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 requirements
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 requirements, notifiers
19 * User mode requirements 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 * requirement is removed and a new qos target is computed. This way when the
24 * requirement 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
30 #include <linux/pm_qos_params.h>
31 #include <linux/sched.h>
32 #include <linux/smp_lock.h>
33 #include <linux/spinlock.h>
34 #include <linux/slab.h>
35 #include <linux/time.h>
37 #include <linux/device.h>
38 #include <linux/miscdevice.h>
39 #include <linux/string.h>
40 #include <linux/platform_device.h>
41 #include <linux/init.h>
43 #include <linux/uaccess.h>
46 * locking rule: all changes to target_value or requirements or notifiers lists
47 * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
48 * held, taken with _irqsave. One lock to rule them all
50 struct requirement_list {
51 struct list_head list;
60 static s32 max_compare(s32 v1, s32 v2);
61 static s32 min_compare(s32 v1, s32 v2);
63 struct pm_qos_object {
64 struct requirement_list requirements;
65 struct blocking_notifier_head *notifiers;
66 struct miscdevice pm_qos_power_miscdev;
70 s32 (*comparitor)(s32, s32);
73 static struct pm_qos_object null_pm_qos;
74 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
75 static struct pm_qos_object cpu_dma_pm_qos = {
76 .requirements = {LIST_HEAD_INIT(cpu_dma_pm_qos.requirements.list)},
77 .notifiers = &cpu_dma_lat_notifier,
78 .name = "cpu_dma_latency",
79 .default_value = 2000 * USEC_PER_SEC,
80 .target_value = 2000 * USEC_PER_SEC,
81 .comparitor = min_compare
84 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
85 static struct pm_qos_object network_lat_pm_qos = {
86 .requirements = {LIST_HEAD_INIT(network_lat_pm_qos.requirements.list)},
87 .notifiers = &network_lat_notifier,
88 .name = "network_latency",
89 .default_value = 2000 * USEC_PER_SEC,
90 .target_value = 2000 * USEC_PER_SEC,
91 .comparitor = min_compare
95 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
96 static struct pm_qos_object network_throughput_pm_qos = {
98 {LIST_HEAD_INIT(network_throughput_pm_qos.requirements.list)},
99 .notifiers = &network_throughput_notifier,
100 .name = "network_throughput",
103 .comparitor = max_compare
107 static struct pm_qos_object *pm_qos_array[] = {
111 &network_throughput_pm_qos
114 static DEFINE_SPINLOCK(pm_qos_lock);
116 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
117 size_t count, loff_t *f_pos);
118 static int pm_qos_power_open(struct inode *inode, struct file *filp);
119 static int pm_qos_power_release(struct inode *inode, struct file *filp);
121 static const struct file_operations pm_qos_power_fops = {
122 .write = pm_qos_power_write,
123 .open = pm_qos_power_open,
124 .release = pm_qos_power_release,
127 /* static helper functions */
128 static s32 max_compare(s32 v1, s32 v2)
133 static s32 min_compare(s32 v1, s32 v2)
139 static void update_target(int target)
142 struct requirement_list *node;
144 int call_notifier = 0;
146 spin_lock_irqsave(&pm_qos_lock, flags);
147 extreme_value = pm_qos_array[target]->default_value;
148 list_for_each_entry(node,
149 &pm_qos_array[target]->requirements.list, list) {
150 extreme_value = pm_qos_array[target]->comparitor(
151 extreme_value, node->value);
153 if (pm_qos_array[target]->target_value != extreme_value) {
155 pm_qos_array[target]->target_value = extreme_value;
156 pr_debug(KERN_ERR "new target for qos %d is %d\n", target,
157 pm_qos_array[target]->target_value);
159 spin_unlock_irqrestore(&pm_qos_lock, flags);
162 blocking_notifier_call_chain(pm_qos_array[target]->notifiers,
163 (unsigned long) extreme_value, NULL);
166 static int register_pm_qos_misc(struct pm_qos_object *qos)
168 qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
169 qos->pm_qos_power_miscdev.name = qos->name;
170 qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
172 return misc_register(&qos->pm_qos_power_miscdev);
175 static int find_pm_qos_object_by_minor(int minor)
179 for (pm_qos_class = 0;
180 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
182 pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
189 * pm_qos_requirement - returns current system wide qos expectation
190 * @pm_qos_class: identification of which qos value is requested
192 * This function returns the current target value in an atomic manner.
194 int pm_qos_requirement(int pm_qos_class)
199 spin_lock_irqsave(&pm_qos_lock, flags);
200 ret_val = pm_qos_array[pm_qos_class]->target_value;
201 spin_unlock_irqrestore(&pm_qos_lock, flags);
205 EXPORT_SYMBOL_GPL(pm_qos_requirement);
208 * pm_qos_add_requirement - inserts new qos request into the list
209 * @pm_qos_class: identifies which list of qos request to us
210 * @name: identifies the request
211 * @value: defines the qos request
213 * This function inserts a new entry in the pm_qos_class list of requested qos
214 * performance charactoistics. It recomputes the agregate QoS expectations for
215 * the pm_qos_class of parrameters.
217 int pm_qos_add_requirement(int pm_qos_class, char *name, s32 value)
219 struct requirement_list *dep;
222 dep = kzalloc(sizeof(struct requirement_list), GFP_KERNEL);
224 if (value == PM_QOS_DEFAULT_VALUE)
225 dep->value = pm_qos_array[pm_qos_class]->default_value;
228 dep->name = kstrdup(name, GFP_KERNEL);
232 spin_lock_irqsave(&pm_qos_lock, flags);
234 &pm_qos_array[pm_qos_class]->requirements.list);
235 spin_unlock_irqrestore(&pm_qos_lock, flags);
236 update_target(pm_qos_class);
245 EXPORT_SYMBOL_GPL(pm_qos_add_requirement);
248 * pm_qos_update_requirement - modifies an existing qos request
249 * @pm_qos_class: identifies which list of qos request to us
250 * @name: identifies the request
251 * @value: defines the qos request
253 * Updates an existing qos requierement for the pm_qos_class of parameters along
254 * with updating the target pm_qos_class value.
256 * If the named request isn't in the lest then no change is made.
258 int pm_qos_update_requirement(int pm_qos_class, char *name, s32 new_value)
261 struct requirement_list *node;
262 int pending_update = 0;
264 spin_lock_irqsave(&pm_qos_lock, flags);
265 list_for_each_entry(node,
266 &pm_qos_array[pm_qos_class]->requirements.list, list) {
267 if (strcmp(node->name, name) == 0) {
268 if (new_value == PM_QOS_DEFAULT_VALUE)
270 pm_qos_array[pm_qos_class]->default_value;
272 node->value = new_value;
277 spin_unlock_irqrestore(&pm_qos_lock, flags);
279 update_target(pm_qos_class);
283 EXPORT_SYMBOL_GPL(pm_qos_update_requirement);
286 * pm_qos_remove_requirement - modifies an existing qos request
287 * @pm_qos_class: identifies which list of qos request to us
288 * @name: identifies the request
290 * Will remove named qos request from pm_qos_class list of parrameters and
291 * recompute the current target value for the pm_qos_class.
293 void pm_qos_remove_requirement(int pm_qos_class, char *name)
296 struct requirement_list *node;
297 int pending_update = 0;
299 spin_lock_irqsave(&pm_qos_lock, flags);
300 list_for_each_entry(node,
301 &pm_qos_array[pm_qos_class]->requirements.list, list) {
302 if (strcmp(node->name, name) == 0) {
304 list_del(&node->list);
310 spin_unlock_irqrestore(&pm_qos_lock, flags);
312 update_target(pm_qos_class);
314 EXPORT_SYMBOL_GPL(pm_qos_remove_requirement);
317 * pm_qos_add_notifier - sets notification entry for changes to target value
318 * @pm_qos_class: identifies which qos target changes should be notified.
319 * @notifier: notifier block managed by caller.
321 * will register the notifier into a notification chain that gets called
322 * uppon changes to the pm_qos_class target value.
324 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
328 retval = blocking_notifier_chain_register(
329 pm_qos_array[pm_qos_class]->notifiers, notifier);
333 EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
336 * pm_qos_remove_notifier - deletes notification entry from chain.
337 * @pm_qos_class: identifies which qos target changes are notified.
338 * @notifier: notifier block to be removed.
340 * will remove the notifier from the notification chain that gets called
341 * uppon changes to the pm_qos_class target value.
343 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
347 retval = blocking_notifier_chain_unregister(
348 pm_qos_array[pm_qos_class]->notifiers, notifier);
352 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
354 #define PID_NAME_LEN sizeof("process_1234567890")
355 static char name[PID_NAME_LEN];
357 static int pm_qos_power_open(struct inode *inode, struct file *filp)
363 pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
364 if (pm_qos_class >= 0) {
365 filp->private_data = (void *)pm_qos_class;
366 sprintf(name, "process_%d", current->pid);
367 ret = pm_qos_add_requirement(pm_qos_class, name,
368 PM_QOS_DEFAULT_VALUE);
379 static int pm_qos_power_release(struct inode *inode, struct file *filp)
383 pm_qos_class = (long)filp->private_data;
384 sprintf(name, "process_%d", current->pid);
385 pm_qos_remove_requirement(pm_qos_class, name);
390 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
391 size_t count, loff_t *f_pos)
396 pm_qos_class = (long)filp->private_data;
397 if (count != sizeof(s32))
399 if (copy_from_user(&value, buf, sizeof(s32)))
401 sprintf(name, "process_%d", current->pid);
402 pm_qos_update_requirement(pm_qos_class, name, value);
408 static int __init pm_qos_power_init(void)
412 ret = register_pm_qos_misc(&cpu_dma_pm_qos);
414 printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
417 ret = register_pm_qos_misc(&network_lat_pm_qos);
419 printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
422 ret = register_pm_qos_misc(&network_throughput_pm_qos);
425 "pm_qos_param: network_throughput setup failed\n");
430 late_initcall(pm_qos_power_init);