[RFC][PATCH 3/3] ACPI / PM: Avoid resuming devices in ACPI PM domain during system suspend

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Rework the ACPI PM domain's PM callbacks to avoid resuming devices
during system suspend (in order to modify their wakeup settings etc.)
if that isn't necessary.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/acpi/device_pm.c |   43 ++++++++++++++++++++++++++++++++++++-------
 1 file changed, 36 insertions(+), 7 deletions(-)

Index: linux-pm/include/acpi/acpi_bus.h
===================================================================
--- linux-pm.orig/include/acpi/acpi_bus.h
+++ linux-pm/include/acpi/acpi_bus.h
@@ -261,7 +261,8 @@ struct acpi_device_power_flags {
 	u32 inrush_current:1;	/* Serialize Dx->D0 */
 	u32 power_removed:1;	/* Optimize Dx->D0 */
 	u32 ignore_parent:1;	/* Power is independent of parent power state */
-	u32 reserved:27;
+	u32 dsw_present:1;	/* _DSW present? */
+	u32 reserved:26;
 };
 
 struct acpi_device_power_state {
Index: linux-pm/drivers/acpi/scan.c
===================================================================
--- linux-pm.orig/drivers/acpi/scan.c
+++ linux-pm/drivers/acpi/scan.c
@@ -1551,9 +1551,13 @@ static void acpi_bus_get_power_flags(str
 	 */
 	if (acpi_has_method(device->handle, "_PSC"))
 		device->power.flags.explicit_get = 1;
+
 	if (acpi_has_method(device->handle, "_IRC"))
 		device->power.flags.inrush_current = 1;
 
+	if (acpi_has_method(device->handle, "_DSW"))
+		device->power.flags.dsw_present = 1;
+
 	/*
 	 * Enumerate supported power management states
 	 */
Index: linux-pm/drivers/acpi/device_pm.c
===================================================================
--- linux-pm.orig/drivers/acpi/device_pm.c
+++ linux-pm/drivers/acpi/device_pm.c
@@ -900,18 +900,46 @@ EXPORT_SYMBOL_GPL(acpi_dev_resume_early)
  */
 int acpi_subsys_prepare(struct device *dev)
 {
-	/*
-	 * Devices having power.ignore_children set may still be necessary for
-	 * suspending their children in the next phase of device suspend.
-	 */
-	if (dev->power.ignore_children)
-		pm_runtime_resume(dev);
+	struct acpi_device *adev = ACPI_COMPANION(dev);
+	u32 sys_target;
+	int ret, state;
+
+	ret = pm_generic_prepare(dev);
+	if (ret < 0)
+		return ret;
+
+	if (!adev || !pm_runtime_suspended(dev)
+	    || device_may_wakeup(dev) != !!adev->wakeup.prepare_count)
+		return 0;
+
+	sys_target = acpi_target_system_state();
+	if (sys_target == ACPI_STATE_S0)
+		return 1;
+
+	if (adev->power.flags.dsw_present)
+		return 0;
 
-	return pm_generic_prepare(dev);
+	ret = acpi_dev_pm_get_state(dev, adev, sys_target, NULL, &state);
+	return !ret && state == adev->power.state;
 }
 EXPORT_SYMBOL_GPL(acpi_subsys_prepare);
 
 /**
+ * acpi_subsys_complete - Finalize device's resume during system resume.
+ * @dev: Device to handle.
+ */
+void acpi_subsys_complete(struct device *dev)
+{
+	/*
+	 * If the device had been runtime-suspended before the system went into
+	 * the sleep state it is going out of and it has never been resumed till
+	 * now, resume it in case the firmware powered it up.
+	 */
+	if (dev->power.direct_complete)
+		pm_request_resume(dev);
+}
+
+/**
  * acpi_subsys_suspend - Run the device driver's suspend callback.
  * @dev: Device to handle.
  *
@@ -979,6 +1007,7 @@ static struct dev_pm_domain acpi_general
 #endif
 #ifdef CONFIG_PM_SLEEP
 		.prepare = acpi_subsys_prepare,
+		.complete = acpi_subsys_complete,
 		.suspend = acpi_subsys_suspend,
 		.suspend_late = acpi_subsys_suspend_late,
 		.resume_early = acpi_subsys_resume_early,