[PATCH] ACPI / hotplug / PCI: Runtime resume bridges before bus rescans

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

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

If a PCI bridge (or PCIe port) that is runtime-suspended gets an
ACPI hotplug notification, such as a bus check, it has to be resumed
before re-scanning the devices below it, or those devices will not
be accessible and will be treated as hot-removed.

Make that happen and let the bridge suspend again after the bus
below it has been re-scanned.

This is a replacement for commit 16468c783cb4 (ACPI / hotplug / PCI:
Runtime resume bridge before rescan) that has been reverted,
because it introduced a system resume regression (due to missing
bridge->pci_dev checks that are necessary in case the notification
is targeted at the host bridge) and it is necessary for the code
added by commit 006d44e49a25 (PCI: Add runtime PM support for PCIe
ports) to work as expected.

Tested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/pci/hotplug/acpiphp_glue.c |    6 ++++++
 1 file changed, 6 insertions(+)

Index: linux-pm/drivers/pci/hotplug/acpiphp_glue.c
===================================================================
--- linux-pm.orig/drivers/pci/hotplug/acpiphp_glue.c
+++ linux-pm/drivers/pci/hotplug/acpiphp_glue.c
@@ -675,6 +675,9 @@ static void acpiphp_check_bridge(struct
 	if (bridge->is_going_away)
 		return;
 
+	if (bridge->pci_dev)
+		pm_runtime_get_sync(&bridge->pci_dev->dev);
+
 	list_for_each_entry(slot, &bridge->slots, node) {
 		struct pci_bus *bus = slot->bus;
 		struct pci_dev *dev, *tmp;
@@ -694,6 +697,9 @@ static void acpiphp_check_bridge(struct
 			disable_slot(slot);
 		}
 	}
+
+	if (bridge->pci_dev)
+		pm_runtime_put(&bridge->pci_dev->dev);
 }
 
 /*