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