2 * sleep.c - ACPI sleep support.
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
9 * This file is released under the GPLv2.
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>
22 #include <acpi/acpi_bus.h>
23 #include <acpi/acpi_drivers.h>
28 u8 sleep_states[ACPI_S_STATE_COUNT];
30 static void acpi_sleep_tts_switch(u32 acpi_state)
32 union acpi_object in_arg = { ACPI_TYPE_INTEGER };
33 struct acpi_object_list arg_list = { 1, &in_arg };
34 acpi_status status = AE_OK;
36 in_arg.integer.value = acpi_state;
37 status = acpi_evaluate_object(NULL, "\\_TTS", &arg_list, NULL);
38 if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) {
40 * OS can't evaluate the _TTS object correctly. Some warning
41 * message will be printed. But it won't break anything.
43 printk(KERN_NOTICE "Failure in evaluating _TTS object\n");
47 static int tts_notify_reboot(struct notifier_block *this,
48 unsigned long code, void *x)
50 acpi_sleep_tts_switch(ACPI_STATE_S5);
54 static struct notifier_block tts_notifier = {
55 .notifier_call = tts_notify_reboot,
60 static int acpi_sleep_prepare(u32 acpi_state)
62 #ifdef CONFIG_ACPI_SLEEP
63 /* do we have a wakeup address for S2 and S3? */
64 if (acpi_state == ACPI_STATE_S3) {
65 if (!acpi_wakeup_address) {
68 acpi_set_firmware_waking_vector(
69 (acpi_physical_address)acpi_wakeup_address);
72 ACPI_FLUSH_CPU_CACHE();
73 acpi_enable_wakeup_device_prep(acpi_state);
75 printk(KERN_INFO PREFIX "Preparing to enter system sleep state S%d\n",
77 acpi_enter_sleep_state_prep(acpi_state);
81 #ifdef CONFIG_ACPI_SLEEP
82 static u32 acpi_target_sleep_state = ACPI_STATE_S0;
84 * ACPI 1.0 wants us to execute _PTS before suspending devices, so we allow the
85 * user to request that behavior by using the 'acpi_old_suspend_ordering'
86 * kernel command line option that causes the following variable to be set.
88 static bool old_suspend_ordering;
90 void __init acpi_old_suspend_ordering(void)
92 old_suspend_ordering = true;
96 * acpi_pm_disable_gpes - Disable the GPEs.
98 static int acpi_pm_disable_gpes(void)
100 acpi_disable_all_gpes();
105 * __acpi_pm_prepare - Prepare the platform to enter the target state.
107 * If necessary, set the firmware waking vector and do arch-specific
108 * nastiness to get the wakeup code to the waking vector.
110 static int __acpi_pm_prepare(void)
112 int error = acpi_sleep_prepare(acpi_target_sleep_state);
115 acpi_target_sleep_state = ACPI_STATE_S0;
120 * acpi_pm_prepare - Prepare the platform to enter the target sleep
121 * state and disable the GPEs.
123 static int acpi_pm_prepare(void)
125 int error = __acpi_pm_prepare();
128 acpi_disable_all_gpes();
133 * acpi_pm_finish - Instruct the platform to leave a sleep state.
135 * This is called after we wake back up (or if entering the sleep state
138 static void acpi_pm_finish(void)
140 u32 acpi_state = acpi_target_sleep_state;
142 if (acpi_state == ACPI_STATE_S0)
145 printk(KERN_INFO PREFIX "Waking up from system sleep state S%d\n",
147 acpi_disable_wakeup_device(acpi_state);
148 acpi_leave_sleep_state(acpi_state);
150 /* reset firmware waking vector */
151 acpi_set_firmware_waking_vector((acpi_physical_address) 0);
153 acpi_target_sleep_state = ACPI_STATE_S0;
157 * acpi_pm_end - Finish up suspend sequence.
159 static void acpi_pm_end(void)
162 * This is necessary in case acpi_pm_finish() is not called during a
163 * failing transition to a sleep state.
165 acpi_target_sleep_state = ACPI_STATE_S0;
166 acpi_sleep_tts_switch(acpi_target_sleep_state);
168 #else /* !CONFIG_ACPI_SLEEP */
169 #define acpi_target_sleep_state ACPI_STATE_S0
170 #endif /* CONFIG_ACPI_SLEEP */
172 #ifdef CONFIG_SUSPEND
174 * According to the ACPI specification the BIOS should make sure that ACPI is
175 * enabled and SCI_EN bit is set on wake-up from S1 - S3 sleep states. Still,
176 * some BIOSes don't do that and therefore we use acpi_enable() to enable ACPI
177 * on such systems during resume. Unfortunately that doesn't help in
178 * particularly pathological cases in which SCI_EN has to be set directly on
179 * resume, although the specification states very clearly that this flag is
180 * owned by the hardware. The set_sci_en_on_resume variable will be set in such
183 static bool set_sci_en_on_resume;
185 extern void do_suspend_lowlevel(void);
187 static u32 acpi_suspend_states[] = {
188 [PM_SUSPEND_ON] = ACPI_STATE_S0,
189 [PM_SUSPEND_STANDBY] = ACPI_STATE_S1,
190 [PM_SUSPEND_MEM] = ACPI_STATE_S3,
191 [PM_SUSPEND_MAX] = ACPI_STATE_S5
195 * acpi_suspend_begin - Set the target system sleep state to the state
196 * associated with given @pm_state, if supported.
198 static int acpi_suspend_begin(suspend_state_t pm_state)
200 u32 acpi_state = acpi_suspend_states[pm_state];
203 if (sleep_states[acpi_state]) {
204 acpi_target_sleep_state = acpi_state;
205 acpi_sleep_tts_switch(acpi_target_sleep_state);
207 printk(KERN_ERR "ACPI does not support this state: %d\n",
215 * acpi_suspend_enter - Actually enter a sleep state.
218 * Flush caches and go to sleep. For STR we have to call arch-specific
219 * assembly, which in turn call acpi_enter_sleep_state().
220 * It's unfortunate, but it works. Please fix if you're feeling frisky.
222 static int acpi_suspend_enter(suspend_state_t pm_state)
224 acpi_status status = AE_OK;
225 unsigned long flags = 0;
226 u32 acpi_state = acpi_target_sleep_state;
228 ACPI_FLUSH_CPU_CACHE();
230 /* Do arch specific saving of state. */
231 if (acpi_state == ACPI_STATE_S3) {
232 int error = acpi_save_state_mem();
238 local_irq_save(flags);
239 acpi_enable_wakeup_device(acpi_state);
240 switch (acpi_state) {
243 status = acpi_enter_sleep_state(acpi_state);
247 do_suspend_lowlevel();
251 /* If ACPI is not enabled by the BIOS, we need to enable it here. */
252 if (set_sci_en_on_resume)
253 acpi_write_bit_register(ACPI_BITREG_SCI_ENABLE, 1);
257 /* Reprogram control registers and execute _BFS */
258 acpi_leave_sleep_state_prep(acpi_state);
260 /* ACPI 3.0 specs (P62) says that it's the responsibility
261 * of the OSPM to clear the status bit [ implying that the
262 * POWER_BUTTON event should not reach userspace ]
264 if (ACPI_SUCCESS(status) && (acpi_state == ACPI_STATE_S3))
265 acpi_clear_event(ACPI_EVENT_POWER_BUTTON);
268 * Disable and clear GPE status before interrupt is enabled. Some GPEs
269 * (like wakeup GPE) haven't handler, this can avoid such GPE misfire.
270 * acpi_leave_sleep_state will reenable specific GPEs later
272 acpi_disable_all_gpes();
274 local_irq_restore(flags);
275 printk(KERN_DEBUG "Back to C!\n");
277 /* restore processor state */
278 if (acpi_state == ACPI_STATE_S3)
279 acpi_restore_state_mem();
281 return ACPI_SUCCESS(status) ? 0 : -EFAULT;
284 static int acpi_suspend_state_valid(suspend_state_t pm_state)
290 case PM_SUSPEND_STANDBY:
292 acpi_state = acpi_suspend_states[pm_state];
294 return sleep_states[acpi_state];
300 static struct platform_suspend_ops acpi_suspend_ops = {
301 .valid = acpi_suspend_state_valid,
302 .begin = acpi_suspend_begin,
303 .prepare_late = acpi_pm_prepare,
304 .enter = acpi_suspend_enter,
305 .wake = acpi_pm_finish,
310 * acpi_suspend_begin_old - Set the target system sleep state to the
311 * state associated with given @pm_state, if supported, and
312 * execute the _PTS control method. This function is used if the
313 * pre-ACPI 2.0 suspend ordering has been requested.
315 static int acpi_suspend_begin_old(suspend_state_t pm_state)
317 int error = acpi_suspend_begin(pm_state);
320 error = __acpi_pm_prepare();
325 * The following callbacks are used if the pre-ACPI 2.0 suspend ordering has
328 static struct platform_suspend_ops acpi_suspend_ops_old = {
329 .valid = acpi_suspend_state_valid,
330 .begin = acpi_suspend_begin_old,
331 .prepare_late = acpi_pm_disable_gpes,
332 .enter = acpi_suspend_enter,
333 .wake = acpi_pm_finish,
335 .recover = acpi_pm_finish,
338 static int __init init_old_suspend_ordering(const struct dmi_system_id *d)
340 old_suspend_ordering = true;
344 static int __init init_set_sci_en_on_resume(const struct dmi_system_id *d)
346 set_sci_en_on_resume = true;
350 static struct dmi_system_id __initdata acpisleep_dmi_table[] = {
352 .callback = init_old_suspend_ordering,
353 .ident = "Abit KN9 (nForce4 variant)",
355 DMI_MATCH(DMI_BOARD_VENDOR, "http://www.abit.com.tw/"),
356 DMI_MATCH(DMI_BOARD_NAME, "KN9 Series(NF-CK804)"),
360 .callback = init_old_suspend_ordering,
361 .ident = "HP xw4600 Workstation",
363 DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
364 DMI_MATCH(DMI_PRODUCT_NAME, "HP xw4600 Workstation"),
368 .callback = init_set_sci_en_on_resume,
369 .ident = "Apple MacBook 1,1",
371 DMI_MATCH(DMI_SYS_VENDOR, "Apple Computer, Inc."),
372 DMI_MATCH(DMI_PRODUCT_NAME, "MacBook1,1"),
376 .callback = init_set_sci_en_on_resume,
377 .ident = "Apple MacMini 1,1",
379 DMI_MATCH(DMI_SYS_VENDOR, "Apple Computer, Inc."),
380 DMI_MATCH(DMI_PRODUCT_NAME, "Macmini1,1"),
384 .callback = init_old_suspend_ordering,
385 .ident = "Asus Pundit P1-AH2 (M2N8L motherboard)",
387 DMI_MATCH(DMI_BOARD_VENDOR, "ASUSTek Computer INC."),
388 DMI_MATCH(DMI_BOARD_NAME, "M2N8L"),
392 .callback = init_set_sci_en_on_resume,
393 .ident = "Toshiba Satellite L300",
395 DMI_MATCH(DMI_SYS_VENDOR, "TOSHIBA"),
396 DMI_MATCH(DMI_PRODUCT_NAME, "Satellite L300"),
400 .callback = init_set_sci_en_on_resume,
401 .ident = "Hewlett-Packard HP G7000 Notebook PC",
403 DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
404 DMI_MATCH(DMI_PRODUCT_NAME, "HP G7000 Notebook PC"),
408 .callback = init_set_sci_en_on_resume,
409 .ident = "Hewlett-Packard HP Pavilion dv3 Notebook PC",
411 DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
412 DMI_MATCH(DMI_PRODUCT_NAME, "HP Pavilion dv3 Notebook PC"),
416 .callback = init_set_sci_en_on_resume,
417 .ident = "Hewlett-Packard Pavilion dv4",
419 DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
420 DMI_MATCH(DMI_PRODUCT_NAME, "HP Pavilion dv4"),
424 .callback = init_old_suspend_ordering,
425 .ident = "Panasonic CF51-2L",
427 DMI_MATCH(DMI_BOARD_VENDOR,
428 "Matsushita Electric Industrial Co.,Ltd."),
429 DMI_MATCH(DMI_BOARD_NAME, "CF51-2L"),
434 #endif /* CONFIG_SUSPEND */
436 #ifdef CONFIG_HIBERNATION
438 * The ACPI specification wants us to save NVS memory regions during hibernation
439 * and to restore them during the subsequent resume. However, it is not certain
440 * if this mechanism is going to work on all machines, so we allow the user to
441 * disable this mechanism using the 'acpi_sleep=s4_nonvs' kernel command line
444 static bool s4_no_nvs;
446 void __init acpi_s4_no_nvs(void)
451 static unsigned long s4_hardware_signature;
452 static struct acpi_table_facs *facs;
453 static bool nosigcheck;
455 void __init acpi_no_s4_hw_signature(void)
460 static int acpi_hibernation_begin(void)
464 error = s4_no_nvs ? 0 : hibernate_nvs_alloc();
466 acpi_target_sleep_state = ACPI_STATE_S4;
467 acpi_sleep_tts_switch(acpi_target_sleep_state);
473 static int acpi_hibernation_pre_snapshot(void)
475 int error = acpi_pm_prepare();
478 hibernate_nvs_save();
483 static int acpi_hibernation_enter(void)
485 acpi_status status = AE_OK;
486 unsigned long flags = 0;
488 ACPI_FLUSH_CPU_CACHE();
490 local_irq_save(flags);
491 acpi_enable_wakeup_device(ACPI_STATE_S4);
492 /* This shouldn't return. If it returns, we have a problem */
493 status = acpi_enter_sleep_state(ACPI_STATE_S4);
494 /* Reprogram control registers and execute _BFS */
495 acpi_leave_sleep_state_prep(ACPI_STATE_S4);
496 local_irq_restore(flags);
498 return ACPI_SUCCESS(status) ? 0 : -EFAULT;
501 static void acpi_hibernation_finish(void)
503 hibernate_nvs_free();
507 static void acpi_hibernation_leave(void)
510 * If ACPI is not enabled by the BIOS and the boot kernel, we need to
514 /* Reprogram control registers and execute _BFS */
515 acpi_leave_sleep_state_prep(ACPI_STATE_S4);
516 /* Check the hardware signature */
517 if (facs && s4_hardware_signature != facs->hardware_signature) {
518 printk(KERN_EMERG "ACPI: Hardware changed while hibernated, "
520 panic("ACPI S4 hardware signature mismatch");
522 /* Restore the NVS memory area */
523 hibernate_nvs_restore();
526 static void acpi_pm_enable_gpes(void)
528 acpi_enable_all_runtime_gpes();
531 static struct platform_hibernation_ops acpi_hibernation_ops = {
532 .begin = acpi_hibernation_begin,
534 .pre_snapshot = acpi_hibernation_pre_snapshot,
535 .finish = acpi_hibernation_finish,
536 .prepare = acpi_pm_prepare,
537 .enter = acpi_hibernation_enter,
538 .leave = acpi_hibernation_leave,
539 .pre_restore = acpi_pm_disable_gpes,
540 .restore_cleanup = acpi_pm_enable_gpes,
544 * acpi_hibernation_begin_old - Set the target system sleep state to
545 * ACPI_STATE_S4 and execute the _PTS control method. This
546 * function is used if the pre-ACPI 2.0 suspend ordering has been
549 static int acpi_hibernation_begin_old(void)
553 * The _TTS object should always be evaluated before the _PTS object.
554 * When the old_suspended_ordering is true, the _PTS object is
555 * evaluated in the acpi_sleep_prepare.
557 acpi_sleep_tts_switch(ACPI_STATE_S4);
559 error = acpi_sleep_prepare(ACPI_STATE_S4);
563 error = hibernate_nvs_alloc();
565 acpi_target_sleep_state = ACPI_STATE_S4;
570 static int acpi_hibernation_pre_snapshot_old(void)
572 int error = acpi_pm_disable_gpes();
575 hibernate_nvs_save();
581 * The following callbacks are used if the pre-ACPI 2.0 suspend ordering has
584 static struct platform_hibernation_ops acpi_hibernation_ops_old = {
585 .begin = acpi_hibernation_begin_old,
587 .pre_snapshot = acpi_hibernation_pre_snapshot_old,
588 .finish = acpi_hibernation_finish,
589 .prepare = acpi_pm_disable_gpes,
590 .enter = acpi_hibernation_enter,
591 .leave = acpi_hibernation_leave,
592 .pre_restore = acpi_pm_disable_gpes,
593 .restore_cleanup = acpi_pm_enable_gpes,
594 .recover = acpi_pm_finish,
596 #endif /* CONFIG_HIBERNATION */
598 int acpi_suspend(u32 acpi_state)
600 suspend_state_t states[] = {
601 [1] = PM_SUSPEND_STANDBY,
602 [3] = PM_SUSPEND_MEM,
606 if (acpi_state < 6 && states[acpi_state])
607 return pm_suspend(states[acpi_state]);
613 #ifdef CONFIG_PM_SLEEP
615 * acpi_pm_device_sleep_state - return preferred power state of ACPI device
616 * in the system sleep state given by %acpi_target_sleep_state
617 * @dev: device to examine; its driver model wakeup flags control
618 * whether it should be able to wake up the system
619 * @d_min_p: used to store the upper limit of allowed states range
620 * Return value: preferred power state of the device on success, -ENODEV on
621 * failure (ie. if there's no 'struct acpi_device' for @dev)
623 * Find the lowest power (highest number) ACPI device power state that
624 * device @dev can be in while the system is in the sleep state represented
625 * by %acpi_target_sleep_state. If @wake is nonzero, the device should be
626 * able to wake up the system from this sleep state. If @d_min_p is set,
627 * the highest power (lowest number) device power state of @dev allowed
628 * in this system sleep state is stored at the location pointed to by it.
630 * The caller must ensure that @dev is valid before using this function.
631 * The caller is also responsible for figuring out if the device is
632 * supposed to be able to wake up the system and passing this information
636 int acpi_pm_device_sleep_state(struct device *dev, int *d_min_p)
638 acpi_handle handle = DEVICE_ACPI_HANDLE(dev);
639 struct acpi_device *adev;
640 char acpi_method[] = "_SxD";
641 unsigned long long d_min, d_max;
643 if (!handle || ACPI_FAILURE(acpi_bus_get_device(handle, &adev))) {
644 printk(KERN_DEBUG "ACPI handle has no context!\n");
648 acpi_method[2] = '0' + acpi_target_sleep_state;
650 * If the sleep state is S0, we will return D3, but if the device has
651 * _S0W, we will use the value from _S0W
653 d_min = ACPI_STATE_D0;
654 d_max = ACPI_STATE_D3;
657 * If present, _SxD methods return the minimum D-state (highest power
658 * state) we can use for the corresponding S-states. Otherwise, the
659 * minimum D-state is D0 (ACPI 3.x).
661 * NOTE: We rely on acpi_evaluate_integer() not clobbering the integer
662 * provided -- that's our fault recovery, we ignore retval.
664 if (acpi_target_sleep_state > ACPI_STATE_S0)
665 acpi_evaluate_integer(handle, acpi_method, NULL, &d_min);
668 * If _PRW says we can wake up the system from the target sleep state,
669 * the D-state returned by _SxD is sufficient for that (we assume a
670 * wakeup-aware driver if wake is set). Still, if _SxW exists
671 * (ACPI 3.x), it should return the maximum (lowest power) D-state that
672 * can wake the system. _S0W may be valid, too.
674 if (acpi_target_sleep_state == ACPI_STATE_S0 ||
675 (device_may_wakeup(dev) && adev->wakeup.state.enabled &&
676 adev->wakeup.sleep_state <= acpi_target_sleep_state)) {
679 acpi_method[3] = 'W';
680 status = acpi_evaluate_integer(handle, acpi_method, NULL,
682 if (ACPI_FAILURE(status)) {
684 } else if (d_max < d_min) {
685 /* Warn the user of the broken DSDT */
686 printk(KERN_WARNING "ACPI: Wrong value from %s\n",
699 * acpi_pm_device_sleep_wake - enable or disable the system wake-up
700 * capability of given device
701 * @dev: device to handle
702 * @enable: 'true' - enable, 'false' - disable the wake-up capability
704 int acpi_pm_device_sleep_wake(struct device *dev, bool enable)
707 struct acpi_device *adev;
710 if (!device_can_wakeup(dev))
713 handle = DEVICE_ACPI_HANDLE(dev);
714 if (!handle || ACPI_FAILURE(acpi_bus_get_device(handle, &adev))) {
715 dev_dbg(dev, "ACPI handle has no context in %s!\n", __func__);
720 acpi_enable_wakeup_device_power(adev, acpi_target_sleep_state) :
721 acpi_disable_wakeup_device_power(adev);
723 dev_info(dev, "wake-up capability %s by ACPI\n",
724 enable ? "enabled" : "disabled");
730 static void acpi_power_off_prepare(void)
732 /* Prepare to power off the system */
733 acpi_sleep_prepare(ACPI_STATE_S5);
734 acpi_disable_all_gpes();
737 static void acpi_power_off(void)
739 /* acpi_sleep_prepare(ACPI_STATE_S5) should have already been called */
740 printk(KERN_DEBUG "%s called\n", __func__);
742 acpi_enable_wakeup_device(ACPI_STATE_S5);
743 acpi_enter_sleep_state(ACPI_STATE_S5);
747 * ACPI 2.0 created the optional _GTS and _BFS,
748 * but industry adoption has been neither rapid nor broad.
750 * Linux gets into trouble when it executes poorly validated
751 * paths through the BIOS, so disable _GTS and _BFS by default,
752 * but do speak up and offer the option to enable them.
754 void __init acpi_gts_bfs_check(void)
758 if (ACPI_SUCCESS(acpi_get_handle(ACPI_ROOT_OBJECT, METHOD_NAME__GTS, &dummy)))
760 printk(KERN_NOTICE PREFIX "BIOS offers _GTS\n");
761 printk(KERN_NOTICE PREFIX "If \"acpi.gts=1\" improves suspend, "
762 "please notify linux-acpi@vger.kernel.org\n");
764 if (ACPI_SUCCESS(acpi_get_handle(ACPI_ROOT_OBJECT, METHOD_NAME__BFS, &dummy)))
766 printk(KERN_NOTICE PREFIX "BIOS offers _BFS\n");
767 printk(KERN_NOTICE PREFIX "If \"acpi.bfs=1\" improves resume, "
768 "please notify linux-acpi@vger.kernel.org\n");
772 int __init acpi_sleep_init(void)
776 #ifdef CONFIG_SUSPEND
779 dmi_check_system(acpisleep_dmi_table);
785 sleep_states[ACPI_STATE_S0] = 1;
786 printk(KERN_INFO PREFIX "(supports S0");
788 #ifdef CONFIG_SUSPEND
789 for (i = ACPI_STATE_S1; i < ACPI_STATE_S4; i++) {
790 status = acpi_get_sleep_type_data(i, &type_a, &type_b);
791 if (ACPI_SUCCESS(status)) {
797 suspend_set_ops(old_suspend_ordering ?
798 &acpi_suspend_ops_old : &acpi_suspend_ops);
801 #ifdef CONFIG_HIBERNATION
802 status = acpi_get_sleep_type_data(ACPI_STATE_S4, &type_a, &type_b);
803 if (ACPI_SUCCESS(status)) {
804 hibernation_set_ops(old_suspend_ordering ?
805 &acpi_hibernation_ops_old : &acpi_hibernation_ops);
806 sleep_states[ACPI_STATE_S4] = 1;
809 acpi_get_table(ACPI_SIG_FACS, 1,
810 (struct acpi_table_header **)&facs);
812 s4_hardware_signature =
813 facs->hardware_signature;
817 status = acpi_get_sleep_type_data(ACPI_STATE_S5, &type_a, &type_b);
818 if (ACPI_SUCCESS(status)) {
819 sleep_states[ACPI_STATE_S5] = 1;
821 pm_power_off_prepare = acpi_power_off_prepare;
822 pm_power_off = acpi_power_off;
826 * Register the tts_notifier to reboot notifier list so that the _TTS
827 * object can also be evaluated when the system enters S5.
829 register_reboot_notifier(&tts_notifier);
830 acpi_gts_bfs_check();