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>
49 * locking rule: all changes to constraints or notifiers lists
50 * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
51 * held, taken with _irqsave. One lock to rule them all
53 struct pm_qos_object {
54 struct pm_qos_constraints *constraints;
55 struct miscdevice pm_qos_power_miscdev;
59 static DEFINE_SPINLOCK(pm_qos_lock);
61 static struct pm_qos_object null_pm_qos;
63 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
64 static struct pm_qos_constraints cpu_dma_constraints = {
65 .list = PLIST_HEAD_INIT(cpu_dma_constraints.list),
66 .target_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
67 .default_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
69 .notifiers = &cpu_dma_lat_notifier,
71 static struct pm_qos_object cpu_dma_pm_qos = {
72 .constraints = &cpu_dma_constraints,
73 .name = "cpu_dma_latency",
76 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
77 static struct pm_qos_constraints network_lat_constraints = {
78 .list = PLIST_HEAD_INIT(network_lat_constraints.list),
79 .target_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
80 .default_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
82 .notifiers = &network_lat_notifier,
84 static struct pm_qos_object network_lat_pm_qos = {
85 .constraints = &network_lat_constraints,
86 .name = "network_latency",
90 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
91 static struct pm_qos_constraints network_tput_constraints = {
92 .list = PLIST_HEAD_INIT(network_tput_constraints.list),
93 .target_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
94 .default_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
96 .notifiers = &network_throughput_notifier,
98 static struct pm_qos_object network_throughput_pm_qos = {
99 .constraints = &network_tput_constraints,
100 .name = "network_throughput",
104 static struct pm_qos_object *pm_qos_array[] = {
108 &network_throughput_pm_qos
111 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
112 size_t count, loff_t *f_pos);
113 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
114 size_t count, loff_t *f_pos);
115 static int pm_qos_power_open(struct inode *inode, struct file *filp);
116 static int pm_qos_power_release(struct inode *inode, struct file *filp);
118 static const struct file_operations pm_qos_power_fops = {
119 .write = pm_qos_power_write,
120 .read = pm_qos_power_read,
121 .open = pm_qos_power_open,
122 .release = pm_qos_power_release,
123 .llseek = noop_llseek,
126 /* unlocked internal variant */
127 static inline int pm_qos_get_value(struct pm_qos_constraints *c)
129 if (plist_head_empty(&c->list))
130 return c->default_value;
134 return plist_first(&c->list)->prio;
137 return plist_last(&c->list)->prio;
140 /* runtime check for not using enum */
142 return PM_QOS_DEFAULT_VALUE;
146 s32 pm_qos_read_value(struct pm_qos_constraints *c)
148 return c->target_value;
151 static inline void pm_qos_set_value(struct pm_qos_constraints *c, s32 value)
153 c->target_value = value;
157 * pm_qos_update_target - manages the constraints list and calls the notifiers
159 * @c: constraints data struct
160 * @node: request to add to the list, to update or to remove
161 * @action: action to take on the constraints list
162 * @value: value of the request to add or update
164 * This function returns 1 if the aggregated constraint value has changed, 0
167 int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node,
168 enum pm_qos_req_action action, int value)
171 int prev_value, curr_value, new_value;
173 spin_lock_irqsave(&pm_qos_lock, flags);
174 prev_value = pm_qos_get_value(c);
175 if (value == PM_QOS_DEFAULT_VALUE)
176 new_value = c->default_value;
181 case PM_QOS_REMOVE_REQ:
182 plist_del(node, &c->list);
184 case PM_QOS_UPDATE_REQ:
186 * to change the list, we atomically remove, reinit
187 * with new value and add, then see if the extremal
190 plist_del(node, &c->list);
192 plist_node_init(node, new_value);
193 plist_add(node, &c->list);
200 curr_value = pm_qos_get_value(c);
201 pm_qos_set_value(c, curr_value);
203 spin_unlock_irqrestore(&pm_qos_lock, flags);
205 if (prev_value != curr_value) {
206 blocking_notifier_call_chain(c->notifiers,
207 (unsigned long)curr_value,
216 * pm_qos_request - returns current system wide qos expectation
217 * @pm_qos_class: identification of which qos value is requested
219 * This function returns the current target value.
221 int pm_qos_request(int pm_qos_class)
223 return pm_qos_read_value(pm_qos_array[pm_qos_class]->constraints);
225 EXPORT_SYMBOL_GPL(pm_qos_request);
227 int pm_qos_request_active(struct pm_qos_request *req)
229 return req->pm_qos_class != 0;
231 EXPORT_SYMBOL_GPL(pm_qos_request_active);
234 * pm_qos_work_fn - the timeout handler of pm_qos_update_request_timeout
235 * @work: work struct for the delayed work (timeout)
237 * This cancels the timeout request by falling back to the default at timeout.
239 static void pm_qos_work_fn(struct work_struct *work)
241 struct pm_qos_request *req = container_of(to_delayed_work(work),
242 struct pm_qos_request,
245 pm_qos_update_request(req, PM_QOS_DEFAULT_VALUE);
249 * pm_qos_add_request - inserts new qos request into the list
250 * @req: pointer to a preallocated handle
251 * @pm_qos_class: identifies which list of qos request to use
252 * @value: defines the qos request
254 * This function inserts a new entry in the pm_qos_class list of requested qos
255 * performance characteristics. It recomputes the aggregate QoS expectations
256 * for the pm_qos_class of parameters and initializes the pm_qos_request
257 * handle. Caller needs to save this handle for later use in updates and
261 void pm_qos_add_request(struct pm_qos_request *req,
262 int pm_qos_class, s32 value)
264 if (!req) /*guard against callers passing in null */
267 if (pm_qos_request_active(req)) {
268 WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
271 req->pm_qos_class = pm_qos_class;
272 INIT_DELAYED_WORK(&req->work, pm_qos_work_fn);
273 pm_qos_update_target(pm_qos_array[pm_qos_class]->constraints,
274 &req->node, PM_QOS_ADD_REQ, value);
276 EXPORT_SYMBOL_GPL(pm_qos_add_request);
279 * pm_qos_update_request - modifies an existing qos request
280 * @req : handle to list element holding a pm_qos request to use
281 * @value: defines the qos request
283 * Updates an existing qos request for the pm_qos_class of parameters along
284 * with updating the target pm_qos_class value.
286 * Attempts are made to make this code callable on hot code paths.
288 void pm_qos_update_request(struct pm_qos_request *req,
291 if (!req) /*guard against callers passing in null */
294 if (!pm_qos_request_active(req)) {
295 WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
299 if (delayed_work_pending(&req->work))
300 cancel_delayed_work_sync(&req->work);
302 if (new_value != req->node.prio)
303 pm_qos_update_target(
304 pm_qos_array[req->pm_qos_class]->constraints,
305 &req->node, PM_QOS_UPDATE_REQ, new_value);
307 EXPORT_SYMBOL_GPL(pm_qos_update_request);
310 * pm_qos_update_request_timeout - modifies an existing qos request temporarily.
311 * @req : handle to list element holding a pm_qos request to use
312 * @new_value: defines the temporal qos request
313 * @timeout_us: the effective duration of this qos request in usecs.
315 * After timeout_us, this qos request is cancelled automatically.
317 void pm_qos_update_request_timeout(struct pm_qos_request *req, s32 new_value,
318 unsigned long timeout_us)
322 if (WARN(!pm_qos_request_active(req),
323 "%s called for unknown object.", __func__))
326 if (delayed_work_pending(&req->work))
327 cancel_delayed_work_sync(&req->work);
329 if (new_value != req->node.prio)
330 pm_qos_update_target(
331 pm_qos_array[req->pm_qos_class]->constraints,
332 &req->node, PM_QOS_UPDATE_REQ, new_value);
334 schedule_delayed_work(&req->work, usecs_to_jiffies(timeout_us));
338 * pm_qos_remove_request - modifies an existing qos request
339 * @req: handle to request list element
341 * Will remove pm qos request from the list of constraints and
342 * recompute the current target value for the pm_qos_class. Call this
343 * on slow code paths.
345 void pm_qos_remove_request(struct pm_qos_request *req)
347 if (!req) /*guard against callers passing in null */
349 /* silent return to keep pcm code cleaner */
351 if (!pm_qos_request_active(req)) {
352 WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
356 if (delayed_work_pending(&req->work))
357 cancel_delayed_work_sync(&req->work);
359 pm_qos_update_target(pm_qos_array[req->pm_qos_class]->constraints,
360 &req->node, PM_QOS_REMOVE_REQ,
361 PM_QOS_DEFAULT_VALUE);
362 memset(req, 0, sizeof(*req));
364 EXPORT_SYMBOL_GPL(pm_qos_remove_request);
367 * pm_qos_add_notifier - sets notification entry for changes to target value
368 * @pm_qos_class: identifies which qos target changes should be notified.
369 * @notifier: notifier block managed by caller.
371 * will register the notifier into a notification chain that gets called
372 * upon changes to the pm_qos_class target value.
374 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
378 retval = blocking_notifier_chain_register(
379 pm_qos_array[pm_qos_class]->constraints->notifiers,
384 EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
387 * pm_qos_remove_notifier - deletes notification entry from chain.
388 * @pm_qos_class: identifies which qos target changes are notified.
389 * @notifier: notifier block to be removed.
391 * will remove the notifier from the notification chain that gets called
392 * upon changes to the pm_qos_class target value.
394 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
398 retval = blocking_notifier_chain_unregister(
399 pm_qos_array[pm_qos_class]->constraints->notifiers,
404 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
406 /* User space interface to PM QoS classes via misc devices */
407 static int register_pm_qos_misc(struct pm_qos_object *qos)
409 qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
410 qos->pm_qos_power_miscdev.name = qos->name;
411 qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
413 return misc_register(&qos->pm_qos_power_miscdev);
416 static int find_pm_qos_object_by_minor(int minor)
420 for (pm_qos_class = 0;
421 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
423 pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
429 static int pm_qos_power_open(struct inode *inode, struct file *filp)
433 pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
434 if (pm_qos_class >= 0) {
435 struct pm_qos_request *req = kzalloc(sizeof(*req), GFP_KERNEL);
439 pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
440 filp->private_data = req;
447 static int pm_qos_power_release(struct inode *inode, struct file *filp)
449 struct pm_qos_request *req;
451 req = filp->private_data;
452 pm_qos_remove_request(req);
459 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
460 size_t count, loff_t *f_pos)
464 struct pm_qos_request *req = filp->private_data;
468 if (!pm_qos_request_active(req))
471 spin_lock_irqsave(&pm_qos_lock, flags);
472 value = pm_qos_get_value(pm_qos_array[req->pm_qos_class]->constraints);
473 spin_unlock_irqrestore(&pm_qos_lock, flags);
475 return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
478 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
479 size_t count, loff_t *f_pos)
482 struct pm_qos_request *req;
484 if (count == sizeof(s32)) {
485 if (copy_from_user(&value, buf, sizeof(s32)))
487 } else if (count <= 11) { /* ASCII perhaps? */
488 char ascii_value[11];
489 unsigned long int ulval;
492 if (copy_from_user(ascii_value, buf, count))
496 if (ascii_value[10] == '\n')
497 ascii_value[10] = '\0';
501 ascii_value[count] = '\0';
503 ret = strict_strtoul(ascii_value, 16, &ulval);
505 pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret);
508 value = (s32)lower_32_bits(ulval);
513 req = filp->private_data;
514 pm_qos_update_request(req, value);
520 static int __init pm_qos_power_init(void)
525 BUILD_BUG_ON(ARRAY_SIZE(pm_qos_array) != PM_QOS_NUM_CLASSES);
527 for (i = 1; i < PM_QOS_NUM_CLASSES; i++) {
528 ret = register_pm_qos_misc(pm_qos_array[i]);
530 printk(KERN_ERR "pm_qos_param: %s setup failed\n",
531 pm_qos_array[i]->name);
539 late_initcall(pm_qos_power_init);