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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/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 #include <linux/mutex.h>
  31
  32 /*
  33  * dbs is used in this file as a shortform for demandbased switching
  34  * It helps to keep variable names smaller, simpler
  35  */
  36
  37 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
  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 static unsigned int def_sampling_rate;
  52 #define MIN_SAMPLING_RATE_RATIO                 (2)
  53 /* for correct statistics, we need at least 10 ticks between each measure */
  54 #define MIN_STAT_SAMPLING_RATE                  (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
  55 #define MIN_SAMPLING_RATE                       (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
  56 #define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
  57 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (1000)
  58 #define DEF_SAMPLING_DOWN_FACTOR                (1)
  59 #define MAX_SAMPLING_DOWN_FACTOR                (10)
  60 #define TRANSITION_LATENCY_LIMIT                (10 * 1000)
  61
  62 static void do_dbs_timer(void *data);
  63
  64 struct cpu_dbs_info_s {
  65         struct cpufreq_policy *cur_policy;
  66         unsigned int prev_cpu_idle_up;
  67         unsigned int prev_cpu_idle_down;
  68         unsigned int enable;
  69 };
  70 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
  71
  72 static unsigned int dbs_enable; /* number of CPUs using this policy */
  73
  74 static DEFINE_MUTEX (dbs_mutex);
  75 static DECLARE_WORK     (dbs_work, do_dbs_timer, NULL);
  76
  77 static struct workqueue_struct *dbs_workq;
  78
  79 struct dbs_tuners {
  80         unsigned int sampling_rate;
  81         unsigned int sampling_down_factor;
  82         unsigned int up_threshold;
  83         unsigned int ignore_nice;
  84 };
  85
  86 static struct dbs_tuners dbs_tuners_ins = {
  87         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
  88         .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
  89         .ignore_nice = 0,
  90 };
  91
  92 static inline unsigned int get_cpu_idle_time(unsigned int cpu)
  93 {
  94         return  kstat_cpu(cpu).cpustat.idle +
  95                 kstat_cpu(cpu).cpustat.iowait +
  96                 ( dbs_tuners_ins.ignore_nice ?
  97                   kstat_cpu(cpu).cpustat.nice :
  98                   0);
  99 }
 100
 101 /************************** sysfs interface ************************/
 102 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 103 {
 104         return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
 105 }
 106
 107 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 108 {
 109         return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 110 }
 111
 112 #define define_one_ro(_name)            \
 113 static struct freq_attr _name =         \
 114 __ATTR(_name, 0444, show_##_name, NULL)
 115
 116 define_one_ro(sampling_rate_max);
 117 define_one_ro(sampling_rate_min);
 118
 119 /* cpufreq_ondemand Governor Tunables */
 120 #define show_one(file_name, object)                                     \
 121 static ssize_t show_##file_name                                         \
 122 (struct cpufreq_policy *unused, char *buf)                              \
 123 {                                                                       \
 124         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 125 }
 126 show_one(sampling_rate, sampling_rate);
 127 show_one(sampling_down_factor, sampling_down_factor);
 128 show_one(up_threshold, up_threshold);
 129 show_one(ignore_nice_load, ignore_nice);
 130
 131 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
 132                 const char *buf, size_t count)
 133 {
 134         unsigned int input;
 135         int ret;
 136         ret = sscanf (buf, "%u", &input);
 137         if (ret != 1 )
 138                 return -EINVAL;
 139
 140         if (input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 141                 return -EINVAL;
 142
 143         mutex_lock(&dbs_mutex);
 144         dbs_tuners_ins.sampling_down_factor = input;
 145         mutex_unlock(&dbs_mutex);
 146
 147         return count;
 148 }
 149
 150 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 151                 const char *buf, size_t count)
 152 {
 153         unsigned int input;
 154         int ret;
 155         ret = sscanf (buf, "%u", &input);
 156
 157         mutex_lock(&dbs_mutex);
 158         if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
 159                 mutex_unlock(&dbs_mutex);
 160                 return -EINVAL;
 161         }
 162
 163         dbs_tuners_ins.sampling_rate = input;
 164         mutex_unlock(&dbs_mutex);
 165
 166         return count;
 167 }
 168
 169 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 170                 const char *buf, size_t count)
 171 {
 172         unsigned int input;
 173         int ret;
 174         ret = sscanf (buf, "%u", &input);
 175
 176         mutex_lock(&dbs_mutex);
 177         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 178                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 179                 mutex_unlock(&dbs_mutex);
 180                 return -EINVAL;
 181         }
 182
 183         dbs_tuners_ins.up_threshold = input;
 184         mutex_unlock(&dbs_mutex);
 185
 186         return count;
 187 }
 188
 189 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 190                 const char *buf, size_t count)
 191 {
 192         unsigned int input;
 193         int ret;
 194
 195         unsigned int j;
 196
 197         ret = sscanf (buf, "%u", &input);
 198         if ( ret != 1 )
 199                 return -EINVAL;
 200
 201         if ( input > 1 )
 202                 input = 1;
 203
 204         mutex_lock(&dbs_mutex);
 205         if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
 206                 mutex_unlock(&dbs_mutex);
 207                 return count;
 208         }
 209         dbs_tuners_ins.ignore_nice = input;
 210
 211         /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
 212         for_each_online_cpu(j) {
 213                 struct cpu_dbs_info_s *j_dbs_info;
 214                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 215                 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 216                 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
 217         }
 218         mutex_unlock(&dbs_mutex);
 219
 220         return count;
 221 }
 222
 223 #define define_one_rw(_name) \
 224 static struct freq_attr _name = \
 225 __ATTR(_name, 0644, show_##_name, store_##_name)
 226
 227 define_one_rw(sampling_rate);
 228 define_one_rw(sampling_down_factor);
 229 define_one_rw(up_threshold);
 230 define_one_rw(ignore_nice_load);
 231
 232 static struct attribute * dbs_attributes[] = {
 233         &sampling_rate_max.attr,
 234         &sampling_rate_min.attr,
 235         &sampling_rate.attr,
 236         &sampling_down_factor.attr,
 237         &up_threshold.attr,
 238         &ignore_nice_load.attr,
 239         NULL
 240 };
 241
 242 static struct attribute_group dbs_attr_group = {
 243         .attrs = dbs_attributes,
 244         .name = "ondemand",
 245 };
 246
 247 /************************** sysfs end ************************/
 248
 249 static void dbs_check_cpu(int cpu)
 250 {
 251         unsigned int idle_ticks, up_idle_ticks, total_ticks;
 252         unsigned int freq_next;
 253         unsigned int freq_down_sampling_rate;
 254         static int down_skip[NR_CPUS];
 255         struct cpu_dbs_info_s *this_dbs_info;
 256
 257         struct cpufreq_policy *policy;
 258         unsigned int j;
 259
 260         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 261         if (!this_dbs_info->enable)
 262                 return;
 263
 264         policy = this_dbs_info->cur_policy;
 265         /*
 266          * Every sampling_rate, we check, if current idle time is less
 267          * than 20% (default), then we try to increase frequency
 268          * Every sampling_rate*sampling_down_factor, we look for a the lowest
 269          * frequency which can sustain the load while keeping idle time over
 270          * 30%. If such a frequency exist, we try to decrease to this frequency.
 271          *
 272          * Any frequency increase takes it to the maximum frequency.
 273          * Frequency reduction happens at minimum steps of
 274          * 5% (default) of current frequency
 275          */
 276
 277         /* Check for frequency increase */
 278         idle_ticks = UINT_MAX;
 279         for_each_cpu_mask(j, policy->cpus) {
 280                 unsigned int tmp_idle_ticks, total_idle_ticks;
 281                 struct cpu_dbs_info_s *j_dbs_info;
 282
 283                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 284                 total_idle_ticks = get_cpu_idle_time(j);
 285                 tmp_idle_ticks = total_idle_ticks -
 286                         j_dbs_info->prev_cpu_idle_up;
 287                 j_dbs_info->prev_cpu_idle_up = total_idle_ticks;
 288
 289                 if (tmp_idle_ticks < idle_ticks)
 290                         idle_ticks = tmp_idle_ticks;
 291         }
 292
 293         /* Scale idle ticks by 100 and compare with up and down ticks */
 294         idle_ticks *= 100;
 295         up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
 296                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 297
 298         if (idle_ticks < up_idle_ticks) {
 299                 down_skip[cpu] = 0;
 300                 for_each_cpu_mask(j, policy->cpus) {
 301                         struct cpu_dbs_info_s *j_dbs_info;
 302
 303                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 304                         j_dbs_info->prev_cpu_idle_down =
 305                                         j_dbs_info->prev_cpu_idle_up;
 306                 }
 307                 /* if we are already at full speed then break out early */
 308                 if (policy->cur == policy->max)
 309                         return;
 310
 311                 __cpufreq_driver_target(policy, policy->max,
 312                         CPUFREQ_RELATION_H);
 313                 return;
 314         }
 315
 316         /* Check for frequency decrease */
 317         down_skip[cpu]++;
 318         if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
 319                 return;
 320
 321         idle_ticks = UINT_MAX;
 322         for_each_cpu_mask(j, policy->cpus) {
 323                 unsigned int tmp_idle_ticks, total_idle_ticks;
 324                 struct cpu_dbs_info_s *j_dbs_info;
 325
 326                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 327                 /* Check for frequency decrease */
 328                 total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
 329                 tmp_idle_ticks = total_idle_ticks -
 330                         j_dbs_info->prev_cpu_idle_down;
 331                 j_dbs_info->prev_cpu_idle_down = total_idle_ticks;
 332
 333                 if (tmp_idle_ticks < idle_ticks)
 334                         idle_ticks = tmp_idle_ticks;
 335         }
 336
 337         down_skip[cpu] = 0;
 338         /* if we cannot reduce the frequency anymore, break out early */
 339         if (policy->cur == policy->min)
 340                 return;
 341
 342         /* Compute how many ticks there are between two measurements */
 343         freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
 344                 dbs_tuners_ins.sampling_down_factor;
 345         total_ticks = usecs_to_jiffies(freq_down_sampling_rate);
 346
 347         /*
 348          * The optimal frequency is the frequency that is the lowest that
 349          * can support the current CPU usage without triggering the up
 350          * policy. To be safe, we focus 10 points under the threshold.
 351          */
 352         freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks;
 353         freq_next = (freq_next * policy->cur) /
 354                         (dbs_tuners_ins.up_threshold - 10);
 355
 356         if (freq_next < policy->min)
 357                 freq_next = policy->min;
 358
 359         if (freq_next <= ((policy->cur * 95) / 100))
 360                 __cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);
 361 }
 362
 363 static void do_dbs_timer(void *data)
 364 {
 365         int i;
 366         mutex_lock(&dbs_mutex);
 367         for_each_online_cpu(i)
 368                 dbs_check_cpu(i);
 369         queue_delayed_work(dbs_workq, &dbs_work,
 370                            usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 371         mutex_unlock(&dbs_mutex);
 372 }
 373
 374 static inline void dbs_timer_init(void)
 375 {
 376         INIT_WORK(&dbs_work, do_dbs_timer, NULL);
 377         if (!dbs_workq)
 378                 dbs_workq = create_singlethread_workqueue("ondemand");
 379         if (!dbs_workq) {
 380                 printk(KERN_ERR "ondemand: Cannot initialize kernel thread\n");
 381                 return;
 382         }
 383         queue_delayed_work(dbs_workq, &dbs_work,
 384                            usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 385         return;
 386 }
 387
 388 static inline void dbs_timer_exit(void)
 389 {
 390         if (dbs_workq)
 391                 cancel_rearming_delayed_workqueue(dbs_workq, &dbs_work);
 392 }
 393
 394 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 395                                    unsigned int event)
 396 {
 397         unsigned int cpu = policy->cpu;
 398         struct cpu_dbs_info_s *this_dbs_info;
 399         unsigned int j;
 400
 401         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 402
 403         switch (event) {
 404         case CPUFREQ_GOV_START:
 405                 if ((!cpu_online(cpu)) ||
 406                     (!policy->cur))
 407                         return -EINVAL;
 408
 409                 if (policy->cpuinfo.transition_latency >
 410                                 (TRANSITION_LATENCY_LIMIT * 1000)) {
 411                         printk(KERN_WARNING "ondemand governor failed to load "
 412                                "due to too long transition latency\n");
 413                         return -EINVAL;
 414                 }
 415                 if (this_dbs_info->enable) /* Already enabled */
 416                         break;
 417
 418                 mutex_lock(&dbs_mutex);
 419                 for_each_cpu_mask(j, policy->cpus) {
 420                         struct cpu_dbs_info_s *j_dbs_info;
 421                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 422                         j_dbs_info->cur_policy = policy;
 423
 424                         j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 425                         j_dbs_info->prev_cpu_idle_down
 426                                 = j_dbs_info->prev_cpu_idle_up;
 427                 }
 428                 this_dbs_info->enable = 1;
 429                 sysfs_create_group(&policy->kobj, &dbs_attr_group);
 430                 dbs_enable++;
 431                 /*
 432                  * Start the timerschedule work, when this governor
 433                  * is used for first time
 434                  */
 435                 if (dbs_enable == 1) {
 436                         unsigned int latency;
 437                         /* policy latency is in nS. Convert it to uS first */
 438                         latency = policy->cpuinfo.transition_latency / 1000;
 439                         if (latency == 0)
 440                                 latency = 1;
 441
 442                         def_sampling_rate = latency *
 443                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 444
 445                         if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
 446                                 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 447
 448                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 449                         dbs_timer_init();
 450                 }
 451
 452                 mutex_unlock(&dbs_mutex);
 453                 break;
 454
 455         case CPUFREQ_GOV_STOP:
 456                 mutex_lock(&dbs_mutex);
 457                 this_dbs_info->enable = 0;
 458                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 459                 dbs_enable--;
 460                 /*
 461                  * Stop the timerschedule work, when this governor
 462                  * is used for first time
 463                  */
 464                 if (dbs_enable == 0)
 465                         dbs_timer_exit();
 466
 467                 mutex_unlock(&dbs_mutex);
 468
 469                 break;
 470
 471         case CPUFREQ_GOV_LIMITS:
 472                 mutex_lock(&dbs_mutex);
 473                 if (policy->max < this_dbs_info->cur_policy->cur)
 474                         __cpufreq_driver_target(
 475                                         this_dbs_info->cur_policy,
 476                                         policy->max, CPUFREQ_RELATION_H);
 477                 else if (policy->min > this_dbs_info->cur_policy->cur)
 478                         __cpufreq_driver_target(
 479                                         this_dbs_info->cur_policy,
 480                                         policy->min, CPUFREQ_RELATION_L);
 481                 mutex_unlock(&dbs_mutex);
 482                 break;
 483         }
 484         return 0;
 485 }
 486
 487 static struct cpufreq_governor cpufreq_gov_dbs = {
 488         .name           = "ondemand",
 489         .governor       = cpufreq_governor_dbs,
 490         .owner          = THIS_MODULE,
 491 };
 492
 493 static int __init cpufreq_gov_dbs_init(void)
 494 {
 495         return cpufreq_register_governor(&cpufreq_gov_dbs);
 496 }
 497
 498 static void __exit cpufreq_gov_dbs_exit(void)
 499 {
 500         /* Make sure that the scheduled work is indeed not running.
 501            Assumes the timer has been cancelled first. */
 502         if (dbs_workq) {
 503                 flush_workqueue(dbs_workq);
 504                 destroy_workqueue(dbs_workq);
 505         }
 506
 507         cpufreq_unregister_governor(&cpufreq_gov_dbs);
 508 }
 509
 510
 511 MODULE_AUTHOR ("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 512 MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 513                 "Low Latency Frequency Transition capable processors");
 514 MODULE_LICENSE ("GPL");
 515
 516 module_init(cpufreq_gov_dbs_init);
 517 module_exit(cpufreq_gov_dbs_exit);