Currently at root bridge preparation, the corresponding ACPI device will be set as the companion, however for a Hyper-V virtual PCI root bridge, there is no corresponding ACPI device, because a Hyper-V virtual PCI root bridge is discovered via VMBus rather than ACPI table. In order to support this, we need to make pcibios_root_bridge_prepare() work with cfg->parent being NULL. Use a NULL pointer as the ACPI device if there is no corresponding ACPI device, and this is fine because: 1) ACPI_COMPANION_SET() can work with the second parameter being NULL, 2) semantically, if a NULL pointer is set via ACPI_COMPANION_SET(), ACPI_COMPANION() (the read API for this field) will return NULL, and since ACPI_COMPANION() may return NULL, so users must have handled the cases where it returns NULL, and 3) since there is no corresponding ACPI device, it would be wrong to use any other value here. Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx> --- arch/arm64/kernel/pci.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c index 5148ae242780..2276689b5411 100644 --- a/arch/arm64/kernel/pci.c +++ b/arch/arm64/kernel/pci.c @@ -90,7 +90,17 @@ int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge) return 0; cfg = bridge->bus->sysdata; - adev = to_acpi_device(cfg->parent); + + /* + * On Hyper-V there is no corresponding ACPI device for a root bridge, + * therefore ->parent is set as NULL by the driver. And set 'adev' as + * NULL in this case because there is no proper ACPI device. + */ + if (!cfg->parent) + adev = NULL; + else + adev = to_acpi_device(cfg->parent); + bus_dev = &bridge->bus->dev; ACPI_COMPANION_SET(&bridge->dev, adev); -- 2.32.0
