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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * drivers/cpufreq/cpufreq_governor.c4 *5 * CPUFREQ governors common code6 *7 * Copyright (C) 2001 Russell King8 * (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.9 * (C) 2003 Jun Nakajima <jun.nakajima@intel.com>10 * (C) 2009 Alexander Clouter <alex@digriz.org.uk>11 * (c) 2012 Viresh Kumar <viresh.kumar@linaro.org>12 */13 14#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt15 16#include <linux/export.h>17#include <linux/kernel_stat.h>18#include <linux/slab.h>19 20#include "cpufreq_governor.h"21 22#define CPUFREQ_DBS_MIN_SAMPLING_INTERVAL (2 * TICK_NSEC / NSEC_PER_USEC)23 24static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs);25 26static DEFINE_MUTEX(gov_dbs_data_mutex);27 28/* Common sysfs tunables */29/*30 * sampling_rate_store - update sampling rate effective immediately if needed.31 *32 * If new rate is smaller than the old, simply updating33 * dbs.sampling_rate might not be appropriate. For example, if the34 * original sampling_rate was 1 second and the requested new sampling rate is 1035 * ms because the user needs immediate reaction from ondemand governor, but not36 * sure if higher frequency will be required or not, then, the governor may37 * change the sampling rate too late; up to 1 second later. Thus, if we are38 * reducing the sampling rate, we need to make the new value effective39 * immediately.40 *41 * This must be called with dbs_data->mutex held, otherwise traversing42 * policy_dbs_list isn't safe.43 */44ssize_t sampling_rate_store(struct gov_attr_set *attr_set, const char *buf,45 size_t count)46{47 struct dbs_data *dbs_data = to_dbs_data(attr_set);48 struct policy_dbs_info *policy_dbs;49 unsigned int sampling_interval;50 int ret;51 52 ret = sscanf(buf, "%u", &sampling_interval);53 if (ret != 1 || sampling_interval < CPUFREQ_DBS_MIN_SAMPLING_INTERVAL)54 return -EINVAL;55 56 dbs_data->sampling_rate = sampling_interval;57 58 /*59 * We are operating under dbs_data->mutex and so the list and its60 * entries can't be freed concurrently.61 */62 list_for_each_entry(policy_dbs, &attr_set->policy_list, list) {63 mutex_lock(&policy_dbs->update_mutex);64 /*65 * On 32-bit architectures this may race with the66 * sample_delay_ns read in dbs_update_util_handler(), but that67 * really doesn't matter. If the read returns a value that's68 * too big, the sample will be skipped, but the next invocation69 * of dbs_update_util_handler() (when the update has been70 * completed) will take a sample.71 *72 * If this runs in parallel with dbs_work_handler(), we may end73 * up overwriting the sample_delay_ns value that it has just74 * written, but it will be corrected next time a sample is75 * taken, so it shouldn't be significant.76 */77 gov_update_sample_delay(policy_dbs, 0);78 mutex_unlock(&policy_dbs->update_mutex);79 }80 81 return count;82}83EXPORT_SYMBOL_GPL(sampling_rate_store);84 85/**86 * gov_update_cpu_data - Update CPU load data.87 * @dbs_data: Top-level governor data pointer.88 *89 * Update CPU load data for all CPUs in the domain governed by @dbs_data90 * (that may be a single policy or a bunch of them if governor tunables are91 * system-wide).92 *93 * Call under the @dbs_data mutex.94 */95void gov_update_cpu_data(struct dbs_data *dbs_data)96{97 struct policy_dbs_info *policy_dbs;98 99 list_for_each_entry(policy_dbs, &dbs_data->attr_set.policy_list, list) {100 unsigned int j;101 102 for_each_cpu(j, policy_dbs->policy->cpus) {103 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);104 105 j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_update_time,106 dbs_data->io_is_busy);107 if (dbs_data->ignore_nice_load)108 j_cdbs->prev_cpu_nice = kcpustat_field(&kcpustat_cpu(j), CPUTIME_NICE, j);109 }110 }111}112EXPORT_SYMBOL_GPL(gov_update_cpu_data);113 114unsigned int dbs_update(struct cpufreq_policy *policy)115{116 struct policy_dbs_info *policy_dbs = policy->governor_data;117 struct dbs_data *dbs_data = policy_dbs->dbs_data;118 unsigned int ignore_nice = dbs_data->ignore_nice_load;119 unsigned int max_load = 0, idle_periods = UINT_MAX;120 unsigned int sampling_rate, io_busy, j;121 122 /*123 * Sometimes governors may use an additional multiplier to increase124 * sample delays temporarily. Apply that multiplier to sampling_rate125 * so as to keep the wake-up-from-idle detection logic a bit126 * conservative.127 */128 sampling_rate = dbs_data->sampling_rate * policy_dbs->rate_mult;129 /*130 * For the purpose of ondemand, waiting for disk IO is an indication131 * that you're performance critical, and not that the system is actually132 * idle, so do not add the iowait time to the CPU idle time then.133 */134 io_busy = dbs_data->io_is_busy;135 136 /* Get Absolute Load */137 for_each_cpu(j, policy->cpus) {138 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);139 u64 update_time, cur_idle_time;140 unsigned int idle_time, time_elapsed;141 unsigned int load;142 143 cur_idle_time = get_cpu_idle_time(j, &update_time, io_busy);144 145 time_elapsed = update_time - j_cdbs->prev_update_time;146 j_cdbs->prev_update_time = update_time;147 148 idle_time = cur_idle_time - j_cdbs->prev_cpu_idle;149 j_cdbs->prev_cpu_idle = cur_idle_time;150 151 if (ignore_nice) {152 u64 cur_nice = kcpustat_field(&kcpustat_cpu(j), CPUTIME_NICE, j);153 154 idle_time += div_u64(cur_nice - j_cdbs->prev_cpu_nice, NSEC_PER_USEC);155 j_cdbs->prev_cpu_nice = cur_nice;156 }157 158 if (unlikely(!time_elapsed)) {159 /*160 * That can only happen when this function is called161 * twice in a row with a very short interval between the162 * calls, so the previous load value can be used then.163 */164 load = j_cdbs->prev_load;165 } else if (unlikely((int)idle_time > 2 * sampling_rate &&166 j_cdbs->prev_load)) {167 /*168 * If the CPU had gone completely idle and a task has169 * just woken up on this CPU now, it would be unfair to170 * calculate 'load' the usual way for this elapsed171 * time-window, because it would show near-zero load,172 * irrespective of how CPU intensive that task actually173 * was. This is undesirable for latency-sensitive bursty174 * workloads.175 *176 * To avoid this, reuse the 'load' from the previous177 * time-window and give this task a chance to start with178 * a reasonably high CPU frequency. However, that179 * shouldn't be over-done, lest we get stuck at a high180 * load (high frequency) for too long, even when the181 * current system load has actually dropped down, so182 * clear prev_load to guarantee that the load will be183 * computed again next time.184 *185 * Detecting this situation is easy: an unusually large186 * 'idle_time' (as compared to the sampling rate)187 * indicates this scenario.188 */189 load = j_cdbs->prev_load;190 j_cdbs->prev_load = 0;191 } else {192 if (time_elapsed >= idle_time) {193 load = 100 * (time_elapsed - idle_time) / time_elapsed;194 } else {195 /*196 * That can happen if idle_time is returned by197 * get_cpu_idle_time_jiffy(). In that case198 * idle_time is roughly equal to the difference199 * between time_elapsed and "busy time" obtained200 * from CPU statistics. Then, the "busy time"201 * can end up being greater than time_elapsed202 * (for example, if jiffies_64 and the CPU203 * statistics are updated by different CPUs),204 * so idle_time may in fact be negative. That205 * means, though, that the CPU was busy all206 * the time (on the rough average) during the207 * last sampling interval and 100 can be208 * returned as the load.209 */210 load = (int)idle_time < 0 ? 100 : 0;211 }212 j_cdbs->prev_load = load;213 }214 215 if (unlikely((int)idle_time > 2 * sampling_rate)) {216 unsigned int periods = idle_time / sampling_rate;217 218 if (periods < idle_periods)219 idle_periods = periods;220 }221 222 if (load > max_load)223 max_load = load;224 }225 226 policy_dbs->idle_periods = idle_periods;227 228 return max_load;229}230EXPORT_SYMBOL_GPL(dbs_update);231 232static void dbs_work_handler(struct work_struct *work)233{234 struct policy_dbs_info *policy_dbs;235 struct cpufreq_policy *policy;236 struct dbs_governor *gov;237 238 policy_dbs = container_of(work, struct policy_dbs_info, work);239 policy = policy_dbs->policy;240 gov = dbs_governor_of(policy);241 242 /*243 * Make sure cpufreq_governor_limits() isn't evaluating load or the244 * ondemand governor isn't updating the sampling rate in parallel.245 */246 mutex_lock(&policy_dbs->update_mutex);247 gov_update_sample_delay(policy_dbs, gov->gov_dbs_update(policy));248 mutex_unlock(&policy_dbs->update_mutex);249 250 /* Allow the utilization update handler to queue up more work. */251 atomic_set(&policy_dbs->work_count, 0);252 /*253 * If the update below is reordered with respect to the sample delay254 * modification, the utilization update handler may end up using a stale255 * sample delay value.256 */257 smp_wmb();258 policy_dbs->work_in_progress = false;259}260 261static void dbs_irq_work(struct irq_work *irq_work)262{263 struct policy_dbs_info *policy_dbs;264 265 policy_dbs = container_of(irq_work, struct policy_dbs_info, irq_work);266 schedule_work_on(smp_processor_id(), &policy_dbs->work);267}268 269static void dbs_update_util_handler(struct update_util_data *data, u64 time,270 unsigned int flags)271{272 struct cpu_dbs_info *cdbs = container_of(data, struct cpu_dbs_info, update_util);273 struct policy_dbs_info *policy_dbs = cdbs->policy_dbs;274 u64 delta_ns, lst;275 276 if (!cpufreq_this_cpu_can_update(policy_dbs->policy))277 return;278 279 /*280 * The work may not be allowed to be queued up right now.281 * Possible reasons:282 * - Work has already been queued up or is in progress.283 * - It is too early (too little time from the previous sample).284 */285 if (policy_dbs->work_in_progress)286 return;287 288 /*289 * If the reads below are reordered before the check above, the value290 * of sample_delay_ns used in the computation may be stale.291 */292 smp_rmb();293 lst = READ_ONCE(policy_dbs->last_sample_time);294 delta_ns = time - lst;295 if ((s64)delta_ns < policy_dbs->sample_delay_ns)296 return;297 298 /*299 * If the policy is not shared, the irq_work may be queued up right away300 * at this point. Otherwise, we need to ensure that only one of the301 * CPUs sharing the policy will do that.302 */303 if (policy_dbs->is_shared) {304 if (!atomic_add_unless(&policy_dbs->work_count, 1, 1))305 return;306 307 /*308 * If another CPU updated last_sample_time in the meantime, we309 * shouldn't be here, so clear the work counter and bail out.310 */311 if (unlikely(lst != READ_ONCE(policy_dbs->last_sample_time))) {312 atomic_set(&policy_dbs->work_count, 0);313 return;314 }315 }316 317 policy_dbs->last_sample_time = time;318 policy_dbs->work_in_progress = true;319 irq_work_queue(&policy_dbs->irq_work);320}321 322static void gov_set_update_util(struct policy_dbs_info *policy_dbs,323 unsigned int delay_us)324{325 struct cpufreq_policy *policy = policy_dbs->policy;326 int cpu;327 328 gov_update_sample_delay(policy_dbs, delay_us);329 policy_dbs->last_sample_time = 0;330 331 for_each_cpu(cpu, policy->cpus) {332 struct cpu_dbs_info *cdbs = &per_cpu(cpu_dbs, cpu);333 334 cpufreq_add_update_util_hook(cpu, &cdbs->update_util,335 dbs_update_util_handler);336 }337}338 339static inline void gov_clear_update_util(struct cpufreq_policy *policy)340{341 int i;342 343 for_each_cpu(i, policy->cpus)344 cpufreq_remove_update_util_hook(i);345 346 synchronize_rcu();347}348 349static struct policy_dbs_info *alloc_policy_dbs_info(struct cpufreq_policy *policy,350 struct dbs_governor *gov)351{352 struct policy_dbs_info *policy_dbs;353 int j;354 355 /* Allocate memory for per-policy governor data. */356 policy_dbs = gov->alloc();357 if (!policy_dbs)358 return NULL;359 360 policy_dbs->policy = policy;361 mutex_init(&policy_dbs->update_mutex);362 atomic_set(&policy_dbs->work_count, 0);363 init_irq_work(&policy_dbs->irq_work, dbs_irq_work);364 INIT_WORK(&policy_dbs->work, dbs_work_handler);365 366 /* Set policy_dbs for all CPUs, online+offline */367 for_each_cpu(j, policy->related_cpus) {368 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);369 370 j_cdbs->policy_dbs = policy_dbs;371 }372 return policy_dbs;373}374 375static void free_policy_dbs_info(struct policy_dbs_info *policy_dbs,376 struct dbs_governor *gov)377{378 int j;379 380 mutex_destroy(&policy_dbs->update_mutex);381 382 for_each_cpu(j, policy_dbs->policy->related_cpus) {383 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);384 385 j_cdbs->policy_dbs = NULL;386 j_cdbs->update_util.func = NULL;387 }388 gov->free(policy_dbs);389}390 391static void cpufreq_dbs_data_release(struct kobject *kobj)392{393 struct dbs_data *dbs_data = to_dbs_data(to_gov_attr_set(kobj));394 struct dbs_governor *gov = dbs_data->gov;395 396 gov->exit(dbs_data);397 kfree(dbs_data);398}399 400int cpufreq_dbs_governor_init(struct cpufreq_policy *policy)401{402 struct dbs_governor *gov = dbs_governor_of(policy);403 struct dbs_data *dbs_data;404 struct policy_dbs_info *policy_dbs;405 int ret = 0;406 407 /* State should be equivalent to EXIT */408 if (policy->governor_data)409 return -EBUSY;410 411 policy_dbs = alloc_policy_dbs_info(policy, gov);412 if (!policy_dbs)413 return -ENOMEM;414 415 /* Protect gov->gdbs_data against concurrent updates. */416 mutex_lock(&gov_dbs_data_mutex);417 418 dbs_data = gov->gdbs_data;419 if (dbs_data) {420 if (WARN_ON(have_governor_per_policy())) {421 ret = -EINVAL;422 goto free_policy_dbs_info;423 }424 policy_dbs->dbs_data = dbs_data;425 policy->governor_data = policy_dbs;426 427 gov_attr_set_get(&dbs_data->attr_set, &policy_dbs->list);428 goto out;429 }430 431 dbs_data = kzalloc(sizeof(*dbs_data), GFP_KERNEL);432 if (!dbs_data) {433 ret = -ENOMEM;434 goto free_policy_dbs_info;435 }436 437 dbs_data->gov = gov;438 gov_attr_set_init(&dbs_data->attr_set, &policy_dbs->list);439 440 ret = gov->init(dbs_data);441 if (ret)442 goto free_dbs_data;443 444 /*445 * The sampling interval should not be less than the transition latency446 * of the CPU and it also cannot be too small for dbs_update() to work447 * correctly.448 */449 dbs_data->sampling_rate = max_t(unsigned int,450 CPUFREQ_DBS_MIN_SAMPLING_INTERVAL,451 cpufreq_policy_transition_delay_us(policy));452 453 if (!have_governor_per_policy())454 gov->gdbs_data = dbs_data;455 456 policy_dbs->dbs_data = dbs_data;457 policy->governor_data = policy_dbs;458 459 gov->kobj_type.sysfs_ops = &governor_sysfs_ops;460 gov->kobj_type.release = cpufreq_dbs_data_release;461 ret = kobject_init_and_add(&dbs_data->attr_set.kobj, &gov->kobj_type,462 get_governor_parent_kobj(policy),463 "%s", gov->gov.name);464 if (!ret)465 goto out;466 467 /* Failure, so roll back. */468 pr_err("initialization failed (dbs_data kobject init error %d)\n", ret);469 470 kobject_put(&dbs_data->attr_set.kobj);471 472 policy->governor_data = NULL;473 474 if (!have_governor_per_policy())475 gov->gdbs_data = NULL;476 gov->exit(dbs_data);477 478free_dbs_data:479 kfree(dbs_data);480 481free_policy_dbs_info:482 free_policy_dbs_info(policy_dbs, gov);483 484out:485 mutex_unlock(&gov_dbs_data_mutex);486 return ret;487}488EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_init);489 490void cpufreq_dbs_governor_exit(struct cpufreq_policy *policy)491{492 struct dbs_governor *gov = dbs_governor_of(policy);493 struct policy_dbs_info *policy_dbs = policy->governor_data;494 struct dbs_data *dbs_data = policy_dbs->dbs_data;495 unsigned int count;496 497 /* Protect gov->gdbs_data against concurrent updates. */498 mutex_lock(&gov_dbs_data_mutex);499 500 count = gov_attr_set_put(&dbs_data->attr_set, &policy_dbs->list);501 502 policy->governor_data = NULL;503 504 if (!count && !have_governor_per_policy())505 gov->gdbs_data = NULL;506 507 free_policy_dbs_info(policy_dbs, gov);508 509 mutex_unlock(&gov_dbs_data_mutex);510}511EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_exit);512 513int cpufreq_dbs_governor_start(struct cpufreq_policy *policy)514{515 struct dbs_governor *gov = dbs_governor_of(policy);516 struct policy_dbs_info *policy_dbs = policy->governor_data;517 struct dbs_data *dbs_data = policy_dbs->dbs_data;518 unsigned int sampling_rate, ignore_nice, j;519 unsigned int io_busy;520 521 if (!policy->cur)522 return -EINVAL;523 524 policy_dbs->is_shared = policy_is_shared(policy);525 policy_dbs->rate_mult = 1;526 527 sampling_rate = dbs_data->sampling_rate;528 ignore_nice = dbs_data->ignore_nice_load;529 io_busy = dbs_data->io_is_busy;530 531 for_each_cpu(j, policy->cpus) {532 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);533 534 j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_update_time, io_busy);535 /*536 * Make the first invocation of dbs_update() compute the load.537 */538 j_cdbs->prev_load = 0;539 540 if (ignore_nice)541 j_cdbs->prev_cpu_nice = kcpustat_field(&kcpustat_cpu(j), CPUTIME_NICE, j);542 }543 544 gov->start(policy);545 546 gov_set_update_util(policy_dbs, sampling_rate);547 return 0;548}549EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_start);550 551void cpufreq_dbs_governor_stop(struct cpufreq_policy *policy)552{553 struct policy_dbs_info *policy_dbs = policy->governor_data;554 555 gov_clear_update_util(policy_dbs->policy);556 irq_work_sync(&policy_dbs->irq_work);557 cancel_work_sync(&policy_dbs->work);558 atomic_set(&policy_dbs->work_count, 0);559 policy_dbs->work_in_progress = false;560}561EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_stop);562 563void cpufreq_dbs_governor_limits(struct cpufreq_policy *policy)564{565 struct policy_dbs_info *policy_dbs;566 567 /* Protect gov->gdbs_data against cpufreq_dbs_governor_exit() */568 mutex_lock(&gov_dbs_data_mutex);569 policy_dbs = policy->governor_data;570 if (!policy_dbs)571 goto out;572 573 mutex_lock(&policy_dbs->update_mutex);574 cpufreq_policy_apply_limits(policy);575 gov_update_sample_delay(policy_dbs, 0);576 mutex_unlock(&policy_dbs->update_mutex);577 578out:579 mutex_unlock(&gov_dbs_data_mutex);580}581EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_limits);582