2 * This module exposes the interface to kernel space for specifying
3 * QoS dependencies. It provides infrastructure for registration of:
5 * Dependents on a QoS value : register requests
6 * Watchers of QoS value : get notified when target QoS value changes
8 * This QoS design is best effort based. Dependents register their QoS needs.
9 * Watchers register to keep track of the current QoS needs of the system.
11 * There are 3 basic classes of QoS parameter: latency, timeout, throughput
12 * each have defined units:
14 * timeout: usec <-- currently not used.
15 * throughput: kbs (kilo byte / sec)
17 * There are lists of pm_qos_objects each one wrapping requests, notifiers
19 * User mode requests on a QOS parameter register themselves to the
20 * subsystem by opening the device node /dev/... and writing there request to
21 * the node. As long as the process holds a file handle open to the node the
22 * client continues to be accounted for. Upon file release the usermode
23 * request is removed and a new qos target is computed. This way when the
24 * request that the application has is cleaned up when closes the file
25 * pointer or exits the pm_qos_object will get an opportunity to clean up.
27 * Mark Gross <mgross@linux.intel.com>
32 #include <linux/pm_qos.h>
33 #include <linux/sched.h>
34 #include <linux/spinlock.h>
35 #include <linux/slab.h>
36 #include <linux/time.h>
38 #include <linux/device.h>
39 #include <linux/miscdevice.h>
40 #include <linux/string.h>
41 #include <linux/platform_device.h>
42 #include <linux/init.h>
43 #include <linux/kernel.h>
45 #include <linux/uaccess.h>
46 #include <linux/export.h>
47 #include <trace/events/power.h>
50 * locking rule: all changes to constraints or notifiers lists
51 * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
52 * held, taken with _irqsave. One lock to rule them all
54 struct pm_qos_object
{
55 struct pm_qos_constraints
*constraints
;
56 struct miscdevice pm_qos_power_miscdev
;
60 static DEFINE_SPINLOCK(pm_qos_lock
);
62 static struct pm_qos_object null_pm_qos
;
64 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier
);
65 static struct pm_qos_constraints cpu_dma_constraints
= {
66 .list
= PLIST_HEAD_INIT(cpu_dma_constraints
.list
),
67 .target_value
= PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE
,
68 .default_value
= PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE
,
69 .no_constraint_value
= PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE
,
71 .notifiers
= &cpu_dma_lat_notifier
,
73 static struct pm_qos_object cpu_dma_pm_qos
= {
74 .constraints
= &cpu_dma_constraints
,
75 .name
= "cpu_dma_latency",
78 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier
);
79 static struct pm_qos_constraints network_lat_constraints
= {
80 .list
= PLIST_HEAD_INIT(network_lat_constraints
.list
),
81 .target_value
= PM_QOS_NETWORK_LAT_DEFAULT_VALUE
,
82 .default_value
= PM_QOS_NETWORK_LAT_DEFAULT_VALUE
,
83 .no_constraint_value
= PM_QOS_NETWORK_LAT_DEFAULT_VALUE
,
85 .notifiers
= &network_lat_notifier
,
87 static struct pm_qos_object network_lat_pm_qos
= {
88 .constraints
= &network_lat_constraints
,
89 .name
= "network_latency",
93 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier
);
94 static struct pm_qos_constraints network_tput_constraints
= {
95 .list
= PLIST_HEAD_INIT(network_tput_constraints
.list
),
96 .target_value
= PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE
,
97 .default_value
= PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE
,
98 .no_constraint_value
= PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE
,
100 .notifiers
= &network_throughput_notifier
,
102 static struct pm_qos_object network_throughput_pm_qos
= {
103 .constraints
= &network_tput_constraints
,
104 .name
= "network_throughput",
108 static struct pm_qos_object
*pm_qos_array
[] = {
112 &network_throughput_pm_qos
115 static ssize_t
pm_qos_power_write(struct file
*filp
, const char __user
*buf
,
116 size_t count
, loff_t
*f_pos
);
117 static ssize_t
pm_qos_power_read(struct file
*filp
, char __user
*buf
,
118 size_t count
, loff_t
*f_pos
);
119 static int pm_qos_power_open(struct inode
*inode
, struct file
*filp
);
120 static int pm_qos_power_release(struct inode
*inode
, struct file
*filp
);
122 static const struct file_operations pm_qos_power_fops
= {
123 .write
= pm_qos_power_write
,
124 .read
= pm_qos_power_read
,
125 .open
= pm_qos_power_open
,
126 .release
= pm_qos_power_release
,
127 .llseek
= noop_llseek
,
130 /* unlocked internal variant */
131 static inline int pm_qos_get_value(struct pm_qos_constraints
*c
)
133 if (plist_head_empty(&c
->list
))
134 return c
->no_constraint_value
;
138 return plist_first(&c
->list
)->prio
;
141 return plist_last(&c
->list
)->prio
;
144 /* runtime check for not using enum */
146 return PM_QOS_DEFAULT_VALUE
;
150 s32
pm_qos_read_value(struct pm_qos_constraints
*c
)
152 return c
->target_value
;
155 static inline void pm_qos_set_value(struct pm_qos_constraints
*c
, s32 value
)
157 c
->target_value
= value
;
161 * pm_qos_update_target - manages the constraints list and calls the notifiers
163 * @c: constraints data struct
164 * @node: request to add to the list, to update or to remove
165 * @action: action to take on the constraints list
166 * @value: value of the request to add or update
168 * This function returns 1 if the aggregated constraint value has changed, 0
171 int pm_qos_update_target(struct pm_qos_constraints
*c
, struct plist_node
*node
,
172 enum pm_qos_req_action action
, int value
)
175 int prev_value
, curr_value
, new_value
;
178 spin_lock_irqsave(&pm_qos_lock
, flags
);
179 prev_value
= pm_qos_get_value(c
);
180 if (value
== PM_QOS_DEFAULT_VALUE
)
181 new_value
= c
->default_value
;
186 case PM_QOS_REMOVE_REQ
:
187 plist_del(node
, &c
->list
);
189 case PM_QOS_UPDATE_REQ
:
191 * to change the list, we atomically remove, reinit
192 * with new value and add, then see if the extremal
195 plist_del(node
, &c
->list
);
197 plist_node_init(node
, new_value
);
198 plist_add(node
, &c
->list
);
205 curr_value
= pm_qos_get_value(c
);
206 pm_qos_set_value(c
, curr_value
);
208 spin_unlock_irqrestore(&pm_qos_lock
, flags
);
210 trace_pm_qos_update_target(action
, prev_value
, curr_value
);
211 if (prev_value
!= curr_value
) {
214 blocking_notifier_call_chain(c
->notifiers
,
215 (unsigned long)curr_value
,
224 * pm_qos_flags_remove_req - Remove device PM QoS flags request.
225 * @pqf: Device PM QoS flags set to remove the request from.
226 * @req: Request to remove from the set.
228 static void pm_qos_flags_remove_req(struct pm_qos_flags
*pqf
,
229 struct pm_qos_flags_request
*req
)
233 list_del(&req
->node
);
234 list_for_each_entry(req
, &pqf
->list
, node
)
237 pqf
->effective_flags
= val
;
241 * pm_qos_update_flags - Update a set of PM QoS flags.
242 * @pqf: Set of flags to update.
243 * @req: Request to add to the set, to modify, or to remove from the set.
244 * @action: Action to take on the set.
245 * @val: Value of the request to add or modify.
247 * Update the given set of PM QoS flags and call notifiers if the aggregate
248 * value has changed. Returns 1 if the aggregate constraint value has changed,
251 bool pm_qos_update_flags(struct pm_qos_flags
*pqf
,
252 struct pm_qos_flags_request
*req
,
253 enum pm_qos_req_action action
, s32 val
)
255 unsigned long irqflags
;
256 s32 prev_value
, curr_value
;
258 spin_lock_irqsave(&pm_qos_lock
, irqflags
);
260 prev_value
= list_empty(&pqf
->list
) ? 0 : pqf
->effective_flags
;
263 case PM_QOS_REMOVE_REQ
:
264 pm_qos_flags_remove_req(pqf
, req
);
266 case PM_QOS_UPDATE_REQ
:
267 pm_qos_flags_remove_req(pqf
, req
);
270 INIT_LIST_HEAD(&req
->node
);
271 list_add_tail(&req
->node
, &pqf
->list
);
272 pqf
->effective_flags
|= val
;
279 curr_value
= list_empty(&pqf
->list
) ? 0 : pqf
->effective_flags
;
281 spin_unlock_irqrestore(&pm_qos_lock
, irqflags
);
283 trace_pm_qos_update_flags(action
, prev_value
, curr_value
);
284 return prev_value
!= curr_value
;
288 * pm_qos_request - returns current system wide qos expectation
289 * @pm_qos_class: identification of which qos value is requested
291 * This function returns the current target value.
293 int pm_qos_request(int pm_qos_class
)
295 return pm_qos_read_value(pm_qos_array
[pm_qos_class
]->constraints
);
297 EXPORT_SYMBOL_GPL(pm_qos_request
);
299 int pm_qos_request_active(struct pm_qos_request
*req
)
301 return req
->pm_qos_class
!= 0;
303 EXPORT_SYMBOL_GPL(pm_qos_request_active
);
305 static void __pm_qos_update_request(struct pm_qos_request
*req
,
308 trace_pm_qos_update_request(req
->pm_qos_class
, new_value
);
310 if (new_value
!= req
->node
.prio
)
311 pm_qos_update_target(
312 pm_qos_array
[req
->pm_qos_class
]->constraints
,
313 &req
->node
, PM_QOS_UPDATE_REQ
, new_value
);
317 * pm_qos_work_fn - the timeout handler of pm_qos_update_request_timeout
318 * @work: work struct for the delayed work (timeout)
320 * This cancels the timeout request by falling back to the default at timeout.
322 static void pm_qos_work_fn(struct work_struct
*work
)
324 struct pm_qos_request
*req
= container_of(to_delayed_work(work
),
325 struct pm_qos_request
,
328 __pm_qos_update_request(req
, PM_QOS_DEFAULT_VALUE
);
332 * pm_qos_add_request - inserts new qos request into the list
333 * @req: pointer to a preallocated handle
334 * @pm_qos_class: identifies which list of qos request to use
335 * @value: defines the qos request
337 * This function inserts a new entry in the pm_qos_class list of requested qos
338 * performance characteristics. It recomputes the aggregate QoS expectations
339 * for the pm_qos_class of parameters and initializes the pm_qos_request
340 * handle. Caller needs to save this handle for later use in updates and
344 void pm_qos_add_request(struct pm_qos_request
*req
,
345 int pm_qos_class
, s32 value
)
347 if (!req
) /*guard against callers passing in null */
350 if (pm_qos_request_active(req
)) {
351 WARN(1, KERN_ERR
"pm_qos_add_request() called for already added request\n");
354 req
->pm_qos_class
= pm_qos_class
;
355 INIT_DELAYED_WORK(&req
->work
, pm_qos_work_fn
);
356 trace_pm_qos_add_request(pm_qos_class
, value
);
357 pm_qos_update_target(pm_qos_array
[pm_qos_class
]->constraints
,
358 &req
->node
, PM_QOS_ADD_REQ
, value
);
360 EXPORT_SYMBOL_GPL(pm_qos_add_request
);
363 * pm_qos_update_request - modifies an existing qos request
364 * @req : handle to list element holding a pm_qos request to use
365 * @value: defines the qos request
367 * Updates an existing qos request for the pm_qos_class of parameters along
368 * with updating the target pm_qos_class value.
370 * Attempts are made to make this code callable on hot code paths.
372 void pm_qos_update_request(struct pm_qos_request
*req
,
375 if (!req
) /*guard against callers passing in null */
378 if (!pm_qos_request_active(req
)) {
379 WARN(1, KERN_ERR
"pm_qos_update_request() called for unknown object\n");
383 cancel_delayed_work_sync(&req
->work
);
384 __pm_qos_update_request(req
, new_value
);
386 EXPORT_SYMBOL_GPL(pm_qos_update_request
);
389 * pm_qos_update_request_timeout - modifies an existing qos request temporarily.
390 * @req : handle to list element holding a pm_qos request to use
391 * @new_value: defines the temporal qos request
392 * @timeout_us: the effective duration of this qos request in usecs.
394 * After timeout_us, this qos request is cancelled automatically.
396 void pm_qos_update_request_timeout(struct pm_qos_request
*req
, s32 new_value
,
397 unsigned long timeout_us
)
401 if (WARN(!pm_qos_request_active(req
),
402 "%s called for unknown object.", __func__
))
405 cancel_delayed_work_sync(&req
->work
);
407 trace_pm_qos_update_request_timeout(req
->pm_qos_class
,
408 new_value
, timeout_us
);
409 if (new_value
!= req
->node
.prio
)
410 pm_qos_update_target(
411 pm_qos_array
[req
->pm_qos_class
]->constraints
,
412 &req
->node
, PM_QOS_UPDATE_REQ
, new_value
);
414 schedule_delayed_work(&req
->work
, usecs_to_jiffies(timeout_us
));
418 * pm_qos_remove_request - modifies an existing qos request
419 * @req: handle to request list element
421 * Will remove pm qos request from the list of constraints and
422 * recompute the current target value for the pm_qos_class. Call this
423 * on slow code paths.
425 void pm_qos_remove_request(struct pm_qos_request
*req
)
427 if (!req
) /*guard against callers passing in null */
429 /* silent return to keep pcm code cleaner */
431 if (!pm_qos_request_active(req
)) {
432 WARN(1, KERN_ERR
"pm_qos_remove_request() called for unknown object\n");
436 cancel_delayed_work_sync(&req
->work
);
438 trace_pm_qos_remove_request(req
->pm_qos_class
, PM_QOS_DEFAULT_VALUE
);
439 pm_qos_update_target(pm_qos_array
[req
->pm_qos_class
]->constraints
,
440 &req
->node
, PM_QOS_REMOVE_REQ
,
441 PM_QOS_DEFAULT_VALUE
);
442 memset(req
, 0, sizeof(*req
));
444 EXPORT_SYMBOL_GPL(pm_qos_remove_request
);
447 * pm_qos_add_notifier - sets notification entry for changes to target value
448 * @pm_qos_class: identifies which qos target changes should be notified.
449 * @notifier: notifier block managed by caller.
451 * will register the notifier into a notification chain that gets called
452 * upon changes to the pm_qos_class target value.
454 int pm_qos_add_notifier(int pm_qos_class
, struct notifier_block
*notifier
)
458 retval
= blocking_notifier_chain_register(
459 pm_qos_array
[pm_qos_class
]->constraints
->notifiers
,
464 EXPORT_SYMBOL_GPL(pm_qos_add_notifier
);
467 * pm_qos_remove_notifier - deletes notification entry from chain.
468 * @pm_qos_class: identifies which qos target changes are notified.
469 * @notifier: notifier block to be removed.
471 * will remove the notifier from the notification chain that gets called
472 * upon changes to the pm_qos_class target value.
474 int pm_qos_remove_notifier(int pm_qos_class
, struct notifier_block
*notifier
)
478 retval
= blocking_notifier_chain_unregister(
479 pm_qos_array
[pm_qos_class
]->constraints
->notifiers
,
484 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier
);
486 /* User space interface to PM QoS classes via misc devices */
487 static int register_pm_qos_misc(struct pm_qos_object
*qos
)
489 qos
->pm_qos_power_miscdev
.minor
= MISC_DYNAMIC_MINOR
;
490 qos
->pm_qos_power_miscdev
.name
= qos
->name
;
491 qos
->pm_qos_power_miscdev
.fops
= &pm_qos_power_fops
;
493 return misc_register(&qos
->pm_qos_power_miscdev
);
496 static int find_pm_qos_object_by_minor(int minor
)
500 for (pm_qos_class
= PM_QOS_CPU_DMA_LATENCY
;
501 pm_qos_class
< PM_QOS_NUM_CLASSES
; pm_qos_class
++) {
503 pm_qos_array
[pm_qos_class
]->pm_qos_power_miscdev
.minor
)
509 static int pm_qos_power_open(struct inode
*inode
, struct file
*filp
)
513 pm_qos_class
= find_pm_qos_object_by_minor(iminor(inode
));
514 if (pm_qos_class
>= PM_QOS_CPU_DMA_LATENCY
) {
515 struct pm_qos_request
*req
= kzalloc(sizeof(*req
), GFP_KERNEL
);
519 pm_qos_add_request(req
, pm_qos_class
, PM_QOS_DEFAULT_VALUE
);
520 filp
->private_data
= req
;
527 static int pm_qos_power_release(struct inode
*inode
, struct file
*filp
)
529 struct pm_qos_request
*req
;
531 req
= filp
->private_data
;
532 pm_qos_remove_request(req
);
539 static ssize_t
pm_qos_power_read(struct file
*filp
, char __user
*buf
,
540 size_t count
, loff_t
*f_pos
)
544 struct pm_qos_request
*req
= filp
->private_data
;
548 if (!pm_qos_request_active(req
))
551 spin_lock_irqsave(&pm_qos_lock
, flags
);
552 value
= pm_qos_get_value(pm_qos_array
[req
->pm_qos_class
]->constraints
);
553 spin_unlock_irqrestore(&pm_qos_lock
, flags
);
555 return simple_read_from_buffer(buf
, count
, f_pos
, &value
, sizeof(s32
));
558 static ssize_t
pm_qos_power_write(struct file
*filp
, const char __user
*buf
,
559 size_t count
, loff_t
*f_pos
)
562 struct pm_qos_request
*req
;
564 if (count
== sizeof(s32
)) {
565 if (copy_from_user(&value
, buf
, sizeof(s32
)))
570 ret
= kstrtos32_from_user(buf
, count
, 16, &value
);
575 req
= filp
->private_data
;
576 pm_qos_update_request(req
, value
);
582 static int __init
pm_qos_power_init(void)
587 BUILD_BUG_ON(ARRAY_SIZE(pm_qos_array
) != PM_QOS_NUM_CLASSES
);
589 for (i
= PM_QOS_CPU_DMA_LATENCY
; i
< PM_QOS_NUM_CLASSES
; i
++) {
590 ret
= register_pm_qos_misc(pm_qos_array
[i
]);
592 printk(KERN_ERR
"pm_qos_param: %s setup failed\n",
593 pm_qos_array
[i
]->name
);
601 late_initcall(pm_qos_power_init
);