[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 |   46 ++++++++++++++++++++++++++++++++++++++++++----
 drivers/acpi/scan.c      |    4 ++++
 include/acpi/acpi_bus.h  |    3 ++-
 3 files changed, 48 insertions(+), 5 deletions(-)

Index: linux-pm/drivers/acpi/device_pm.c
===================================================================
--- linux-pm.orig/drivers/acpi/device_pm.c
+++ linux-pm/drivers/acpi/device_pm.c
@@ -907,20 +907,44 @@ int acpi_subsys_prepare(struct device *d
 	if (dev->power.ignore_children)
 		pm_runtime_resume(dev);
 
+	pm_set_direct_resume(dev, true);
 	return pm_generic_prepare(dev);
 }
 EXPORT_SYMBOL_GPL(acpi_subsys_prepare);
 
 /**
- * acpi_subsys_suspend - Run the device driver's suspend callback.
+ * acpi_subsys_suspend - Handle device suspend stage of system suspend.
  * @dev: Device to handle.
- *
- * Follow PCI and resume devices suspended at run time before running their
- * system suspend callbacks.
  */
 int acpi_subsys_suspend(struct device *dev)
 {
+	struct acpi_device *adev = ACPI_COMPANION(dev);
+	u32 sys_target;
+
+	if (!adev || !pm_runtime_enabled_and_suspended(dev)) {
+		pm_set_direct_resume(dev, false);
+		goto out;
+	}
+	if (!pm_direct_resume_is_set(dev)
+	    || device_may_wakeup(dev) != !!adev->wakeup.prepare_count)
+		goto resume;
+
+	sys_target = acpi_target_system_state();
+	if (sys_target != ACPI_STATE_S0) {
+		int ret, state;
+
+		if (adev->power.flags.dsw_present)
+			goto resume;
+
+		ret = acpi_dev_pm_get_state(dev, adev, sys_target, NULL, &state);
+		if (!ret && state == adev->power.state)
+			return 0;
+	}
+
+ resume:
 	pm_runtime_resume(dev);
+
+ out:
 	return pm_generic_suspend(dev);
 }
 
@@ -954,6 +978,19 @@ int acpi_subsys_resume_early(struct devi
 EXPORT_SYMBOL_GPL(acpi_subsys_resume_early);
 
 /**
+ * acpi_subsys_resume - Handle device resume stage of system resume.
+ * @dev: Device to handle.
+ */
+int acpi_subsys_resume(struct device *dev)
+{
+	if (pm_direct_resume_is_set(dev)) {
+		pm_runtime_resume(dev);
+		return 0;
+	}
+	return pm_generic_resume(dev);
+}
+
+/**
  * acpi_subsys_freeze - Run the device driver's freeze callback.
  * @dev: Device to handle.
  */
@@ -982,6 +1019,7 @@ static struct dev_pm_domain acpi_general
 		.suspend = acpi_subsys_suspend,
 		.suspend_late = acpi_subsys_suspend_late,
 		.resume_early = acpi_subsys_resume_early,
+		.resume = acpi_subsys_resume,
 		.freeze = acpi_subsys_freeze,
 		.poweroff = acpi_subsys_suspend,
 		.poweroff_late = acpi_subsys_suspend_late,
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
 	 */