Re: [PATCH v2] xen: workaround missing device_type property in pci/pcie nodes

[Julien Grall <julien@xxxxxxx>]

On 09/02/2021 19:53, Stefano Stabellini wrote:
> PCI buses differ from default buses in a few important ways, so it is
> important to detect them properly. Normally, PCI buses are expected to
> have the following property:
>
>      device_type = "pci"
>
> In reality, it is not always the case. To handle PCI bus nodes that
> don't have the device_type property, also consider the node name: if the
> node name is "pcie" or "pci" then consider the bus as a PCI bus.
>
> This commit is based on the Linux kernel commit
> d1ac0002dd29 "of: address: Work around missing device_type property in
> pcie nodes".
>
> This fixes Xen boot on RPi4. Some RPi4 kernels have the following node
> on their device trees:
>
> &pcie0 {
>         pci@1,0 {
>                 #address-cells = <3>;
>                 #size-cells = <2>;
>                 ranges;
>
>                 reg = <0 0 0 0 0>;
>
>                 usb@1,0 {
>                                 reg = <0x10000 0 0 0 0>;
>                                 resets = <&reset 
> RASPBERRYPI_FIRMWARE_RESET_ID_USB>;
>                 };
>         };
> };
>
> The pci@1,0 node is a PCI bus. If we parse the node and its children as
> a default bus, the reg property under usb@1,0 would have to be
> interpreted as an address range mappable by the CPU, which is not the
> case and would break.
>
> Link: https://lore.kernel.org/xen-devel/YBmQQ3Tzu++AadKx@xxxxxxxxxxxxxxxx/
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
Acked-by: Julien Grall <jgrall@xxxxxxxxxx>

Cheers,

--
Julien Grall