- 根目录:
- drivers
- acpi
- sleep.c
/*
* sleep.c - ACPI sleep support.
*
* Copyright (c) 2005 Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>
* Copyright (c) 2004 David Shaohua Li <shaohua.li@intel.com>
* Copyright (c) 2000-2003 Patrick Mochel
* Copyright (c) 2003 Open Source Development Lab
*
* This file is released under the GPLv2.
*
*/
#include <linux/delay.h>
#include <linux/irq.h>
#include <linux/dmi.h>
#include <linux/device.h>
#include <linux/suspend.h>
#include <linux/reboot.h>
#include <linux/acpi.h>
#include <asm/io.h>
#include <acpi/acpi_bus.h>
#include <acpi/acpi_drivers.h>
#include "internal.h"
#include "sleep.h"
static u8 sleep_states[ACPI_S_STATE_COUNT];
static void acpi_sleep_tts_switch(u32 acpi_state)
{
union acpi_object in_arg = { ACPI_TYPE_INTEGER };
struct acpi_object_list arg_list = { 1, &in_arg };
acpi_status status = AE_OK;
in_arg.integer.value = acpi_state;
status = acpi_evaluate_object(NULL, "\\_TTS", &arg_list, NULL);
if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) {
/*
* OS can't evaluate the _TTS object correctly. Some warning
* message will be printed. But it won't break anything.
*/
printk(KERN_NOTICE "Failure in evaluating _TTS object\n");
}
}
static int tts_notify_reboot(struct notifier_block *this,
unsigned long code, void *x)
{
acpi_sleep_tts_switch(ACPI_STATE_S5);
return NOTIFY_DONE;
}
static struct notifier_block tts_notifier = {
.notifier_call = tts_notify_reboot,
.next = NULL,
.priority = 0,
};
static int acpi_sleep_prepare(u32 acpi_state)
{
#ifdef CONFIG_ACPI_SLEEP
/* do we have a wakeup address for S2 and S3? */
if (acpi_state == ACPI_STATE_S3) {
if (!acpi_wakeup_address) {
return -EFAULT;
}
acpi_set_firmware_waking_vector(
(acpi_physical_address)acpi_wakeup_address);
}
ACPI_FLUSH_CPU_CACHE();
#endif
printk(KERN_INFO PREFIX "Preparing to enter system sleep state S%d\n",
acpi_state);
acpi_enable_wakeup_devices(acpi_state);
acpi_enter_sleep_state_prep(acpi_state);
return 0;
}
#ifdef CONFIG_ACPI_SLEEP
static u32 acpi_target_sleep_state = ACPI_STATE_S0;
/*
* The ACPI specification wants us to save NVS memory regions during hibernation
* and to restore them during the subsequent resume. Windows does that also for
* suspend to RAM. However, it is known that this mechanism does not work on
* all machines, so we allow the user to disable it with the help of the
* 'acpi_sleep=nonvs' kernel command line option.
*/
static bool nvs_nosave;
void __init acpi_nvs_nosave(void)
{
nvs_nosave = true;
}
/*
* ACPI 1.0 wants us to execute _PTS before suspending devices, so we allow the
* user to request that behavior by using the 'acpi_old_suspend_ordering'
* kernel command line option that causes the following variable to be set.
*/
static bool old_suspend_ordering;
void __init acpi_old_suspend_ordering(void)
{
old_suspend_ordering = true;
}
/**
* acpi_pm_freeze - Disable the GPEs and suspend EC transactions.
*/
static int acpi_pm_freeze(void)
{
acpi_disable_all_gpes();
acpi_os_wait_events_complete(NULL);
acpi_ec_block_transactions();
return 0;
}
/**
* acpi_pre_suspend - Enable wakeup devices, "freeze" EC and save NVS.
*/
static int acpi_pm_pre_suspend(void)
{
acpi_pm_freeze();
return suspend_nvs_save();
}
/**
* __acpi_pm_prepare - Prepare the platform to enter the target state.
*
* If necessary, set the firmware waking vector and do arch-specific
* nastiness to get the wakeup code to the waking vector.
*/
static int __acpi_pm_prepare(void)
{
int error = acpi_sleep_prepare(acpi_target_sleep_state);
if (error)
acpi_target_sleep_state = ACPI_STATE_S0;
return error;
}
/**
* acpi_pm_prepare - Prepare the platform to enter the target sleep
* state and disable the GPEs.
*/
static int acpi_pm_prepare(void)
{
int error = __acpi_pm_prepare();
if (!error)
error = acpi_pm_pre_suspend();
return error;
}
/**
* acpi_pm_finish - Instruct the platform to leave a sleep state.
*
* This is called after we wake back up (or if entering the sleep state
* failed).
*/
static void acpi_pm_finish(void)
{
u32 acpi_state = acpi_target_sleep_state;
acpi_ec_unblock_transactions();
suspend_nvs_free();
if (acpi_state == ACPI_STATE_S0)
return;
printk(KERN_INFO PREFIX "Waking up from system sleep state S%d\n",
acpi_state);
acpi_disable_wakeup_devices(acpi_state);
acpi_leave_sleep_state(acpi_state);
/* reset firmware waking vector */
acpi_set_firmware_waking_vector((acpi_physical_address) 0);
acpi_target_sleep_state = ACPI_STATE_S0;
}
/**
* acpi_pm_end - Finish up suspend sequence.
*/
static void acpi_pm_end(void)
{
/*
* This is necessary in case acpi_pm_finish() is not called during a
* failing transition to a sleep state.
*/
acpi_target_sleep_state = ACPI_STATE_S0;
acpi_sleep_tts_switch(acpi_target_sleep_state);
}
#else /* !CONFIG_ACPI_SLEEP */
#define acpi_target_sleep_state ACPI_STATE_S0
#endif /* CONFIG_ACPI_SLEEP */
#ifdef CONFIG_SUSPEND
static u32 acpi_suspend_states[] = {
[PM_SUSPEND_ON] = ACPI_STATE_S0,
[PM_SUSPEND_STANDBY] = ACPI_STATE_S1,
[PM_SUSPEND_MEM] = ACPI_STATE_S3,
[PM_SUSPEND_MAX] = ACPI_STATE_S5
};
/**
* acpi_suspend_begin - Set the target system sleep state to the state
* associated with given @pm_state, if supported.
*/
static int acpi_suspend_begin(suspend_state_t pm_state)
{
u32 acpi_state = acpi_suspend_states[pm_state];
int error = 0;
error = nvs_nosave ? 0 : suspend_nvs_alloc();
if (error)
return error;
if (sleep_states[acpi_state]) {
acpi_target_sleep_state = acpi_state;
acpi_sleep_tts_switch(acpi_target_sleep_state);
} else {
printk(KERN_ERR "ACPI does not support this state: %d\n",
pm_state);
error = -ENOSYS;
}
return error;
}
/**
* acpi_suspend_enter - Actually enter a sleep state.
* @pm_state: ignored
*
* Flush caches and go to sleep. For STR we have to call arch-specific
* assembly, which in turn call acpi_enter_sleep_state().
* It's unfortunate, but it works. Please fix if you're feeling frisky.
*/
static int acpi_suspend_enter(suspend_state_t pm_state)
{
acpi_status status = AE_OK;
u32 acpi_state = acpi_target_sleep_state;
int error;
ACPI_FLUSH_CPU_CACHE();
switch (acpi_state) {
case ACPI_STATE_S1:
barrier();
status = acpi_enter_sleep_state(acpi_state);
break;
case ACPI_STATE_S3:
error = acpi_suspend_lowlevel();
if (error)
return error;
pr_info(PREFIX "Low-level resume complete\n");
break;
}
/* This violates the spec but is required for bug compatibility. */
acpi_write_bit_register(ACPI_BITREG_SCI_ENABLE, 1);
/* Reprogram control registers and execute _BFS */
acpi_leave_sleep_state_prep(acpi_state);
/* ACPI 3.0 specs (P62) says that it's the responsibility
* of the OSPM to clear the status bit [ implying that the
* POWER_BUTTON event should not reach userspace ]
*/
if (ACPI_SUCCESS(status) && (acpi_state == ACPI_STATE_S3))
acpi_clear_event(ACPI_EVENT_POWER_BUTTON);
/*
* Disable and clear GPE status before interrupt is enabled. Some GPEs
* (like wakeup GPE) haven't handler, this can avoid such GPE misfire.
* acpi_leave_sleep_state will reenable specific GPEs later
*/
acpi_disable_all_gpes();
/* Allow EC transactions to happen. */
acpi_ec_unblock_transactions_early();
suspend_nvs_restore();
return ACPI_SUCCESS(status) ? 0 : -EFAULT;
}
static int acpi_suspend_state_valid(suspend_state_t pm_state)
{
u32 acpi_state;
switch (pm_state) {
case PM_SUSPEND_ON:
case PM_SUSPEND_STANDBY:
case PM_SUSPEND_MEM:
acpi_state = acpi_suspend_states[pm_state];
return sleep_states[acpi_state];
default:
return 0;
}
}
static const struct platform_suspend_ops acpi_suspend_ops = {
.valid = acpi_suspend_state_valid,
.begin = acpi_suspend_begin,
.prepare_late = acpi_pm_prepare,
.enter = acpi_suspend_enter,
.wake = acpi_pm_finish,
.end = acpi_pm_end,
};
/**
* acpi_suspend_begin_old - Set the target system sleep state to the
* state associated with given @pm_state, if supported, and
* execute the _PTS control method. This function is used if the
* pre-ACPI 2.0 suspend ordering has been requested.
*/
static int acpi_suspend_begin_old(suspend_state_t pm_state)
{
int error = acpi_suspend_begin(pm_state);
if (!error)
error = __acpi_pm_prepare();
return error;
}
/*
* The following callbacks are used if the pre-ACPI 2.0 suspend ordering has
* been requested.
*/
static const struct platform_suspend_ops acpi_suspend_ops_old = {
.valid = acpi_suspend_state_valid,
.begin = acpi_suspend_begin_old,
.prepare_late = acpi_pm_pre_suspend,
.enter = acpi_suspend_enter,
.wake = acpi_pm_finish,
.end = acpi_pm_end,
.recover = acpi_pm_finish,
};
static int __init init_old_suspend_ordering(const struct dmi_system_id *d)
{
old_suspend_ordering = true;
return 0;
}
static int __init init_nvs_nosave(const struct dmi_system_id *d)
{
acpi_nvs_nosave();
return 0;
}
static struct dmi_system_id __initdata acpisleep_dmi_table[] = {
{
.callback = init_old_suspend_ordering,
.ident = "Abit KN9 (nForce4 variant)",
.matches = {
DMI_MATCH(DMI_BOARD_VENDOR, "http://www.abit.com.tw/"),
DMI_MATCH(DMI_BOARD_NAME, "KN9 Series(NF-CK804)"),
},
},
{
.callback = init_old_suspend_ordering,
.ident = "HP xw4600 Workstation",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
DMI_MATCH(DMI_PRODUCT_NAME, "HP xw4600 Workstation"),
},
},
{
.callback = init_old_suspend_ordering,
.ident = "Asus Pundit P1-AH2 (M2N8L motherboard)",
.matches = {
DMI_MATCH(DMI_BOARD_VENDOR, "ASUSTek Computer INC."),
DMI_MATCH(DMI_BOARD_NAME, "M2N8L"),
},
},
{
.callback = init_old_suspend_ordering,
.ident = "Panasonic CF51-2L",
.matches = {
DMI_MATCH(DMI_BOARD_VENDOR,
"Matsushita Electric Industrial Co.,Ltd."),
DMI_MATCH(DMI_BOARD_NAME, "CF51-2L"),
},
},
{
.callback = init_nvs_nosave,
.ident = "Sony Vaio VGN-SR11M",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Sony Corporation"),
DMI_MATCH(DMI_PRODUCT_NAME, "VGN-SR11M"),
},
},
{
.callback = init_nvs_nosave,
.ident = "Everex StepNote Series",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Everex Systems, Inc."),
DMI_MATCH(DMI_PRODUCT_NAME, "Everex StepNote Series"),
},
},
{
.callback = init_nvs_nosave,
.ident = "Sony Vaio VPCEB1Z1E",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Sony Corporation"),
DMI_MATCH(DMI_PRODUCT_NAME, "VPCEB1Z1E"),
},
},
{
.callback = init_nvs_nosave,
.ident = "Sony Vaio VGN-NW130D",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Sony Corporation"),
DMI_MATCH(DMI_PRODUCT_NAME, "VGN-NW130D"),
},
},
{
.callback = init_nvs_nosave,
.ident = "Averatec AV1020-ED2",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "AVERATEC"),
DMI_MATCH(DMI_PRODUCT_NAME, "1000 Series"),
},
},
{},
};
#endif /* CONFIG_SUSPEND */
#ifdef CONFIG_HIBERNATION
static unsigned long s4_hardware_signature;
static struct acpi_table_facs *facs;
static bool nosigcheck;
void __init acpi_no_s4_hw_signature(void)
{
nosigcheck = true;
}
static int acpi_hibernation_begin(void)
{
int error;
error = nvs_nosave ? 0 : suspend_nvs_alloc();
if (!error) {
acpi_target_sleep_state = ACPI_STATE_S4;
acpi_sleep_tts_switch(acpi_target_sleep_state);
}
return error;
}
static int acpi_hibernation_enter(void)
{
acpi_status status = AE_OK;
ACPI_FLUSH_CPU_CACHE();
/* This shouldn't return. If it returns, we have a problem */
status = acpi_enter_sleep_state(ACPI_STATE_S4);
/* Reprogram control registers and execute _BFS */
acpi_leave_sleep_state_prep(ACPI_STATE_S4);
return ACPI_SUCCESS(status) ? 0 : -EFAULT;
}
static void acpi_hibernation_leave(void)
{
/*
* If ACPI is not enabled by the BIOS and the boot kernel, we need to
* enable it here.
*/
acpi_enable();
/* Reprogram control registers and execute _BFS */
acpi_leave_sleep_state_prep(ACPI_STATE_S4);
/* Check the hardware signature */
if (facs && s4_hardware_signature != facs->hardware_signature) {
printk(KERN_EMERG "ACPI: Hardware changed while hibernated, "
"cannot resume!\n");
panic("ACPI S4 hardware signature mismatch");
}
/* Restore the NVS memory area */
suspend_nvs_restore();
/* Allow EC transactions to happen. */
acpi_ec_unblock_transactions_early();
}
static void acpi_pm_thaw(void)
{
acpi_ec_unblock_transactions();
acpi_enable_all_runtime_gpes();
}
static const struct platform_hibernation_ops acpi_hibernation_ops = {
.begin = acpi_hibernation_begin,
.end = acpi_pm_end,
.pre_snapshot = acpi_pm_prepare,
.finish = acpi_pm_finish,
.prepare = acpi_pm_prepare,
.enter = acpi_hibernation_enter,
.leave = acpi_hibernation_leave,
.pre_restore = acpi_pm_freeze,
.restore_cleanup = acpi_pm_thaw,
};
/**
* acpi_hibernation_begin_old - Set the target system sleep state to
* ACPI_STATE_S4 and execute the _PTS control method. This
* function is used if the pre-ACPI 2.0 suspend ordering has been
* requested.
*/
static int acpi_hibernation_begin_old(void)
{
int error;
/*
* The _TTS object should always be evaluated before the _PTS object.
* When the old_suspended_ordering is true, the _PTS object is
* evaluated in the acpi_sleep_prepare.
*/
acpi_sleep_tts_switch(ACPI_STATE_S4);
error = acpi_sleep_prepare(ACPI_STATE_S4);
if (!error) {
if (!nvs_nosave)
error = suspend_nvs_alloc();
if (!error)
acpi_target_sleep_state = ACPI_STATE_S4;
}
return error;
}
/*
* The following callbacks are used if the pre-ACPI 2.0 suspend ordering has
* been requested.
*/
static const struct platform_hibernation_ops acpi_hibernation_ops_old = {
.begin = acpi_hibernation_begin_old,
.end = acpi_pm_end,
.pre_snapshot = acpi_pm_pre_suspend,
.prepare = acpi_pm_freeze,
.finish = acpi_pm_finish,
.enter = acpi_hibernation_enter,
.leave = acpi_hibernation_leave,
.pre_restore = acpi_pm_freeze,
.restore_cleanup = acpi_pm_thaw,
.recover = acpi_pm_finish,
};
#endif /* CONFIG_HIBERNATION */
int acpi_suspend(u32 acpi_state)
{
suspend_state_t states[] = {
[1] = PM_SUSPEND_STANDBY,
[3] = PM_SUSPEND_MEM,
[5] = PM_SUSPEND_MAX
};
if (acpi_state < 6 && states[acpi_state])
return pm_suspend(states[acpi_state]);
if (acpi_state == 4)
return hibernate();
return -EINVAL;
}
#ifdef CONFIG_PM
/**
* acpi_pm_device_sleep_state - return preferred power state of ACPI device
* in the system sleep state given by %acpi_target_sleep_state
* @dev: device to examine; its driver model wakeup flags control
* whether it should be able to wake up the system
* @d_min_p: used to store the upper limit of allowed states range
* Return value: preferred power state of the device on success, -ENODEV on
* failure (ie. if there's no 'struct acpi_device' for @dev)
*
* Find the lowest power (highest number) ACPI device power state that
* device @dev can be in while the system is in the sleep state represented
* by %acpi_target_sleep_state. If @wake is nonzero, the device should be
* able to wake up the system from this sleep state. If @d_min_p is set,
* the highest power (lowest number) device power state of @dev allowed
* in this system sleep state is stored at the location pointed to by it.
*
* The caller must ensure that @dev is valid before using this function.
* The caller is also responsible for figuring out if the device is
* supposed to be able to wake up the system and passing this information
* via @wake.
*/
int acpi_pm_device_sleep_state(struct device *dev, int *d_min_p)
{
acpi_handle handle = DEVICE_ACPI_HANDLE(dev);
struct acpi_device *adev;
char acpi_method[] = "_SxD";
unsigned long long d_min, d_max;
if (!handle || ACPI_FAILURE(acpi_bus_get_device(handle, &adev))) {
printk(KERN_DEBUG "ACPI handle has no context!\n");
return -ENODEV;
}
acpi_method[2] = '0' + acpi_target_sleep_state;
/*
* If the sleep state is S0, we will return D3, but if the device has
* _S0W, we will use the value from _S0W
*/
d_min = ACPI_STATE_D0;
d_max = ACPI_STATE_D3;
/*
* If present, _SxD methods return the minimum D-state (highest power
* state) we can use for the corresponding S-states. Otherwise, the
* minimum D-state is D0 (ACPI 3.x).
*
* NOTE: We rely on acpi_evaluate_integer() not clobbering the integer
* provided -- that's our fault recovery, we ignore retval.
*/
if (acpi_target_sleep_state > ACPI_STATE_S0)
acpi_evaluate_integer(handle, acpi_method, NULL, &d_min);
/*
* If _PRW says we can wake up the system from the target sleep state,
* the D-state returned by _SxD is sufficient for that (we assume a
* wakeup-aware driver if wake is set). Still, if _SxW exists
* (ACPI 3.x), it should return the maximum (lowest power) D-state that
* can wake the system. _S0W may be valid, too.
*/
if (acpi_target_sleep_state == ACPI_STATE_S0 ||
(device_may_wakeup(dev) &&
adev->wakeup.sleep_state <= acpi_target_sleep_state)) {
acpi_status status;
acpi_method[3] = 'W';
status = acpi_evaluate_integer(handle, acpi_method, NULL,
&d_max);
if (ACPI_FAILURE(status)) {
if (acpi_target_sleep_state != ACPI_STATE_S0 ||
status != AE_NOT_FOUND)
d_max = d_min;
} else if (d_max < d_min) {
/* Warn the user of the broken DSDT */
printk(KERN_WARNING "ACPI: Wrong value from %s\n",
acpi_method);
/* Sanitize it */
d_min = d_max;
}
}
if (d_min_p)
*d_min_p = d_min;
return d_max;
}
#endif /* CONFIG_PM */
#ifdef CONFIG_PM_SLEEP
/**
* acpi_pm_device_sleep_wake - enable or disable the system wake-up
* capability of given device
* @dev: device to handle
* @enable: 'true' - enable, 'false' - disable the wake-up capability
*/
int acpi_pm_device_sleep_wake(struct device *dev, bool enable)
{
acpi_handle handle;
struct acpi_device *adev;
int error;
if (!device_can_wakeup(dev))
return -EINVAL;
handle = DEVICE_ACPI_HANDLE(dev);
if (!handle || ACPI_FAILURE(acpi_bus_get_device(handle, &adev))) {
dev_dbg(dev, "ACPI handle has no context in %s!\n", __func__);
return -ENODEV;
}
error = enable ?
acpi_enable_wakeup_device_power(adev, acpi_target_sleep_state) :
acpi_disable_wakeup_device_power(adev);
if (!error)
dev_info(dev, "wake-up capability %s by ACPI\n",
enable ? "enabled" : "disabled");
return error;
}
#endif /* CONFIG_PM_SLEEP */
static void acpi_power_off_prepare(void)
{
/* Prepare to power off the system */
acpi_sleep_prepare(ACPI_STATE_S5);
acpi_disable_all_gpes();
}
static void acpi_power_off(void)
{
/* acpi_sleep_prepare(ACPI_STATE_S5) should have already been called */
printk(KERN_DEBUG "%s called\n", __func__);
local_irq_disable();
acpi_enter_sleep_state(ACPI_STATE_S5);
}
/*
* ACPI 2.0 created the optional _GTS and _BFS,
* but industry adoption has been neither rapid nor broad.
*
* Linux gets into trouble when it executes poorly validated
* paths through the BIOS, so disable _GTS and _BFS by default,
* but do speak up and offer the option to enable them.
*/
static void __init acpi_gts_bfs_check(void)
{
acpi_handle dummy;
if (ACPI_SUCCESS(acpi_get_handle(ACPI_ROOT_OBJECT, METHOD_NAME__GTS, &dummy)))
{
printk(KERN_NOTICE PREFIX "BIOS offers _GTS\n");
printk(KERN_NOTICE PREFIX "If \"acpi.gts=1\" improves suspend, "
"please notify linux-acpi@vger.kernel.org\n");
}
if (ACPI_SUCCESS(acpi_get_handle(ACPI_ROOT_OBJECT, METHOD_NAME__BFS, &dummy)))
{
printk(KERN_NOTICE PREFIX "BIOS offers _BFS\n");
printk(KERN_NOTICE PREFIX "If \"acpi.bfs=1\" improves resume, "
"please notify linux-acpi@vger.kernel.org\n");
}
}
int __init acpi_sleep_init(void)
{
acpi_status status;
u8 type_a, type_b;
#ifdef CONFIG_SUSPEND
int i = 0;
dmi_check_system(acpisleep_dmi_table);
#endif
if (acpi_disabled)
return 0;
sleep_states[ACPI_STATE_S0] = 1;
printk(KERN_INFO PREFIX "(supports S0");
#ifdef CONFIG_SUSPEND
for (i = ACPI_STATE_S1; i < ACPI_STATE_S4; i++) {
status = acpi_get_sleep_type_data(i, &type_a, &type_b);
if (ACPI_SUCCESS(status)) {
sleep_states[i] = 1;
printk(" S%d", i);
}
}
suspend_set_ops(old_suspend_ordering ?
&acpi_suspend_ops_old : &acpi_suspend_ops);
#endif
#ifdef CONFIG_HIBERNATION
status = acpi_get_sleep_type_data(ACPI_STATE_S4, &type_a, &type_b);
if (ACPI_SUCCESS(status)) {
hibernation_set_ops(old_suspend_ordering ?
&acpi_hibernation_ops_old : &acpi_hibernation_ops);
sleep_states[ACPI_STATE_S4] = 1;
printk(" S4");
if (!nosigcheck) {
acpi_get_table(ACPI_SIG_FACS, 1,
(struct acpi_table_header **)&facs);
if (facs)
s4_hardware_signature =
facs->hardware_signature;
}
}
#endif
status = acpi_get_sleep_type_data(ACPI_STATE_S5, &type_a, &type_b);
if (ACPI_SUCCESS(status)) {
sleep_states[ACPI_STATE_S5] = 1;
printk(" S5");
pm_power_off_prepare = acpi_power_off_prepare;
pm_power_off = acpi_power_off;
}
printk(")\n");
/*
* Register the tts_notifier to reboot notifier list so that the _TTS
* object can also be evaluated when the system enters S5.
*/
register_reboot_notifier(&tts_notifier);
acpi_gts_bfs_check();
return 0;
}