From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> In some cases acpi_pci_find_companion() returns an incorrect device object as the ACPI companion for device 0 on the root bus (bus 0). On the affected systems that device is the PCI interface to the host bridge and the "ACPI companion" returned for it corresponds to a non-PCI device located in the SoC (e.g. a sensor on an I2C bus). As a result of this, the ACPI device object "attached" to PCI device 00:00.0 cannot be used for enumerating the device that is really represented by it which (of course) is problematic. Address that issue by preventing acpi_pci_find_companion() from returning a device object with a valid _HID (which by the spec should not be present uder ACPI device objects corresponding to PCI devices) for PCI device 00:00.0. Link: https://lore.kernel.org/linux-acpi/1409ba0c-1580-dc09-e6fe-a0c9bcda6462@xxxxxxxxx/ Reported-by: Daniel Scally <djrscally@xxxxxxxxx> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> --- drivers/pci/pci-acpi.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) Index: linux-pm/drivers/pci/pci-acpi.c =================================================================== --- linux-pm.orig/drivers/pci/pci-acpi.c +++ linux-pm/drivers/pci/pci-acpi.c @@ -1162,14 +1162,32 @@ void acpi_pci_remove_bus(struct pci_bus static struct acpi_device *acpi_pci_find_companion(struct device *dev) { struct pci_dev *pci_dev = to_pci_dev(dev); + struct acpi_device *adev; bool check_children; u64 addr; check_children = pci_is_bridge(pci_dev); /* Please ref to ACPI spec for the syntax of _ADR */ addr = (PCI_SLOT(pci_dev->devfn) << 16) | PCI_FUNC(pci_dev->devfn); - return acpi_find_child_device(ACPI_COMPANION(dev->parent), addr, + adev = acpi_find_child_device(ACPI_COMPANION(dev->parent), addr, check_children); + /* + * There may be ACPI device objects in the ACPI namespace that are + * children of the device object representing the host bridge, but don't + * represent PCI devices. Both _HID and _ADR may be present for them, + * even though that is against the specification (for example, see + * Section 6.1 of ACPI 6.3), but in many cases the _ADR returns 0 which + * appears to indicate that they should not be taken into consideration + * as potential companions of PCI devices on the root bus. + * + * To catch this special case, disregard the returned device object if + * it has a valid _HID, addr is 0 and the PCI device at hand is on the + * root bus. + */ + if (adev && adev->pnp.type.platform_id && !addr && !pci_dev->bus->parent) + return NULL; + + return adev; } /**
