1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * drivers/cpufreq/cpufreq_governor.c
4 *
5 * CPUFREQ governors common code
6 *
7 * Copyright (C) 2001 Russell King
8 * (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 ": " fmt
15
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 updating
33 * dbs.sampling_rate might not be appropriate. For example, if the
34 * original sampling_rate was 1 second and the requested new sampling rate is 10
35 * ms because the user needs immediate reaction from ondemand governor, but not
36 * sure if higher frequency will be required or not, then, the governor may
37 * change the sampling rate too late; up to 1 second later. Thus, if we are
38 * reducing the sampling rate, we need to make the new value effective
39 * immediately.
40 *
41 * This must be called with dbs_data->mutex held, otherwise traversing
42 * 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 its
60 * entries can't be freed concurrently.
61 */
62 list_for_each_entry(policy_dbs, &attr_set->policy_list, list) {
63 mutex_lock(lock: &policy_dbs->update_mutex);
64 /*
65 * On 32-bit architectures this may race with the
66 * sample_delay_ns read in dbs_update_util_handler(), but that
67 * really doesn't matter. If the read returns a value that's
68 * too big, the sample will be skipped, but the next invocation
69 * of dbs_update_util_handler() (when the update has been
70 * completed) will take a sample.
71 *
72 * If this runs in parallel with dbs_work_handler(), we may end
73 * up overwriting the sample_delay_ns value that it has just
74 * written, but it will be corrected next time a sample is
75 * taken, so it shouldn't be significant.
76 */
77 gov_update_sample_delay(policy_dbs, delay_us: 0);
78 mutex_unlock(lock: &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_data
90 * (that may be a single policy or a bunch of them if governor tunables are
91 * 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(cpu: j, wall: &j_cdbs->prev_update_time,
106 io_busy: dbs_data->io_is_busy);
107 if (dbs_data->ignore_nice_load)
108 j_cdbs->prev_cpu_nice = kcpustat_field(kcpustat: &kcpustat_cpu(j), usage: CPUTIME_NICE, cpu: 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 increase
124 * sample delays temporarily. Apply that multiplier to sampling_rate
125 * so as to keep the wake-up-from-idle detection logic a bit
126 * 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 indication
131 * that you're performance critical, and not that the system is actually
132 * 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(cpu: j, wall: &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 /*
149 * cur_idle_time could be smaller than j_cdbs->prev_cpu_idle if
150 * it's obtained from get_cpu_idle_time_jiffy() when NOHZ is
151 * off, where idle_time is calculated by the difference between
152 * time elapsed in jiffies and "busy time" obtained from CPU
153 * statistics. If a CPU is 100% busy, the time elapsed and busy
154 * time should grow with the same amount in two consecutive
155 * samples, but in practice there could be a tiny difference,
156 * making the accumulated idle time decrease sometimes. Hence,
157 * in this case, idle_time should be regarded as 0 in order to
158 * make the further process correct.
159 */
160 if (cur_idle_time > j_cdbs->prev_cpu_idle)
161 idle_time = cur_idle_time - j_cdbs->prev_cpu_idle;
162 else
163 idle_time = 0;
164
165 j_cdbs->prev_cpu_idle = cur_idle_time;
166
167 if (ignore_nice) {
168 u64 cur_nice = kcpustat_field(kcpustat: &kcpustat_cpu(j), usage: CPUTIME_NICE, cpu: j);
169
170 idle_time += div_u64(dividend: cur_nice - j_cdbs->prev_cpu_nice, NSEC_PER_USEC);
171 j_cdbs->prev_cpu_nice = cur_nice;
172 }
173
174 if (unlikely(!time_elapsed)) {
175 /*
176 * That can only happen when this function is called
177 * twice in a row with a very short interval between the
178 * calls, so the previous load value can be used then.
179 */
180 load = j_cdbs->prev_load;
181 } else if (unlikely(idle_time > 2 * sampling_rate &&
182 j_cdbs->prev_load)) {
183 /*
184 * If the CPU had gone completely idle and a task has
185 * just woken up on this CPU now, it would be unfair to
186 * calculate 'load' the usual way for this elapsed
187 * time-window, because it would show near-zero load,
188 * irrespective of how CPU intensive that task actually
189 * was. This is undesirable for latency-sensitive bursty
190 * workloads.
191 *
192 * To avoid this, reuse the 'load' from the previous
193 * time-window and give this task a chance to start with
194 * a reasonably high CPU frequency. However, that
195 * shouldn't be over-done, lest we get stuck at a high
196 * load (high frequency) for too long, even when the
197 * current system load has actually dropped down, so
198 * clear prev_load to guarantee that the load will be
199 * computed again next time.
200 *
201 * Detecting this situation is easy: an unusually large
202 * 'idle_time' (as compared to the sampling rate)
203 * indicates this scenario.
204 */
205 load = j_cdbs->prev_load;
206 j_cdbs->prev_load = 0;
207 } else {
208 if (time_elapsed > idle_time)
209 load = 100 * (time_elapsed - idle_time) / time_elapsed;
210 else
211 load = 0;
212
213 j_cdbs->prev_load = load;
214 }
215
216 if (unlikely(idle_time > 2 * sampling_rate)) {
217 unsigned int periods = idle_time / sampling_rate;
218
219 if (periods < idle_periods)
220 idle_periods = periods;
221 }
222
223 if (load > max_load)
224 max_load = load;
225 }
226
227 policy_dbs->idle_periods = idle_periods;
228
229 return max_load;
230}
231EXPORT_SYMBOL_GPL(dbs_update);
232
233static void dbs_work_handler(struct work_struct *work)
234{
235 struct policy_dbs_info *policy_dbs;
236 struct cpufreq_policy *policy;
237 struct dbs_governor *gov;
238
239 policy_dbs = container_of(work, struct policy_dbs_info, work);
240 policy = policy_dbs->policy;
241 gov = dbs_governor_of(policy);
242
243 /*
244 * Make sure cpufreq_governor_limits() isn't evaluating load or the
245 * ondemand governor isn't updating the sampling rate in parallel.
246 */
247 mutex_lock(lock: &policy_dbs->update_mutex);
248 gov_update_sample_delay(policy_dbs, delay_us: gov->gov_dbs_update(policy));
249 mutex_unlock(lock: &policy_dbs->update_mutex);
250
251 /* Allow the utilization update handler to queue up more work. */
252 atomic_set(v: &policy_dbs->work_count, i: 0);
253 /*
254 * If the update below is reordered with respect to the sample delay
255 * modification, the utilization update handler may end up using a stale
256 * sample delay value.
257 */
258 smp_wmb();
259 policy_dbs->work_in_progress = false;
260}
261
262static void dbs_irq_work(struct irq_work *irq_work)
263{
264 struct policy_dbs_info *policy_dbs;
265
266 policy_dbs = container_of(irq_work, struct policy_dbs_info, irq_work);
267 schedule_work_on(smp_processor_id(), work: &policy_dbs->work);
268}
269
270static void dbs_update_util_handler(struct update_util_data *data, u64 time,
271 unsigned int flags)
272{
273 struct cpu_dbs_info *cdbs = container_of(data, struct cpu_dbs_info, update_util);
274 struct policy_dbs_info *policy_dbs = cdbs->policy_dbs;
275 u64 delta_ns, lst;
276
277 if (!cpufreq_this_cpu_can_update(policy: policy_dbs->policy))
278 return;
279
280 /*
281 * The work may not be allowed to be queued up right now.
282 * Possible reasons:
283 * - Work has already been queued up or is in progress.
284 * - It is too early (too little time from the previous sample).
285 */
286 if (policy_dbs->work_in_progress)
287 return;
288
289 /*
290 * If the reads below are reordered before the check above, the value
291 * of sample_delay_ns used in the computation may be stale.
292 */
293 smp_rmb();
294 lst = READ_ONCE(policy_dbs->last_sample_time);
295 delta_ns = time - lst;
296 if ((s64)delta_ns < policy_dbs->sample_delay_ns)
297 return;
298
299 /*
300 * If the policy is not shared, the irq_work may be queued up right away
301 * at this point. Otherwise, we need to ensure that only one of the
302 * CPUs sharing the policy will do that.
303 */
304 if (policy_dbs->is_shared) {
305 if (!atomic_add_unless(v: &policy_dbs->work_count, a: 1, u: 1))
306 return;
307
308 /*
309 * If another CPU updated last_sample_time in the meantime, we
310 * shouldn't be here, so clear the work counter and bail out.
311 */
312 if (unlikely(lst != READ_ONCE(policy_dbs->last_sample_time))) {
313 atomic_set(v: &policy_dbs->work_count, i: 0);
314 return;
315 }
316 }
317
318 policy_dbs->last_sample_time = time;
319 policy_dbs->work_in_progress = true;
320 irq_work_queue(work: &policy_dbs->irq_work);
321}
322
323static void gov_set_update_util(struct policy_dbs_info *policy_dbs,
324 unsigned int delay_us)
325{
326 struct cpufreq_policy *policy = policy_dbs->policy;
327 int cpu;
328
329 gov_update_sample_delay(policy_dbs, delay_us);
330 policy_dbs->last_sample_time = 0;
331
332 for_each_cpu(cpu, policy->cpus) {
333 struct cpu_dbs_info *cdbs = &per_cpu(cpu_dbs, cpu);
334
335 cpufreq_add_update_util_hook(cpu, data: &cdbs->update_util,
336 func: dbs_update_util_handler);
337 }
338}
339
340static inline void gov_clear_update_util(struct cpufreq_policy *policy)
341{
342 int i;
343
344 for_each_cpu(i, policy->cpus)
345 cpufreq_remove_update_util_hook(cpu: i);
346
347 synchronize_rcu();
348}
349
350static struct policy_dbs_info *alloc_policy_dbs_info(struct cpufreq_policy *policy,
351 struct dbs_governor *gov)
352{
353 struct policy_dbs_info *policy_dbs;
354 int j;
355
356 /* Allocate memory for per-policy governor data. */
357 policy_dbs = gov->alloc();
358 if (!policy_dbs)
359 return NULL;
360
361 policy_dbs->policy = policy;
362 mutex_init(&policy_dbs->update_mutex);
363 atomic_set(v: &policy_dbs->work_count, i: 0);
364 init_irq_work(work: &policy_dbs->irq_work, func: dbs_irq_work);
365 INIT_WORK(&policy_dbs->work, dbs_work_handler);
366
367 /* Set policy_dbs for all CPUs, online+offline */
368 for_each_cpu(j, policy->related_cpus) {
369 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
370
371 j_cdbs->policy_dbs = policy_dbs;
372 }
373 return policy_dbs;
374}
375
376static void free_policy_dbs_info(struct policy_dbs_info *policy_dbs,
377 struct dbs_governor *gov)
378{
379 int j;
380
381 mutex_destroy(lock: &policy_dbs->update_mutex);
382
383 for_each_cpu(j, policy_dbs->policy->related_cpus) {
384 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
385
386 j_cdbs->policy_dbs = NULL;
387 j_cdbs->update_util.func = NULL;
388 }
389 gov->free(policy_dbs);
390}
391
392static void cpufreq_dbs_data_release(struct kobject *kobj)
393{
394 struct dbs_data *dbs_data = to_dbs_data(attr_set: to_gov_attr_set(kobj));
395 struct dbs_governor *gov = dbs_data->gov;
396
397 gov->exit(dbs_data);
398 kfree(objp: dbs_data);
399}
400
401int cpufreq_dbs_governor_init(struct cpufreq_policy *policy)
402{
403 struct dbs_governor *gov = dbs_governor_of(policy);
404 struct dbs_data *dbs_data;
405 struct policy_dbs_info *policy_dbs;
406 int ret = 0;
407
408 /* State should be equivalent to EXIT */
409 if (policy->governor_data)
410 return -EBUSY;
411
412 policy_dbs = alloc_policy_dbs_info(policy, gov);
413 if (!policy_dbs)
414 return -ENOMEM;
415
416 /* Protect gov->gdbs_data against concurrent updates. */
417 mutex_lock(lock: &gov_dbs_data_mutex);
418
419 dbs_data = gov->gdbs_data;
420 if (dbs_data) {
421 if (WARN_ON(have_governor_per_policy())) {
422 ret = -EINVAL;
423 goto free_policy_dbs_info;
424 }
425 policy_dbs->dbs_data = dbs_data;
426 policy->governor_data = policy_dbs;
427
428 gov_attr_set_get(attr_set: &dbs_data->attr_set, list_node: &policy_dbs->list);
429 goto out;
430 }
431
432 dbs_data = kzalloc(sizeof(*dbs_data), GFP_KERNEL);
433 if (!dbs_data) {
434 ret = -ENOMEM;
435 goto free_policy_dbs_info;
436 }
437
438 dbs_data->gov = gov;
439 gov_attr_set_init(attr_set: &dbs_data->attr_set, list_node: &policy_dbs->list);
440
441 ret = gov->init(dbs_data);
442 if (ret)
443 goto free_dbs_data;
444
445 /*
446 * The sampling interval should not be less than the transition latency
447 * of the CPU and it also cannot be too small for dbs_update() to work
448 * correctly.
449 */
450 dbs_data->sampling_rate = max_t(unsigned int,
451 CPUFREQ_DBS_MIN_SAMPLING_INTERVAL,
452 cpufreq_policy_transition_delay_us(policy));
453
454 if (!have_governor_per_policy())
455 gov->gdbs_data = dbs_data;
456
457 policy_dbs->dbs_data = dbs_data;
458 policy->governor_data = policy_dbs;
459
460 gov->kobj_type.sysfs_ops = &governor_sysfs_ops;
461 gov->kobj_type.release = cpufreq_dbs_data_release;
462 ret = kobject_init_and_add(kobj: &dbs_data->attr_set.kobj, ktype: &gov->kobj_type,
463 parent: get_governor_parent_kobj(policy),
464 fmt: "%s", gov->gov.name);
465 if (!ret)
466 goto out;
467
468 /* Failure, so roll back. */
469 pr_err("initialization failed (dbs_data kobject init error %d)\n", ret);
470
471 kobject_put(kobj: &dbs_data->attr_set.kobj);
472
473 policy->governor_data = NULL;
474
475 if (!have_governor_per_policy())
476 gov->gdbs_data = NULL;
477 gov->exit(dbs_data);
478
479free_dbs_data:
480 kfree(objp: dbs_data);
481
482free_policy_dbs_info:
483 free_policy_dbs_info(policy_dbs, gov);
484
485out:
486 mutex_unlock(lock: &gov_dbs_data_mutex);
487 return ret;
488}
489EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_init);
490
491void cpufreq_dbs_governor_exit(struct cpufreq_policy *policy)
492{
493 struct dbs_governor *gov = dbs_governor_of(policy);
494 struct policy_dbs_info *policy_dbs = policy->governor_data;
495 struct dbs_data *dbs_data = policy_dbs->dbs_data;
496 unsigned int count;
497
498 /* Protect gov->gdbs_data against concurrent updates. */
499 mutex_lock(lock: &gov_dbs_data_mutex);
500
501 count = gov_attr_set_put(attr_set: &dbs_data->attr_set, list_node: &policy_dbs->list);
502
503 policy->governor_data = NULL;
504
505 if (!count && !have_governor_per_policy())
506 gov->gdbs_data = NULL;
507
508 free_policy_dbs_info(policy_dbs, gov);
509
510 mutex_unlock(lock: &gov_dbs_data_mutex);
511}
512EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_exit);
513
514int cpufreq_dbs_governor_start(struct cpufreq_policy *policy)
515{
516 struct dbs_governor *gov = dbs_governor_of(policy);
517 struct policy_dbs_info *policy_dbs = policy->governor_data;
518 struct dbs_data *dbs_data = policy_dbs->dbs_data;
519 unsigned int sampling_rate, ignore_nice, j;
520 unsigned int io_busy;
521
522 if (!policy->cur)
523 return -EINVAL;
524
525 policy_dbs->is_shared = policy_is_shared(policy);
526 policy_dbs->rate_mult = 1;
527
528 sampling_rate = dbs_data->sampling_rate;
529 ignore_nice = dbs_data->ignore_nice_load;
530 io_busy = dbs_data->io_is_busy;
531
532 for_each_cpu(j, policy->cpus) {
533 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);
534
535 j_cdbs->prev_cpu_idle = get_cpu_idle_time(cpu: j, wall: &j_cdbs->prev_update_time, io_busy);
536 /*
537 * Make the first invocation of dbs_update() compute the load.
538 */
539 j_cdbs->prev_load = 0;
540
541 if (ignore_nice)
542 j_cdbs->prev_cpu_nice = kcpustat_field(kcpustat: &kcpustat_cpu(j), usage: CPUTIME_NICE, cpu: j);
543 }
544
545 gov->start(policy);
546
547 gov_set_update_util(policy_dbs, delay_us: sampling_rate);
548 return 0;
549}
550EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_start);
551
552void cpufreq_dbs_governor_stop(struct cpufreq_policy *policy)
553{
554 struct policy_dbs_info *policy_dbs = policy->governor_data;
555
556 gov_clear_update_util(policy: policy_dbs->policy);
557 irq_work_sync(work: &policy_dbs->irq_work);
558 cancel_work_sync(work: &policy_dbs->work);
559 atomic_set(v: &policy_dbs->work_count, i: 0);
560 policy_dbs->work_in_progress = false;
561}
562EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_stop);
563
564void cpufreq_dbs_governor_limits(struct cpufreq_policy *policy)
565{
566 struct policy_dbs_info *policy_dbs;
567
568 /* Protect gov->gdbs_data against cpufreq_dbs_governor_exit() */
569 mutex_lock(lock: &gov_dbs_data_mutex);
570 policy_dbs = policy->governor_data;
571 if (!policy_dbs)
572 goto out;
573
574 mutex_lock(lock: &policy_dbs->update_mutex);
575 cpufreq_policy_apply_limits(policy);
576 gov_update_sample_delay(policy_dbs, delay_us: 0);
577 mutex_unlock(lock: &policy_dbs->update_mutex);
578
579out:
580 mutex_unlock(lock: &gov_dbs_data_mutex);
581}
582EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_limits);
583