PCI/ACPI: Fix companion lookup for device 0 on the root bus (aa0b1574) · Commits · 戴 / test

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>

drivers/pci/pci-acpi.c

+21 −1

Original line number	Diff line number	Diff line
		@@ -1162,14 +1162,34 @@ void acpi_pci_remove_bus(struct pci_bus *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_is_root_bus(pci_dev->bus))
		return NULL;

		return adev;
		}

		/**

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