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         /* Reprogram control registers and execute _BFS */
 237         acpi_leave_sleep_state_prep(acpi_state);
 238
 239         /* ACPI 3.0 specs (P62) says that it's the responsibility
 240          * of the OSPM to clear the status bit [ implying that the
 241          * POWER_BUTTON event should not reach userspace ]
 242          */
 243         if (ACPI_SUCCESS(status) && (acpi_state == ACPI_STATE_S3))
 244                 acpi_clear_event(ACPI_EVENT_POWER_BUTTON);
 245
 246         /*
 247          * Disable and clear GPE status before interrupt is enabled. Some GPEs
 248          * (like wakeup GPE) haven't handler, this can avoid such GPE misfire.
 249          * acpi_leave_sleep_state will reenable specific GPEs later
 250          */
 251         acpi_hw_disable_all_gpes();
 252
 253         local_irq_restore(flags);
 254         printk(KERN_DEBUG "Back to C!\n");
 255
 256         /* restore processor state */
 257         if (acpi_state == ACPI_STATE_S3)
 258                 acpi_restore_state_mem();
 259
 260         return ACPI_SUCCESS(status) ? 0 : -EFAULT;
 261 }
 262
 263 static int acpi_suspend_state_valid(suspend_state_t pm_state)
 264 {
 265         u32 acpi_state;
 266
 267         switch (pm_state) {
 268         case PM_SUSPEND_ON:
 269         case PM_SUSPEND_STANDBY:
 270         case PM_SUSPEND_MEM:
 271                 acpi_state = acpi_suspend_states[pm_state];
 272
 273                 return sleep_states[acpi_state];
 274         default:
 275                 return 0;
 276         }
 277 }
 278
 279 static struct platform_suspend_ops acpi_suspend_ops = {
 280         .valid = acpi_suspend_state_valid,
 281         .begin = acpi_suspend_begin,
 282         .prepare = acpi_pm_prepare,
 283         .enter = acpi_suspend_enter,
 284         .finish = acpi_pm_finish,
 285         .end = acpi_pm_end,
 286 };
 287
 288 /**
 289  *      acpi_suspend_begin_old - Set the target system sleep state to the
 290  *              state associated with given @pm_state, if supported, and
 291  *              execute the _PTS control method.  This function is used if the
 292  *              pre-ACPI 2.0 suspend ordering has been requested.
 293  */
 294 static int acpi_suspend_begin_old(suspend_state_t pm_state)
 295 {
 296         int error = acpi_suspend_begin(pm_state);
 297
 298         if (!error)
 299                 error = __acpi_pm_prepare();
 300         return error;
 301 }
 302
 303 /*
 304  * The following callbacks are used if the pre-ACPI 2.0 suspend ordering has
 305  * been requested.
 306  */
 307 static struct platform_suspend_ops acpi_suspend_ops_old = {
 308         .valid = acpi_suspend_state_valid,
 309         .begin = acpi_suspend_begin_old,
 310         .prepare = acpi_pm_disable_gpes,
 311         .enter = acpi_suspend_enter,
 312         .finish = acpi_pm_finish,
 313         .end = acpi_pm_end,
 314         .recover = acpi_pm_finish,
 315 };
 316
 317 static int __init init_old_suspend_ordering(const struct dmi_system_id *d)
 318 {
 319         old_suspend_ordering = true;
 320         return 0;
 321 }
 322
 323 static struct dmi_system_id __initdata acpisleep_dmi_table[] = {
 324         {
 325         .callback = init_old_suspend_ordering,
 326         .ident = "Abit KN9 (nForce4 variant)",
 327         .matches = {
 328                 DMI_MATCH(DMI_BOARD_VENDOR, "http://www.abit.com.tw/"),
 329                 DMI_MATCH(DMI_BOARD_NAME, "KN9 Series(NF-CK804)"),
 330                 },
 331         },
 332         {},
 333 };
 334 #endif /* CONFIG_SUSPEND */
 335
 336 #ifdef CONFIG_HIBERNATION
 337 static unsigned long s4_hardware_signature;
 338 static struct acpi_table_facs *facs;
 339 static bool nosigcheck;
 340
 341 void __init acpi_no_s4_hw_signature(void)
 342 {
 343         nosigcheck = true;
 344 }
 345
 346 static int acpi_hibernation_begin(void)
 347 {
 348         acpi_target_sleep_state = ACPI_STATE_S4;
 349         acpi_sleep_tts_switch(acpi_target_sleep_state);
 350         return 0;
 351 }
 352
 353 static int acpi_hibernation_enter(void)
 354 {
 355         acpi_status status = AE_OK;
 356         unsigned long flags = 0;
 357
 358         ACPI_FLUSH_CPU_CACHE();
 359
 360         local_irq_save(flags);
 361         acpi_enable_wakeup_device(ACPI_STATE_S4);
 362         /* This shouldn't return.  If it returns, we have a problem */
 363         status = acpi_enter_sleep_state(ACPI_STATE_S4);
 364         /* Reprogram control registers and execute _BFS */
 365         acpi_leave_sleep_state_prep(ACPI_STATE_S4);
 366         local_irq_restore(flags);
 367
 368         return ACPI_SUCCESS(status) ? 0 : -EFAULT;
 369 }
 370
 371 static void acpi_hibernation_leave(void)
 372 {
 373         /*
 374          * If ACPI is not enabled by the BIOS and the boot kernel, we need to
 375          * enable it here.
 376          */
 377         acpi_enable();
 378         /* Reprogram control registers and execute _BFS */
 379         acpi_leave_sleep_state_prep(ACPI_STATE_S4);
 380         /* Check the hardware signature */
 381         if (facs && s4_hardware_signature != facs->hardware_signature) {
 382                 printk(KERN_EMERG "ACPI: Hardware changed while hibernated, "
 383                         "cannot resume!\n");
 384                 panic("ACPI S4 hardware signature mismatch");
 385         }
 386 }
 387
 388 static void acpi_pm_enable_gpes(void)
 389 {
 390         acpi_hw_enable_all_runtime_gpes();
 391 }
 392
 393 static struct platform_hibernation_ops acpi_hibernation_ops = {
 394         .begin = acpi_hibernation_begin,
 395         .end = acpi_pm_end,
 396         .pre_snapshot = acpi_pm_prepare,
 397         .finish = acpi_pm_finish,
 398         .prepare = acpi_pm_prepare,
 399         .enter = acpi_hibernation_enter,
 400         .leave = acpi_hibernation_leave,
 401         .pre_restore = acpi_pm_disable_gpes,
 402         .restore_cleanup = acpi_pm_enable_gpes,
 403 };
 404
 405 /**
 406  *      acpi_hibernation_begin_old - Set the target system sleep state to
 407  *              ACPI_STATE_S4 and execute the _PTS control method.  This
 408  *              function is used if the pre-ACPI 2.0 suspend ordering has been
 409  *              requested.
 410  */
 411 static int acpi_hibernation_begin_old(void)
 412 {
 413         int error;
 414         /*
 415          * The _TTS object should always be evaluated before the _PTS object.
 416          * When the old_suspended_ordering is true, the _PTS object is
 417          * evaluated in the acpi_sleep_prepare.
 418          */
 419         acpi_sleep_tts_switch(ACPI_STATE_S4);
 420
 421         error = acpi_sleep_prepare(ACPI_STATE_S4);
 422
 423         if (!error)
 424                 acpi_target_sleep_state = ACPI_STATE_S4;
 425         return error;
 426 }
 427
 428 /*
 429  * The following callbacks are used if the pre-ACPI 2.0 suspend ordering has
 430  * been requested.
 431  */
 432 static struct platform_hibernation_ops acpi_hibernation_ops_old = {
 433         .begin = acpi_hibernation_begin_old,
 434         .end = acpi_pm_end,
 435         .pre_snapshot = acpi_pm_disable_gpes,
 436         .finish = acpi_pm_finish,
 437         .prepare = acpi_pm_disable_gpes,
 438         .enter = acpi_hibernation_enter,
 439         .leave = acpi_hibernation_leave,
 440         .pre_restore = acpi_pm_disable_gpes,
 441         .restore_cleanup = acpi_pm_enable_gpes,
 442         .recover = acpi_pm_finish,
 443 };
 444 #endif /* CONFIG_HIBERNATION */
 445
 446 int acpi_suspend(u32 acpi_state)
 447 {
 448         suspend_state_t states[] = {
 449                 [1] = PM_SUSPEND_STANDBY,
 450                 [3] = PM_SUSPEND_MEM,
 451                 [5] = PM_SUSPEND_MAX
 452         };
 453
 454         if (acpi_state < 6 && states[acpi_state])
 455                 return pm_suspend(states[acpi_state]);
 456         if (acpi_state == 4)
 457                 return hibernate();
 458         return -EINVAL;
 459 }
 460
 461 #ifdef CONFIG_PM_SLEEP
 462 /**
 463  *      acpi_pm_device_sleep_state - return preferred power state of ACPI device
 464  *              in the system sleep state given by %acpi_target_sleep_state
 465  *      @dev: device to examine; its driver model wakeup flags control
 466  *              whether it should be able to wake up the system
 467  *      @d_min_p: used to store the upper limit of allowed states range
 468  *      Return value: preferred power state of the device on success, -ENODEV on
 469  *              failure (ie. if there's no 'struct acpi_device' for @dev)
 470  *
 471  *      Find the lowest power (highest number) ACPI device power state that
 472  *      device @dev can be in while the system is in the sleep state represented
 473  *      by %acpi_target_sleep_state.  If @wake is nonzero, the device should be
 474  *      able to wake up the system from this sleep state.  If @d_min_p is set,
 475  *      the highest power (lowest number) device power state of @dev allowed
 476  *      in this system sleep state is stored at the location pointed to by it.
 477  *
 478  *      The caller must ensure that @dev is valid before using this function.
 479  *      The caller is also responsible for figuring out if the device is
 480  *      supposed to be able to wake up the system and passing this information
 481  *      via @wake.
 482  */
 483
 484 int acpi_pm_device_sleep_state(struct device *dev, int *d_min_p)
 485 {
 486         acpi_handle handle = DEVICE_ACPI_HANDLE(dev);
 487         struct acpi_device *adev;
 488         char acpi_method[] = "_SxD";
 489         unsigned long d_min, d_max;
 490
 491         if (!handle || ACPI_FAILURE(acpi_bus_get_device(handle, &adev))) {
 492                 printk(KERN_DEBUG "ACPI handle has no context!\n");
 493                 return -ENODEV;
 494         }
 495
 496         acpi_method[2] = '0' + acpi_target_sleep_state;
 497         /*
 498          * If the sleep state is S0, we will return D3, but if the device has
 499          * _S0W, we will use the value from _S0W
 500          */
 501         d_min = ACPI_STATE_D0;
 502         d_max = ACPI_STATE_D3;
 503
 504         /*
 505          * If present, _SxD methods return the minimum D-state (highest power
 506          * state) we can use for the corresponding S-states.  Otherwise, the
 507          * minimum D-state is D0 (ACPI 3.x).
 508          *
 509          * NOTE: We rely on acpi_evaluate_integer() not clobbering the integer
 510          * provided -- that's our fault recovery, we ignore retval.
 511          */
 512         if (acpi_target_sleep_state > ACPI_STATE_S0)
 513                 acpi_evaluate_integer(handle, acpi_method, NULL, &d_min);
 514
 515         /*
 516          * If _PRW says we can wake up the system from the target sleep state,
 517          * the D-state returned by _SxD is sufficient for that (we assume a
 518          * wakeup-aware driver if wake is set).  Still, if _SxW exists
 519          * (ACPI 3.x), it should return the maximum (lowest power) D-state that
 520          * can wake the system.  _S0W may be valid, too.
 521          */
 522         if (acpi_target_sleep_state == ACPI_STATE_S0 ||
 523             (device_may_wakeup(dev) && adev->wakeup.state.enabled &&
 524              adev->wakeup.sleep_state <= acpi_target_sleep_state)) {
 525                 acpi_status status;
 526
 527                 acpi_method[3] = 'W';
 528                 status = acpi_evaluate_integer(handle, acpi_method, NULL,
 529                                                 &d_max);
 530                 if (ACPI_FAILURE(status)) {
 531                         d_max = d_min;
 532                 } else if (d_max < d_min) {
 533                         /* Warn the user of the broken DSDT */
 534                         printk(KERN_WARNING "ACPI: Wrong value from %s\n",
 535                                 acpi_method);
 536                         /* Sanitize it */
 537                         d_min = d_max;
 538                 }
 539         }
 540
 541         if (d_min_p)
 542                 *d_min_p = d_min;
 543         return d_max;
 544 }
 545
 546 /**
 547  *      acpi_pm_device_sleep_wake - enable or disable the system wake-up
 548  *                                  capability of given device
 549  *      @dev: device to handle
 550  *      @enable: 'true' - enable, 'false' - disable the wake-up capability
 551  */
 552 int acpi_pm_device_sleep_wake(struct device *dev, bool enable)
 553 {
 554         acpi_handle handle;
 555         struct acpi_device *adev;
 556
 557         if (!device_may_wakeup(dev))
 558                 return -EINVAL;
 559
 560         handle = DEVICE_ACPI_HANDLE(dev);
 561         if (!handle || ACPI_FAILURE(acpi_bus_get_device(handle, &adev))) {
 562                 printk(KERN_DEBUG "ACPI handle has no context!\n");
 563                 return -ENODEV;
 564         }
 565
 566         return enable ?
 567                 acpi_enable_wakeup_device_power(adev, acpi_target_sleep_state) :
 568                 acpi_disable_wakeup_device_power(adev);
 569 }
 570 #endif
 571
 572 static void acpi_power_off_prepare(void)
 573 {
 574         /* Prepare to power off the system */
 575         acpi_sleep_prepare(ACPI_STATE_S5);
 576         acpi_hw_disable_all_gpes();
 577 }
 578
 579 static void acpi_power_off(void)
 580 {
 581         /* acpi_sleep_prepare(ACPI_STATE_S5) should have already been called */
 582         printk("%s called\n", __func__);
 583         local_irq_disable();
 584         acpi_enable_wakeup_device(ACPI_STATE_S5);
 585         acpi_enter_sleep_state(ACPI_STATE_S5);
 586 }
 587
 588 int __init acpi_sleep_init(void)
 589 {
 590         acpi_status status;
 591         u8 type_a, type_b;
 592 #ifdef CONFIG_SUSPEND
 593         int i = 0;
 594
 595         dmi_check_system(acpisleep_dmi_table);
 596 #endif
 597
 598         if (acpi_disabled)
 599                 return 0;
 600
 601         sleep_states[ACPI_STATE_S0] = 1;
 602         printk(KERN_INFO PREFIX "(supports S0");
 603
 604 #ifdef CONFIG_SUSPEND
 605         for (i = ACPI_STATE_S1; i < ACPI_STATE_S4; i++) {
 606                 status = acpi_get_sleep_type_data(i, &type_a, &type_b);
 607                 if (ACPI_SUCCESS(status)) {
 608                         sleep_states[i] = 1;
 609                         printk(" S%d", i);
 610                 }
 611         }
 612
 613         suspend_set_ops(old_suspend_ordering ?
 614                 &acpi_suspend_ops_old : &acpi_suspend_ops);
 615 #endif
 616
 617 #ifdef CONFIG_HIBERNATION
 618         status = acpi_get_sleep_type_data(ACPI_STATE_S4, &type_a, &type_b);
 619         if (ACPI_SUCCESS(status)) {
 620                 hibernation_set_ops(old_suspend_ordering ?
 621                         &acpi_hibernation_ops_old : &acpi_hibernation_ops);
 622                 sleep_states[ACPI_STATE_S4] = 1;
 623                 printk(" S4");
 624                 if (!nosigcheck) {
 625                         acpi_get_table_by_index(ACPI_TABLE_INDEX_FACS,
 626                                 (struct acpi_table_header **)&facs);
 627                         if (facs)
 628                                 s4_hardware_signature =
 629                                         facs->hardware_signature;
 630                 }
 631         }
 632 #endif
 633         status = acpi_get_sleep_type_data(ACPI_STATE_S5, &type_a, &type_b);
 634         if (ACPI_SUCCESS(status)) {
 635                 sleep_states[ACPI_STATE_S5] = 1;
 636                 printk(" S5");
 637                 pm_power_off_prepare = acpi_power_off_prepare;
 638                 pm_power_off = acpi_power_off;
 639         }
 640         printk(")\n");
 641         /*
 642          * Register the tts_notifier to reboot notifier list so that the _TTS
 643          * object can also be evaluated when the system enters S5.
 644          */
 645         register_reboot_notifier(&tts_notifier);
 646         return 0;
 647 }