Root/kernel/power/qos.c

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.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#include <linux/kernel.h>
44
45#include <linux/uaccess.h>
46#include <linux/export.h>
47
48/*
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
52 */
53struct pm_qos_object {
54    struct pm_qos_constraints *constraints;
55    struct miscdevice pm_qos_power_miscdev;
56    char *name;
57};
58
59static DEFINE_SPINLOCK(pm_qos_lock);
60
61static struct pm_qos_object null_pm_qos;
62
63static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
64static 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,
68    .type = PM_QOS_MIN,
69    .notifiers = &cpu_dma_lat_notifier,
70};
71static struct pm_qos_object cpu_dma_pm_qos = {
72    .constraints = &cpu_dma_constraints,
73    .name = "cpu_dma_latency",
74};
75
76static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
77static 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,
81    .type = PM_QOS_MIN,
82    .notifiers = &network_lat_notifier,
83};
84static struct pm_qos_object network_lat_pm_qos = {
85    .constraints = &network_lat_constraints,
86    .name = "network_latency",
87};
88
89
90static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
91static 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,
95    .type = PM_QOS_MAX,
96    .notifiers = &network_throughput_notifier,
97};
98static struct pm_qos_object network_throughput_pm_qos = {
99    .constraints = &network_tput_constraints,
100    .name = "network_throughput",
101};
102
103
104static struct pm_qos_object *pm_qos_array[] = {
105    &null_pm_qos,
106    &cpu_dma_pm_qos,
107    &network_lat_pm_qos,
108    &network_throughput_pm_qos
109};
110
111static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
112        size_t count, loff_t *f_pos);
113static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
114        size_t count, loff_t *f_pos);
115static int pm_qos_power_open(struct inode *inode, struct file *filp);
116static int pm_qos_power_release(struct inode *inode, struct file *filp);
117
118static 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,
124};
125
126/* unlocked internal variant */
127static inline int pm_qos_get_value(struct pm_qos_constraints *c)
128{
129    if (plist_head_empty(&c->list))
130        return c->default_value;
131
132    switch (c->type) {
133    case PM_QOS_MIN:
134        return plist_first(&c->list)->prio;
135
136    case PM_QOS_MAX:
137        return plist_last(&c->list)->prio;
138
139    default:
140        /* runtime check for not using enum */
141        BUG();
142    }
143}
144
145s32 pm_qos_read_value(struct pm_qos_constraints *c)
146{
147    return c->target_value;
148}
149
150static inline void pm_qos_set_value(struct pm_qos_constraints *c, s32 value)
151{
152    c->target_value = value;
153}
154
155/**
156 * pm_qos_update_target - manages the constraints list and calls the notifiers
157 * if needed
158 * @c: constraints data struct
159 * @node: request to add to the list, to update or to remove
160 * @action: action to take on the constraints list
161 * @value: value of the request to add or update
162 *
163 * This function returns 1 if the aggregated constraint value has changed, 0
164 * otherwise.
165 */
166int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node,
167             enum pm_qos_req_action action, int value)
168{
169    unsigned long flags;
170    int prev_value, curr_value, new_value;
171
172    spin_lock_irqsave(&pm_qos_lock, flags);
173    prev_value = pm_qos_get_value(c);
174    if (value == PM_QOS_DEFAULT_VALUE)
175        new_value = c->default_value;
176    else
177        new_value = value;
178
179    switch (action) {
180    case PM_QOS_REMOVE_REQ:
181        plist_del(node, &c->list);
182        break;
183    case PM_QOS_UPDATE_REQ:
184        /*
185         * to change the list, we atomically remove, reinit
186         * with new value and add, then see if the extremal
187         * changed
188         */
189        plist_del(node, &c->list);
190    case PM_QOS_ADD_REQ:
191        plist_node_init(node, new_value);
192        plist_add(node, &c->list);
193        break;
194    default:
195        /* no action */
196        ;
197    }
198
199    curr_value = pm_qos_get_value(c);
200    pm_qos_set_value(c, curr_value);
201
202    spin_unlock_irqrestore(&pm_qos_lock, flags);
203
204    if (prev_value != curr_value) {
205        blocking_notifier_call_chain(c->notifiers,
206                         (unsigned long)curr_value,
207                         NULL);
208        return 1;
209    } else {
210        return 0;
211    }
212}
213
214/**
215 * pm_qos_request - returns current system wide qos expectation
216 * @pm_qos_class: identification of which qos value is requested
217 *
218 * This function returns the current target value.
219 */
220int pm_qos_request(int pm_qos_class)
221{
222    return pm_qos_read_value(pm_qos_array[pm_qos_class]->constraints);
223}
224EXPORT_SYMBOL_GPL(pm_qos_request);
225
226int pm_qos_request_active(struct pm_qos_request *req)
227{
228    return req->pm_qos_class != 0;
229}
230EXPORT_SYMBOL_GPL(pm_qos_request_active);
231
232/**
233 * pm_qos_work_fn - the timeout handler of pm_qos_update_request_timeout
234 * @work: work struct for the delayed work (timeout)
235 *
236 * This cancels the timeout request by falling back to the default at timeout.
237 */
238static void pm_qos_work_fn(struct work_struct *work)
239{
240    struct pm_qos_request *req = container_of(to_delayed_work(work),
241                          struct pm_qos_request,
242                          work);
243
244    pm_qos_update_request(req, PM_QOS_DEFAULT_VALUE);
245}
246
247/**
248 * pm_qos_add_request - inserts new qos request into the list
249 * @req: pointer to a preallocated handle
250 * @pm_qos_class: identifies which list of qos request to use
251 * @value: defines the qos request
252 *
253 * This function inserts a new entry in the pm_qos_class list of requested qos
254 * performance characteristics. It recomputes the aggregate QoS expectations
255 * for the pm_qos_class of parameters and initializes the pm_qos_request
256 * handle. Caller needs to save this handle for later use in updates and
257 * removal.
258 */
259
260void pm_qos_add_request(struct pm_qos_request *req,
261            int pm_qos_class, s32 value)
262{
263    if (!req) /*guard against callers passing in null */
264        return;
265
266    if (pm_qos_request_active(req)) {
267        WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
268        return;
269    }
270    req->pm_qos_class = pm_qos_class;
271    INIT_DELAYED_WORK(&req->work, pm_qos_work_fn);
272    pm_qos_update_target(pm_qos_array[pm_qos_class]->constraints,
273                 &req->node, PM_QOS_ADD_REQ, value);
274}
275EXPORT_SYMBOL_GPL(pm_qos_add_request);
276
277/**
278 * pm_qos_update_request - modifies an existing qos request
279 * @req : handle to list element holding a pm_qos request to use
280 * @value: defines the qos request
281 *
282 * Updates an existing qos request for the pm_qos_class of parameters along
283 * with updating the target pm_qos_class value.
284 *
285 * Attempts are made to make this code callable on hot code paths.
286 */
287void pm_qos_update_request(struct pm_qos_request *req,
288               s32 new_value)
289{
290    if (!req) /*guard against callers passing in null */
291        return;
292
293    if (!pm_qos_request_active(req)) {
294        WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
295        return;
296    }
297
298    if (delayed_work_pending(&req->work))
299        cancel_delayed_work_sync(&req->work);
300
301    if (new_value != req->node.prio)
302        pm_qos_update_target(
303            pm_qos_array[req->pm_qos_class]->constraints,
304            &req->node, PM_QOS_UPDATE_REQ, new_value);
305}
306EXPORT_SYMBOL_GPL(pm_qos_update_request);
307
308/**
309 * pm_qos_update_request_timeout - modifies an existing qos request temporarily.
310 * @req : handle to list element holding a pm_qos request to use
311 * @new_value: defines the temporal qos request
312 * @timeout_us: the effective duration of this qos request in usecs.
313 *
314 * After timeout_us, this qos request is cancelled automatically.
315 */
316void pm_qos_update_request_timeout(struct pm_qos_request *req, s32 new_value,
317                   unsigned long timeout_us)
318{
319    if (!req)
320        return;
321    if (WARN(!pm_qos_request_active(req),
322         "%s called for unknown object.", __func__))
323        return;
324
325    if (delayed_work_pending(&req->work))
326        cancel_delayed_work_sync(&req->work);
327
328    if (new_value != req->node.prio)
329        pm_qos_update_target(
330            pm_qos_array[req->pm_qos_class]->constraints,
331            &req->node, PM_QOS_UPDATE_REQ, new_value);
332
333    schedule_delayed_work(&req->work, usecs_to_jiffies(timeout_us));
334}
335
336/**
337 * pm_qos_remove_request - modifies an existing qos request
338 * @req: handle to request list element
339 *
340 * Will remove pm qos request from the list of constraints and
341 * recompute the current target value for the pm_qos_class. Call this
342 * on slow code paths.
343 */
344void pm_qos_remove_request(struct pm_qos_request *req)
345{
346    if (!req) /*guard against callers passing in null */
347        return;
348        /* silent return to keep pcm code cleaner */
349
350    if (!pm_qos_request_active(req)) {
351        WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
352        return;
353    }
354
355    if (delayed_work_pending(&req->work))
356        cancel_delayed_work_sync(&req->work);
357
358    pm_qos_update_target(pm_qos_array[req->pm_qos_class]->constraints,
359                 &req->node, PM_QOS_REMOVE_REQ,
360                 PM_QOS_DEFAULT_VALUE);
361    memset(req, 0, sizeof(*req));
362}
363EXPORT_SYMBOL_GPL(pm_qos_remove_request);
364
365/**
366 * pm_qos_add_notifier - sets notification entry for changes to target value
367 * @pm_qos_class: identifies which qos target changes should be notified.
368 * @notifier: notifier block managed by caller.
369 *
370 * will register the notifier into a notification chain that gets called
371 * upon changes to the pm_qos_class target value.
372 */
373int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
374{
375    int retval;
376
377    retval = blocking_notifier_chain_register(
378            pm_qos_array[pm_qos_class]->constraints->notifiers,
379            notifier);
380
381    return retval;
382}
383EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
384
385/**
386 * pm_qos_remove_notifier - deletes notification entry from chain.
387 * @pm_qos_class: identifies which qos target changes are notified.
388 * @notifier: notifier block to be removed.
389 *
390 * will remove the notifier from the notification chain that gets called
391 * upon changes to the pm_qos_class target value.
392 */
393int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
394{
395    int retval;
396
397    retval = blocking_notifier_chain_unregister(
398            pm_qos_array[pm_qos_class]->constraints->notifiers,
399            notifier);
400
401    return retval;
402}
403EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
404
405/* User space interface to PM QoS classes via misc devices */
406static int register_pm_qos_misc(struct pm_qos_object *qos)
407{
408    qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
409    qos->pm_qos_power_miscdev.name = qos->name;
410    qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
411
412    return misc_register(&qos->pm_qos_power_miscdev);
413}
414
415static int find_pm_qos_object_by_minor(int minor)
416{
417    int pm_qos_class;
418
419    for (pm_qos_class = 0;
420        pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
421        if (minor ==
422            pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
423            return pm_qos_class;
424    }
425    return -1;
426}
427
428static int pm_qos_power_open(struct inode *inode, struct file *filp)
429{
430    long pm_qos_class;
431
432    pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
433    if (pm_qos_class >= 0) {
434        struct pm_qos_request *req = kzalloc(sizeof(*req), GFP_KERNEL);
435        if (!req)
436            return -ENOMEM;
437
438        pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
439        filp->private_data = req;
440
441        return 0;
442    }
443    return -EPERM;
444}
445
446static int pm_qos_power_release(struct inode *inode, struct file *filp)
447{
448    struct pm_qos_request *req;
449
450    req = filp->private_data;
451    pm_qos_remove_request(req);
452    kfree(req);
453
454    return 0;
455}
456
457
458static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
459        size_t count, loff_t *f_pos)
460{
461    s32 value;
462    unsigned long flags;
463    struct pm_qos_request *req = filp->private_data;
464
465    if (!req)
466        return -EINVAL;
467    if (!pm_qos_request_active(req))
468        return -EINVAL;
469
470    spin_lock_irqsave(&pm_qos_lock, flags);
471    value = pm_qos_get_value(pm_qos_array[req->pm_qos_class]->constraints);
472    spin_unlock_irqrestore(&pm_qos_lock, flags);
473
474    return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
475}
476
477static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
478        size_t count, loff_t *f_pos)
479{
480    s32 value;
481    struct pm_qos_request *req;
482
483    if (count == sizeof(s32)) {
484        if (copy_from_user(&value, buf, sizeof(s32)))
485            return -EFAULT;
486    } else if (count <= 11) { /* ASCII perhaps? */
487        char ascii_value[11];
488        unsigned long int ulval;
489        int ret;
490
491        if (copy_from_user(ascii_value, buf, count))
492            return -EFAULT;
493
494        if (count > 10) {
495            if (ascii_value[10] == '\n')
496                ascii_value[10] = '\0';
497            else
498                return -EINVAL;
499        } else {
500            ascii_value[count] = '\0';
501        }
502        ret = strict_strtoul(ascii_value, 16, &ulval);
503        if (ret) {
504            pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret);
505            return -EINVAL;
506        }
507        value = (s32)lower_32_bits(ulval);
508    } else {
509        return -EINVAL;
510    }
511
512    req = filp->private_data;
513    pm_qos_update_request(req, value);
514
515    return count;
516}
517
518
519static int __init pm_qos_power_init(void)
520{
521    int ret = 0;
522    int i;
523
524    BUILD_BUG_ON(ARRAY_SIZE(pm_qos_array) != PM_QOS_NUM_CLASSES);
525
526    for (i = 1; i < PM_QOS_NUM_CLASSES; i++) {
527        ret = register_pm_qos_misc(pm_qos_array[i]);
528        if (ret < 0) {
529            printk(KERN_ERR "pm_qos_param: %s setup failed\n",
530                   pm_qos_array[i]->name);
531            return ret;
532        }
533    }
534
535    return ret;
536}
537
538late_initcall(pm_qos_power_init);
539

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