drivers/acpi/sleep/main.c

   1 /*
   2  * sleep.c - ACPI sleep support.
   3  *
   4  * Copyright (c) 2005 Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>
   5  * Copyright (c) 2004 David Shaohua Li <shaohua.li@intel.com>
   6  * Copyright (c) 2000-2003 Patrick Mochel
   7  * Copyright (c) 2003 Open Source Development Lab
   8  *
   9  * This file is released under the GPLv2.
  10  *
  11  */
  12
  13 #include <linux/delay.h>
  14 #include <linux/irq.h>
  15 #include <linux/dmi.h>
  16 #include <linux/device.h>
  17 #include <linux/suspend.h>
  18 #include <linux/reboot.h>
  19
  20 #include <asm/io.h>
  21
  22 #include <acpi/acpi_bus.h>
  23 #include <acpi/acpi_drivers.h>
  24 #include "sleep.h"
  25
  26 u8 sleep_states[ACPI_S_STATE_COUNT];
  27
  28 static void acpi_sleep_tts_switch(u32 acpi_state)
  29 {
  30         union acpi_object in_arg = { ACPI_TYPE_INTEGER };
  31         struct acpi_object_list arg_list = { 1, &in_arg };
  32         acpi_status status = AE_OK;
  33
  34         in_arg.integer.value = acpi_state;
  35         status = acpi_evaluate_object(NULL, "\\_TTS", &arg_list, NULL);
  36         if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) {
  37                 /*
  38                  * OS can't evaluate the _TTS object correctly. Some warning
  39                  * message will be printed. But it won't break anything.
  40                  */
  41                 printk(KERN_NOTICE "Failure in evaluating _TTS object\n");
  42         }
  43 }
  44
  45 static int tts_notify_reboot(struct notifier_block *this,
  46                         unsigned long code, void *x)
  47 {
  48         acpi_sleep_tts_switch(ACPI_STATE_S5);
  49         return NOTIFY_DONE;
  50 }
  51
  52 static struct notifier_block tts_notifier = {
  53         .notifier_call  = tts_notify_reboot,
  54         .next           = NULL,
  55         .priority       = 0,
  56 };
  57
  58 static int acpi_sleep_prepare(u32 acpi_state)
  59 {
  60 #ifdef CONFIG_ACPI_SLEEP
  61         /* do we have a wakeup address for S2 and S3? */
  62         if (acpi_state == ACPI_STATE_S3) {
  63                 if (!acpi_wakeup_address) {
  64                         return -EFAULT;
  65                 }
  66                 acpi_set_firmware_waking_vector(
  67                                 (acpi_physical_address)acpi_wakeup_address);
  68
  69         }
  70         ACPI_FLUSH_CPU_CACHE();
  71         acpi_enable_wakeup_device_prep(acpi_state);
  72 #endif
  73         printk(KERN_INFO PREFIX "Preparing to enter system sleep state S%d\n",
  74                 acpi_state);
  75         acpi_enter_sleep_state_prep(acpi_state);
  76         return 0;
  77 }
  78
  79 #ifdef CONFIG_PM_SLEEP
  80 static u32 acpi_target_sleep_state = ACPI_STATE_S0;
  81
  82 /*
  83  * ACPI 1.0 wants us to execute _PTS before suspending devices, so we allow the
  84  * user to request that behavior by using the 'acpi_old_suspend_ordering'
  85  * kernel command line option that causes the following variable to be set.
  86  */
  87 static bool old_suspend_ordering;
  88
  89 void __init acpi_old_suspend_ordering(void)
  90 {
  91         old_suspend_ordering = true;
  92 }
  93
  94 /**
  95  *      acpi_pm_disable_gpes - Disable the GPEs.
  96  */
  97 static int acpi_pm_disable_gpes(void)
  98 {
  99         acpi_hw_disable_all_gpes();
 100         return 0;
 101 }
 102
 103 /**
 104  *      __acpi_pm_prepare - Prepare the platform to enter the target state.
 105  *
 106  *      If necessary, set the firmware waking vector and do arch-specific
 107  *      nastiness to get the wakeup code to the waking vector.
 108  */
 109 static int __acpi_pm_prepare(void)
 110 {
 111         int error = acpi_sleep_prepare(acpi_target_sleep_state);
 112
 113         if (error)
 114                 acpi_target_sleep_state = ACPI_STATE_S0;
 115         return error;
 116 }
 117
 118 /**
 119  *      acpi_pm_prepare - Prepare the platform to enter the target sleep
 120  *              state and disable the GPEs.
 121  */
 122 static int acpi_pm_prepare(void)
 123 {
 124         int error = __acpi_pm_prepare();
 125
 126         if (!error)
 127                 acpi_hw_disable_all_gpes();
 128         return error;
 129 }
 130
 131 /**
 132  *      acpi_pm_finish - Instruct the platform to leave a sleep state.
 133  *
 134  *      This is called after we wake back up (or if entering the sleep state
 135  *      failed).
 136  */
 137 static void acpi_pm_finish(void)
 138 {
 139         u32 acpi_state = acpi_target_sleep_state;
 140
 141         if (acpi_state == ACPI_STATE_S0)
 142                 return;
 143
 144         printk(KERN_INFO PREFIX "Waking up from system sleep state S%d\n",
 145                 acpi_state);
 146         acpi_disable_wakeup_device(acpi_state);
 147         acpi_leave_sleep_state(acpi_state);
 148
 149         /* reset firmware waking vector */
 150         acpi_set_firmware_waking_vector((acpi_physical_address) 0);
 151
 152         acpi_target_sleep_state = ACPI_STATE_S0;
 153 }
 154
 155 /**
 156  *      acpi_pm_end - Finish up suspend sequence.
 157  */
 158 static void acpi_pm_end(void)
 159 {
 160         /*
 161          * This is necessary in case acpi_pm_finish() is not called during a
 162          * failing transition to a sleep state.
 163          */
 164         acpi_target_sleep_state = ACPI_STATE_S0;
 165         acpi_sleep_tts_switch(acpi_target_sleep_state);
 166 }
 167 #endif /* CONFIG_PM_SLEEP */
 168
 169 #ifdef CONFIG_SUSPEND
 170 extern void do_suspend_lowlevel(void);
 171
 172 static u32 acpi_suspend_states[] = {
 173         [PM_SUSPEND_ON] = ACPI_STATE_S0,
 174         [PM_SUSPEND_STANDBY] = ACPI_STATE_S1,
 175         [PM_SUSPEND_MEM] = ACPI_STATE_S3,
 176         [PM_SUSPEND_MAX] = ACPI_STATE_S5
 177 };
 178
 179 /**
 180  *      acpi_suspend_begin - Set the target system sleep state to the state
 181  *              associated with given @pm_state, if supported.
 182  */
 183 static int acpi_suspend_begin(suspend_state_t pm_state)
 184 {
 185         u32 acpi_state = acpi_suspend_states[pm_state];
 186         int error = 0;
 187
 188         if (sleep_states[acpi_state]) {
 189                 acpi_target_sleep_state = acpi_state;
 190                 acpi_sleep_tts_switch(acpi_target_sleep_state);
 191         } else {
 192                 printk(KERN_ERR "ACPI does not support this state: %d\n",
 193                         pm_state);
 194                 error = -ENOSYS;
 195         }
 196         return error;
 197 }
 198
 199 /**
 200  *      acpi_suspend_enter - Actually enter a sleep state.
 201  *      @pm_state: ignored
 202  *
 203  *      Flush caches and go to sleep. For STR we have to call arch-specific
 204  *      assembly, which in turn call acpi_enter_sleep_state().
 205  *      It's unfortunate, but it works. Please fix if you're feeling frisky.
 206  */
 207 static int acpi_suspend_enter(suspend_state_t pm_state)
 208 {
 209         acpi_status status = AE_OK;
 210         unsigned long flags = 0;
 211         u32 acpi_state = acpi_target_sleep_state;
 212
 213         ACPI_FLUSH_CPU_CACHE();
 214
 215         /* Do arch specific saving of state. */
 216         if (acpi_state == ACPI_STATE_S3) {
 217                 int error = acpi_save_state_mem();
 218
 219                 if (error)
 220                         return error;
 221         }
 222
 223         local_irq_save(flags);
 224         acpi_enable_wakeup_device(acpi_state);
 225         switch (acpi_state) {
 226         case ACPI_STATE_S1:
 227                 barrier();
 228                 status = acpi_enter_sleep_state(acpi_state);
 229                 break;
 230
 231         case ACPI_STATE_S3:
 232                 do_suspend_lowlevel();
 233                 break;
 234         }
 235
 236         /* If ACPI is not enabled by the BIOS, we need to enable it here. */
 237         acpi_enable();
 238         /* Reprogram control registers and execute _BFS */
 239         acpi_leave_sleep_state_prep(acpi_state);
 240
 241         /* ACPI 3.0 specs (P62) says that it's the responsibility
 242          * of the OSPM to clear the status bit [ implying that the
 243          * POWER_BUTTON event should not reach userspace ]
 244          */
 245         if (ACPI_SUCCESS(status) && (acpi_state == ACPI_STATE_S3))
 246                 acpi_clear_event(ACPI_EVENT_POWER_BUTTON);
 247
 248         /*
 249          * Disable and clear GPE status before interrupt is enabled. Some GPEs
 250          * (like wakeup GPE) haven't handler, this can avoid such GPE misfire.
 251          * acpi_leave_sleep_state will reenable specific GPEs later
 252          */
 253         acpi_hw_disable_all_gpes();
 254
 255         local_irq_restore(flags);
 256         printk(KERN_DEBUG "Back to C!\n");
 257
 258         /* restore processor state */
 259         if (acpi_state == ACPI_STATE_S3)
 260                 acpi_restore_state_mem();
 261
 262         return ACPI_SUCCESS(status) ? 0 : -EFAULT;
 263 }
 264
 265 static int acpi_suspend_state_valid(suspend_state_t pm_state)
 266 {
 267         u32 acpi_state;
 268
 269         switch (pm_state) {
 270         case PM_SUSPEND_ON:
 271         case PM_SUSPEND_STANDBY:
 272         case PM_SUSPEND_MEM:
 273                 acpi_state = acpi_suspend_states[pm_state];
 274
 275                 return sleep_states[acpi_state];
 276         default:
 277                 return 0;
 278         }
 279 }
 280
 281 static struct platform_suspend_ops acpi_suspend_ops = {
 282         .valid = acpi_suspend_state_valid,
 283         .begin = acpi_suspend_begin,
 284         .prepare = acpi_pm_prepare,
 285         .enter = acpi_suspend_enter,
 286         .finish = acpi_pm_finish,
 287         .end = acpi_pm_end,
 288 };
 289
 290 /**
 291  *      acpi_suspend_begin_old - Set the target system sleep state to the
 292  *              state associated with given @pm_state, if supported, and
 293  *              execute the _PTS control method.  This function is used if the
 294  *              pre-ACPI 2.0 suspend ordering has been requested.
 295  */
 296 static int acpi_suspend_begin_old(suspend_state_t pm_state)
 297 {
 298         int error = acpi_suspend_begin(pm_state);
 299
 300         if (!error)
 301                 error = __acpi_pm_prepare();
 302         return error;
 303 }
 304
 305 /*
 306  * The following callbacks are used if the pre-ACPI 2.0 suspend ordering has
 307  * been requested.
 308  */
 309 static struct platform_suspend_ops acpi_suspend_ops_old = {
 310         .valid = acpi_suspend_state_valid,
 311         .begin = acpi_suspend_begin_old,
 312         .prepare = acpi_pm_disable_gpes,
 313         .enter = acpi_suspend_enter,
 314         .finish = acpi_pm_finish,
 315         .end = acpi_pm_end,
 316         .recover = acpi_pm_finish,
 317 };
 318
 319 static int __init init_old_suspend_ordering(const struct dmi_system_id *d)
 320 {
 321         old_suspend_ordering = true;
 322         return 0;
 323 }
 324
 325 static struct dmi_system_id __initdata acpisleep_dmi_table[] = {
 326         {
 327         .callback = init_old_suspend_ordering,
 328         .ident = "Abit KN9 (nForce4 variant)",
 329         .matches = {
 330                 DMI_MATCH(DMI_BOARD_VENDOR, "http://www.abit.com.tw/"),
 331                 DMI_MATCH(DMI_BOARD_NAME, "KN9 Series(NF-CK804)"),
 332                 },
 333         },
 334         {},
 335 };
 336 #endif /* CONFIG_SUSPEND */
 337
 338 #ifdef CONFIG_HIBERNATION
 339 static unsigned long s4_hardware_signature;
 340 static struct acpi_table_facs *facs;
 341 static bool nosigcheck;
 342
 343 void __init acpi_no_s4_hw_signature(void)
 344 {
 345         nosigcheck = true;
 346 }
 347
 348 static int acpi_hibernation_begin(void)
 349 {
 350         acpi_target_sleep_state = ACPI_STATE_S4;
 351         acpi_sleep_tts_switch(acpi_target_sleep_state);
 352         return 0;
 353 }
 354
 355 static int acpi_hibernation_enter(void)
 356 {
 357         acpi_status status = AE_OK;
 358         unsigned long flags = 0;
 359
 360         ACPI_FLUSH_CPU_CACHE();
 361
 362         local_irq_save(flags);
 363         acpi_enable_wakeup_device(ACPI_STATE_S4);
 364         /* This shouldn't return.  If it returns, we have a problem */
 365         status = acpi_enter_sleep_state(ACPI_STATE_S4);
 366         /* Reprogram control registers and execute _BFS */
 367         acpi_leave_sleep_state_prep(ACPI_STATE_S4);
 368         local_irq_restore(flags);
 369
 370         return ACPI_SUCCESS(status) ? 0 : -EFAULT;
 371 }
 372
 373 static void acpi_hibernation_leave(void)
 374 {
 375         /*
 376          * If ACPI is not enabled by the BIOS and the boot kernel, we need to
 377          * enable it here.
 378          */
 379         acpi_enable();
 380         /* Reprogram control registers and execute _BFS */
 381         acpi_leave_sleep_state_prep(ACPI_STATE_S4);
 382         /* Check the hardware signature */
 383         if (facs && s4_hardware_signature != facs->hardware_signature) {
 384                 printk(KERN_EMERG "ACPI: Hardware changed while hibernated, "
 385                         "cannot resume!\n");
 386                 panic("ACPI S4 hardware signature mismatch");
 387         }
 388 }
 389
 390 static void acpi_pm_enable_gpes(void)
 391 {
 392         acpi_hw_enable_all_runtime_gpes();
 393 }
 394
 395 static struct platform_hibernation_ops acpi_hibernation_ops = {
 396         .begin = acpi_hibernation_begin,
 397         .end = acpi_pm_end,
 398         .pre_snapshot = acpi_pm_prepare,
 399         .finish = acpi_pm_finish,
 400         .prepare = acpi_pm_prepare,
 401         .enter = acpi_hibernation_enter,
 402         .leave = acpi_hibernation_leave,
 403         .pre_restore = acpi_pm_disable_gpes,
 404         .restore_cleanup = acpi_pm_enable_gpes,
 405 };
 406
 407 /**
 408  *      acpi_hibernation_begin_old - Set the target system sleep state to
 409  *              ACPI_STATE_S4 and execute the _PTS control method.  This
 410  *              function is used if the pre-ACPI 2.0 suspend ordering has been
 411  *              requested.
 412  */
 413 static int acpi_hibernation_begin_old(void)
 414 {
 415         int error;
 416         /*
 417          * The _TTS object should always be evaluated before the _PTS object.
 418          * When the old_suspended_ordering is true, the _PTS object is
 419          * evaluated in the acpi_sleep_prepare.
 420          */
 421         acpi_sleep_tts_switch(ACPI_STATE_S4);
 422
 423         error = acpi_sleep_prepare(ACPI_STATE_S4);
 424
 425         if (!error)
 426                 acpi_target_sleep_state = ACPI_STATE_S4;
 427         return error;
 428 }
 429
 430 /*
 431  * The following callbacks are used if the pre-ACPI 2.0 suspend ordering has
 432  * been requested.
 433  */
 434 static struct platform_hibernation_ops acpi_hibernation_ops_old = {
 435         .begin = acpi_hibernation_begin_old,
 436         .end = acpi_pm_end,
 437         .pre_snapshot = acpi_pm_disable_gpes,
 438         .finish = acpi_pm_finish,
 439         .prepare = acpi_pm_disable_gpes,
 440         .enter = acpi_hibernation_enter,
 441         .leave = acpi_hibernation_leave,
 442         .pre_restore = acpi_pm_disable_gpes,
 443         .restore_cleanup = acpi_pm_enable_gpes,
 444         .recover = acpi_pm_finish,
 445 };
 446 #endif /* CONFIG_HIBERNATION */
 447
 448 int acpi_suspend(u32 acpi_state)
 449 {
 450         suspend_state_t states[] = {
 451                 [1] = PM_SUSPEND_STANDBY,
 452                 [3] = PM_SUSPEND_MEM,
 453                 [5] = PM_SUSPEND_MAX
 454         };
 455
 456         if (acpi_state < 6 && states[acpi_state])
 457                 return pm_suspend(states[acpi_state]);
 458         if (acpi_state == 4)
 459                 return hibernate();
 460         return -EINVAL;
 461 }
 462
 463 #ifdef CONFIG_PM_SLEEP
 464 /**
 465  *      acpi_pm_device_sleep_state - return preferred power state of ACPI device
 466  *              in the system sleep state given by %acpi_target_sleep_state
 467  *      @dev: device to examine; its driver model wakeup flags control
 468  *              whether it should be able to wake up the system
 469  *      @d_min_p: used to store the upper limit of allowed states range
 470  *      Return value: preferred power state of the device on success, -ENODEV on
 471  *              failure (ie. if there's no 'struct acpi_device' for @dev)
 472  *
 473  *      Find the lowest power (highest number) ACPI device power state that
 474  *      device @dev can be in while the system is in the sleep state represented
 475  *      by %acpi_target_sleep_state.  If @wake is nonzero, the device should be
 476  *      able to wake up the system from this sleep state.  If @d_min_p is set,
 477  *      the highest power (lowest number) device power state of @dev allowed
 478  *      in this system sleep state is stored at the location pointed to by it.
 479  *
 480  *      The caller must ensure that @dev is valid before using this function.
 481  *      The caller is also responsible for figuring out if the device is
 482  *      supposed to be able to wake up the system and passing this information
 483  *      via @wake.
 484  */
 485
 486 int acpi_pm_device_sleep_state(struct device *dev, int *d_min_p)
 487 {
 488         acpi_handle handle = DEVICE_ACPI_HANDLE(dev);
 489         struct acpi_device *adev;
 490         char acpi_method[] = "_SxD";
 491         unsigned long d_min, d_max;
 492
 493         if (!handle || ACPI_FAILURE(acpi_bus_get_device(handle, &adev))) {
 494                 printk(KERN_DEBUG "ACPI handle has no context!\n");
 495                 return -ENODEV;
 496         }
 497
 498         acpi_method[2] = '0' + acpi_target_sleep_state;
 499         /*
 500          * If the sleep state is S0, we will return D3, but if the device has
 501          * _S0W, we will use the value from _S0W
 502          */
 503         d_min = ACPI_STATE_D0;
 504         d_max = ACPI_STATE_D3;
 505
 506         /*
 507          * If present, _SxD methods return the minimum D-state (highest power
 508          * state) we can use for the corresponding S-states.  Otherwise, the
 509          * minimum D-state is D0 (ACPI 3.x).
 510          *
 511          * NOTE: We rely on acpi_evaluate_integer() not clobbering the integer
 512          * provided -- that's our fault recovery, we ignore retval.
 513          */
 514         if (acpi_target_sleep_state > ACPI_STATE_S0)
 515                 acpi_evaluate_integer(handle, acpi_method, NULL, &d_min);
 516
 517         /*
 518          * If _PRW says we can wake up the system from the target sleep state,
 519          * the D-state returned by _SxD is sufficient for that (we assume a
 520          * wakeup-aware driver if wake is set).  Still, if _SxW exists
 521          * (ACPI 3.x), it should return the maximum (lowest power) D-state that
 522          * can wake the system.  _S0W may be valid, too.
 523          */
 524         if (acpi_target_sleep_state == ACPI_STATE_S0 ||
 525             (device_may_wakeup(dev) && adev->wakeup.state.enabled &&
 526              adev->wakeup.sleep_state <= acpi_target_sleep_state)) {
 527                 acpi_status status;
 528
 529                 acpi_method[3] = 'W';
 530                 status = acpi_evaluate_integer(handle, acpi_method, NULL,
 531                                                 &d_max);
 532                 if (ACPI_FAILURE(status)) {
 533                         d_max = d_min;
 534                 } else if (d_max < d_min) {
 535                         /* Warn the user of the broken DSDT */
 536                         printk(KERN_WARNING "ACPI: Wrong value from %s\n",
 537                                 acpi_method);
 538                         /* Sanitize it */
 539                         d_min = d_max;
 540                 }
 541         }
 542
 543         if (d_min_p)
 544                 *d_min_p = d_min;
 545         return d_max;
 546 }
 547
 548 /**
 549  *      acpi_pm_device_sleep_wake - enable or disable the system wake-up
 550  *                                  capability of given device
 551  *      @dev: device to handle
 552  *      @enable: 'true' - enable, 'false' - disable the wake-up capability
 553  */
 554 int acpi_pm_device_sleep_wake(struct device *dev, bool enable)
 555 {
 556         acpi_handle handle;
 557         struct acpi_device *adev;
 558
 559         if (!device_may_wakeup(dev))
 560                 return -EINVAL;
 561
 562         handle = DEVICE_ACPI_HANDLE(dev);
 563         if (!handle || ACPI_FAILURE(acpi_bus_get_device(handle, &adev))) {
 564                 printk(KERN_DEBUG "ACPI handle has no context!\n");
 565                 return -ENODEV;
 566         }
 567
 568         return enable ?
 569                 acpi_enable_wakeup_device_power(adev, acpi_target_sleep_state) :
 570                 acpi_disable_wakeup_device_power(adev);
 571 }
 572 #endif
 573
 574 static void acpi_power_off_prepare(void)
 575 {
 576         /* Prepare to power off the system */
 577         acpi_sleep_prepare(ACPI_STATE_S5);
 578         acpi_hw_disable_all_gpes();
 579 }
 580
 581 static void acpi_power_off(void)
 582 {
 583         /* acpi_sleep_prepare(ACPI_STATE_S5) should have already been called */
 584         printk("%s called\n", __func__);
 585         local_irq_disable();
 586         acpi_enable_wakeup_device(ACPI_STATE_S5);
 587         acpi_enter_sleep_state(ACPI_STATE_S5);
 588 }
 589
 590 int __init acpi_sleep_init(void)
 591 {
 592         acpi_status status;
 593         u8 type_a, type_b;
 594 #ifdef CONFIG_SUSPEND
 595         int i = 0;
 596
 597         dmi_check_system(acpisleep_dmi_table);
 598 #endif
 599
 600         if (acpi_disabled)
 601                 return 0;
 602
 603         sleep_states[ACPI_STATE_S0] = 1;
 604         printk(KERN_INFO PREFIX "(supports S0");
 605
 606 #ifdef CONFIG_SUSPEND
 607         for (i = ACPI_STATE_S1; i < ACPI_STATE_S4; i++) {
 608                 status = acpi_get_sleep_type_data(i, &type_a, &type_b);
 609                 if (ACPI_SUCCESS(status)) {
 610                         sleep_states[i] = 1;
 611                         printk(" S%d", i);
 612                 }
 613         }
 614
 615         suspend_set_ops(old_suspend_ordering ?
 616                 &acpi_suspend_ops_old : &acpi_suspend_ops);
 617 #endif
 618
 619 #ifdef CONFIG_HIBERNATION
 620         status = acpi_get_sleep_type_data(ACPI_STATE_S4, &type_a, &type_b);
 621         if (ACPI_SUCCESS(status)) {
 622                 hibernation_set_ops(old_suspend_ordering ?
 623                         &acpi_hibernation_ops_old : &acpi_hibernation_ops);
 624                 sleep_states[ACPI_STATE_S4] = 1;
 625                 printk(" S4");
 626                 if (!nosigcheck) {
 627                         acpi_get_table_by_index(ACPI_TABLE_INDEX_FACS,
 628                                 (struct acpi_table_header **)&facs);
 629                         if (facs)
 630                                 s4_hardware_signature =
 631                                         facs->hardware_signature;
 632                 }
 633         }
 634 #endif
 635         status = acpi_get_sleep_type_data(ACPI_STATE_S5, &type_a, &type_b);
 636         if (ACPI_SUCCESS(status)) {
 637                 sleep_states[ACPI_STATE_S5] = 1;
 638                 printk(" S5");
 639                 pm_power_off_prepare = acpi_power_off_prepare;
 640                 pm_power_off = acpi_power_off;
 641         }
 642         printk(")\n");
 643         /*
 644          * Register the tts_notifier to reboot notifier list so that the _TTS
 645          * object can also be evaluated when the system enters S5.
 646          */
 647         register_reboot_notifier(&tts_notifier);
 648         return 0;
 649 }