ACPI: Add the support for _TTS object

The _TTS object is defined in the section 7.3 of acpi 3.0b spec.
    The _TTS control method is executed by the OSPM at the beginning of
the sleep transition process for S1,S2, S3, S4, and orderly S5 shutdown.
OS will invoke _TTS before it has notified any native mode device drivers
of the sleep state transition. The target sleeping state value is passed to
the _TTS control method.

    The _TTS control method is also executed by the OSPM at the end of
any sleep transition process when the system transitions to S0 from
S1, S2, S3, or S4. The _TTS object should be evaluated after it has
notified any native mode device drivers of the end of the sleep state
transition. The working state value (0) is passed to the _TTS control method.

    So it is necessary to add the support for _TTS object. The _TTS object
will be evaluated if it exists.
    At the same time a block notifier is added to the reboot notifier list so
that the _TTS object will also be evaluated when the system shutdown.

lenb: note that as of Sep 2008, I've not yet seen _TTS in any shipping BIOS.
So this patch is to future-proof Linux, rather than fix the installed base.

http://bugzilla.kernel.org/show_bug.cgi?id=11132

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Li Shaohua <shaohua.li@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/sleep/main.c

@@ -15,6 +15,7 @@
 #include <linux/dmi.h>
 #include <linux/device.h>
 #include <linux/suspend.h>
+#include <linux/reboot.h>
 
 #include <asm/io.h>
 
@@ -24,6 +25,36 @@
 
 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
@@ -131,6 +162,7 @@ static void acpi_pm_end(void)
 	 * failing transition to a sleep state.
 	 */
 	acpi_target_sleep_state = ACPI_STATE_S0;
+	acpi_sleep_tts_switch(acpi_target_sleep_state);
 }
 #endif /* CONFIG_PM_SLEEP */
 
@@ -155,6 +187,7 @@ static int acpi_suspend_begin(suspend_state_t pm_state)
 
 	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);
@@ -313,6 +346,7 @@ void __init acpi_no_s4_hw_signature(void)
 static int acpi_hibernation_begin(void)
 {
 	acpi_target_sleep_state = ACPI_STATE_S4;
+	acpi_sleep_tts_switch(acpi_target_sleep_state);
 	return 0;
 }
 
@@ -376,7 +410,15 @@ static struct platform_hibernation_ops acpi_hibernation_ops = {
  */
 static int acpi_hibernation_begin_old(void)
 {
-	int error = acpi_sleep_prepare(ACPI_STATE_S4);
+	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)
 		acpi_target_sleep_state = ACPI_STATE_S4;
@@ -596,5 +638,10 @@ int __init acpi_sleep_init(void)
 		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);
 	return 0;
 }