Any frequency increase takes it to the maximum frequency.
 323          * Frequency reduction happens at minimum steps of
 324          * 5% (default) of max_frequency
 325          */
 326
 327         /* Check for frequency increase */
 328         total_idle_ticks = get_cpu_idle_time(cpu);
 329         idle_ticks = total_idle_ticks -
 330                 this_dbs_info->prev_cpu_idle_up;
 331         this_dbs_info->prev_cpu_idle_up = total_idle_ticks;
 332
 333         for_each_cpu_mask(j, policy->cpus) {
 334                 unsigned int tmp_idle_ticks;
 335                 struct cpu_dbs_info_s *j_dbs_info;
 336
 337                 if (j == cpu)
 338                         continue;
 339
 340                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 341                 /* Check for frequency increase */
 342                 total_idle_ticks = get_cpu_idle_time(j);
 343                 tmp_idle_ticks = total_idle_ticks -
 344                         j_dbs_info->prev_cpu_idle_up;
 345                 j_dbs_info->prev_cpu_idle_up = total_idle_ticks;
 346
 347                 if (tmp_idle_ticks < idle_ticks)
 348                         idle_ticks = tmp_idle_ticks;
 349         }
 350
 351         /* Scale idle ticks by 100 and compare with up and down ticks */
 352         idle_ticks *= 100;
 353         up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
 354                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 355
 356         if (idle_ticks < up_idle_ticks) {
 357                 down_skip[cpu] = 0;
 358                 this_dbs_info->prev_cpu_idle_down = total_idle_ticks;
 359                 /* if we are already at full speed then break out early */
 360                 if (policy->cur == policy->max)
 361                         return;
 362
 363                 __cpufreq_driver_target(policy, policy->max,
 364                         CPUFREQ_RELATION_H);
 365                 return;
 366         }
 367
 368         /* Check for frequency decrease */
 369         down_skip[cpu]++;
 370         if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
 371                 return;
 372
 373         total_idle_ticks = this_dbs_info->prev_cpu_idle_up;
 374         idle_ticks = total_idle_ticks -
 375                 this_dbs_info->prev_cpu_idle_down;
 376         this_dbs_info->prev_cpu_idle_down = total_idle_ticks;
 377
 378         for_each_cpu_mask(j, policy->cpus) {
 379                 unsigned int tmp_idle_ticks;
 380                 struct cpu_dbs_info_s *j_dbs_info;
 381
 382                 if (j == cpu)
 383                         continue;
 384
 385                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 386                 /* Check for frequency decrease */
 387                 total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
 388                 tmp_idle_ticks = total_idle_ticks -
 389                         j_dbs_info->prev_cpu_idle_down;
 390                 j_dbs_info->prev_cpu_idle_down = total_idle_ticks;
 391
 392                 if (tmp_idle_ticks < idle_ticks)
 393                         idle_ticks = tmp_idle_ticks;
 394         }
 395
 396         /* Scale idle ticks by 100 and compare with up and down ticks */
 397         idle_ticks *= 100;
 398         down_skip[cpu] = 0;
 399
 400         freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
 401                 dbs_tuners_ins.sampling_down_factor;
 402         down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) *
 403                 usecs_to_jiffies(freq_down_sampling_rate);
 404
 405         if (idle_ticks > down_idle_ticks ) {
 406                 /* if we are already at the lowest speed then break out early
 407                  * or if we 'cannot' reduce the speed as the user might want
 408                  * freq_step to be zero */
 409                 if (policy->cur == policy->min || dbs_tuners_ins.freq_step == 0)
 410                         return;
 411
 412                 freq_down_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
 413
 414                 /* max freq cannot be less than 100. But who knows.... */
 415                 if (unlikely(freq_down_step == 0))
 416                         freq_down_step = 5;
 417
 418                 __cpufreq_driver_target(policy,
 419                         policy->cur - freq_down_step,
 420                         CPUFREQ_RELATION_H);
 421                 return;
 422         }
 423 }
 424
 425 static void do_dbs_timer(void *data)
 426 {
 427         int i;
 428         down(&dbs_sem);
 429         for_each_online_cpu(i)
 430                 dbs_check_cpu(i);
 431         schedule_delayed_work(&dbs_work,
 432                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 433         up(&dbs_sem);
 434 }
 435
 436 static inline void dbs_timer_init(void)
 437 {
 438         INIT_WORK(&dbs_work, do_dbs_timer, NULL);
 439         schedule_delayed_work(&dbs_work,
 440                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 441         return;
 442 }
 443
 444 static inline void dbs_timer_exit(void)
 445 {
 446         cancel_delayed_work(&dbs_work);
 447         return;
 448 }
 449
 450 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 451                                    unsigned int event)
 452 {
 453         unsigned int cpu = policy->cpu;
 454         struct cpu_dbs_info_s *this_dbs_info;
 455         unsigned int j;
 456
 457         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 458
 459         switch (event) {
 460         case CPUFREQ_GOV_START:
 461                 if ((!cpu_online(cpu)) ||
 462                     (!policy->cur))
 463                         return -EINVAL;
 464
 465                 if (policy->cpuinfo.transition_latency >
 466                                 (TRANSITION_LATENCY_LIMIT * 1000))
 467                         return -EINVAL;
 468                 if (this_dbs_info->enable) /* Already enabled */
 469                         break;
 470
 471                 down(&dbs_sem);
 472                 for_each_cpu_mask(j, policy->cpus) {
 473                         struct cpu_dbs_info_s *j_dbs_info;
 474                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 475                         j_dbs_info->cur_policy = policy;
 476
 477                         j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 478                         j_dbs_info->prev_cpu_idle_down
 479                                 = j_dbs_info->prev_cpu_idle_up;
 480                 }
 481                 this_dbs_info->enable = 1;
 482                 sysfs_create_group(&policy->kobj, &dbs_attr_group);
 483                 dbs_enable++;
 484                 /*
 485                  * Start the timerschedule work, when this governor
 486                  * is used for first time
 487                  */
 488                 if (dbs_enable == 1) {
 489                         unsigned int latency;
 490                         /* policy latency is in nS. Convert it to uS first */
 491
 492                         latency = policy->cpuinfo.transition_latency;
 493                         if (latency < 1000)
 494                                 latency = 1000;
 495
 496                         def_sampling_rate = (latency / 1000) *
 497                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 498                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 499                         dbs_tuners_ins.ignore_nice = 0;
 500                         dbs_tuners_ins.freq_step = 5;
 501
 502                         dbs_timer_init();
 503                 }
 504
 505                 up(&dbs_sem);
 506                 break;
 507
 508         case CPUFREQ_GOV_STOP:
 509                 down(&dbs_sem);
 510                 this_dbs_info->enable = 0;
 511                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 512                 dbs_enable--;
 513                 /*
 514                  * Stop the timerschedule work, when this governor
 515                  * is used for first time
 516                  */
 517                 if (dbs_enable == 0)
 518                         dbs_timer_exit();
 519
 520                 up(&dbs_sem);
 521
 522                 break;
 523
 524         case CPUFREQ_GOV_LIMITS:
 525                 down(&dbs_sem);
 526                 if (policy->max < this_dbs_info->cur_policy->cur)
 527                         __cpufreq_driver_target(
 528                                         this_dbs_info->cur_policy,
 529                                         policy->max, CPUFREQ_RELATION_H);
 530                 else if (policy->min > this_dbs_info->cur_policy->cur)
 531                         __cpufreq_driver_target(
 532                                         this_dbs_info->cur_policy,
 533                                         policy->min, CPUFREQ_RELATION_L);
 534                 up(&dbs_sem);
 535                 break;
 536         }
 537         return 0;
 538 }
 539
 540 static struct cpufreq_governor cpufreq_gov_dbs = {
 541         .name           = "ondemand",
 542         .governor       = cpufreq_governor_dbs,
 543         .owner          = THIS_MODULE,
 544 };
 545
 546 static int __init cpufreq_gov_dbs_init(void)
 547 {
 548         return cpufreq_register_governor(&cpufreq_gov_dbs);
 549 }
 550
 551 static void __exit cpufreq_gov_dbs_exit(void)
 552 {
 553         /* Make sure that the scheduled work is indeed not running */
 554         flush_scheduled_work();
 555
 556         cpufreq_unregister_governor(&cpufreq_gov_dbs);
 557 }
 558
 559
 560 MODULE_AUTHOR ("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 561 MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 562                 "Low Latency Frequency Transition capable processors");
 563 MODULE_LICENSE ("GPL");
 564
 565 module_init(cpufreq_gov_dbs_init);
 566 module_exit(cpufreq_gov_dbs_exit);