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PCI/ACPI: Fix companion lookup for device 0 on the root bus
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. [bhelgaas: use pci_is_root_bus()] Link: https://lore.kernel.org/linux-acpi/1409ba0c-1580-dc09-e6fe-a0c9bcda6462@gmail.com/ Link: https://lore.kernel.org/r/4673285.9aE2nYKHPr@kreacher Reported-by: Daniel Scally <djrscally@gmail.com> Tested-by: Daniel Scally <djrscally@gmail.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Daniel Scally <djrscally@gmail.com>
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@ -1162,14 +1162,34 @@ void acpi_pci_remove_bus(struct pci_bus *bus)
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static struct acpi_device *acpi_pci_find_companion(struct device *dev)
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{
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struct pci_dev *pci_dev = to_pci_dev(dev);
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struct acpi_device *adev;
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bool check_children;
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u64 addr;
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check_children = pci_is_bridge(pci_dev);
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/* Please ref to ACPI spec for the syntax of _ADR */
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addr = (PCI_SLOT(pci_dev->devfn) << 16) | PCI_FUNC(pci_dev->devfn);
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return acpi_find_child_device(ACPI_COMPANION(dev->parent), addr,
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adev = acpi_find_child_device(ACPI_COMPANION(dev->parent), addr,
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check_children);
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/*
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* There may be ACPI device objects in the ACPI namespace that are
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* children of the device object representing the host bridge, but don't
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* represent PCI devices. Both _HID and _ADR may be present for them,
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* even though that is against the specification (for example, see
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* Section 6.1 of ACPI 6.3), but in many cases the _ADR returns 0 which
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* appears to indicate that they should not be taken into consideration
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* as potential companions of PCI devices on the root bus.
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*
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* To catch this special case, disregard the returned device object if
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* it has a valid _HID, addr is 0 and the PCI device at hand is on the
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* root bus.
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*/
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if (adev && adev->pnp.type.platform_id && !addr &&
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pci_is_root_bus(pci_dev->bus))
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return NULL;
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return adev;
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}
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/**
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