1 /*
2 * This module exposes the interface to kernel space for specifying
3 * QoS dependencies. It provides infrastructure for registration of:
4 *
5 * Dependents on a QoS value : register requests
6 * Watchers of QoS value : get notified when target QoS value changes
7 *
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.
10 *
11 * There are 3 basic classes of QoS parameter: latency, timeout, throughput
12 * each have defined units:
13 * latency: usec
14 * timeout: usec <-- currently not used.
15 * throughput: kbs (kilo byte / sec)
16 *
17 * There are lists of pm_qos_objects each one wrapping requests, notifiers
18 *
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.
26 *
27 * Mark Gross <mgross@linux.intel.com>
28 */
29
30 /*#define DEBUG*/
31
32 #include <linux/pm_qos_params.h>
33 #include <linux/sched.h>
34 #include <linux/spinlock.h>
35 #include <linux/slab.h>
36 #include <linux/time.h>
37 #include <linux/fs.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
44 #include <linux/uaccess.h>
45
46 /*
47 * locking rule: all changes to requests or notifiers lists
48 * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
49 * held, taken with _irqsave. One lock to rule them all
50 */
51 enum pm_qos_type {
52 PM_QOS_MAX, /* return the largest value */
53 PM_QOS_MIN /* return the smallest value */
54 };
55
56 struct pm_qos_object {
57 struct plist_head requests;
58 struct blocking_notifier_head *notifiers;
59 struct miscdevice pm_qos_power_miscdev;
60 char *name;
61 s32 default_value;
62 enum pm_qos_type type;
63 };
64
65 static DEFINE_SPINLOCK(pm_qos_lock);
66
67 static struct pm_qos_object null_pm_qos;
68 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
69 static struct pm_qos_object cpu_dma_pm_qos = {
70 .requests = PLIST_HEAD_INIT(cpu_dma_pm_qos.requests, pm_qos_lock),
71 .notifiers = &cpu_dma_lat_notifier,
72 .name = "cpu_dma_latency",
73 .default_value = 2000 * USEC_PER_SEC,
74 .type = PM_QOS_MIN,
75 };
76
77 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
78 static struct pm_qos_object network_lat_pm_qos = {
79 .requests = PLIST_HEAD_INIT(network_lat_pm_qos.requests, pm_qos_lock),
80 .notifiers = &network_lat_notifier,
81 .name = "network_latency",
82 .default_value = 2000 * USEC_PER_SEC,
83 .type = PM_QOS_MIN
84 };
85
86
87 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
88 static struct pm_qos_object network_throughput_pm_qos = {
89 .requests = PLIST_HEAD_INIT(network_throughput_pm_qos.requests, pm_qos_lock),
90 .notifiers = &network_throughput_notifier,
91 .name = "network_throughput",
92 .default_value = 0,
93 .type = PM_QOS_MAX,
94 };
95
96
97 static struct pm_qos_object *pm_qos_array[] = {
98 &null_pm_qos,
99 &cpu_dma_pm_qos,
100 &network_lat_pm_qos,
101 &network_throughput_pm_qos
102 };
103
104 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
105 size_t count, loff_t *f_pos);
106 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
107 size_t count, loff_t *f_pos);
108 static int pm_qos_power_open(struct inode *inode, struct file *filp);
109 static int pm_qos_power_release(struct inode *inode, struct file *filp);
110
111 static const struct file_operations pm_qos_power_fops = {
112 .write = pm_qos_power_write,
113 .read = pm_qos_power_read,
114 .open = pm_qos_power_open,
115 .release = pm_qos_power_release,
116 .llseek = noop_llseek,
117 };
118
119 /* unlocked internal variant */
pm_qos_get_value(struct pm_qos_object * o)120 static inline int pm_qos_get_value(struct pm_qos_object *o)
121 {
122 if (plist_head_empty(&o->requests))
123 return o->default_value;
124
125 switch (o->type) {
126 case PM_QOS_MIN:
127 return plist_first(&o->requests)->prio;
128
129 case PM_QOS_MAX:
130 return plist_last(&o->requests)->prio;
131
132 default:
133 /* runtime check for not using enum */
134 BUG();
135 }
136 }
137
update_target(struct pm_qos_object * o,struct plist_node * node,int del,int value)138 static void update_target(struct pm_qos_object *o, struct plist_node *node,
139 int del, int value)
140 {
141 unsigned long flags;
142 int prev_value, curr_value;
143
144 spin_lock_irqsave(&pm_qos_lock, flags);
145 prev_value = pm_qos_get_value(o);
146 /* PM_QOS_DEFAULT_VALUE is a signal that the value is unchanged */
147 if (value != PM_QOS_DEFAULT_VALUE) {
148 /*
149 * to change the list, we atomically remove, reinit
150 * with new value and add, then see if the extremal
151 * changed
152 */
153 plist_del(node, &o->requests);
154 plist_node_init(node, value);
155 plist_add(node, &o->requests);
156 } else if (del) {
157 plist_del(node, &o->requests);
158 } else {
159 plist_add(node, &o->requests);
160 }
161 curr_value = pm_qos_get_value(o);
162 spin_unlock_irqrestore(&pm_qos_lock, flags);
163
164 if (prev_value != curr_value)
165 blocking_notifier_call_chain(o->notifiers,
166 (unsigned long)curr_value,
167 NULL);
168 }
169
register_pm_qos_misc(struct pm_qos_object * qos)170 static int register_pm_qos_misc(struct pm_qos_object *qos)
171 {
172 qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
173 qos->pm_qos_power_miscdev.name = qos->name;
174 qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
175
176 return misc_register(&qos->pm_qos_power_miscdev);
177 }
178
find_pm_qos_object_by_minor(int minor)179 static int find_pm_qos_object_by_minor(int minor)
180 {
181 int pm_qos_class;
182
183 for (pm_qos_class = 0;
184 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
185 if (minor ==
186 pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
187 return pm_qos_class;
188 }
189 return -1;
190 }
191
192 /**
193 * pm_qos_request - returns current system wide qos expectation
194 * @pm_qos_class: identification of which qos value is requested
195 *
196 * This function returns the current target value in an atomic manner.
197 */
pm_qos_request(int pm_qos_class)198 int pm_qos_request(int pm_qos_class)
199 {
200 unsigned long flags;
201 int value;
202
203 spin_lock_irqsave(&pm_qos_lock, flags);
204 value = pm_qos_get_value(pm_qos_array[pm_qos_class]);
205 spin_unlock_irqrestore(&pm_qos_lock, flags);
206
207 return value;
208 }
209 EXPORT_SYMBOL_GPL(pm_qos_request);
210
pm_qos_request_active(struct pm_qos_request_list * req)211 int pm_qos_request_active(struct pm_qos_request_list *req)
212 {
213 return req->pm_qos_class != 0;
214 }
215 EXPORT_SYMBOL_GPL(pm_qos_request_active);
216
217 /**
218 * pm_qos_add_request - inserts new qos request into the list
219 * @dep: pointer to a preallocated handle
220 * @pm_qos_class: identifies which list of qos request to use
221 * @value: defines the qos request
222 *
223 * This function inserts a new entry in the pm_qos_class list of requested qos
224 * performance characteristics. It recomputes the aggregate QoS expectations
225 * for the pm_qos_class of parameters and initializes the pm_qos_request_list
226 * handle. Caller needs to save this handle for later use in updates and
227 * removal.
228 */
229
pm_qos_add_request(struct pm_qos_request_list * dep,int pm_qos_class,s32 value)230 void pm_qos_add_request(struct pm_qos_request_list *dep,
231 int pm_qos_class, s32 value)
232 {
233 struct pm_qos_object *o = pm_qos_array[pm_qos_class];
234 int new_value;
235
236 if (pm_qos_request_active(dep)) {
237 WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
238 return;
239 }
240 if (value == PM_QOS_DEFAULT_VALUE)
241 new_value = o->default_value;
242 else
243 new_value = value;
244 plist_node_init(&dep->list, new_value);
245 dep->pm_qos_class = pm_qos_class;
246 update_target(o, &dep->list, 0, PM_QOS_DEFAULT_VALUE);
247 }
248 EXPORT_SYMBOL_GPL(pm_qos_add_request);
249
250 /**
251 * pm_qos_update_request - modifies an existing qos request
252 * @pm_qos_req : handle to list element holding a pm_qos request to use
253 * @value: defines the qos request
254 *
255 * Updates an existing qos request for the pm_qos_class of parameters along
256 * with updating the target pm_qos_class value.
257 *
258 * Attempts are made to make this code callable on hot code paths.
259 */
pm_qos_update_request(struct pm_qos_request_list * pm_qos_req,s32 new_value)260 void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
261 s32 new_value)
262 {
263 s32 temp;
264 struct pm_qos_object *o;
265
266 if (!pm_qos_req) /*guard against callers passing in null */
267 return;
268
269 if (!pm_qos_request_active(pm_qos_req)) {
270 WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
271 return;
272 }
273
274 o = pm_qos_array[pm_qos_req->pm_qos_class];
275
276 if (new_value == PM_QOS_DEFAULT_VALUE)
277 temp = o->default_value;
278 else
279 temp = new_value;
280
281 if (temp != pm_qos_req->list.prio)
282 update_target(o, &pm_qos_req->list, 0, temp);
283 }
284 EXPORT_SYMBOL_GPL(pm_qos_update_request);
285
286 /**
287 * pm_qos_remove_request - modifies an existing qos request
288 * @pm_qos_req: handle to request list element
289 *
290 * Will remove pm qos request from the list of requests and
291 * recompute the current target value for the pm_qos_class. Call this
292 * on slow code paths.
293 */
pm_qos_remove_request(struct pm_qos_request_list * pm_qos_req)294 void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req)
295 {
296 struct pm_qos_object *o;
297
298 if (pm_qos_req == NULL)
299 return;
300 /* silent return to keep pcm code cleaner */
301
302 if (!pm_qos_request_active(pm_qos_req)) {
303 WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
304 return;
305 }
306
307 o = pm_qos_array[pm_qos_req->pm_qos_class];
308 update_target(o, &pm_qos_req->list, 1, PM_QOS_DEFAULT_VALUE);
309 memset(pm_qos_req, 0, sizeof(*pm_qos_req));
310 }
311 EXPORT_SYMBOL_GPL(pm_qos_remove_request);
312
313 /**
314 * pm_qos_add_notifier - sets notification entry for changes to target value
315 * @pm_qos_class: identifies which qos target changes should be notified.
316 * @notifier: notifier block managed by caller.
317 *
318 * will register the notifier into a notification chain that gets called
319 * upon changes to the pm_qos_class target value.
320 */
pm_qos_add_notifier(int pm_qos_class,struct notifier_block * notifier)321 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
322 {
323 int retval;
324
325 retval = blocking_notifier_chain_register(
326 pm_qos_array[pm_qos_class]->notifiers, notifier);
327
328 return retval;
329 }
330 EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
331
332 /**
333 * pm_qos_remove_notifier - deletes notification entry from chain.
334 * @pm_qos_class: identifies which qos target changes are notified.
335 * @notifier: notifier block to be removed.
336 *
337 * will remove the notifier from the notification chain that gets called
338 * upon changes to the pm_qos_class target value.
339 */
pm_qos_remove_notifier(int pm_qos_class,struct notifier_block * notifier)340 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
341 {
342 int retval;
343
344 retval = blocking_notifier_chain_unregister(
345 pm_qos_array[pm_qos_class]->notifiers, notifier);
346
347 return retval;
348 }
349 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
350
pm_qos_power_open(struct inode * inode,struct file * filp)351 static int pm_qos_power_open(struct inode *inode, struct file *filp)
352 {
353 long pm_qos_class;
354
355 pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
356 if (pm_qos_class >= 0) {
357 struct pm_qos_request_list *req = kzalloc(sizeof(*req), GFP_KERNEL);
358 if (!req)
359 return -ENOMEM;
360
361 pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
362 filp->private_data = req;
363
364 if (filp->private_data)
365 return 0;
366 }
367 return -EPERM;
368 }
369
pm_qos_power_release(struct inode * inode,struct file * filp)370 static int pm_qos_power_release(struct inode *inode, struct file *filp)
371 {
372 struct pm_qos_request_list *req;
373
374 req = filp->private_data;
375 pm_qos_remove_request(req);
376 kfree(req);
377
378 return 0;
379 }
380
381
pm_qos_power_read(struct file * filp,char __user * buf,size_t count,loff_t * f_pos)382 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
383 size_t count, loff_t *f_pos)
384 {
385 s32 value;
386 unsigned long flags;
387 struct pm_qos_object *o;
388 struct pm_qos_request_list *pm_qos_req = filp->private_data;;
389
390 if (!pm_qos_req)
391 return -EINVAL;
392 if (!pm_qos_request_active(pm_qos_req))
393 return -EINVAL;
394
395 o = pm_qos_array[pm_qos_req->pm_qos_class];
396 spin_lock_irqsave(&pm_qos_lock, flags);
397 value = pm_qos_get_value(o);
398 spin_unlock_irqrestore(&pm_qos_lock, flags);
399
400 return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
401 }
402
pm_qos_power_write(struct file * filp,const char __user * buf,size_t count,loff_t * f_pos)403 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
404 size_t count, loff_t *f_pos)
405 {
406 s32 value;
407 int x;
408 char ascii_value[11];
409 struct pm_qos_request_list *pm_qos_req;
410
411 if (count == sizeof(s32)) {
412 if (copy_from_user(&value, buf, sizeof(s32)))
413 return -EFAULT;
414 } else if (count == 11) { /* len('0x12345678/0') */
415 if (copy_from_user(ascii_value, buf, 11))
416 return -EFAULT;
417 if (strlen(ascii_value) != 10)
418 return -EINVAL;
419 x = sscanf(ascii_value, "%x", &value);
420 if (x != 1)
421 return -EINVAL;
422 pr_debug("%s, %d, 0x%x\n", ascii_value, x, value);
423 } else
424 return -EINVAL;
425
426 pm_qos_req = filp->private_data;
427 pm_qos_update_request(pm_qos_req, value);
428
429 return count;
430 }
431
432
pm_qos_power_init(void)433 static int __init pm_qos_power_init(void)
434 {
435 int ret = 0;
436
437 ret = register_pm_qos_misc(&cpu_dma_pm_qos);
438 if (ret < 0) {
439 printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
440 return ret;
441 }
442 ret = register_pm_qos_misc(&network_lat_pm_qos);
443 if (ret < 0) {
444 printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
445 return ret;
446 }
447 ret = register_pm_qos_misc(&network_throughput_pm_qos);
448 if (ret < 0)
449 printk(KERN_ERR
450 "pm_qos_param: network_throughput setup failed\n");
451
452 return ret;
453 }
454
455 late_initcall(pm_qos_power_init);
456