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 #include <linux/interrupt.h>
  27
  28 #include "../base.h"
  29 #include "power.h"
  30
  31 /*
  32  * The entries in the dpm_list list are in a depth first order, simply
  33  * because children are guaranteed to be discovered after parents, and
  34  * are inserted at the back of the list on discovery.
  35  *
  36  * Since device_pm_add() may be called with a device semaphore held,
  37  * we must never try to acquire a device semaphore while holding
  38  * dpm_list_mutex.
  39  */
  40
  41 LIST_HEAD(dpm_list);
  42
  43 static DEFINE_MUTEX(dpm_list_mtx);
  44
  45 /*
  46  * Set once the preparation of devices for a PM transition has started, reset
  47  * before starting to resume devices.  Protected by dpm_list_mtx.
  48  */
  49 static bool transition_started;
  50
  51 /**
  52  *      device_pm_lock - lock the list of active devices used by the PM core
  53  */
  54 void device_pm_lock(void)
  55 {
  56         mutex_lock(&dpm_list_mtx);
  57 }
  58
  59 /**
  60  *      device_pm_unlock - unlock the list of active devices used by the PM core
  61  */
  62 void device_pm_unlock(void)
  63 {
  64         mutex_unlock(&dpm_list_mtx);
  65 }
  66
  67 /**
  68  *      device_pm_add - add a device to the list of active devices
  69  *      @dev:   Device to be added to the list
  70  */
  71 void device_pm_add(struct device *dev)
  72 {
  73         pr_debug("PM: Adding info for %s:%s\n",
  74                  dev->bus ? dev->bus->name : "No Bus",
  75                  kobject_name(&dev->kobj));
  76         mutex_lock(&dpm_list_mtx);
  77         if (dev->parent) {
  78                 if (dev->parent->power.status >= DPM_SUSPENDING)
  79                         dev_warn(dev, "parent %s should not be sleeping\n",
  80                                  dev_name(dev->parent));
  81         } else if (transition_started) {
  82                 /*
  83                  * We refuse to register parentless devices while a PM
  84                  * transition is in progress in order to avoid leaving them
  85                  * unhandled down the road
  86                  */
  87                 dev_WARN(dev, "Parentless device registered during a PM transaction\n");
  88         }
  89
  90         list_add_tail(&dev->power.entry, &dpm_list);
  91         mutex_unlock(&dpm_list_mtx);
  92 }
  93
  94 /**
  95  *      device_pm_remove - remove a device from the list of active devices
  96  *      @dev:   Device to be removed from the list
  97  *
  98  *      This function also removes the device's PM-related sysfs attributes.
  99  */
 100 void device_pm_remove(struct device *dev)
 101 {
 102         pr_debug("PM: Removing info for %s:%s\n",
 103                  dev->bus ? dev->bus->name : "No Bus",
 104                  kobject_name(&dev->kobj));
 105         mutex_lock(&dpm_list_mtx);
 106         list_del_init(&dev->power.entry);
 107         mutex_unlock(&dpm_list_mtx);
 108 }
 109
 110 /**
 111  *      device_pm_move_before - move device in dpm_list
 112  *      @deva:  Device to move in dpm_list
 113  *      @devb:  Device @deva should come before
 114  */
 115 void device_pm_move_before(struct device *deva, struct device *devb)
 116 {
 117         pr_debug("PM: Moving %s:%s before %s:%s\n",
 118                  deva->bus ? deva->bus->name : "No Bus",
 119                  kobject_name(&deva->kobj),
 120                  devb->bus ? devb->bus->name : "No Bus",
 121                  kobject_name(&devb->kobj));
 122         /* Delete deva from dpm_list and reinsert before devb. */
 123         list_move_tail(&deva->power.entry, &devb->power.entry);
 124 }
 125
 126 /**
 127  *      device_pm_move_after - move device in dpm_list
 128  *      @deva:  Device to move in dpm_list
 129  *      @devb:  Device @deva should come after
 130  */
 131 void device_pm_move_after(struct device *deva, struct device *devb)
 132 {
 133         pr_debug("PM: Moving %s:%s after %s:%s\n",
 134                  deva->bus ? deva->bus->name : "No Bus",
 135                  kobject_name(&deva->kobj),
 136                  devb->bus ? devb->bus->name : "No Bus",
 137                  kobject_name(&devb->kobj));
 138         /* Delete deva from dpm_list and reinsert after devb. */
 139         list_move(&deva->power.entry, &devb->power.entry);
 140 }
 141
 142 /**
 143  *      device_pm_move_last - move device to end of dpm_list
 144  *      @dev:   Device to move in dpm_list
 145  */
 146 void device_pm_move_last(struct device *dev)
 147 {
 148         pr_debug("PM: Moving %s:%s to end of list\n",
 149                  dev->bus ? dev->bus->name : "No Bus",
 150                  kobject_name(&dev->kobj));
 151         list_move_tail(&dev->power.entry, &dpm_list);
 152 }
 153
 154 /**
 155  *      pm_op - execute the PM operation appropiate for given PM event
 156  *      @dev:   Device.
 157  *      @ops:   PM operations to choose from.
 158  *      @state: PM transition of the system being carried out.
 159  */
 160 static int pm_op(struct device *dev, struct dev_pm_ops *ops,
 161                         pm_message_t state)
 162 {
 163         int error = 0;
 164
 165         switch (state.event) {
 166 #ifdef CONFIG_SUSPEND
 167         case PM_EVENT_SUSPEND:
 168                 if (ops->suspend) {
 169                         error = ops->suspend(dev);
 170                         suspend_report_result(ops->suspend, error);
 171                 }
 172                 break;
 173         case PM_EVENT_RESUME:
 174                 if (ops->resume) {
 175                         error = ops->resume(dev);
 176                         suspend_report_result(ops->resume, error);
 177                 }
 178                 break;
 179 #endif /* CONFIG_SUSPEND */
 180 #ifdef CONFIG_HIBERNATION
 181         case PM_EVENT_FREEZE:
 182         case PM_EVENT_QUIESCE:
 183                 if (ops->freeze) {
 184                         error = ops->freeze(dev);
 185                         suspend_report_result(ops->freeze, error);
 186                 }
 187                 break;
 188         case PM_EVENT_HIBERNATE:
 189                 if (ops->poweroff) {
 190                         error = ops->poweroff(dev);
 191                         suspend_report_result(ops->poweroff, error);
 192                 }
 193                 break;
 194         case PM_EVENT_THAW:
 195         case PM_EVENT_RECOVER:
 196                 if (ops->thaw) {
 197                         error = ops->thaw(dev);
 198                         suspend_report_result(ops->thaw, error);
 199                 }
 200                 break;
 201         case PM_EVENT_RESTORE:
 202                 if (ops->restore) {
 203                         error = ops->restore(dev);
 204                         suspend_report_result(ops->restore, error);
 205                 }
 206                 break;
 207 #endif /* CONFIG_HIBERNATION */
 208         default:
 209                 error = -EINVAL;
 210         }
 211         return error;
 212 }
 213
 214 /**
 215  *      pm_noirq_op - execute the PM operation appropiate for given PM event
 216  *      @dev:   Device.
 217  *      @ops:   PM operations to choose from.
 218  *      @state: PM transition of the system being carried out.
 219  *
 220  *      The operation is executed with interrupts disabled by the only remaining
 221  *      functional CPU in the system.
 222  */
 223 static int pm_noirq_op(struct device *dev, struct dev_pm_ops *ops,
 224                         pm_message_t state)
 225 {
 226         int error = 0;
 227
 228         switch (state.event) {
 229 #ifdef CONFIG_SUSPEND
 230         case PM_EVENT_SUSPEND:
 231                 if (ops->suspend_noirq) {
 232                         error = ops->suspend_noirq(dev);
 233                         suspend_report_result(ops->suspend_noirq, error);
 234                 }
 235                 break;
 236         case PM_EVENT_RESUME:
 237                 if (ops->resume_noirq) {
 238                         error = ops->resume_noirq(dev);
 239                         suspend_report_result(ops->resume_noirq, error);
 240                 }
 241                 break;
 242 #endif /* CONFIG_SUSPEND */
 243 #ifdef CONFIG_HIBERNATION
 244         case PM_EVENT_FREEZE:
 245         case PM_EVENT_QUIESCE:
 246                 if (ops->freeze_noirq) {
 247                         error = ops->freeze_noirq(dev);
 248                         suspend_report_result(ops->freeze_noirq, error);
 249                 }
 250                 break;
 251         case PM_EVENT_HIBERNATE:
 252                 if (ops->poweroff_noirq) {
 253                         error = ops->poweroff_noirq(dev);
 254                         suspend_report_result(ops->poweroff_noirq, error);
 255                 }
 256                 break;
 257         case PM_EVENT_THAW:
 258         case PM_EVENT_RECOVER:
 259                 if (ops->thaw_noirq) {
 260                         error = ops->thaw_noirq(dev);
 261                         suspend_report_result(ops->thaw_noirq, error);
 262                 }
 263                 break;
 264         case PM_EVENT_RESTORE:
 265                 if (ops->restore_noirq) {
 266                         error = ops->restore_noirq(dev);
 267                         suspend_report_result(ops->restore_noirq, error);
 268                 }
 269                 break;
 270 #endif /* CONFIG_HIBERNATION */
 271         default:
 272                 error = -EINVAL;
 273         }
 274         return error;
 275 }
 276
 277 static char *pm_verb(int event)
 278 {
 279         switch (event) {
 280         case PM_EVENT_SUSPEND:
 281                 return "suspend";
 282         case PM_EVENT_RESUME:
 283                 return "resume";
 284         case PM_EVENT_FREEZE:
 285                 return "freeze";
 286         case PM_EVENT_QUIESCE:
 287                 return "quiesce";
 288         case PM_EVENT_HIBERNATE:
 289                 return "hibernate";
 290         case PM_EVENT_THAW:
 291                 return "thaw";
 292         case PM_EVENT_RESTORE:
 293                 return "restore";
 294         case PM_EVENT_RECOVER:
 295                 return "recover";
 296         default:
 297                 return "(unknown PM event)";
 298         }
 299 }
 300
 301 static void pm_dev_dbg(struct device *dev, pm_message_t state, char *info)
 302 {
 303         dev_dbg(dev, "%s%s%s\n", info, pm_verb(state.event),
 304                 ((state.event & PM_EVENT_SLEEP) && device_may_wakeup(dev)) ?
 305                 ", may wakeup" : "");
 306 }
 307
 308 static void pm_dev_err(struct device *dev, pm_message_t state, char *info,
 309                         int error)
 310 {
 311         printk(KERN_ERR "PM: Device %s failed to %s%s: error %d\n",
 312                 kobject_name(&dev->kobj), pm_verb(state.event), info, error);
 313 }
 314
 315 /*------------------------- Resume routines -------------------------*/
 316
 317 /**
 318  *      device_resume_noirq - Power on one device (early resume).
 319  *      @dev:   Device.
 320  *      @state: PM transition of the system being carried out.
 321  *
 322  *      Must be called with interrupts disabled.
 323  */
 324 static int device_resume_noirq(struct device *dev, pm_message_t state)
 325 {
 326         int error = 0;
 327
 328         TRACE_DEVICE(dev);
 329         TRACE_RESUME(0);
 330
 331         if (!dev->bus)
 332                 goto End;
 333
 334         if (dev->bus->pm) {
 335                 pm_dev_dbg(dev, state, "EARLY ");
 336                 error = pm_noirq_op(dev, dev->bus->pm, state);
 337         }
 338  End:
 339         TRACE_RESUME(error);
 340         return error;
 341 }
 342
 343 /**
 344  *      dpm_resume_noirq - Power on all regular (non-sysdev) devices.
 345  *      @state: PM transition of the system being carried out.
 346  *
 347  *      Call the "noirq" resume handlers for all devices marked as
 348  *      DPM_OFF_IRQ and enable device drivers to receive interrupts.
 349  *
 350  *      Must be called under dpm_list_mtx.  Device drivers should not receive
 351  *      interrupts while it's being executed.
 352  */
 353 void dpm_resume_noirq(pm_message_t state)
 354 {
 355         struct device *dev;
 356
 357         mutex_lock(&dpm_list_mtx);
 358         list_for_each_entry(dev, &dpm_list, power.entry)
 359                 if (dev->power.status > DPM_OFF) {
 360                         int error;
 361
 362                         dev->power.status = DPM_OFF;
 363                         error = device_resume_noirq(dev, state);
 364                         if (error)
 365                                 pm_dev_err(dev, state, " early", error);
 366                 }
 367         mutex_unlock(&dpm_list_mtx);
 368         resume_device_irqs();
 369 }
 370 EXPORT_SYMBOL_GPL(dpm_resume_noirq);
 371
 372 /**
 373  *      device_resume - Restore state for one device.
 374  *      @dev:   Device.
 375  *      @state: PM transition of the system being carried out.
 376  */
 377 static int device_resume(struct device *dev, pm_message_t state)
 378 {
 379         int error = 0;
 380
 381         TRACE_DEVICE(dev);
 382         TRACE_RESUME(0);
 383
 384         down(&dev->sem);
 385
 386         if (dev->bus) {
 387                 if (dev->bus->pm) {
 388                         pm_dev_dbg(dev, state, "");
 389                         error = pm_op(dev, dev->bus->pm, state);
 390                 } else if (dev->bus->resume) {
 391                         pm_dev_dbg(dev, state, "legacy ");
 392                         error = dev->bus->resume(dev);
 393                 }
 394                 if (error)
 395                         goto End;
 396         }
 397
 398         if (dev->type) {
 399                 if (dev->type->pm) {
 400                         pm_dev_dbg(dev, state, "type ");
 401                         error = pm_op(dev, dev->type->pm, state);
 402                 }
 403                 if (error)
 404                         goto End;
 405         }
 406
 407         if (dev->class) {
 408                 if (dev->class->pm) {
 409                         pm_dev_dbg(dev, state, "class ");
 410                         error = pm_op(dev, dev->class->pm, state);
 411                 } else if (dev->class->resume) {
 412                         pm_dev_dbg(dev, state, "legacy class ");
 413                         error = dev->class->resume(dev);
 414                 }
 415         }
 416  End:
 417         up(&dev->sem);
 418
 419         TRACE_RESUME(error);
 420         return error;
 421 }
 422
 423 /**
 424  *      dpm_resume - Resume every device.
 425  *      @state: PM transition of the system being carried out.
 426  *
 427  *      Execute the appropriate "resume" callback for all devices the status of
 428  *      which indicates that they are inactive.
 429  */
 430 static void dpm_resume(pm_message_t state)
 431 {
 432         struct list_head list;
 433
 434         INIT_LIST_HEAD(&list);
 435         mutex_lock(&dpm_list_mtx);
 436         transition_started = false;
 437         while (!list_empty(&dpm_list)) {
 438                 struct device *dev = to_device(dpm_list.next);
 439
 440                 get_device(dev);
 441                 if (dev->power.status >= DPM_OFF) {
 442                         int error;
 443
 444                         dev->power.status = DPM_RESUMING;
 445                         mutex_unlock(&dpm_list_mtx);
 446
 447                         error = device_resume(dev, state);
 448
 449                         mutex_lock(&dpm_list_mtx);
 450                         if (error)
 451                                 pm_dev_err(dev, state, "", error);
 452                 } else if (dev->power.status == DPM_SUSPENDING) {
 453                         /* Allow new children of the device to be registered */
 454                         dev->power.status = DPM_RESUMING;
 455                 }
 456                 if (!list_empty(&dev->power.entry))
 457                         list_move_tail(&dev->power.entry, &list);
 458                 put_device(dev);
 459         }
 460         list_splice(&list, &dpm_list);
 461         mutex_unlock(&dpm_list_mtx);
 462 }
 463
 464 /**
 465  *      device_complete - Complete a PM transition for given device
 466  *      @dev:   Device.
 467  *      @state: PM transition of the system being carried out.
 468  */
 469 static void device_complete(struct device *dev, pm_message_t state)
 470 {
 471         down(&dev->sem);
 472
 473         if (dev->class && dev->class->pm && dev->class->pm->complete) {
 474                 pm_dev_dbg(dev, state, "completing class ");
 475                 dev->class->pm->complete(dev);
 476         }
 477
 478         if (dev->type && dev->type->pm && dev->type->pm->complete) {
 479                 pm_dev_dbg(dev, state, "completing type ");
 480                 dev->type->pm->complete(dev);
 481         }
 482
 483         if (dev->bus && dev->bus->pm && dev->bus->pm->complete) {
 484                 pm_dev_dbg(dev, state, "completing ");
 485                 dev->bus->pm->complete(dev);
 486         }
 487
 488         up(&dev->sem);
 489 }
 490
 491 /**
 492  *      dpm_complete - Complete a PM transition for all devices.
 493  *      @state: PM transition of the system being carried out.
 494  *
 495  *      Execute the ->complete() callbacks for all devices that are not marked
 496  *      as DPM_ON.
 497  */
 498 static void dpm_complete(pm_message_t state)
 499 {
 500         struct list_head list;
 501
 502         INIT_LIST_HEAD(&list);
 503         mutex_lock(&dpm_list_mtx);
 504         while (!list_empty(&dpm_list)) {
 505                 struct device *dev = to_device(dpm_list.prev);
 506
 507                 get_device(dev);
 508                 if (dev->power.status > DPM_ON) {
 509                         dev->power.status = DPM_ON;
 510                         mutex_unlock(&dpm_list_mtx);
 511
 512                         device_complete(dev, state);
 513
 514                         mutex_lock(&dpm_list_mtx);
 515                 }
 516                 if (!list_empty(&dev->power.entry))
 517                         list_move(&dev->power.entry, &list);
 518                 put_device(dev);
 519         }
 520         list_splice(&list, &dpm_list);
 521         mutex_unlock(&dpm_list_mtx);
 522 }
 523
 524 /**
 525  *      dpm_resume_end - Restore state of each device in system.
 526  *      @state: PM transition of the system being carried out.
 527  *
 528  *      Resume all the devices, unlock them all, and allow new
 529  *      devices to be registered once again.
 530  */
 531 void dpm_resume_end(pm_message_t state)
 532 {
 533         might_sleep();
 534         dpm_resume(state);
 535         dpm_complete(state);
 536 }
 537 EXPORT_SYMBOL_GPL(dpm_resume_end);
 538
 539
 540 /*------------------------- Suspend routines -------------------------*/
 541
 542 /**
 543  *      resume_event - return a PM message representing the resume event
 544  *                     corresponding to given sleep state.
 545  *      @sleep_state: PM message representing a sleep state.
 546  */
 547 static pm_message_t resume_event(pm_message_t sleep_state)
 548 {
 549         switch (sleep_state.event) {
 550         case PM_EVENT_SUSPEND:
 551                 return PMSG_RESUME;
 552         case PM_EVENT_FREEZE:
 553         case PM_EVENT_QUIESCE:
 554                 return PMSG_RECOVER;
 555         case PM_EVENT_HIBERNATE:
 556                 return PMSG_RESTORE;
 557         }
 558         return PMSG_ON;
 559 }
 560
 561 /**
 562  *      device_suspend_noirq - Shut down one device (late suspend).
 563  *      @dev:   Device.
 564  *      @state: PM transition of the system being carried out.
 565  *
 566  *      This is called with interrupts off and only a single CPU running.
 567  */
 568 static int device_suspend_noirq(struct device *dev, pm_message_t state)
 569 {
 570         int error = 0;
 571
 572         if (!dev->bus)
 573                 return 0;
 574
 575         if (dev->bus->pm) {
 576                 pm_dev_dbg(dev, state, "LATE ");
 577                 error = pm_noirq_op(dev, dev->bus->pm, state);
 578         }
 579         return error;
 580 }
 581
 582 /**
 583  *      dpm_suspend_noirq - Power down all regular (non-sysdev) devices.
 584  *      @state: PM transition of the system being carried out.
 585  *
 586  *      Prevent device drivers from receiving interrupts and call the "noirq"
 587  *      suspend handlers.
 588  *
 589  *      Must be called under dpm_list_mtx.
 590  */
 591 int dpm_suspend_noirq(pm_message_t state)
 592 {
 593         struct device *dev;
 594         int error = 0;
 595
 596         suspend_device_irqs();
 597         mutex_lock(&dpm_list_mtx);
 598         list_for_each_entry_reverse(dev, &dpm_list, power.entry) {
 599                 error = device_suspend_noirq(dev, state);
 600                 if (error) {
 601                         pm_dev_err(dev, state, " late", error);
 602                         break;
 603                 }
 604                 dev->power.status = DPM_OFF_IRQ;
 605         }
 606         mutex_unlock(&dpm_list_mtx);
 607         if (error)
 608                 dpm_resume_noirq(resume_event(state));
 609         return error;
 610 }
 611 EXPORT_SYMBOL_GPL(dpm_suspend_noirq);
 612
 613 /**
 614  *      device_suspend - Save state of one device.
 615  *      @dev:   Device.
 616  *      @state: PM transition of the system being carried out.
 617  */
 618 static int device_suspend(struct device *dev, pm_message_t state)
 619 {
 620         int error = 0;
 621
 622         down(&dev->sem);
 623
 624         if (dev->class) {
 625                 if (dev->class->pm) {
 626                         pm_dev_dbg(dev, state, "class ");
 627                         error = pm_op(dev, dev->class->pm, state);
 628                 } else if (dev->class->suspend) {
 629                         pm_dev_dbg(dev, state, "legacy class ");
 630                         error = dev->class->suspend(dev, state);
 631                         suspend_report_result(dev->class->suspend, error);
 632                 }
 633                 if (error)
 634                         goto End;
 635         }
 636
 637         if (dev->type) {
 638                 if (dev->type->pm) {
 639                         pm_dev_dbg(dev, state, "type ");
 640                         error = pm_op(dev, dev->type->pm, state);
 641                 }
 642                 if (error)
 643                         goto End;
 644         }
 645
 646         if (dev->bus) {
 647                 if (dev->bus->pm) {
 648                         pm_dev_dbg(dev, state, "");
 649                         error = pm_op(dev, dev->bus->pm, state);
 650                 } else if (dev->bus->suspend) {
 651                         pm_dev_dbg(dev, state, "legacy ");
 652                         error = dev->bus->suspend(dev, state);
 653                         suspend_report_result(dev->bus->suspend, error);
 654                 }
 655         }
 656  End:
 657         up(&dev->sem);
 658
 659         return error;
 660 }
 661
 662 /**
 663  *      dpm_suspend - Suspend every device.
 664  *      @state: PM transition of the system being carried out.
 665  *
 666  *      Execute the appropriate "suspend" callbacks for all devices.
 667  */
 668 static int dpm_suspend(pm_message_t state)
 669 {
 670         struct list_head list;
 671         int error = 0;
 672
 673         INIT_LIST_HEAD(&list);
 674         mutex_lock(&dpm_list_mtx);
 675         while (!list_empty(&dpm_list)) {
 676                 struct device *dev = to_device(dpm_list.prev);
 677
 678                 get_device(dev);
 679                 mutex_unlock(&dpm_list_mtx);
 680
 681                 error = device_suspend(dev, state);
 682
 683                 mutex_lock(&dpm_list_mtx);
 684                 if (error) {
 685                         pm_dev_err(dev, state, "", error);
 686                         put_device(dev);
 687                         break;
 688                 }
 689                 dev->power.status = DPM_OFF;
 690                 if (!list_empty(&dev->power.entry))
 691                         list_move(&dev->power.entry, &list);
 692                 put_device(dev);
 693         }
 694         list_splice(&list, dpm_list.prev);
 695         mutex_unlock(&dpm_list_mtx);
 696         return error;
 697 }
 698
 699 /**
 700  *      device_prepare - Execute the ->prepare() callback(s) for given device.
 701  *      @dev:   Device.
 702  *      @state: PM transition of the system being carried out.
 703  */
 704 static int device_prepare(struct device *dev, pm_message_t state)
 705 {
 706         int error = 0;
 707
 708         down(&dev->sem);
 709
 710         if (dev->bus && dev->bus->pm && dev->bus->pm->prepare) {
 711                 pm_dev_dbg(dev, state, "preparing ");
 712                 error = dev->bus->pm->prepare(dev);
 713                 suspend_report_result(dev->bus->pm->prepare, error);
 714                 if (error)
 715                         goto End;
 716         }
 717
 718         if (dev->type && dev->type->pm && dev->type->pm->prepare) {
 719                 pm_dev_dbg(dev, state, "preparing type ");
 720                 error = dev->type->pm->prepare(dev);
 721                 suspend_report_result(dev->type->pm->prepare, error);
 722                 if (error)
 723                         goto End;
 724         }
 725
 726         if (dev->class && dev->class->pm && dev->class->pm->prepare) {
 727                 pm_dev_dbg(dev, state, "preparing class ");
 728                 error = dev->class->pm->prepare(dev);
 729                 suspend_report_result(dev->class->pm->prepare, error);
 730         }
 731  End:
 732         up(&dev->sem);
 733
 734         return error;
 735 }
 736
 737 /**
 738  *      dpm_prepare - Prepare all devices for a PM transition.
 739  *      @state: PM transition of the system being carried out.
 740  *
 741  *      Execute the ->prepare() callback for all devices.
 742  */
 743 static int dpm_prepare(pm_message_t state)
 744 {
 745         struct list_head list;
 746         int error = 0;
 747
 748         INIT_LIST_HEAD(&list);
 749         mutex_lock(&dpm_list_mtx);
 750         transition_started = true;
 751         while (!list_empty(&dpm_list)) {
 752                 struct device *dev = to_device(dpm_list.next);
 753
 754                 get_device(dev);
 755                 dev->power.status = DPM_PREPARING;
 756                 mutex_unlock(&dpm_list_mtx);
 757
 758                 error = device_prepare(dev, state);
 759
 760                 mutex_lock(&dpm_list_mtx);
 761                 if (error) {
 762                         dev->power.status = DPM_ON;
 763                         if (error == -EAGAIN) {
 764                                 put_device(dev);
 765                                 continue;
 766                         }
 767                         printk(KERN_ERR "PM: Failed to prepare device %s "
 768                                 "for power transition: error %d\n",
 769                                 kobject_name(&dev->kobj), error);
 770                         put_device(dev);
 771                         break;
 772                 }
 773                 dev->power.status = DPM_SUSPENDING;
 774                 if (!list_empty(&dev->power.entry))
 775                         list_move_tail(&dev->power.entry, &list);
 776                 put_device(dev);
 777         }
 778         list_splice(&list, &dpm_list);
 779         mutex_unlock(&dpm_list_mtx);
 780         return error;
 781 }
 782
 783 /**
 784  *      dpm_suspend_start - Save state and stop all devices in system.
 785  *      @state: PM transition of the system being carried out.
 786  *
 787  *      Prepare and suspend all devices.
 788  */
 789 int dpm_suspend_start(pm_message_t state)
 790 {
 791         int error;
 792
 793         might_sleep();
 794         error = dpm_prepare(state);
 795         if (!error)
 796                 error = dpm_suspend(state);
 797         return error;
 798 }
 799 EXPORT_SYMBOL_GPL(dpm_suspend_start);
 800
 801 void __suspend_report_result(const char *function, void *fn, int ret)
 802 {
 803         if (ret)
 804                 printk(KERN_ERR "%s(): %pF returns %d\n", function, fn, ret);
 805 }
 806 EXPORT_SYMBOL_GPL(__suspend_report_result);