On Wed, Aug 31, 2022 at 10:17 AM Robert Richter <rrichter@xxxxxxx> wrote:
>
> A lookup of a host bridge's corresponding acpi device (struct
> acpi_device) is not possible, for example:
>
> adev = ACPI_COMPANION(&host_bridge->dev);
Hmm.
x86 has this code in pcibios_root_bridge_prepare():
if (!bridge->dev.parent) {
struct pci_sysdata *sd = bridge->bus->sysdata;
ACPI_COMPANION_SET(&bridge->dev, sd->companion);
}
which should set the ACPI companion for the host bridge.
Moreover, on my x86 desktop /sys/devices/pci0000\:00/ (which is the
host bridge AFAICS) has
firmware_node -> ../LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00
so clearly the ACPI companion is there.
Are we talking about ARM64 here?
> This could be useful to find a host bridge's fwnode handle and to
> determine and call additional host bridge ACPI parameters and methods
> such as HID/CID or _UID.
>
> Make this work by linking the host bridge to its ACPI fw node.
>
> Signed-off-by: Robert Richter <rrichter@xxxxxxx>
> ---
> drivers/acpi/pci_root.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index d57cf8454b93..846c979e4c29 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -1083,6 +1083,7 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
> goto out_release_info;
>
> host_bridge = to_pci_host_bridge(bus->bridge);
> + host_bridge->dev.fwnode = acpi_fwnode_handle(device);
So this would be replacing the existing mechanism on x86, right?
> if (!(root->osc_control_set & OSC_PCI_EXPRESS_NATIVE_HP_CONTROL))
> host_bridge->native_pcie_hotplug = 0;
> if (!(root->osc_control_set & OSC_PCI_SHPC_NATIVE_HP_CONTROL))
> --
