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,
75 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
76 static struct pm_qos_constraints network_lat_constraints = {
77 .list = PLIST_HEAD_INIT(network_lat_constraints.list),
78 .target_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
79 .default_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
81 .notifiers = &network_lat_notifier,
83 static struct pm_qos_object network_lat_pm_qos = {
84 .constraints = &network_lat_constraints,
85 .name = "network_latency",
89 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
90 static struct pm_qos_constraints network_tput_constraints = {
91 .list = PLIST_HEAD_INIT(network_tput_constraints.list),
92 .target_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
93 .default_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
95 .notifiers = &network_throughput_notifier,
97 static struct pm_qos_object network_throughput_pm_qos = {
98 .constraints = &network_tput_constraints,
99 .name = "network_throughput",
103 static struct pm_qos_object *pm_qos_array[] = {
107 &network_throughput_pm_qos
110 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
111 size_t count, loff_t *f_pos);
112 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
113 size_t count, loff_t *f_pos);
114 static int pm_qos_power_open(struct inode *inode, struct file *filp);
115 static int pm_qos_power_release(struct inode *inode, struct file *filp);
117 static const struct file_operations pm_qos_power_fops = {
118 .write = pm_qos_power_write,
119 .read = pm_qos_power_read,
120 .open = pm_qos_power_open,
121 .release = pm_qos_power_release,
122 .llseek = noop_llseek,
125 /* unlocked internal variant */
126 static inline int pm_qos_get_value(struct pm_qos_constraints *c)
128 if (plist_head_empty(&c->list))
129 return c->default_value;
133 return plist_first(&c->list)->prio;
136 return plist_last(&c->list)->prio;
139 /* runtime check for not using enum */
144 s32 pm_qos_read_value(struct pm_qos_constraints *c)
146 return c->target_value;
149 static inline void pm_qos_set_value(struct pm_qos_constraints *c, s32 value)
151 c->target_value = value;
155 * pm_qos_update_target - manages the constraints list and calls the notifiers
157 * @c: constraints data struct
158 * @node: request to add to the list, to update or to remove
159 * @action: action to take on the constraints list
160 * @value: value of the request to add or update
162 * This function returns 1 if the aggregated constraint value has changed, 0
165 int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node,
166 enum pm_qos_req_action action, int value)
169 int prev_value, curr_value, new_value;
171 spin_lock_irqsave(&pm_qos_lock, flags);
172 prev_value = pm_qos_get_value(c);
173 if (value == PM_QOS_DEFAULT_VALUE)
174 new_value = c->default_value;
179 case PM_QOS_REMOVE_REQ:
180 plist_del(node, &c->list);
182 case PM_QOS_UPDATE_REQ:
184 * to change the list, we atomically remove, reinit
185 * with new value and add, then see if the extremal
188 plist_del(node, &c->list);
190 plist_node_init(node, new_value);
191 plist_add(node, &c->list);
198 curr_value = pm_qos_get_value(c);
199 pm_qos_set_value(c, curr_value);
201 spin_unlock_irqrestore(&pm_qos_lock, flags);
203 if (prev_value != curr_value) {
204 blocking_notifier_call_chain(c->notifiers,
205 (unsigned long)curr_value,
214 * pm_qos_request - returns current system wide qos expectation
215 * @pm_qos_class: identification of which qos value is requested
217 * This function returns the current target value.
219 int pm_qos_request(int pm_qos_class)
221 return pm_qos_read_value(pm_qos_array[pm_qos_class]->constraints);
223 EXPORT_SYMBOL_GPL(pm_qos_request);
225 int pm_qos_request_active(struct pm_qos_request *req)
227 return req->pm_qos_class != 0;
229 EXPORT_SYMBOL_GPL(pm_qos_request_active);
232 * pm_qos_add_request - inserts new qos request into the list
233 * @req: pointer to a preallocated handle
234 * @pm_qos_class: identifies which list of qos request to use
235 * @value: defines the qos request
237 * This function inserts a new entry in the pm_qos_class list of requested qos
238 * performance characteristics. It recomputes the aggregate QoS expectations
239 * for the pm_qos_class of parameters and initializes the pm_qos_request
240 * handle. Caller needs to save this handle for later use in updates and
244 void pm_qos_add_request(struct pm_qos_request *req,
245 int pm_qos_class, s32 value)
247 if (!req) /*guard against callers passing in null */
250 if (pm_qos_request_active(req)) {
251 WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
254 req->pm_qos_class = pm_qos_class;
255 pm_qos_update_target(pm_qos_array[pm_qos_class]->constraints,
256 &req->node, PM_QOS_ADD_REQ, value);
258 EXPORT_SYMBOL_GPL(pm_qos_add_request);
261 * pm_qos_update_request - modifies an existing qos request
262 * @req : handle to list element holding a pm_qos request to use
263 * @value: defines the qos request
265 * Updates an existing qos request for the pm_qos_class of parameters along
266 * with updating the target pm_qos_class value.
268 * Attempts are made to make this code callable on hot code paths.
270 void pm_qos_update_request(struct pm_qos_request *req,
273 if (!req) /*guard against callers passing in null */
276 if (!pm_qos_request_active(req)) {
277 WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
281 if (new_value != req->node.prio)
282 pm_qos_update_target(
283 pm_qos_array[req->pm_qos_class]->constraints,
284 &req->node, PM_QOS_UPDATE_REQ, new_value);
286 EXPORT_SYMBOL_GPL(pm_qos_update_request);
289 * pm_qos_remove_request - modifies an existing qos request
290 * @req: handle to request list element
292 * Will remove pm qos request from the list of constraints and
293 * recompute the current target value for the pm_qos_class. Call this
294 * on slow code paths.
296 void pm_qos_remove_request(struct pm_qos_request *req)
298 if (!req) /*guard against callers passing in null */
300 /* silent return to keep pcm code cleaner */
302 if (!pm_qos_request_active(req)) {
303 WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
307 pm_qos_update_target(pm_qos_array[req->pm_qos_class]->constraints,
308 &req->node, PM_QOS_REMOVE_REQ,
309 PM_QOS_DEFAULT_VALUE);
310 memset(req, 0, sizeof(*req));
312 EXPORT_SYMBOL_GPL(pm_qos_remove_request);
315 * pm_qos_add_notifier - sets notification entry for changes to target value
316 * @pm_qos_class: identifies which qos target changes should be notified.
317 * @notifier: notifier block managed by caller.
319 * will register the notifier into a notification chain that gets called
320 * upon changes to the pm_qos_class target value.
322 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
326 retval = blocking_notifier_chain_register(
327 pm_qos_array[pm_qos_class]->constraints->notifiers,
332 EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
335 * pm_qos_remove_notifier - deletes notification entry from chain.
336 * @pm_qos_class: identifies which qos target changes are notified.
337 * @notifier: notifier block to be removed.
339 * will remove the notifier from the notification chain that gets called
340 * upon changes to the pm_qos_class target value.
342 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
346 retval = blocking_notifier_chain_unregister(
347 pm_qos_array[pm_qos_class]->constraints->notifiers,
352 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
354 /* User space interface to PM QoS classes via misc devices */
355 static int register_pm_qos_misc(struct pm_qos_object *qos)
357 qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
358 qos->pm_qos_power_miscdev.name = qos->name;
359 qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
361 return misc_register(&qos->pm_qos_power_miscdev);
364 static int find_pm_qos_object_by_minor(int minor)
368 for (pm_qos_class = 0;
369 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
371 pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
377 static int pm_qos_power_open(struct inode *inode, struct file *filp)
381 pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
382 if (pm_qos_class >= 0) {
383 struct pm_qos_request *req = kzalloc(sizeof(*req), GFP_KERNEL);
387 pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
388 filp->private_data = req;
395 static int pm_qos_power_release(struct inode *inode, struct file *filp)
397 struct pm_qos_request *req;
399 req = filp->private_data;
400 pm_qos_remove_request(req);
407 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
408 size_t count, loff_t *f_pos)
412 struct pm_qos_request *req = filp->private_data;
416 if (!pm_qos_request_active(req))
419 spin_lock_irqsave(&pm_qos_lock, flags);
420 value = pm_qos_get_value(pm_qos_array[req->pm_qos_class]->constraints);
421 spin_unlock_irqrestore(&pm_qos_lock, flags);
423 return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
426 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
427 size_t count, loff_t *f_pos)
430 struct pm_qos_request *req;
432 if (count == sizeof(s32)) {
433 if (copy_from_user(&value, buf, sizeof(s32)))
435 } else if (count <= 11) { /* ASCII perhaps? */
436 char ascii_value[11];
437 unsigned long int ulval;
440 if (copy_from_user(ascii_value, buf, count))
444 if (ascii_value[10] == '\n')
445 ascii_value[10] = '\0';
449 ascii_value[count] = '\0';
451 ret = strict_strtoul(ascii_value, 16, &ulval);
453 pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret);
456 value = (s32)lower_32_bits(ulval);
461 req = filp->private_data;
462 pm_qos_update_request(req, value);
468 static int __init pm_qos_power_init(void)
472 ret = register_pm_qos_misc(&cpu_dma_pm_qos);
474 printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
477 ret = register_pm_qos_misc(&network_lat_pm_qos);
479 printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
482 ret = register_pm_qos_misc(&network_throughput_pm_qos);
485 "pm_qos_param: network_throughput setup failed\n");
490 late_initcall(pm_qos_power_init);