kernel/power/qos.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * This module exposes the interface to kernel space for specifying
   4  * QoS dependencies.  It provides infrastructure for registration of:
   5  *
   6  * Dependents on a QoS value : register requests
   7  * Watchers of QoS value : get notified when target QoS value changes
   8  *
   9  * This QoS design is best effort based.  Dependents register their QoS needs.
  10  * Watchers register to keep track of the current QoS needs of the system.
  11  *
  12  * There are 3 basic classes of QoS parameter: latency, timeout, throughput
  13  * each have defined units:
  14  * latency: usec
  15  * timeout: usec <-- currently not used.
  16  * throughput: kbs (kilo byte / sec)
  17  *
  18  * There are lists of pm_qos_objects each one wrapping requests, notifiers
  19  *
  20  * User mode requests on a QOS parameter register themselves to the
  21  * subsystem by opening the device node /dev/... and writing there request to
  22  * the node.  As long as the process holds a file handle open to the node the
  23  * client continues to be accounted for.  Upon file release the usermode
  24  * request is removed and a new qos target is computed.  This way when the
  25  * request that the application has is cleaned up when closes the file
  26  * pointer or exits the pm_qos_object will get an opportunity to clean up.
  27  *
  28  * Mark Gross <mgross@linux.intel.com>
  29  */
  30
  31 /*#define DEBUG*/
  32
  33 #include <linux/pm_qos.h>
  34 #include <linux/sched.h>
  35 #include <linux/spinlock.h>
  36 #include <linux/slab.h>
  37 #include <linux/time.h>
  38 #include <linux/fs.h>
  39 #include <linux/device.h>
  40 #include <linux/miscdevice.h>
  41 #include <linux/string.h>
  42 #include <linux/platform_device.h>
  43 #include <linux/init.h>
  44 #include <linux/kernel.h>
  45 #include <linux/debugfs.h>
  46 #include <linux/seq_file.h>
  47
  48 #include <linux/uaccess.h>
  49 #include <linux/export.h>
  50 #include <trace/events/power.h>
  51
  52 /*
  53  * locking rule: all changes to constraints or notifiers lists
  54  * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
  55  * held, taken with _irqsave.  One lock to rule them all
  56  */
  57 struct pm_qos_object {
  58         struct pm_qos_constraints *constraints;
  59         struct miscdevice pm_qos_power_miscdev;
  60         char *name;
  61 };
  62
  63 static DEFINE_SPINLOCK(pm_qos_lock);
  64
  65 static struct pm_qos_object null_pm_qos;
  66
  67 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
  68 static struct pm_qos_constraints cpu_dma_constraints = {
  69         .list = PLIST_HEAD_INIT(cpu_dma_constraints.list),
  70         .target_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
  71         .default_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
  72         .no_constraint_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
  73         .type = PM_QOS_MIN,
  74         .notifiers = &cpu_dma_lat_notifier,
  75 };
  76 static struct pm_qos_object cpu_dma_pm_qos = {
  77         .constraints = &cpu_dma_constraints,
  78         .name = "cpu_dma_latency",
  79 };
  80
  81 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
  82 static struct pm_qos_constraints network_lat_constraints = {
  83         .list = PLIST_HEAD_INIT(network_lat_constraints.list),
  84         .target_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
  85         .default_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
  86         .no_constraint_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
  87         .type = PM_QOS_MIN,
  88         .notifiers = &network_lat_notifier,
  89 };
  90 static struct pm_qos_object network_lat_pm_qos = {
  91         .constraints = &network_lat_constraints,
  92         .name = "network_latency",
  93 };
  94
  95
  96 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
  97 static struct pm_qos_constraints network_tput_constraints = {
  98         .list = PLIST_HEAD_INIT(network_tput_constraints.list),
  99         .target_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
 100         .default_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
 101         .no_constraint_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
 102         .type = PM_QOS_MAX,
 103         .notifiers = &network_throughput_notifier,
 104 };
 105 static struct pm_qos_object network_throughput_pm_qos = {
 106         .constraints = &network_tput_constraints,
 107         .name = "network_throughput",
 108 };
 109
 110
 111 static BLOCKING_NOTIFIER_HEAD(memory_bandwidth_notifier);
 112 static struct pm_qos_constraints memory_bw_constraints = {
 113         .list = PLIST_HEAD_INIT(memory_bw_constraints.list),
 114         .target_value = PM_QOS_MEMORY_BANDWIDTH_DEFAULT_VALUE,
 115         .default_value = PM_QOS_MEMORY_BANDWIDTH_DEFAULT_VALUE,
 116         .no_constraint_value = PM_QOS_MEMORY_BANDWIDTH_DEFAULT_VALUE,
 117         .type = PM_QOS_SUM,
 118         .notifiers = &memory_bandwidth_notifier,
 119 };
 120 static struct pm_qos_object memory_bandwidth_pm_qos = {
 121         .constraints = &memory_bw_constraints,
 122         .name = "memory_bandwidth",
 123 };
 124
 125
 126 static struct pm_qos_object *pm_qos_array[] = {
 127         &null_pm_qos,
 128         &cpu_dma_pm_qos,
 129         &network_lat_pm_qos,
 130         &network_throughput_pm_qos,
 131         &memory_bandwidth_pm_qos,
 132 };
 133
 134 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 135                 size_t count, loff_t *f_pos);
 136 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 137                 size_t count, loff_t *f_pos);
 138 static int pm_qos_power_open(struct inode *inode, struct file *filp);
 139 static int pm_qos_power_release(struct inode *inode, struct file *filp);
 140
 141 static const struct file_operations pm_qos_power_fops = {
 142         .write = pm_qos_power_write,
 143         .read = pm_qos_power_read,
 144         .open = pm_qos_power_open,
 145         .release = pm_qos_power_release,
 146         .llseek = noop_llseek,
 147 };
 148
 149 /* unlocked internal variant */
 150 static inline int pm_qos_get_value(struct pm_qos_constraints *c)
 151 {
 152         struct plist_node *node;
 153         int total_value = 0;
 154
 155         if (plist_head_empty(&c->list))
 156                 return c->no_constraint_value;
 157
 158         switch (c->type) {
 159         case PM_QOS_MIN:
 160                 return plist_first(&c->list)->prio;
 161
 162         case PM_QOS_MAX:
 163                 return plist_last(&c->list)->prio;
 164
 165         case PM_QOS_SUM:
 166                 plist_for_each(node, &c->list)
 167                         total_value += node->prio;
 168
 169                 return total_value;
 170
 171         default:
 172                 /* runtime check for not using enum */
 173                 BUG();
 174                 return PM_QOS_DEFAULT_VALUE;
 175         }
 176 }
 177
 178 s32 pm_qos_read_value(struct pm_qos_constraints *c)
 179 {
 180         return c->target_value;
 181 }
 182
 183 static inline void pm_qos_set_value(struct pm_qos_constraints *c, s32 value)
 184 {
 185         c->target_value = value;
 186 }
 187
 188 static int pm_qos_debug_show(struct seq_file *s, void *unused)
 189 {
 190         struct pm_qos_object *qos = (struct pm_qos_object *)s->private;
 191         struct pm_qos_constraints *c;
 192         struct pm_qos_request *req;
 193         char *type;
 194         unsigned long flags;
 195         int tot_reqs = 0;
 196         int active_reqs = 0;
 197
 198         if (IS_ERR_OR_NULL(qos)) {
 199                 pr_err("%s: bad qos param!\n", __func__);
 200                 return -EINVAL;
 201         }
 202         c = qos->constraints;
 203         if (IS_ERR_OR_NULL(c)) {
 204                 pr_err("%s: Bad constraints on qos?\n", __func__);
 205                 return -EINVAL;
 206         }
 207
 208         /* Lock to ensure we have a snapshot */
 209         spin_lock_irqsave(&pm_qos_lock, flags);
 210         if (plist_head_empty(&c->list)) {
 211                 seq_puts(s, "Empty!\n");
 212                 goto out;
 213         }
 214
 215         switch (c->type) {
 216         case PM_QOS_MIN:
 217                 type = "Minimum";
 218                 break;
 219         case PM_QOS_MAX:
 220                 type = "Maximum";
 221                 break;
 222         case PM_QOS_SUM:
 223                 type = "Sum";
 224                 break;
 225         default:
 226                 type = "Unknown";
 227         }
 228
 229         plist_for_each_entry(req, &c->list, node) {
 230                 char *state = "Default";
 231
 232                 if ((req->node).prio != c->default_value) {
 233                         active_reqs++;
 234                         state = "Active";
 235                 }
 236                 tot_reqs++;
 237                 seq_printf(s, "%d: %d: %s\n", tot_reqs,
 238                            (req->node).prio, state);
 239         }
 240
 241         seq_printf(s, "Type=%s, Value=%d, Requests: active=%d / total=%d\n",
 242                    type, pm_qos_get_value(c), active_reqs, tot_reqs);
 243
 244 out:
 245         spin_unlock_irqrestore(&pm_qos_lock, flags);
 246         return 0;
 247 }
 248
 249 DEFINE_SHOW_ATTRIBUTE(pm_qos_debug);
 250
 251 /**
 252  * pm_qos_update_target - manages the constraints list and calls the notifiers
 253  *  if needed
 254  * @c: constraints data struct
 255  * @node: request to add to the list, to update or to remove
 256  * @action: action to take on the constraints list
 257  * @value: value of the request to add or update
 258  *
 259  * This function returns 1 if the aggregated constraint value has changed, 0
 260  *  otherwise.
 261  */
 262 int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node,
 263                          enum pm_qos_req_action action, int value)
 264 {
 265         unsigned long flags;
 266         int prev_value, curr_value, new_value;
 267         int ret;
 268
 269         spin_lock_irqsave(&pm_qos_lock, flags);
 270         prev_value = pm_qos_get_value(c);
 271         if (value == PM_QOS_DEFAULT_VALUE)
 272                 new_value = c->default_value;
 273         else
 274                 new_value = value;
 275
 276         switch (action) {
 277         case PM_QOS_REMOVE_REQ:
 278                 plist_del(node, &c->list);
 279                 break;
 280         case PM_QOS_UPDATE_REQ:
 281                 /*
 282                  * to change the list, we atomically remove, reinit
 283                  * with new value and add, then see if the extremal
 284                  * changed
 285                  */
 286                 plist_del(node, &c->list);
 287                 /* fall through */
 288         case PM_QOS_ADD_REQ:
 289                 plist_node_init(node, new_value);
 290                 plist_add(node, &c->list);
 291                 break;
 292         default:
 293                 /* no action */
 294                 ;
 295         }
 296
 297         curr_value = pm_qos_get_value(c);
 298         pm_qos_set_value(c, curr_value);
 299
 300         spin_unlock_irqrestore(&pm_qos_lock, flags);
 301
 302         trace_pm_qos_update_target(action, prev_value, curr_value);
 303         if (prev_value != curr_value) {
 304                 ret = 1;
 305                 if (c->notifiers)
 306                         blocking_notifier_call_chain(c->notifiers,
 307                                                      (unsigned long)curr_value,
 308                                                      NULL);
 309         } else {
 310                 ret = 0;
 311         }
 312         return ret;
 313 }
 314
 315 /**
 316  * pm_qos_flags_remove_req - Remove device PM QoS flags request.
 317  * @pqf: Device PM QoS flags set to remove the request from.
 318  * @req: Request to remove from the set.
 319  */
 320 static void pm_qos_flags_remove_req(struct pm_qos_flags *pqf,
 321                                     struct pm_qos_flags_request *req)
 322 {
 323         s32 val = 0;
 324
 325         list_del(&req->node);
 326         list_for_each_entry(req, &pqf->list, node)
 327                 val |= req->flags;
 328
 329         pqf->effective_flags = val;
 330 }
 331
 332 /**
 333  * pm_qos_update_flags - Update a set of PM QoS flags.
 334  * @pqf: Set of flags to update.
 335  * @req: Request to add to the set, to modify, or to remove from the set.
 336  * @action: Action to take on the set.
 337  * @val: Value of the request to add or modify.
 338  *
 339  * Update the given set of PM QoS flags and call notifiers if the aggregate
 340  * value has changed.  Returns 1 if the aggregate constraint value has changed,
 341  * 0 otherwise.
 342  */
 343 bool pm_qos_update_flags(struct pm_qos_flags *pqf,
 344                          struct pm_qos_flags_request *req,
 345                          enum pm_qos_req_action action, s32 val)
 346 {
 347         unsigned long irqflags;
 348         s32 prev_value, curr_value;
 349
 350         spin_lock_irqsave(&pm_qos_lock, irqflags);
 351
 352         prev_value = list_empty(&pqf->list) ? 0 : pqf->effective_flags;
 353
 354         switch (action) {
 355         case PM_QOS_REMOVE_REQ:
 356                 pm_qos_flags_remove_req(pqf, req);
 357                 break;
 358         case PM_QOS_UPDATE_REQ:
 359                 pm_qos_flags_remove_req(pqf, req);
 360                 /* fall through */
 361         case PM_QOS_ADD_REQ:
 362                 req->flags = val;
 363                 INIT_LIST_HEAD(&req->node);
 364                 list_add_tail(&req->node, &pqf->list);
 365                 pqf->effective_flags |= val;
 366                 break;
 367         default:
 368                 /* no action */
 369                 ;
 370         }
 371
 372         curr_value = list_empty(&pqf->list) ? 0 : pqf->effective_flags;
 373
 374         spin_unlock_irqrestore(&pm_qos_lock, irqflags);
 375
 376         trace_pm_qos_update_flags(action, prev_value, curr_value);
 377         return prev_value != curr_value;
 378 }
 379
 380 /**
 381  * pm_qos_request - returns current system wide qos expectation
 382  * @pm_qos_class: identification of which qos value is requested
 383  *
 384  * This function returns the current target value.
 385  */
 386 int pm_qos_request(int pm_qos_class)
 387 {
 388         return pm_qos_read_value(pm_qos_array[pm_qos_class]->constraints);
 389 }
 390 EXPORT_SYMBOL_GPL(pm_qos_request);
 391
 392 int pm_qos_request_active(struct pm_qos_request *req)
 393 {
 394         return req->pm_qos_class != 0;
 395 }
 396 EXPORT_SYMBOL_GPL(pm_qos_request_active);
 397
 398 static void __pm_qos_update_request(struct pm_qos_request *req,
 399                            s32 new_value)
 400 {
 401         trace_pm_qos_update_request(req->pm_qos_class, new_value);
 402
 403         if (new_value != req->node.prio)
 404                 pm_qos_update_target(
 405                         pm_qos_array[req->pm_qos_class]->constraints,
 406                         &req->node, PM_QOS_UPDATE_REQ, new_value);
 407 }
 408
 409 /**
 410  * pm_qos_work_fn - the timeout handler of pm_qos_update_request_timeout
 411  * @work: work struct for the delayed work (timeout)
 412  *
 413  * This cancels the timeout request by falling back to the default at timeout.
 414  */
 415 static void pm_qos_work_fn(struct work_struct *work)
 416 {
 417         struct pm_qos_request *req = container_of(to_delayed_work(work),
 418                                                   struct pm_qos_request,
 419                                                   work);
 420
 421         __pm_qos_update_request(req, PM_QOS_DEFAULT_VALUE);
 422 }
 423
 424 /**
 425  * pm_qos_add_request - inserts new qos request into the list
 426  * @req: pointer to a preallocated handle
 427  * @pm_qos_class: identifies which list of qos request to use
 428  * @value: defines the qos request
 429  *
 430  * This function inserts a new entry in the pm_qos_class list of requested qos
 431  * performance characteristics.  It recomputes the aggregate QoS expectations
 432  * for the pm_qos_class of parameters and initializes the pm_qos_request
 433  * handle.  Caller needs to save this handle for later use in updates and
 434  * removal.
 435  */
 436
 437 void pm_qos_add_request(struct pm_qos_request *req,
 438                         int pm_qos_class, s32 value)
 439 {
 440         if (!req) /*guard against callers passing in null */
 441                 return;
 442
 443         if (pm_qos_request_active(req)) {
 444                 WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
 445                 return;
 446         }
 447         req->pm_qos_class = pm_qos_class;
 448         INIT_DELAYED_WORK(&req->work, pm_qos_work_fn);
 449         trace_pm_qos_add_request(pm_qos_class, value);
 450         pm_qos_update_target(pm_qos_array[pm_qos_class]->constraints,
 451                              &req->node, PM_QOS_ADD_REQ, value);
 452 }
 453 EXPORT_SYMBOL_GPL(pm_qos_add_request);
 454
 455 /**
 456  * pm_qos_update_request - modifies an existing qos request
 457  * @req : handle to list element holding a pm_qos request to use
 458  * @value: defines the qos request
 459  *
 460  * Updates an existing qos request for the pm_qos_class of parameters along
 461  * with updating the target pm_qos_class value.
 462  *
 463  * Attempts are made to make this code callable on hot code paths.
 464  */
 465 void pm_qos_update_request(struct pm_qos_request *req,
 466                            s32 new_value)
 467 {
 468         if (!req) /*guard against callers passing in null */
 469                 return;
 470
 471         if (!pm_qos_request_active(req)) {
 472                 WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
 473                 return;
 474         }
 475
 476         cancel_delayed_work_sync(&req->work);
 477         __pm_qos_update_request(req, new_value);
 478 }
 479 EXPORT_SYMBOL_GPL(pm_qos_update_request);
 480
 481 /**
 482  * pm_qos_update_request_timeout - modifies an existing qos request temporarily.
 483  * @req : handle to list element holding a pm_qos request to use
 484  * @new_value: defines the temporal qos request
 485  * @timeout_us: the effective duration of this qos request in usecs.
 486  *
 487  * After timeout_us, this qos request is cancelled automatically.
 488  */
 489 void pm_qos_update_request_timeout(struct pm_qos_request *req, s32 new_value,
 490                                    unsigned long timeout_us)
 491 {
 492         if (!req)
 493                 return;
 494         if (WARN(!pm_qos_request_active(req),
 495                  "%s called for unknown object.", __func__))
 496                 return;
 497
 498         cancel_delayed_work_sync(&req->work);
 499
 500         trace_pm_qos_update_request_timeout(req->pm_qos_class,
 501                                             new_value, timeout_us);
 502         if (new_value != req->node.prio)
 503                 pm_qos_update_target(
 504                         pm_qos_array[req->pm_qos_class]->constraints,
 505                         &req->node, PM_QOS_UPDATE_REQ, new_value);
 506
 507         schedule_delayed_work(&req->work, usecs_to_jiffies(timeout_us));
 508 }
 509
 510 /**
 511  * pm_qos_remove_request - modifies an existing qos request
 512  * @req: handle to request list element
 513  *
 514  * Will remove pm qos request from the list of constraints and
 515  * recompute the current target value for the pm_qos_class.  Call this
 516  * on slow code paths.
 517  */
 518 void pm_qos_remove_request(struct pm_qos_request *req)
 519 {
 520         if (!req) /*guard against callers passing in null */
 521                 return;
 522                 /* silent return to keep pcm code cleaner */
 523
 524         if (!pm_qos_request_active(req)) {
 525                 WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
 526                 return;
 527         }
 528
 529         cancel_delayed_work_sync(&req->work);
 530
 531         trace_pm_qos_remove_request(req->pm_qos_class, PM_QOS_DEFAULT_VALUE);
 532         pm_qos_update_target(pm_qos_array[req->pm_qos_class]->constraints,
 533                              &req->node, PM_QOS_REMOVE_REQ,
 534                              PM_QOS_DEFAULT_VALUE);
 535         memset(req, 0, sizeof(*req));
 536 }
 537 EXPORT_SYMBOL_GPL(pm_qos_remove_request);
 538
 539 /**
 540  * pm_qos_add_notifier - sets notification entry for changes to target value
 541  * @pm_qos_class: identifies which qos target changes should be notified.
 542  * @notifier: notifier block managed by caller.
 543  *
 544  * will register the notifier into a notification chain that gets called
 545  * upon changes to the pm_qos_class target value.
 546  */
 547 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
 548 {
 549         int retval;
 550
 551         retval = blocking_notifier_chain_register(
 552                         pm_qos_array[pm_qos_class]->constraints->notifiers,
 553                         notifier);
 554
 555         return retval;
 556 }
 557 EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
 558
 559 /**
 560  * pm_qos_remove_notifier - deletes notification entry from chain.
 561  * @pm_qos_class: identifies which qos target changes are notified.
 562  * @notifier: notifier block to be removed.
 563  *
 564  * will remove the notifier from the notification chain that gets called
 565  * upon changes to the pm_qos_class target value.
 566  */
 567 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
 568 {
 569         int retval;
 570
 571         retval = blocking_notifier_chain_unregister(
 572                         pm_qos_array[pm_qos_class]->constraints->notifiers,
 573                         notifier);
 574
 575         return retval;
 576 }
 577 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
 578
 579 /* User space interface to PM QoS classes via misc devices */
 580 static int register_pm_qos_misc(struct pm_qos_object *qos, struct dentry *d)
 581 {
 582         qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
 583         qos->pm_qos_power_miscdev.name = qos->name;
 584         qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
 585
 586         debugfs_create_file(qos->name, S_IRUGO, d, (void *)qos,
 587                             &pm_qos_debug_fops);
 588
 589         return misc_register(&qos->pm_qos_power_miscdev);
 590 }
 591
 592 static int find_pm_qos_object_by_minor(int minor)
 593 {
 594         int pm_qos_class;
 595
 596         for (pm_qos_class = PM_QOS_CPU_DMA_LATENCY;
 597                 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
 598                 if (minor ==
 599                         pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
 600                         return pm_qos_class;
 601         }
 602         return -1;
 603 }
 604
 605 static int pm_qos_power_open(struct inode *inode, struct file *filp)
 606 {
 607         long pm_qos_class;
 608
 609         pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 610         if (pm_qos_class >= PM_QOS_CPU_DMA_LATENCY) {
 611                 struct pm_qos_request *req = kzalloc(sizeof(*req), GFP_KERNEL);
 612                 if (!req)
 613                         return -ENOMEM;
 614
 615                 pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
 616                 filp->private_data = req;
 617
 618                 return 0;
 619         }
 620         return -EPERM;
 621 }
 622
 623 static int pm_qos_power_release(struct inode *inode, struct file *filp)
 624 {
 625         struct pm_qos_request *req;
 626
 627         req = filp->private_data;
 628         pm_qos_remove_request(req);
 629         kfree(req);
 630
 631         return 0;
 632 }
 633
 634
 635 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 636                 size_t count, loff_t *f_pos)
 637 {
 638         s32 value;
 639         unsigned long flags;
 640         struct pm_qos_request *req = filp->private_data;
 641
 642         if (!req)
 643                 return -EINVAL;
 644         if (!pm_qos_request_active(req))
 645                 return -EINVAL;
 646
 647         spin_lock_irqsave(&pm_qos_lock, flags);
 648         value = pm_qos_get_value(pm_qos_array[req->pm_qos_class]->constraints);
 649         spin_unlock_irqrestore(&pm_qos_lock, flags);
 650
 651         return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
 652 }
 653
 654 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 655                 size_t count, loff_t *f_pos)
 656 {
 657         s32 value;
 658         struct pm_qos_request *req;
 659
 660         if (count == sizeof(s32)) {
 661                 if (copy_from_user(&value, buf, sizeof(s32)))
 662                         return -EFAULT;
 663         } else {
 664                 int ret;
 665
 666                 ret = kstrtos32_from_user(buf, count, 16, &value);
 667                 if (ret)
 668                         return ret;
 669         }
 670
 671         req = filp->private_data;
 672         pm_qos_update_request(req, value);
 673
 674         return count;
 675 }
 676
 677
 678 static int __init pm_qos_power_init(void)
 679 {
 680         int ret = 0;
 681         int i;
 682         struct dentry *d;
 683
 684         BUILD_BUG_ON(ARRAY_SIZE(pm_qos_array) != PM_QOS_NUM_CLASSES);
 685
 686         d = debugfs_create_dir("pm_qos", NULL);
 687
 688         for (i = PM_QOS_CPU_DMA_LATENCY; i < PM_QOS_NUM_CLASSES; i++) {
 689                 ret = register_pm_qos_misc(pm_qos_array[i], d);
 690                 if (ret < 0) {
 691                         pr_err("%s: %s setup failed\n",
 692                                __func__, pm_qos_array[i]->name);
 693                         return ret;
 694                 }
 695         }
 696
 697         return ret;
 698 }
 699
 700 late_initcall(pm_qos_power_init);