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

[Rafael J. Wysocki]

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

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

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
 drivers/acpi/device_pm.c |   31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

Index: linux-pm/drivers/acpi/device_pm.c
===================================================================
--- linux-pm.orig/drivers/acpi/device_pm.c
+++ linux-pm/drivers/acpi/device_pm.c
@@ -812,6 +812,13 @@ int acpi_dev_runtime_resume(struct devic
 	struct acpi_device *adev = acpi_dev_pm_get_node(dev);
 	int error;
 
+	/*
+	 * This only matters during system suspend, if acpi_subsys_prepare()
+	 * has returned 1.  In that case, we may be resumed through a child
+	 * runtime resume, in which case our system suspend callbacks will need
+	 * to be executed, so power.no_suspend has to be cleared.
+	 */
+	dev->power.no_suspend = false;
 	if (!adev)
 		return 0;
 
@@ -912,12 +919,28 @@ EXPORT_SYMBOL_GPL(acpi_dev_resume_early)
  */
 int acpi_subsys_prepare(struct device *dev)
 {
+	struct acpi_device *adev = acpi_dev_pm_get_node(dev);
+	u32 target_state;
+	int error, state;
+
+	if (!adev || !pm_runtime_enabled_and_suspended(dev))
+		return pm_generic_prepare(dev);
+
+	target_state = acpi_target_system_state();
+	error = acpi_dev_pm_get_state(dev, adev, target_state, NULL, &state);
+	if (error || state != adev->power.state
+	    || device_may_wakeup(dev) != !!adev->wakeup.prepare_count) {
+		pm_runtime_resume(dev);
+		return pm_generic_prepare(dev);
+	}
 	/*
-	 * Follow PCI and resume devices suspended at run time before running
-	 * their system suspend callbacks.
+	 * If this is a wakeup device, wakeup power has been enabled already for
+	 * it during the preceding runtime suspend.  Caveat: "sleep state" is
+	 * one of the _DSW arguments, but that shouldn't matter for the devices
+	 * using acpi_general_pm_domain.
 	 */
-	pm_runtime_resume(dev);
-	return pm_generic_prepare(dev);
+	error =  pm_generic_prepare(dev);
+	return error ? error : 1;
 }
 EXPORT_SYMBOL_GPL(acpi_subsys_prepare);
 

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