1 // SPDX-License-Identifier: GPL-2.0-only
3 * Power Management Quality of Service (PM QoS) support base.
5 * Copyright (C) 2020 Intel Corporation
8 * Mark Gross <mgross@linux.intel.com>
9 * Rafael J. Wysocki <rafael.j.wysocki@intel.com>
11 * Provided here is an interface for specifying PM QoS dependencies. It allows
12 * entities depending on QoS constraints to register their requests which are
13 * aggregated as appropriate to produce effective constraints (target values)
14 * that can be monitored by entities needing to respect them, either by polling
15 * or through a built-in notification mechanism.
17 * In addition to the basic functionality, more specific interfaces for managing
18 * global CPU latency QoS requests and frequency QoS requests are provided.
23 #include <linux/pm_qos.h>
24 #include <linux/sched.h>
25 #include <linux/spinlock.h>
26 #include <linux/slab.h>
27 #include <linux/time.h>
29 #include <linux/device.h>
30 #include <linux/miscdevice.h>
31 #include <linux/string.h>
32 #include <linux/platform_device.h>
33 #include <linux/init.h>
34 #include <linux/kernel.h>
35 #include <linux/debugfs.h>
36 #include <linux/seq_file.h>
38 #include <linux/uaccess.h>
39 #include <linux/export.h>
40 #include <trace/events/power.h>
43 * locking rule: all changes to constraints or notifiers lists
44 * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
45 * held, taken with _irqsave. One lock to rule them all
47 static DEFINE_SPINLOCK(pm_qos_lock);
50 * pm_qos_read_value - Return the current effective constraint value.
51 * @c: List of PM QoS constraint requests.
53 s32 pm_qos_read_value(struct pm_qos_constraints *c)
55 return READ_ONCE(c->target_value);
58 static int pm_qos_get_value(struct pm_qos_constraints *c)
60 if (plist_head_empty(&c->list))
61 return c->no_constraint_value;
65 return plist_first(&c->list)->prio;
68 return plist_last(&c->list)->prio;
71 WARN(1, "Unknown PM QoS type in %s\n", __func__);
72 return PM_QOS_DEFAULT_VALUE;
76 static void pm_qos_set_value(struct pm_qos_constraints *c, s32 value)
78 WRITE_ONCE(c->target_value, value);
82 * pm_qos_update_target - Update a list of PM QoS constraint requests.
83 * @c: List of PM QoS requests.
84 * @node: Target list entry.
85 * @action: Action to carry out (add, update or remove).
86 * @value: New request value for the target list entry.
88 * Update the given list of PM QoS constraint requests, @c, by carrying an
89 * @action involving the @node list entry and @value on it.
91 * The recognized values of @action are PM_QOS_ADD_REQ (store @value in @node
92 * and add it to the list), PM_QOS_UPDATE_REQ (remove @node from the list, store
93 * @value in it and add it to the list again), and PM_QOS_REMOVE_REQ (remove
94 * @node from the list, ignore @value).
96 * Return: 1 if the aggregate constraint value has changed, 0 otherwise.
98 int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node,
99 enum pm_qos_req_action action, int value)
101 int prev_value, curr_value, new_value;
104 spin_lock_irqsave(&pm_qos_lock, flags);
106 prev_value = pm_qos_get_value(c);
107 if (value == PM_QOS_DEFAULT_VALUE)
108 new_value = c->default_value;
113 case PM_QOS_REMOVE_REQ:
114 plist_del(node, &c->list);
116 case PM_QOS_UPDATE_REQ:
118 * To change the list, atomically remove, reinit with new value
119 * and add, then see if the aggregate has changed.
121 plist_del(node, &c->list);
124 plist_node_init(node, new_value);
125 plist_add(node, &c->list);
132 curr_value = pm_qos_get_value(c);
133 pm_qos_set_value(c, curr_value);
135 spin_unlock_irqrestore(&pm_qos_lock, flags);
137 trace_pm_qos_update_target(action, prev_value, curr_value);
139 if (prev_value == curr_value)
143 blocking_notifier_call_chain(c->notifiers, curr_value, NULL);
149 * pm_qos_flags_remove_req - Remove device PM QoS flags request.
150 * @pqf: Device PM QoS flags set to remove the request from.
151 * @req: Request to remove from the set.
153 static void pm_qos_flags_remove_req(struct pm_qos_flags *pqf,
154 struct pm_qos_flags_request *req)
158 list_del(&req->node);
159 list_for_each_entry(req, &pqf->list, node)
162 pqf->effective_flags = val;
166 * pm_qos_update_flags - Update a set of PM QoS flags.
167 * @pqf: Set of PM QoS flags to update.
168 * @req: Request to add to the set, to modify, or to remove from the set.
169 * @action: Action to take on the set.
170 * @val: Value of the request to add or modify.
172 * Return: 1 if the aggregate constraint value has changed, 0 otherwise.
174 bool pm_qos_update_flags(struct pm_qos_flags *pqf,
175 struct pm_qos_flags_request *req,
176 enum pm_qos_req_action action, s32 val)
178 unsigned long irqflags;
179 s32 prev_value, curr_value;
181 spin_lock_irqsave(&pm_qos_lock, irqflags);
183 prev_value = list_empty(&pqf->list) ? 0 : pqf->effective_flags;
186 case PM_QOS_REMOVE_REQ:
187 pm_qos_flags_remove_req(pqf, req);
189 case PM_QOS_UPDATE_REQ:
190 pm_qos_flags_remove_req(pqf, req);
194 INIT_LIST_HEAD(&req->node);
195 list_add_tail(&req->node, &pqf->list);
196 pqf->effective_flags |= val;
203 curr_value = list_empty(&pqf->list) ? 0 : pqf->effective_flags;
205 spin_unlock_irqrestore(&pm_qos_lock, irqflags);
207 trace_pm_qos_update_flags(action, prev_value, curr_value);
209 return prev_value != curr_value;
212 #ifdef CONFIG_CPU_IDLE
213 /* Definitions related to the CPU latency QoS. */
215 static struct pm_qos_constraints cpu_latency_constraints = {
216 .list = PLIST_HEAD_INIT(cpu_latency_constraints.list),
217 .target_value = PM_QOS_CPU_LATENCY_DEFAULT_VALUE,
218 .default_value = PM_QOS_CPU_LATENCY_DEFAULT_VALUE,
219 .no_constraint_value = PM_QOS_CPU_LATENCY_DEFAULT_VALUE,
224 * cpu_latency_qos_limit - Return current system-wide CPU latency QoS limit.
226 s32 cpu_latency_qos_limit(void)
228 return pm_qos_read_value(&cpu_latency_constraints);
232 * cpu_latency_qos_request_active - Check the given PM QoS request.
233 * @req: PM QoS request to check.
235 * Return: 'true' if @req has been added to the CPU latency QoS list, 'false'
238 bool cpu_latency_qos_request_active(struct pm_qos_request *req)
240 return req->qos == &cpu_latency_constraints;
242 EXPORT_SYMBOL_GPL(cpu_latency_qos_request_active);
244 static void cpu_latency_qos_apply(struct pm_qos_request *req,
245 enum pm_qos_req_action action, s32 value)
247 int ret = pm_qos_update_target(req->qos, &req->node, action, value);
249 wake_up_all_idle_cpus();
253 * cpu_latency_qos_add_request - Add new CPU latency QoS request.
254 * @req: Pointer to a preallocated handle.
255 * @value: Requested constraint value.
257 * Use @value to initialize the request handle pointed to by @req, insert it as
258 * a new entry to the CPU latency QoS list and recompute the effective QoS
259 * constraint for that list.
261 * Callers need to save the handle for later use in updates and removal of the
262 * QoS request represented by it.
264 void cpu_latency_qos_add_request(struct pm_qos_request *req, s32 value)
269 if (cpu_latency_qos_request_active(req)) {
270 WARN(1, KERN_ERR "%s called for already added request\n", __func__);
274 trace_pm_qos_add_request(value);
276 req->qos = &cpu_latency_constraints;
277 cpu_latency_qos_apply(req, PM_QOS_ADD_REQ, value);
279 EXPORT_SYMBOL_GPL(cpu_latency_qos_add_request);
282 * cpu_latency_qos_update_request - Modify existing CPU latency QoS request.
283 * @req : QoS request to update.
284 * @new_value: New requested constraint value.
286 * Use @new_value to update the QoS request represented by @req in the CPU
287 * latency QoS list along with updating the effective constraint value for that
290 void cpu_latency_qos_update_request(struct pm_qos_request *req, s32 new_value)
295 if (!cpu_latency_qos_request_active(req)) {
296 WARN(1, KERN_ERR "%s called for unknown object\n", __func__);
300 trace_pm_qos_update_request(new_value);
302 if (new_value == req->node.prio)
305 cpu_latency_qos_apply(req, PM_QOS_UPDATE_REQ, new_value);
307 EXPORT_SYMBOL_GPL(cpu_latency_qos_update_request);
310 * cpu_latency_qos_remove_request - Remove existing CPU latency QoS request.
311 * @req: QoS request to remove.
313 * Remove the CPU latency QoS request represented by @req from the CPU latency
314 * QoS list along with updating the effective constraint value for that list.
316 void cpu_latency_qos_remove_request(struct pm_qos_request *req)
321 if (!cpu_latency_qos_request_active(req)) {
322 WARN(1, KERN_ERR "%s called for unknown object\n", __func__);
326 trace_pm_qos_remove_request(PM_QOS_DEFAULT_VALUE);
328 cpu_latency_qos_apply(req, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE);
329 memset(req, 0, sizeof(*req));
331 EXPORT_SYMBOL_GPL(cpu_latency_qos_remove_request);
333 /* User space interface to the CPU latency QoS via misc device. */
335 static int cpu_latency_qos_open(struct inode *inode, struct file *filp)
337 struct pm_qos_request *req;
339 req = kzalloc(sizeof(*req), GFP_KERNEL);
343 cpu_latency_qos_add_request(req, PM_QOS_DEFAULT_VALUE);
344 filp->private_data = req;
349 static int cpu_latency_qos_release(struct inode *inode, struct file *filp)
351 struct pm_qos_request *req = filp->private_data;
353 filp->private_data = NULL;
355 cpu_latency_qos_remove_request(req);
361 static ssize_t cpu_latency_qos_read(struct file *filp, char __user *buf,
362 size_t count, loff_t *f_pos)
364 struct pm_qos_request *req = filp->private_data;
368 if (!req || !cpu_latency_qos_request_active(req))
371 spin_lock_irqsave(&pm_qos_lock, flags);
372 value = pm_qos_get_value(&cpu_latency_constraints);
373 spin_unlock_irqrestore(&pm_qos_lock, flags);
375 return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
378 static ssize_t cpu_latency_qos_write(struct file *filp, const char __user *buf,
379 size_t count, loff_t *f_pos)
383 if (count == sizeof(s32)) {
384 if (copy_from_user(&value, buf, sizeof(s32)))
389 ret = kstrtos32_from_user(buf, count, 16, &value);
394 cpu_latency_qos_update_request(filp->private_data, value);
399 static const struct file_operations cpu_latency_qos_fops = {
400 .write = cpu_latency_qos_write,
401 .read = cpu_latency_qos_read,
402 .open = cpu_latency_qos_open,
403 .release = cpu_latency_qos_release,
404 .llseek = noop_llseek,
407 static struct miscdevice cpu_latency_qos_miscdev = {
408 .minor = MISC_DYNAMIC_MINOR,
409 .name = "cpu_dma_latency",
410 .fops = &cpu_latency_qos_fops,
413 static int __init cpu_latency_qos_init(void)
417 ret = misc_register(&cpu_latency_qos_miscdev);
419 pr_err("%s: %s setup failed\n", __func__,
420 cpu_latency_qos_miscdev.name);
424 late_initcall(cpu_latency_qos_init);
425 #endif /* CONFIG_CPU_IDLE */
427 /* Definitions related to the frequency QoS below. */
429 static inline bool freq_qos_value_invalid(s32 value)
431 return value < 0 && value != PM_QOS_DEFAULT_VALUE;
435 * freq_constraints_init - Initialize frequency QoS constraints.
436 * @qos: Frequency QoS constraints to initialize.
438 void freq_constraints_init(struct freq_constraints *qos)
440 struct pm_qos_constraints *c;
443 plist_head_init(&c->list);
444 c->target_value = FREQ_QOS_MIN_DEFAULT_VALUE;
445 c->default_value = FREQ_QOS_MIN_DEFAULT_VALUE;
446 c->no_constraint_value = FREQ_QOS_MIN_DEFAULT_VALUE;
447 c->type = PM_QOS_MAX;
448 c->notifiers = &qos->min_freq_notifiers;
449 BLOCKING_INIT_NOTIFIER_HEAD(c->notifiers);
452 plist_head_init(&c->list);
453 c->target_value = FREQ_QOS_MAX_DEFAULT_VALUE;
454 c->default_value = FREQ_QOS_MAX_DEFAULT_VALUE;
455 c->no_constraint_value = FREQ_QOS_MAX_DEFAULT_VALUE;
456 c->type = PM_QOS_MIN;
457 c->notifiers = &qos->max_freq_notifiers;
458 BLOCKING_INIT_NOTIFIER_HEAD(c->notifiers);
462 * freq_qos_read_value - Get frequency QoS constraint for a given list.
463 * @qos: Constraints to evaluate.
464 * @type: QoS request type.
466 s32 freq_qos_read_value(struct freq_constraints *qos,
467 enum freq_qos_req_type type)
473 ret = IS_ERR_OR_NULL(qos) ?
474 FREQ_QOS_MIN_DEFAULT_VALUE :
475 pm_qos_read_value(&qos->min_freq);
478 ret = IS_ERR_OR_NULL(qos) ?
479 FREQ_QOS_MAX_DEFAULT_VALUE :
480 pm_qos_read_value(&qos->max_freq);
491 * freq_qos_apply - Add/modify/remove frequency QoS request.
492 * @req: Constraint request to apply.
493 * @action: Action to perform (add/update/remove).
494 * @value: Value to assign to the QoS request.
496 * This is only meant to be called from inside pm_qos, not drivers.
498 int freq_qos_apply(struct freq_qos_request *req,
499 enum pm_qos_req_action action, s32 value)
505 ret = pm_qos_update_target(&req->qos->min_freq, &req->pnode,
509 ret = pm_qos_update_target(&req->qos->max_freq, &req->pnode,
520 * freq_qos_add_request - Insert new frequency QoS request into a given list.
521 * @qos: Constraints to update.
522 * @req: Preallocated request object.
523 * @type: Request type.
524 * @value: Request value.
526 * Insert a new entry into the @qos list of requests, recompute the effective
527 * QoS constraint value for that list and initialize the @req object. The
528 * caller needs to save that object for later use in updates and removal.
530 * Return 1 if the effective constraint value has changed, 0 if the effective
531 * constraint value has not changed, or a negative error code on failures.
533 int freq_qos_add_request(struct freq_constraints *qos,
534 struct freq_qos_request *req,
535 enum freq_qos_req_type type, s32 value)
539 if (IS_ERR_OR_NULL(qos) || !req || freq_qos_value_invalid(value))
542 if (WARN(freq_qos_request_active(req),
543 "%s() called for active request\n", __func__))
548 ret = freq_qos_apply(req, PM_QOS_ADD_REQ, value);
556 EXPORT_SYMBOL_GPL(freq_qos_add_request);
559 * freq_qos_update_request - Modify existing frequency QoS request.
560 * @req: Request to modify.
561 * @new_value: New request value.
563 * Update an existing frequency QoS request along with the effective constraint
564 * value for the list of requests it belongs to.
566 * Return 1 if the effective constraint value has changed, 0 if the effective
567 * constraint value has not changed, or a negative error code on failures.
569 int freq_qos_update_request(struct freq_qos_request *req, s32 new_value)
571 if (!req || freq_qos_value_invalid(new_value))
574 if (WARN(!freq_qos_request_active(req),
575 "%s() called for unknown object\n", __func__))
578 if (req->pnode.prio == new_value)
581 return freq_qos_apply(req, PM_QOS_UPDATE_REQ, new_value);
583 EXPORT_SYMBOL_GPL(freq_qos_update_request);
586 * freq_qos_remove_request - Remove frequency QoS request from its list.
587 * @req: Request to remove.
589 * Remove the given frequency QoS request from the list of constraints it
590 * belongs to and recompute the effective constraint value for that list.
592 * Return 1 if the effective constraint value has changed, 0 if the effective
593 * constraint value has not changed, or a negative error code on failures.
595 int freq_qos_remove_request(struct freq_qos_request *req)
602 if (WARN(!freq_qos_request_active(req),
603 "%s() called for unknown object\n", __func__))
606 ret = freq_qos_apply(req, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE);
612 EXPORT_SYMBOL_GPL(freq_qos_remove_request);
615 * freq_qos_add_notifier - Add frequency QoS change notifier.
616 * @qos: List of requests to add the notifier to.
617 * @type: Request type.
618 * @notifier: Notifier block to add.
620 int freq_qos_add_notifier(struct freq_constraints *qos,
621 enum freq_qos_req_type type,
622 struct notifier_block *notifier)
626 if (IS_ERR_OR_NULL(qos) || !notifier)
631 ret = blocking_notifier_chain_register(qos->min_freq.notifiers,
635 ret = blocking_notifier_chain_register(qos->max_freq.notifiers,
645 EXPORT_SYMBOL_GPL(freq_qos_add_notifier);
648 * freq_qos_remove_notifier - Remove frequency QoS change notifier.
649 * @qos: List of requests to remove the notifier from.
650 * @type: Request type.
651 * @notifier: Notifier block to remove.
653 int freq_qos_remove_notifier(struct freq_constraints *qos,
654 enum freq_qos_req_type type,
655 struct notifier_block *notifier)
659 if (IS_ERR_OR_NULL(qos) || !notifier)
664 ret = blocking_notifier_chain_unregister(qos->min_freq.notifiers,
668 ret = blocking_notifier_chain_unregister(qos->max_freq.notifiers,
678 EXPORT_SYMBOL_GPL(freq_qos_remove_notifier);