From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> The initial configuration of ACPI power resources on some systems implies that some PCI devices on them are initially in D3cold. In some cases, especially for PCIe Root Ports, this is a "logical" D3cold, meaning that the configuration space of the device is accessible, but some of its functionality may be missing, but it very well may be real D3cold, in which case the device will not be accessible at all. However, the PCI bus type driver will need to access its configuration space in order to enumerate it. To prevent possible device enumeration failures that may ensue as a result of ACPI power resources being initially in the "off" state, power up all children of the host bridge ACPI device object that hold valid _ADR objects (which indicates that they will be enumerated by the PCI bus type driver) and do that to all children of the ACPI device objects corresponding to PCI bridges (including PCIe ports). Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> --- drivers/acpi/pci_root.c | 2 ++ drivers/pci/pci-acpi.c | 3 +++ 2 files changed, 5 insertions(+) Index: linux-pm/drivers/acpi/pci_root.c =================================================================== --- linux-pm.orig/drivers/acpi/pci_root.c +++ linux-pm/drivers/acpi/pci_root.c @@ -927,6 +927,8 @@ struct pci_bus *acpi_pci_root_create(str host_bridge->preserve_config = 1; ACPI_FREE(obj); + acpi_dev_power_up_children_with_adr(device); + pci_scan_child_bus(bus); pci_set_host_bridge_release(host_bridge, acpi_pci_root_release_info, info); Index: linux-pm/drivers/pci/pci-acpi.c =================================================================== --- linux-pm.orig/drivers/pci/pci-acpi.c +++ linux-pm/drivers/pci/pci-acpi.c @@ -1374,6 +1374,9 @@ void pci_acpi_setup(struct device *dev, acpi_pci_wakeup(pci_dev, false); acpi_device_power_add_dependent(adev, dev); + + if (pci_is_bridge(pci_dev)) + acpi_dev_power_up_children_with_adr(adev); } void pci_acpi_cleanup(struct device *dev, struct acpi_device *adev)
