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