err.no Git - linux-2.6/blob - drivers/base/power/main.c

   1 /*
   2  * drivers/base/power/main.c - Where the driver meets power management.
   3  *
   4  * Copyright (c) 2003 Patrick Mochel
   5  * Copyright (c) 2003 Open Source Development Lab
   6  *
   7  * This file is released under the GPLv2
   8  *
   9  *
  10  * The driver model core calls device_pm_add() when a device is registered.
  11  * This will intialize the embedded device_pm_info object in the device
  12  * and add it to the list of power-controlled devices. sysfs entries for
  13  * controlling device power management will also be added.
  14  *
  15  * A separate list is used for keeping track of power info, because the power
  16  * domain dependencies may differ from the ancestral dependencies that the
  17  * subsystem list maintains.
  18  */
  19
  20 #include <linux/device.h>
  21 #include <linux/kallsyms.h>
  22 #include <linux/mutex.h>
  23 #include <linux/pm.h>
  24 #include <linux/resume-trace.h>
  25 #include <linux/rwsem.h>
  26
  27 #include "../base.h"
  28 #include "power.h"
  29
  30 /*
  31  * The entries in the dpm_list list are in a depth first order, simply
  32  * because children are guaranteed to be discovered after parents, and
  33  * are inserted at the back of the list on discovery.
  34  *
  35  * Since device_pm_add() may be called with a device semaphore held,
  36  * we must never try to acquire a device semaphore while holding
  37  * dpm_list_mutex.
  38  */
  39
  40 LIST_HEAD(dpm_list);
  41
  42 static DEFINE_MUTEX(dpm_list_mtx);
  43
  44 /*
  45  * Set once the preparation of devices for a PM transition has started, reset
  46  * before starting to resume devices.  Protected by dpm_list_mtx.
  47  */
  48 static bool transition_started;
  49
  50 /**
  51  *      device_pm_lock - lock the list of active devices used by the PM core
  52  */
  53 void device_pm_lock(void)
  54 {
  55         mutex_lock(&dpm_list_mtx);
  56 }
  57
  58 /**
  59  *      device_pm_unlock - unlock the list of active devices used by the PM core
  60  */
  61 void device_pm_unlock(void)
  62 {
  63         mutex_unlock(&dpm_list_mtx);
  64 }
  65
  66 /**
  67  *      device_pm_add - add a device to the list of active devices
  68  *      @dev:   Device to be added to the list
  69  */
  70 int device_pm_add(struct device *dev)
  71 {
  72         int error;
  73
  74         pr_debug("PM: Adding info for %s:%s\n",
  75                  dev->bus ? dev->bus->name : "No Bus",
  76                  kobject_name(&dev->kobj));
  77         mutex_lock(&dpm_list_mtx);
  78         if (dev->parent) {
  79                 if (dev->parent->power.status >= DPM_SUSPENDING) {
  80                         dev_warn(dev, "parent %s is sleeping, will not add\n",
  81                                 dev->parent->bus_id);
  82                         WARN_ON(true);
  83                 }
  84         } else if (transition_started) {
  85                 /*
  86                  * We refuse to register parentless devices while a PM
  87                  * transition is in progress in order to avoid leaving them
  88                  * unhandled down the road
  89                  */
  90                 WARN_ON(true);
  91         }
  92         error = dpm_sysfs_add(dev);
  93         if (!error) {
  94                 dev->power.status = DPM_ON;
  95                 list_add_tail(&dev->power.entry, &dpm_list);
  96         }
  97         mutex_unlock(&dpm_list_mtx);
  98         return error;
  99 }
 100
 101 /**
 102  *      device_pm_remove - remove a device from the list of active devices
 103  *      @dev:   Device to be removed from the list
 104  *
 105  *      This function also removes the device's PM-related sysfs attributes.
 106  */
 107 void device_pm_remove(struct device *dev)
 108 {
 109         pr_debug("PM: Removing info for %s:%s\n",
 110                  dev->bus ? dev->bus->name : "No Bus",
 111                  kobject_name(&dev->kobj));
 112         mutex_lock(&dpm_list_mtx);
 113         dpm_sysfs_remove(dev);
 114         list_del_init(&dev->power.entry);
 115         mutex_unlock(&dpm_list_mtx);
 116 }
 117
 118 /**
 119  *      pm_op - execute the PM operation appropiate for given PM event
 120  *      @dev:   Device.
 121  *      @ops:   PM operations to choose from.
 122  *      @state: PM transition of the system being carried out.
 123  */
 124 static int pm_op(struct device *dev, struct pm_ops *ops, pm_message_t state)
 125 {
 126         int error = 0;
 127
 128         switch (state.event) {
 129 #ifdef CONFIG_SUSPEND
 130         case PM_EVENT_SUSPEND:
 131                 if (ops->suspend) {
 132                         error = ops->suspend(dev);
 133                         suspend_report_result(ops->suspend, error);
 134                 }
 135                 break;
 136         case PM_EVENT_RESUME:
 137                 if (ops->resume) {
 138                         error = ops->resume(dev);
 139                         suspend_report_result(ops->resume, error);
 140                 }
 141                 break;
 142 #endif /* CONFIG_SUSPEND */
 143 #ifdef CONFIG_HIBERNATION
 144         case PM_EVENT_FREEZE:
 145         case PM_EVENT_QUIESCE:
 146                 if (ops->freeze) {
 147                         error = ops->freeze(dev);
 148                         suspend_report_result(ops->freeze, error);
 149                 }
 150                 break;
 151         case PM_EVENT_HIBERNATE:
 152                 if (ops->poweroff) {
 153                         error = ops->poweroff(dev);
 154                         suspend_report_result(ops->poweroff, error);
 155                 }
 156                 break;
 157         case PM_EVENT_THAW:
 158         case PM_EVENT_RECOVER:
 159                 if (ops->thaw) {
 160                         error = ops->thaw(dev);
 161                         suspend_report_result(ops->thaw, error);
 162                 }
 163                 break;
 164         case PM_EVENT_RESTORE:
 165                 if (ops->restore) {
 166                         error = ops->restore(dev);
 167                         suspend_report_result(ops->restore, error);
 168                 }
 169                 break;
 170 #endif /* CONFIG_HIBERNATION */
 171         default:
 172                 error = -EINVAL;
 173         }
 174         return error;
 175 }
 176
 177 /**
 178  *      pm_noirq_op - execute the PM operation appropiate for given PM event
 179  *      @dev:   Device.
 180  *      @ops:   PM operations to choose from.
 181  *      @state: PM transition of the system being carried out.
 182  *
 183  *      The operation is executed with interrupts disabled by the only remaining
 184  *      functional CPU in the system.
 185  */
 186 static int pm_noirq_op(struct device *dev, struct pm_ext_ops *ops,
 187                         pm_message_t state)
 188 {
 189         int error = 0;
 190
 191         switch (state.event) {
 192 #ifdef CONFIG_SUSPEND
 193         case PM_EVENT_SUSPEND:
 194                 if (ops->suspend_noirq) {
 195                         error = ops->suspend_noirq(dev);
 196                         suspend_report_result(ops->suspend_noirq, error);
 197                 }
 198                 break;
 199         case PM_EVENT_RESUME:
 200                 if (ops->resume_noirq) {
 201                         error = ops->resume_noirq(dev);
 202                         suspend_report_result(ops->resume_noirq, error);
 203                 }
 204                 break;
 205 #endif /* CONFIG_SUSPEND */
 206 #ifdef CONFIG_HIBERNATION
 207         case PM_EVENT_FREEZE:
 208         case PM_EVENT_QUIESCE:
 209                 if (ops->freeze_noirq) {
 210                         error = ops->freeze_noirq(dev);
 211                         suspend_report_result(ops->freeze_noirq, error);
 212                 }
 213                 break;
 214         case PM_EVENT_HIBERNATE:
 215                 if (ops->poweroff_noirq) {
 216                         error = ops->poweroff_noirq(dev);
 217                         suspend_report_result(ops->poweroff_noirq, error);
 218                 }
 219                 break;
 220         case PM_EVENT_THAW:
 221         case PM_EVENT_RECOVER:
 222                 if (ops->thaw_noirq) {
 223                         error = ops->thaw_noirq(dev);
 224                         suspend_report_result(ops->thaw_noirq, error);
 225                 }
 226                 break;
 227         case PM_EVENT_RESTORE:
 228                 if (ops->restore_noirq) {
 229                         error = ops->restore_noirq(dev);
 230                         suspend_report_result(ops->restore_noirq, error);
 231                 }
 232                 break;
 233 #endif /* CONFIG_HIBERNATION */
 234         default:
 235                 error = -EINVAL;
 236         }
 237         return error;
 238 }
 239
 240 static char *pm_verb(int event)
 241 {
 242         switch (event) {
 243         case PM_EVENT_SUSPEND:
 244                 return "suspend";
 245         case PM_EVENT_RESUME:
 246                 return "resume";
 247         case PM_EVENT_FREEZE:
 248                 return "freeze";
 249         case PM_EVENT_QUIESCE:
 250                 return "quiesce";
 251         case PM_EVENT_HIBERNATE:
 252                 return "hibernate";
 253         case PM_EVENT_THAW:
 254                 return "thaw";
 255         case PM_EVENT_RESTORE:
 256                 return "restore";
 257         case PM_EVENT_RECOVER:
 258                 return "recover";
 259         default:
 260                 return "(unknown PM event)";
 261         }
 262 }
 263
 264 static void pm_dev_dbg(struct device *dev, pm_message_t state, char *info)
 265 {
 266         dev_dbg(dev, "%s%s%s\n", info, pm_verb(state.event),
 267                 ((state.event & PM_EVENT_SLEEP) && device_may_wakeup(dev)) ?
 268                 ", may wakeup" : "");
 269 }
 270
 271 static void pm_dev_err(struct device *dev, pm_message_t state, char *info,
 272                         int error)
 273 {
 274         printk(KERN_ERR "PM: Device %s failed to %s%s: error %d\n",
 275                 kobject_name(&dev->kobj), pm_verb(state.event), info, error);
 276 }
 277
 278 /*------------------------- Resume routines -------------------------*/
 279
 280 /**
 281  *      resume_device_noirq - Power on one device (early resume).
 282  *      @dev:   Device.
 283  *      @state: PM transition of the system being carried out.
 284  *
 285  *      Must be called with interrupts disabled.
 286  */
 287 static int resume_device_noirq(struct device *dev, pm_message_t state)
 288 {
 289         int error = 0;
 290
 291         TRACE_DEVICE(dev);
 292         TRACE_RESUME(0);
 293
 294         if (!dev->bus)
 295                 goto End;
 296
 297         if (dev->bus->pm) {
 298                 pm_dev_dbg(dev, state, "EARLY ");
 299                 error = pm_noirq_op(dev, dev->bus->pm, state);
 300         } else if (dev->bus->resume_early) {
 301                 pm_dev_dbg(dev, state, "legacy EARLY ");
 302                 error = dev->bus->resume_early(dev);
 303         }
 304  End:
 305         TRACE_RESUME(error);
 306         return error;
 307 }
 308
 309 /**
 310  *      dpm_power_up - Power on all regular (non-sysdev) devices.
 311  *      @state: PM transition of the system being carried out.
 312  *
 313  *      Execute the appropriate "noirq resume" callback for all devices marked
 314  *      as DPM_OFF_IRQ.
 315  *
 316  *      Must be called with interrupts disabled and only one CPU running.
 317  */
 318 static void dpm_power_up(pm_message_t state)
 319 {
 320         struct device *dev;
 321
 322         list_for_each_entry(dev, &dpm_list, power.entry)
 323                 if (dev->power.status > DPM_OFF) {
 324                         int error;
 325
 326                         dev->power.status = DPM_OFF;
 327                         error = resume_device_noirq(dev, state);
 328                         if (error)
 329                                 pm_dev_err(dev, state, " early", error);
 330                 }
 331 }
 332
 333 /**
 334  *      device_power_up - Turn on all devices that need special attention.
 335  *      @state: PM transition of the system being carried out.
 336  *
 337  *      Power on system devices, then devices that required we shut them down
 338  *      with interrupts disabled.
 339  *
 340  *      Must be called with interrupts disabled.
 341  */
 342 void device_power_up(pm_message_t state)
 343 {
 344         sysdev_resume();
 345         dpm_power_up(state);
 346 }
 347 EXPORT_SYMBOL_GPL(device_power_up);
 348
 349 /**
 350  *      resume_device - Restore state for one device.
 351  *      @dev:   Device.
 352  *      @state: PM transition of the system being carried out.
 353  */
 354 static int resume_device(struct device *dev, pm_message_t state)
 355 {
 356         int error = 0;
 357
 358         TRACE_DEVICE(dev);
 359         TRACE_RESUME(0);
 360
 361         down(&dev->sem);
 362
 363         if (dev->bus) {
 364                 if (dev->bus->pm) {
 365                         pm_dev_dbg(dev, state, "");
 366                         error = pm_op(dev, &dev->bus->pm->base, state);
 367                 } else if (dev->bus->resume) {
 368                         pm_dev_dbg(dev, state, "legacy ");
 369                         error = dev->bus->resume(dev);
 370                 }
 371                 if (error)
 372                         goto End;
 373         }
 374
 375         if (dev->type) {
 376                 if (dev->type->pm) {
 377                         pm_dev_dbg(dev, state, "type ");
 378                         error = pm_op(dev, dev->type->pm, state);
 379                 } else if (dev->type->resume) {
 380                         pm_dev_dbg(dev, state, "legacy type ");
 381                         error = dev->type->resume(dev);
 382                 }
 383                 if (error)
 384                         goto End;
 385         }
 386
 387         if (dev->class) {
 388                 if (dev->class->pm) {
 389                         pm_dev_dbg(dev, state, "class ");
 390                         error = pm_op(dev, dev->class->pm, state);
 391                 } else if (dev->class->resume) {
 392                         pm_dev_dbg(dev, state, "legacy class ");
 393                         error = dev->class->resume(dev);
 394                 }
 395         }
 396  End:
 397         up(&dev->sem);
 398
 399         TRACE_RESUME(error);
 400         return error;
 401 }
 402
 403 /**
 404  *      dpm_resume - Resume every device.
 405  *      @state: PM transition of the system being carried out.
 406  *
 407  *      Execute the appropriate "resume" callback for all devices the status of
 408  *      which indicates that they are inactive.
 409  */
 410 static void dpm_resume(pm_message_t state)
 411 {
 412         struct list_head list;
 413
 414         INIT_LIST_HEAD(&list);
 415         mutex_lock(&dpm_list_mtx);
 416         transition_started = false;
 417         while (!list_empty(&dpm_list)) {
 418                 struct device *dev = to_device(dpm_list.next);
 419
 420                 get_device(dev);
 421                 if (dev->power.status >= DPM_OFF) {
 422                         int error;
 423
 424                         dev->power.status = DPM_RESUMING;
 425                         mutex_unlock(&dpm_list_mtx);
 426
 427                         error = resume_device(dev, state);
 428
 429                         mutex_lock(&dpm_list_mtx);
 430                         if (error)
 431                                 pm_dev_err(dev, state, "", error);
 432                 } else if (dev->power.status == DPM_SUSPENDING) {
 433                         /* Allow new children of the device to be registered */
 434                         dev->power.status = DPM_RESUMING;
 435                 }
 436                 if (!list_empty(&dev->power.entry))
 437                         list_move_tail(&dev->power.entry, &list);
 438                 put_device(dev);
 439         }
 440         list_splice(&list, &dpm_list);
 441         mutex_unlock(&dpm_list_mtx);
 442 }
 443
 444 /**
 445  *      complete_device - Complete a PM transition for given device
 446  *      @dev:   Device.
 447  *      @state: PM transition of the system being carried out.
 448  */
 449 static void complete_device(struct device *dev, pm_message_t state)
 450 {
 451         down(&dev->sem);
 452
 453         if (dev->class && dev->class->pm && dev->class->pm->complete) {
 454                 pm_dev_dbg(dev, state, "completing class ");
 455                 dev->class->pm->complete(dev);
 456         }
 457
 458         if (dev->type && dev->type->pm && dev->type->pm->complete) {
 459                 pm_dev_dbg(dev, state, "completing type ");
 460                 dev->type->pm->complete(dev);
 461         }
 462
 463         if (dev->bus && dev->bus->pm && dev->bus->pm->base.complete) {
 464                 pm_dev_dbg(dev, state, "completing ");
 465                 dev->bus->pm->base.complete(dev);
 466         }
 467
 468         up(&dev->sem);
 469 }
 470
 471 /**
 472  *      dpm_complete - Complete a PM transition for all devices.
 473  *      @state: PM transition of the system being carried out.
 474  *
 475  *      Execute the ->complete() callbacks for all devices that are not marked
 476  *      as DPM_ON.
 477  */
 478 static void dpm_complete(pm_message_t state)
 479 {
 480         struct list_head list;
 481
 482         INIT_LIST_HEAD(&list);
 483         mutex_lock(&dpm_list_mtx);
 484         while (!list_empty(&dpm_list)) {
 485                 struct device *dev = to_device(dpm_list.prev);
 486
 487                 get_device(dev);
 488                 if (dev->power.status > DPM_ON) {
 489                         dev->power.status = DPM_ON;
 490                         mutex_unlock(&dpm_list_mtx);
 491
 492                         complete_device(dev, state);
 493
 494                         mutex_lock(&dpm_list_mtx);
 495                 }
 496                 if (!list_empty(&dev->power.entry))
 497                         list_move(&dev->power.entry, &list);
 498                 put_device(dev);
 499         }
 500         list_splice(&list, &dpm_list);
 501         mutex_unlock(&dpm_list_mtx);
 502 }
 503
 504 /**
 505  *      device_resume - Restore state of each device in system.
 506  *      @state: PM transition of the system being carried out.
 507  *
 508  *      Resume all the devices, unlock them all, and allow new
 509  *      devices to be registered once again.
 510  */
 511 void device_resume(pm_message_t state)
 512 {
 513         might_sleep();
 514         dpm_resume(state);
 515         dpm_complete(state);
 516 }
 517 EXPORT_SYMBOL_GPL(device_resume);
 518
 519
 520 /*------------------------- Suspend routines -------------------------*/
 521
 522 /**
 523  *      resume_event - return a PM message representing the resume event
 524  *                     corresponding to given sleep state.
 525  *      @sleep_state: PM message representing a sleep state.
 526  */
 527 static pm_message_t resume_event(pm_message_t sleep_state)
 528 {
 529         switch (sleep_state.event) {
 530         case PM_EVENT_SUSPEND:
 531                 return PMSG_RESUME;
 532         case PM_EVENT_FREEZE:
 533         case PM_EVENT_QUIESCE:
 534                 return PMSG_RECOVER;
 535         case PM_EVENT_HIBERNATE:
 536                 return PMSG_RESTORE;
 537         }
 538         return PMSG_ON;
 539 }
 540
 541 /**
 542  *      suspend_device_noirq - Shut down one device (late suspend).
 543  *      @dev:   Device.
 544  *      @state: PM transition of the system being carried out.
 545  *
 546  *      This is called with interrupts off and only a single CPU running.
 547  */
 548 static int suspend_device_noirq(struct device *dev, pm_message_t state)
 549 {
 550         int error = 0;
 551
 552         if (!dev->bus)
 553                 return 0;
 554
 555         if (dev->bus->pm) {
 556                 pm_dev_dbg(dev, state, "LATE ");
 557                 error = pm_noirq_op(dev, dev->bus->pm, state);
 558         } else if (dev->bus->suspend_late) {
 559                 pm_dev_dbg(dev, state, "legacy LATE ");
 560                 error = dev->bus->suspend_late(dev, state);
 561                 suspend_report_result(dev->bus->suspend_late, error);
 562         }
 563         return error;
 564 }
 565
 566 /**
 567  *      device_power_down - Shut down special devices.
 568  *      @state: PM transition of the system being carried out.
 569  *
 570  *      Power down devices that require interrupts to be disabled.
 571  *      Then power down system devices.
 572  *
 573  *      Must be called with interrupts disabled and only one CPU running.
 574  */
 575 int device_power_down(pm_message_t state)
 576 {
 577         struct device *dev;
 578         int error = 0;
 579
 580         list_for_each_entry_reverse(dev, &dpm_list, power.entry) {
 581                 error = suspend_device_noirq(dev, state);
 582                 if (error) {
 583                         pm_dev_err(dev, state, " late", error);
 584                         break;
 585                 }
 586                 dev->power.status = DPM_OFF_IRQ;
 587         }
 588         if (!error)
 589                 error = sysdev_suspend(state);
 590         if (error)
 591                 dpm_power_up(resume_event(state));
 592         return error;
 593 }
 594 EXPORT_SYMBOL_GPL(device_power_down);
 595
 596 /**
 597  *      suspend_device - Save state of one device.
 598  *      @dev:   Device.
 599  *      @state: PM transition of the system being carried out.
 600  */
 601 static int suspend_device(struct device *dev, pm_message_t state)
 602 {
 603         int error = 0;
 604
 605         down(&dev->sem);
 606
 607         if (dev->class) {
 608                 if (dev->class->pm) {
 609                         pm_dev_dbg(dev, state, "class ");
 610                         error = pm_op(dev, dev->class->pm, state);
 611                 } else if (dev->class->suspend) {
 612                         pm_dev_dbg(dev, state, "legacy class ");
 613                         error = dev->class->suspend(dev, state);
 614                         suspend_report_result(dev->class->suspend, error);
 615                 }
 616                 if (error)
 617                         goto End;
 618         }
 619
 620         if (dev->type) {
 621                 if (dev->type->pm) {
 622                         pm_dev_dbg(dev, state, "type ");
 623                         error = pm_op(dev, dev->type->pm, state);
 624                 } else if (dev->type->suspend) {
 625                         pm_dev_dbg(dev, state, "legacy type ");
 626                         error = dev->type->suspend(dev, state);
 627                         suspend_report_result(dev->type->suspend, error);
 628                 }
 629                 if (error)
 630                         goto End;
 631         }
 632
 633         if (dev->bus) {
 634                 if (dev->bus->pm) {
 635                         pm_dev_dbg(dev, state, "");
 636                         error = pm_op(dev, &dev->bus->pm->base, state);
 637                 } else if (dev->bus->suspend) {
 638                         pm_dev_dbg(dev, state, "legacy ");
 639                         error = dev->bus->suspend(dev, state);
 640                         suspend_report_result(dev->bus->suspend, error);
 641                 }
 642         }
 643  End:
 644         up(&dev->sem);
 645
 646         return error;
 647 }
 648
 649 /**
 650  *      dpm_suspend - Suspend every device.
 651  *      @state: PM transition of the system being carried out.
 652  *
 653  *      Execute the appropriate "suspend" callbacks for all devices.
 654  */
 655 static int dpm_suspend(pm_message_t state)
 656 {
 657         struct list_head list;
 658         int error = 0;
 659
 660         INIT_LIST_HEAD(&list);
 661         mutex_lock(&dpm_list_mtx);
 662         while (!list_empty(&dpm_list)) {
 663                 struct device *dev = to_device(dpm_list.prev);
 664
 665                 get_device(dev);
 666                 mutex_unlock(&dpm_list_mtx);
 667
 668                 error = suspend_device(dev, state);
 669
 670                 mutex_lock(&dpm_list_mtx);
 671                 if (error) {
 672                         pm_dev_err(dev, state, "", error);
 673                         put_device(dev);
 674                         break;
 675                 }
 676                 dev->power.status = DPM_OFF;
 677                 if (!list_empty(&dev->power.entry))
 678                         list_move(&dev->power.entry, &list);
 679                 put_device(dev);
 680         }
 681         list_splice(&list, dpm_list.prev);
 682         mutex_unlock(&dpm_list_mtx);
 683         return error;
 684 }
 685
 686 /**
 687  *      prepare_device - Execute the ->prepare() callback(s) for given device.
 688  *      @dev:   Device.
 689  *      @state: PM transition of the system being carried out.
 690  */
 691 static int prepare_device(struct device *dev, pm_message_t state)
 692 {
 693         int error = 0;
 694
 695         down(&dev->sem);
 696
 697         if (dev->bus && dev->bus->pm && dev->bus->pm->base.prepare) {
 698                 pm_dev_dbg(dev, state, "preparing ");
 699                 error = dev->bus->pm->base.prepare(dev);
 700                 suspend_report_result(dev->bus->pm->base.prepare, error);
 701                 if (error)
 702                         goto End;
 703         }
 704
 705         if (dev->type && dev->type->pm && dev->type->pm->prepare) {
 706                 pm_dev_dbg(dev, state, "preparing type ");
 707                 error = dev->type->pm->prepare(dev);
 708                 suspend_report_result(dev->type->pm->prepare, error);
 709                 if (error)
 710                         goto End;
 711         }
 712
 713         if (dev->class && dev->class->pm && dev->class->pm->prepare) {
 714                 pm_dev_dbg(dev, state, "preparing class ");
 715                 error = dev->class->pm->prepare(dev);
 716                 suspend_report_result(dev->class->pm->prepare, error);
 717         }
 718  End:
 719         up(&dev->sem);
 720
 721         return error;
 722 }
 723
 724 /**
 725  *      dpm_prepare - Prepare all devices for a PM transition.
 726  *      @state: PM transition of the system being carried out.
 727  *
 728  *      Execute the ->prepare() callback for all devices.
 729  */
 730 static int dpm_prepare(pm_message_t state)
 731 {
 732         struct list_head list;
 733         int error = 0;
 734
 735         INIT_LIST_HEAD(&list);
 736         mutex_lock(&dpm_list_mtx);
 737         transition_started = true;
 738         while (!list_empty(&dpm_list)) {
 739                 struct device *dev = to_device(dpm_list.next);
 740
 741                 get_device(dev);
 742                 dev->power.status = DPM_PREPARING;
 743                 mutex_unlock(&dpm_list_mtx);
 744
 745                 error = prepare_device(dev, state);
 746
 747                 mutex_lock(&dpm_list_mtx);
 748                 if (error) {
 749                         dev->power.status = DPM_ON;
 750                         if (error == -EAGAIN) {
 751                                 put_device(dev);
 752                                 continue;
 753                         }
 754                         printk(KERN_ERR "PM: Failed to prepare device %s "
 755                                 "for power transition: error %d\n",
 756                                 kobject_name(&dev->kobj), error);
 757                         put_device(dev);
 758                         break;
 759                 }
 760                 dev->power.status = DPM_SUSPENDING;
 761                 if (!list_empty(&dev->power.entry))
 762                         list_move_tail(&dev->power.entry, &list);
 763                 put_device(dev);
 764         }
 765         list_splice(&list, &dpm_list);
 766         mutex_unlock(&dpm_list_mtx);
 767         return error;
 768 }
 769
 770 /**
 771  *      device_suspend - Save state and stop all devices in system.
 772  *      @state: PM transition of the system being carried out.
 773  *
 774  *      Prepare and suspend all devices.
 775  */
 776 int device_suspend(pm_message_t state)
 777 {
 778         int error;
 779
 780         might_sleep();
 781         error = dpm_prepare(state);
 782         if (!error)
 783                 error = dpm_suspend(state);
 784         return error;
 785 }
 786 EXPORT_SYMBOL_GPL(device_suspend);
 787
 788 void __suspend_report_result(const char *function, void *fn, int ret)
 789 {
 790         if (ret) {
 791                 printk(KERN_ERR "%s(): ", function);
 792                 print_fn_descriptor_symbol("%s returns ", fn);
 793                 printk("%d\n", ret);
 794         }
 795 }
 796 EXPORT_SYMBOL_GPL(__suspend_report_result);