[RFC][PATCH 4/7] ACPI Suspend: Call _PTS before suspending devices

["Rafael J. Wysocki" <rjw@sisk.pl>]

From: Rafael J. Wysocki <rjw@sisk.pl>

The ACPI 1.0 specification wants us to put devices into low power
states after executing the _PTS global control methods, while ACPI
2.0 and later want us to do that in the reverse order.  The current
suspend code follows ACPI 2.0 in that respect which causes some
ACPI 1.0x systems to hang during suspend (ref.
http://bugzilla.kernel.org/show_bug.cgi?id=9528).

Make the suspend code execute _PTS before putting devices into low
power (ie. in accordance with ACPI 1.0x) and provide a command line
option to override the default if need be.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 Documentation/kernel-parameters.txt |    5 +++
 drivers/acpi/sleep/main.c           |   51 ++++++++++++++++++++++++++----------
 2 files changed, 43 insertions(+), 13 deletions(-)

Index: linux-2.6/drivers/acpi/sleep/main.c
===================================================================
--- linux-2.6.orig/drivers/acpi/sleep/main.c
+++ linux-2.6/drivers/acpi/sleep/main.c
@@ -26,6 +26,21 @@ u8 sleep_states[ACPI_S_STATE_COUNT];
 
 #ifdef CONFIG_PM_SLEEP
 static u32 acpi_target_sleep_state = ACPI_STATE_S0;
+static bool acpi_sleep_finish_wake_up;
+
+/*
+ * ACPI 2.0 and later want us to execute _PTS after suspending devices, so we
+ * allow the user to request that behavior by using the 'acpi_new_pts_ordering'
+ * kernel command line option that causes the following variable to be set.
+ */
+static bool new_pts_ordering;
+
+static int __init acpi_new_pts_ordering(char *str)
+{
+	new_pts_ordering = true;
+	return 1;
+}
+__setup("acpi_new_pts_ordering", acpi_new_pts_ordering);
 #endif
 
 int acpi_sleep_prepare(u32 acpi_state)
@@ -74,6 +89,14 @@ static int acpi_pm_open(suspend_state_t 
 
 	if (sleep_states[acpi_state]) {
 		acpi_target_sleep_state = acpi_state;
+		if (new_pts_ordering)
+			return 0;
+
+		error = acpi_sleep_prepare(acpi_state);
+		if (error)
+			acpi_target_sleep_state = ACPI_STATE_S0;
+		else
+			acpi_sleep_finish_wake_up = true;
 	} else {
 		printk(KERN_ERR "ACPI does not support this state: %d\n",
 			pm_state);
@@ -91,15 +114,17 @@ static int acpi_pm_open(suspend_state_t 
 
 static int acpi_pm_prepare(void)
 {
-	int error;
+	if (new_pts_ordering) {
+		int error = acpi_sleep_prepare(acpi_target_sleep_state);
 
-	error = acpi_sleep_prepare(acpi_target_sleep_state);
-	if (error)
-		acpi_target_sleep_state = ACPI_STATE_S0;
-	else if (!ACPI_SUCCESS(acpi_hw_disable_all_gpes()))
-		error = -EFAULT;
+		if (error) {
+			acpi_target_sleep_state = ACPI_STATE_S0;
+			return error;
+		}
+		acpi_sleep_finish_wake_up = true;
+	}
 
-	return error;
+	return ACPI_SUCCESS(acpi_hw_disable_all_gpes()) ? 0 : -EFAULT;
 }
 
 /**
@@ -123,10 +148,8 @@ static int acpi_pm_enter(suspend_state_t
 	if (acpi_state == ACPI_STATE_S3) {
 		int error = acpi_save_state_mem();
 
-		if (error) {
-			acpi_target_sleep_state = ACPI_STATE_S0;
+		if (error)
 			return error;
-		}
 	}
 
 	local_irq_save(flags);
@@ -187,6 +210,7 @@ static void acpi_pm_finish(void)
 	acpi_set_firmware_waking_vector((acpi_physical_address) 0);
 
 	acpi_target_sleep_state = ACPI_STATE_S0;
+	acpi_sleep_finish_wake_up = false;
 
 #ifdef CONFIG_X86
 	if (init_8259A_after_S1) {
@@ -203,10 +227,11 @@ static void acpi_pm_finish(void)
 static void acpi_pm_close(void)
 {
 	/*
-	 * This is necessary in case acpi_pm_finish() is not called during a
-	 * failing transition to a sleep state.
+	 * This is necessary in case acpi_pm_finish() is not called directly
+	 * during a failing transition to a sleep state.
 	 */
-	acpi_target_sleep_state = ACPI_STATE_S0;
+	if (acpi_sleep_finish_wake_up)
+		acpi_pm_finish();
 }
 
 static int acpi_pm_state_valid(suspend_state_t pm_state)
Index: linux-2.6/Documentation/kernel-parameters.txt
===================================================================
--- linux-2.6.orig/Documentation/kernel-parameters.txt
+++ linux-2.6/Documentation/kernel-parameters.txt
@@ -167,6 +167,11 @@ and is between 256 and 4096 characters. 
 	acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
 			Format: <irq>,<irq>...
 
+	acpi_new_pts_ordering [HW,ACPI]
+			Enforce the ACPI 2.0 ordering of the _PTS control
+			method wrt putting devices into low power states
+			default: pre ACPI 2.0 ordering of _PTS
+
 	acpi_no_auto_ssdt	[HW,ACPI] Disable automatic loading of SSDT
 
 	acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS