1 /* 2 * drivers/cpufreq/cpufreq_conservative.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 * (C) 2004 Alexander Clouter <alex-kernel@digriz.org.uk> 8 * 9 * This program is free software; you can redistribute it and/or modify 10 * it under the terms of the GNU General Public License version 2 as 11 * published by the Free Software Foundation. 12 */ 13 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/kernel_stat.h> 30 #include <linux/percpu.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 (0) 39 #define MAX_FREQUENCY_UP_THRESHOLD (100) 40 41 #define DEF_FREQUENCY_DOWN_THRESHOLD (20) 42 #define MIN_FREQUENCY_DOWN_THRESHOLD (0) 43 #define MAX_FREQUENCY_DOWN_THRESHOLD (100) 44 45 /* 46 * The polling frequency of this governor depends on the capability of 47 * the processor. Default polling frequency is 1000 times the transition 48 * latency of the processor. The governor will work on any processor with 49 * transition latency <= 10mS, using appropriate sampling 50 * rate. 51 * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL) 52 * this governor will not work. 53 * All times here are in uS. 54 */ 55 static unsigned int def_sampling_rate; 56 #define MIN_SAMPLING_RATE (def_sampling_rate / 2) 57 #define MAX_SAMPLING_RATE (500 * def_sampling_rate) 58 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (100000) 59 #define DEF_SAMPLING_DOWN_FACTOR (5) 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 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 unsigned int ignore_nice; 83 unsigned int freq_step; 84 }; 85 86 static 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 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_conservative 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(down_threshold, down_threshold); 130 show_one(ignore_nice_load, ignore_nice); 131 show_one(freq_step, freq_step); 132 133 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused, 134 const char *buf, size_t count) 135 { 136 unsigned int input; 137 int ret; 138 ret = sscanf (buf, "%u", &input); 139 if (ret != 1 ) 140 return -EINVAL; 141 142 down(&dbs_sem); 143 dbs_tuners_ins.sampling_down_factor = input; 144 up(&dbs_sem); 145 146 return count; 147 } 148 149 static ssize_t store_sampling_rate(struct cpufreq_policy *unused, 150 const char *buf, size_t count) 151 { 152 unsigned int input; 153 int ret; 154 ret = sscanf (buf, "%u", &input); 155 156 down(&dbs_sem); 157 if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) { 158 up(&dbs_sem); 159 return -EINVAL; 160 } 161 162 dbs_tuners_ins.sampling_rate = input; 163 up(&dbs_sem); 164 165 return count; 166 } 167 168 static ssize_t store_up_threshold(struct cpufreq_policy *unused, 169 const char *buf, size_t count) 170 { 171 unsigned int input; 172 int ret; 173 ret = sscanf (buf, "%u", &input); 174 175 down(&dbs_sem); 176 if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD || 177 input < MIN_FREQUENCY_UP_THRESHOLD || 178 input <= dbs_tuners_ins.down_threshold) { 179 up(&dbs_sem); 180 return -EINVAL; 181 } 182 183 dbs_tuners_ins.up_threshold = input; 184 up(&dbs_sem); 185 186 return count; 187 } 188 189 static ssize_t store_down_threshold(struct cpufreq_policy *unused, 190 const char *buf, size_t count) 191 { 192 unsigned int input; 193 int ret; 194 ret = sscanf (buf, "%u", &input); 195 196 down(&dbs_sem); 197 if (ret != 1 || input > MAX_FREQUENCY_DOWN_THRESHOLD || 198 input < MIN_FREQUENCY_DOWN_THRESHOLD || 199 input >= dbs_tuners_ins.up_threshold) { 200 up(&dbs_sem); 201 return -EINVAL; 202 } 203 204 dbs_tuners_ins.down_threshold = input; 205 up(&dbs_sem); 206 207 return count; 208 } 209 210 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy, 211 const char *buf, size_t count) 212 { 213 unsigned int input; 214 int ret; 215 216 unsigned int j; 217 218 ret = sscanf (buf, "%u", &input); 219 if ( ret != 1 ) 220 return -EINVAL; 221 222 if ( input > 1 ) 223 input = 1; 224 225 down(&dbs_sem); 226 if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */ 227 up(&dbs_sem); 228 return count; 229 } 230 dbs_tuners_ins.ignore_nice = input; 231 232 /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */ 233 for_each_online_cpu(j) { 234 struct cpu_dbs_info_s *j_dbs_info; 235 j_dbs_info = &per_cpu(cpu_dbs_info, j); 236 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j); 237 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up; 238 } 239 up(&dbs_sem); 240 241 return count; 242 } 243 244 static ssize_t store_freq_step(struct cpufreq_policy *policy, 245 const char *buf, size_t count) 246 { 247 unsigned int input; 248 int ret; 249 250 ret = sscanf (buf, "%u", &input); 251 252 if ( ret != 1 ) 253 return -EINVAL; 254 255 if ( input > 100 ) 256 input = 100; 257 258 /* no need to test here if freq_step is zero as the user might actually 259 * want this, they would be crazy though :) */ 260 down(&dbs_sem); 261 dbs_tuners_ins.freq_step = input; 262 up(&dbs_sem); 263 264 return count; 265 } 266 267 #define define_one_rw(_name) \ 268 static struct freq_attr _name = \ 269 __ATTR(_name, 0644, show_##_name, store_##_name) 270 271 define_one_rw(sampling_rate); 272 define_one_rw(sampling_down_factor); 273 define_one_rw(up_threshold); 274 define_one_rw(down_threshold); 275 define_one_rw(ignore_nice_load); 276 define_one_rw(freq_step); 277 278 static struct attribute * dbs_attributes[] = { 279 &sampling_rate_max.attr, 280 &sampling_rate_min.attr, 281 &sampling_rate.attr, 282 &sampling_down_factor.attr, 283 &up_threshold.attr, 284 &down_threshold.attr, 285 &ignore_nice_load.attr, 286 &freq_step.attr, 287 NULL 288 }; 289 290 static struct attribute_group dbs_attr_group = { 291 .attrs = dbs_attributes, 292 .name = "conservative", 293 }; 294 295 /************************** sysfs end ************************/ 296 297 static void dbs_check_cpu(int cpu) 298 { 299 unsigned int idle_ticks, up_idle_ticks, down_idle_ticks; 300 unsigned int freq_step; 301 unsigned int freq_down_sampling_rate; 302 static int down_skip[NR_CPUS]; 303 static int requested_freq[NR_CPUS]; 304 static unsigned short init_flag = 0; 305 struct cpu_dbs_info_s *this_dbs_info; 306 struct cpu_dbs_info_s *dbs_info; 307 308 struct cpufreq_policy *policy; 309 unsigned int j; 310 311 this_dbs_info = &per_cpu(cpu_dbs_info, cpu); 312 if (!this_dbs_info->enable) 313 return; 314 315 policy = this_dbs_info->cur_policy; 316 317 if ( init_flag == 0 ) { 318 for_each_online_cpu(j) { 319 dbs_info = &per_cpu(cpu_dbs_info, j); 320 requested_freq[j] = dbs_info->cur_policy->cur; 321 } 322 init_flag = 1; 323 } 324 325 /* 326 * The default safe range is 20% to 80% 327 * Every sampling_rate, we check 328 * - If current idle time is less than 20%, then we try to 329 * increase frequency 330 * Every sampling_rate*sampling_down_factor, we check 331 * - If current idle time is more than 80%, then we try to 332 * decrease frequency 333 * 334 * Any frequency increase takes it to the maximum frequency. 335 * Frequency reduction happens at minimum steps of 336 * 5% (default) of max_frequency 337 */ 338 339 /* Check for frequency increase */ 340 341 idle_ticks = UINT_MAX; 342 for_each_cpu_mask(j, policy->cpus) { 343 unsigned int tmp_idle_ticks, total_idle_ticks; 344 struct cpu_dbs_info_s *j_dbs_info; 345 346 j_dbs_info = &per_cpu(cpu_dbs_info, j); 347 /* Check for frequency increase */ 348 total_idle_ticks = get_cpu_idle_time(j); 349 tmp_idle_ticks = total_idle_ticks - 350 j_dbs_info->prev_cpu_idle_up; 351 j_dbs_info->prev_cpu_idle_up = total_idle_ticks; 352 353 if (tmp_idle_ticks < idle_ticks) 354 idle_ticks = tmp_idle_ticks; 355 } 356 357 /* Scale idle ticks by 100 and compare with up and down ticks */ 358 idle_ticks *= 100; 359 up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) * 360 usecs_to_jiffies(dbs_tuners_ins.sampling_rate); 361 362 if (idle_ticks < up_idle_ticks) { 363 down_skip[cpu] = 0; 364 for_each_cpu_mask(j, policy->cpus) { 365 struct cpu_dbs_info_s *j_dbs_info; 366 367 j_dbs_info = &per_cpu(cpu_dbs_info, j); 368 j_dbs_info->prev_cpu_idle_down = 369 j_dbs_info->prev_cpu_idle_up; 370 } 371 /* if we are already at full speed then break out early */ 372 if (requested_freq[cpu] == policy->max) 373 return; 374 375 freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100; 376 377 /* max freq cannot be less than 100. But who knows.... */ 378 if (unlikely(freq_step == 0)) 379 freq_step = 5; 380 381 requested_freq[cpu] += freq_step; 382 if (requested_freq[cpu] > policy->max) 383 requested_freq[cpu] = policy->max; 384 385 __cpufreq_driver_target(policy, requested_freq[cpu], 386 CPUFREQ_RELATION_H); 387 return; 388 } 389 390 /* Check for frequency decrease */ 391 down_skip[cpu]++; 392 if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor) 393 return; 394 395 idle_ticks = UINT_MAX; 396 for_each_cpu_mask(j, policy->cpus) { 397 unsigned int tmp_idle_ticks, total_idle_ticks; 398 struct cpu_dbs_info_s *j_dbs_info; 399 400 j_dbs_info = &per_cpu(cpu_dbs_info, j); 401 total_idle_ticks = j_dbs_info->prev_cpu_idle_up; 402 tmp_idle_ticks = total_idle_ticks - 403 j_dbs_info->prev_cpu_idle_down; 404 j_dbs_info->prev_cpu_idle_down = total_idle_ticks; 405 406 if (tmp_idle_ticks < idle_ticks) 407 idle_ticks = tmp_idle_ticks; 408 } 409 410 /* Scale idle ticks by 100 and compare with up and down ticks */ 411 idle_ticks *= 100; 412 down_skip[cpu] = 0; 413 414 freq_down_sampling_rate = dbs_tuners_ins.sampling_rate * 415 dbs_tuners_ins.sampling_down_factor; 416 down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) * 417 usecs_to_jiffies(freq_down_sampling_rate); 418 419 if (idle_ticks > down_idle_ticks) { 420 /* if we are already at the lowest speed then break out early 421 * or if we 'cannot' reduce the speed as the user might want 422 * freq_step to be zero */ 423 if (requested_freq[cpu] == policy->min 424 || dbs_tuners_ins.freq_step == 0) 425 return; 426 427 freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100; 428 429 /* max freq cannot be less than 100. But who knows.... */ 430 if (unlikely(freq_step == 0)) 431 freq_step = 5; 432 433 requested_freq[cpu] -= freq_step; 434 if (requested_freq[cpu] < policy->min) 435 requested_freq[cpu] = policy->min; 436 437 __cpufreq_driver_target(policy, 438 requested_freq[cpu], 439 CPUFREQ_RELATION_H); 440 return; 441 } 442 } 443 444 static void do_dbs_timer(void *data) 445 { 446 int i; 447 down(&dbs_sem); 448 for_each_online_cpu(i) 449 dbs_check_cpu(i); 450 schedule_delayed_work(&dbs_work, 451 usecs_to_jiffies(dbs_tuners_ins.sampling_rate)); 452 up(&dbs_sem); 453 } 454 455 static inline void dbs_timer_init(void) 456 { 457 INIT_WORK(&dbs_work, do_dbs_timer, NULL); 458 schedule_delayed_work(&dbs_work, 459 usecs_to_jiffies(dbs_tuners_ins.sampling_rate)); 460 return; 461 } 462 463 static inline void dbs_timer_exit(void) 464 { 465 cancel_delayed_work(&dbs_work); 466 return; 467 } 468 469 static int cpufreq_governor_dbs(struct cpufreq_policy *policy, 470 unsigned int event) 471 { 472 unsigned int cpu = policy->cpu; 473 struct cpu_dbs_info_s *this_dbs_info; 474 unsigned int j; 475 476 this_dbs_info = &per_cpu(cpu_dbs_info, cpu); 477 478 switch (event) { 479 case CPUFREQ_GOV_START: 480 if ((!cpu_online(cpu)) || 481 (!policy->cur)) 482 return -EINVAL; 483 484 if (policy->cpuinfo.transition_latency > 485 (TRANSITION_LATENCY_LIMIT * 1000)) 486 return -EINVAL; 487 if (this_dbs_info->enable) /* Already enabled */ 488 break; 489 490 down(&dbs_sem); 491 for_each_cpu_mask(j, policy->cpus) { 492 struct cpu_dbs_info_s *j_dbs_info; 493 j_dbs_info = &per_cpu(cpu_dbs_info, j); 494 j_dbs_info->cur_policy = policy; 495 496 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j); 497 j_dbs_info->prev_cpu_idle_down 498 = j_dbs_info->prev_cpu_idle_up; 499 } 500 this_dbs_info->enable = 1; 501 sysfs_create_group(&policy->kobj, &dbs_attr_group); 502 dbs_enable++; 503 /* 504 * Start the timerschedule work, when this governor 505 * is used for first time 506 */ 507 if (dbs_enable == 1) { 508 unsigned int latency; 509 /* policy latency is in nS. Convert it to uS first */ 510 511 latency = policy->cpuinfo.transition_latency; 512 if (latency < 1000) 513 latency = 1000; 514 515 def_sampling_rate = (latency / 1000) * 516 DEF_SAMPLING_RATE_LATENCY_MULTIPLIER; 517 dbs_tuners_ins.sampling_rate = def_sampling_rate; 518 dbs_tuners_ins.ignore_nice = 0; 519 dbs_tuners_ins.freq_step = 5; 520 521 dbs_timer_init(); 522 } 523 524 up(&dbs_sem); 525 break; 526 527 case CPUFREQ_GOV_STOP: 528 down(&dbs_sem); 529 this_dbs_info->enable = 0; 530 sysfs_remove_group(&policy->kobj, &dbs_attr_group); 531 dbs_enable--; 532 /* 533 * Stop the timerschedule work, when this governor 534 * is used for first time 535 */ 536 if (dbs_enable == 0) 537 dbs_timer_exit(); 538 539 up(&dbs_sem); 540 541 break; 542 543 case CPUFREQ_GOV_LIMITS: 544 down(&dbs_sem); 545 if (policy->max < this_dbs_info->cur_policy->cur) 546 __cpufreq_driver_target( 547 this_dbs_info->cur_policy, 548 policy->max, CPUFREQ_RELATION_H); 549 else if (policy->min > this_dbs_info->cur_policy->cur) 550 __cpufreq_driver_target( 551 this_dbs_info->cur_policy, 552 policy->min, CPUFREQ_RELATION_L); 553 up(&dbs_sem); 554 break; 555 } 556 return 0; 557 } 558 559 static struct cpufreq_governor cpufreq_gov_dbs = { 560 .name = "conservative", 561 .governor = cpufreq_governor_dbs, 562 .owner = THIS_MODULE, 563 }; 564 565 static int __init cpufreq_gov_dbs_init(void) 566 { 567 return cpufreq_register_governor(&cpufreq_gov_dbs); 568 } 569 570 static void __exit cpufreq_gov_dbs_exit(void) 571 { 572 /* Make sure that the scheduled work is indeed not running */ 573 flush_scheduled_work(); 574 575 cpufreq_unregister_governor(&cpufreq_gov_dbs); 576 } 577 578 579 MODULE_AUTHOR ("Alexander Clouter <alex-kernel@digriz.org.uk>"); 580 MODULE_DESCRIPTION ("'cpufreq_conservative' - A dynamic cpufreq governor for " 581 "Low Latency Frequency Transition capable processors " 582 "optimised for use in a battery environment"); 583 MODULE_LICENSE ("GPL"); 584 585 module_init(cpufreq_gov_dbs_init); 586 module_exit(cpufreq_gov_dbs_exit); 587