2 * Devices PM QoS constraints management
4 * Copyright (C) 2011 Texas Instruments, Inc.
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
11 * This module exposes the interface to kernel space for specifying
12 * per-device PM QoS dependencies. It provides infrastructure for registration
15 * Dependents on a QoS value : register requests
16 * Watchers of QoS value : get notified when target QoS value changes
18 * This QoS design is best effort based. Dependents register their QoS needs.
19 * Watchers register to keep track of the current QoS needs of the system.
20 * Watchers can register different types of notification callbacks:
21 * . a per-device notification callback using the dev_pm_qos_*_notifier API.
22 * The notification chain data is stored in the per-device constraint
24 * . a system-wide notification callback using the dev_pm_qos_*_global_notifier
25 * API. The notification chain data is stored in a static variable.
27 * Note about the per-device constraint data struct allocation:
28 * . The per-device constraints data struct ptr is tored into the device
30 * . To minimize the data usage by the per-device constraints, the data struct
31 * is only allocated at the first call to dev_pm_qos_add_request.
32 * . The data is later free'd when the device is removed from the system.
33 * . A global mutex protects the constraints users from the data being
34 * allocated and free'd.
37 #include <linux/pm_qos.h>
38 #include <linux/spinlock.h>
39 #include <linux/slab.h>
40 #include <linux/device.h>
41 #include <linux/mutex.h>
42 #include <linux/export.h>
46 static DEFINE_MUTEX(dev_pm_qos_mtx);
48 static BLOCKING_NOTIFIER_HEAD(dev_pm_notifiers);
51 * __dev_pm_qos_read_value - Get PM QoS constraint for a given device.
52 * @dev: Device to get the PM QoS constraint value for.
54 * This routine must be called with dev->power.lock held.
56 s32 __dev_pm_qos_read_value(struct device *dev)
58 struct pm_qos_constraints *c = dev->power.constraints;
60 return c ? pm_qos_read_value(c) : 0;
64 * dev_pm_qos_read_value - Get PM QoS constraint for a given device (locked).
65 * @dev: Device to get the PM QoS constraint value for.
67 s32 dev_pm_qos_read_value(struct device *dev)
72 spin_lock_irqsave(&dev->power.lock, flags);
73 ret = __dev_pm_qos_read_value(dev);
74 spin_unlock_irqrestore(&dev->power.lock, flags);
81 * @req: constraint request to apply
82 * @action: action to perform add/update/remove, of type enum pm_qos_req_action
83 * @value: defines the qos request
85 * Internal function to update the constraints list using the PM QoS core
86 * code and if needed call the per-device and the global notification
89 static int apply_constraint(struct dev_pm_qos_request *req,
90 enum pm_qos_req_action action, int value)
94 ret = pm_qos_update_target(req->dev->power.constraints,
95 &req->node, action, value);
98 /* Call the global callbacks if needed */
99 curr_value = pm_qos_read_value(req->dev->power.constraints);
100 blocking_notifier_call_chain(&dev_pm_notifiers,
101 (unsigned long)curr_value,
109 * dev_pm_qos_constraints_allocate
110 * @dev: device to allocate data for
112 * Called at the first call to add_request, for constraint data allocation
113 * Must be called with the dev_pm_qos_mtx mutex held
115 static int dev_pm_qos_constraints_allocate(struct device *dev)
117 struct pm_qos_constraints *c;
118 struct blocking_notifier_head *n;
120 c = kzalloc(sizeof(*c), GFP_KERNEL);
124 n = kzalloc(sizeof(*n), GFP_KERNEL);
129 BLOCKING_INIT_NOTIFIER_HEAD(n);
131 plist_head_init(&c->list);
132 c->target_value = PM_QOS_DEV_LAT_DEFAULT_VALUE;
133 c->default_value = PM_QOS_DEV_LAT_DEFAULT_VALUE;
134 c->type = PM_QOS_MIN;
137 spin_lock_irq(&dev->power.lock);
138 dev->power.constraints = c;
139 spin_unlock_irq(&dev->power.lock);
145 * dev_pm_qos_constraints_init - Initalize device's PM QoS constraints pointer.
146 * @dev: target device
148 * Called from the device PM subsystem during device insertion under
151 void dev_pm_qos_constraints_init(struct device *dev)
153 mutex_lock(&dev_pm_qos_mtx);
154 dev->power.constraints = NULL;
155 dev->power.power_state = PMSG_ON;
156 mutex_unlock(&dev_pm_qos_mtx);
160 * dev_pm_qos_constraints_destroy
161 * @dev: target device
163 * Called from the device PM subsystem on device removal under device_pm_lock().
165 void dev_pm_qos_constraints_destroy(struct device *dev)
167 struct dev_pm_qos_request *req, *tmp;
168 struct pm_qos_constraints *c;
171 * If the device's PM QoS resume latency limit has been exposed to user
172 * space, it has to be hidden at this point.
174 dev_pm_qos_hide_latency_limit(dev);
176 mutex_lock(&dev_pm_qos_mtx);
178 dev->power.power_state = PMSG_INVALID;
179 c = dev->power.constraints;
183 /* Flush the constraints list for the device */
184 plist_for_each_entry_safe(req, tmp, &c->list, node) {
186 * Update constraints list and call the notification
187 * callbacks if needed
189 apply_constraint(req, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE);
190 memset(req, 0, sizeof(*req));
193 spin_lock_irq(&dev->power.lock);
194 dev->power.constraints = NULL;
195 spin_unlock_irq(&dev->power.lock);
201 mutex_unlock(&dev_pm_qos_mtx);
205 * dev_pm_qos_add_request - inserts new qos request into the list
206 * @dev: target device for the constraint
207 * @req: pointer to a preallocated handle
208 * @value: defines the qos request
210 * This function inserts a new entry in the device constraints list of
211 * requested qos performance characteristics. It recomputes the aggregate
212 * QoS expectations of parameters and initializes the dev_pm_qos_request
213 * handle. Caller needs to save this handle for later use in updates and
216 * Returns 1 if the aggregated constraint value has changed,
217 * 0 if the aggregated constraint value has not changed,
218 * -EINVAL in case of wrong parameters, -ENOMEM if there's not enough memory
219 * to allocate for data structures, -ENODEV if the device has just been removed
222 int dev_pm_qos_add_request(struct device *dev, struct dev_pm_qos_request *req,
227 if (!dev || !req) /*guard against callers passing in null */
230 if (WARN(dev_pm_qos_request_active(req),
231 "%s() called for already added request\n", __func__))
236 mutex_lock(&dev_pm_qos_mtx);
238 if (!dev->power.constraints) {
239 if (dev->power.power_state.event == PM_EVENT_INVALID) {
240 /* The device has been removed from the system. */
246 * Allocate the constraints data on the first call to
247 * add_request, i.e. only if the data is not already
248 * allocated and if the device has not been removed.
250 ret = dev_pm_qos_constraints_allocate(dev);
255 ret = apply_constraint(req, PM_QOS_ADD_REQ, value);
258 mutex_unlock(&dev_pm_qos_mtx);
262 EXPORT_SYMBOL_GPL(dev_pm_qos_add_request);
265 * dev_pm_qos_update_request - modifies an existing qos request
266 * @req : handle to list element holding a dev_pm_qos request to use
267 * @new_value: defines the qos request
269 * Updates an existing dev PM qos request along with updating the
272 * Attempts are made to make this code callable on hot code paths.
274 * Returns 1 if the aggregated constraint value has changed,
275 * 0 if the aggregated constraint value has not changed,
276 * -EINVAL in case of wrong parameters, -ENODEV if the device has been
277 * removed from the system
279 int dev_pm_qos_update_request(struct dev_pm_qos_request *req,
284 if (!req) /*guard against callers passing in null */
287 if (WARN(!dev_pm_qos_request_active(req),
288 "%s() called for unknown object\n", __func__))
291 mutex_lock(&dev_pm_qos_mtx);
293 if (req->dev->power.constraints) {
294 if (new_value != req->node.prio)
295 ret = apply_constraint(req, PM_QOS_UPDATE_REQ,
298 /* Return if the device has been removed */
302 mutex_unlock(&dev_pm_qos_mtx);
305 EXPORT_SYMBOL_GPL(dev_pm_qos_update_request);
308 * dev_pm_qos_remove_request - modifies an existing qos request
309 * @req: handle to request list element
311 * Will remove pm qos request from the list of constraints and
312 * recompute the current target value. Call this on slow code paths.
314 * Returns 1 if the aggregated constraint value has changed,
315 * 0 if the aggregated constraint value has not changed,
316 * -EINVAL in case of wrong parameters, -ENODEV if the device has been
317 * removed from the system
319 int dev_pm_qos_remove_request(struct dev_pm_qos_request *req)
323 if (!req) /*guard against callers passing in null */
326 if (WARN(!dev_pm_qos_request_active(req),
327 "%s() called for unknown object\n", __func__))
330 mutex_lock(&dev_pm_qos_mtx);
332 if (req->dev->power.constraints) {
333 ret = apply_constraint(req, PM_QOS_REMOVE_REQ,
334 PM_QOS_DEFAULT_VALUE);
335 memset(req, 0, sizeof(*req));
337 /* Return if the device has been removed */
341 mutex_unlock(&dev_pm_qos_mtx);
344 EXPORT_SYMBOL_GPL(dev_pm_qos_remove_request);
347 * dev_pm_qos_add_notifier - sets notification entry for changes to target value
348 * of per-device PM QoS constraints
350 * @dev: target device for the constraint
351 * @notifier: notifier block managed by caller.
353 * Will register the notifier into a notification chain that gets called
354 * upon changes to the target value for the device.
356 int dev_pm_qos_add_notifier(struct device *dev, struct notifier_block *notifier)
360 mutex_lock(&dev_pm_qos_mtx);
362 /* Silently return if the constraints object is not present. */
363 if (dev->power.constraints)
364 retval = blocking_notifier_chain_register(
365 dev->power.constraints->notifiers,
368 mutex_unlock(&dev_pm_qos_mtx);
371 EXPORT_SYMBOL_GPL(dev_pm_qos_add_notifier);
374 * dev_pm_qos_remove_notifier - deletes notification for changes to target value
375 * of per-device PM QoS constraints
377 * @dev: target device for the constraint
378 * @notifier: notifier block to be removed.
380 * Will remove the notifier from the notification chain that gets called
381 * upon changes to the target value.
383 int dev_pm_qos_remove_notifier(struct device *dev,
384 struct notifier_block *notifier)
388 mutex_lock(&dev_pm_qos_mtx);
390 /* Silently return if the constraints object is not present. */
391 if (dev->power.constraints)
392 retval = blocking_notifier_chain_unregister(
393 dev->power.constraints->notifiers,
396 mutex_unlock(&dev_pm_qos_mtx);
399 EXPORT_SYMBOL_GPL(dev_pm_qos_remove_notifier);
402 * dev_pm_qos_add_global_notifier - sets notification entry for changes to
403 * target value of the PM QoS constraints for any device
405 * @notifier: notifier block managed by caller.
407 * Will register the notifier into a notification chain that gets called
408 * upon changes to the target value for any device.
410 int dev_pm_qos_add_global_notifier(struct notifier_block *notifier)
412 return blocking_notifier_chain_register(&dev_pm_notifiers, notifier);
414 EXPORT_SYMBOL_GPL(dev_pm_qos_add_global_notifier);
417 * dev_pm_qos_remove_global_notifier - deletes notification for changes to
418 * target value of PM QoS constraints for any device
420 * @notifier: notifier block to be removed.
422 * Will remove the notifier from the notification chain that gets called
423 * upon changes to the target value for any device.
425 int dev_pm_qos_remove_global_notifier(struct notifier_block *notifier)
427 return blocking_notifier_chain_unregister(&dev_pm_notifiers, notifier);
429 EXPORT_SYMBOL_GPL(dev_pm_qos_remove_global_notifier);
432 * dev_pm_qos_add_ancestor_request - Add PM QoS request for device's ancestor.
433 * @dev: Device whose ancestor to add the request for.
434 * @req: Pointer to the preallocated handle.
435 * @value: Constraint latency value.
437 int dev_pm_qos_add_ancestor_request(struct device *dev,
438 struct dev_pm_qos_request *req, s32 value)
440 struct device *ancestor = dev->parent;
443 while (ancestor && !ancestor->power.ignore_children)
444 ancestor = ancestor->parent;
447 error = dev_pm_qos_add_request(ancestor, req, value);
454 EXPORT_SYMBOL_GPL(dev_pm_qos_add_ancestor_request);
456 #ifdef CONFIG_PM_RUNTIME
457 static void __dev_pm_qos_drop_user_request(struct device *dev)
459 dev_pm_qos_remove_request(dev->power.pq_req);
460 dev->power.pq_req = 0;
464 * dev_pm_qos_expose_latency_limit - Expose PM QoS latency limit to user space.
465 * @dev: Device whose PM QoS latency limit is to be exposed to user space.
466 * @value: Initial value of the latency limit.
468 int dev_pm_qos_expose_latency_limit(struct device *dev, s32 value)
470 struct dev_pm_qos_request *req;
473 if (!device_is_registered(dev) || value < 0)
476 if (dev->power.pq_req)
479 req = kzalloc(sizeof(*req), GFP_KERNEL);
483 ret = dev_pm_qos_add_request(dev, req, value);
487 dev->power.pq_req = req;
488 ret = pm_qos_sysfs_add(dev);
490 __dev_pm_qos_drop_user_request(dev);
494 EXPORT_SYMBOL_GPL(dev_pm_qos_expose_latency_limit);
497 * dev_pm_qos_hide_latency_limit - Hide PM QoS latency limit from user space.
498 * @dev: Device whose PM QoS latency limit is to be hidden from user space.
500 void dev_pm_qos_hide_latency_limit(struct device *dev)
502 if (dev->power.pq_req) {
503 pm_qos_sysfs_remove(dev);
504 __dev_pm_qos_drop_user_request(dev);
507 EXPORT_SYMBOL_GPL(dev_pm_qos_hide_latency_limit);
508 #endif /* CONFIG_PM_RUNTIME */