[RFC PATCH 6/7] dt-bindings: arm: Add virtio transport for SCMI

[Rob Herring]

On Fri, Sep 18, 2020 at 06:55:58PM +0200, Peter Hilber wrote:
> From: Igor Skalkin <igor.skalkin at opensynergy.com>
> 
> Document the properties for arm,scmi-virtio compatible nodes. The
> backing virtio SCMI device is described in patch [1].
> 
> [1] https://lists.oasis-open.org/archives/virtio-comment/202005/msg00096.html
> 
> Co-developed-by: Peter Hilber <peter.hilber at opensynergy.com>
> Signed-off-by: Peter Hilber <peter.hilber at opensynergy.com>
> Signed-off-by: Igor Skalkin <igor.skalkin at opensynergy.com>
> ---
>  .../devicetree/bindings/arm/arm,scmi.txt      | 38 ++++++++++++++++++-
>  1 file changed, 36 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/arm/arm,scmi.txt b/Documentation/devicetree/bindings/arm/arm,scmi.txt
> index 55deb68230eb..844ff3c40a49 100644
> --- a/Documentation/devicetree/bindings/arm/arm,scmi.txt
> +++ b/Documentation/devicetree/bindings/arm/arm,scmi.txt
> @@ -13,6 +13,9 @@ the device tree.
>  Required properties:
>  
>  The scmi node with the following properties shall be under the /firmware/ node.
> +Some properties are specific to a transport type.
> +
> +shmem-based transports (mailbox, smc/hvc):
>  
>  - compatible : shall be "arm,scmi" or "arm,scmi-smc" for smc/hvc transports
>  - mboxes: List of phandle and mailbox channel specifiers. It should contain
> @@ -21,6 +24,17 @@ The scmi node with the following properties shall be under the /firmware/ node.
>  	  supported.
>  - shmem : List of phandle pointing to the shared memory(SHM) area as per
>  	  generic mailbox client binding.
> +
> +Virtio transport:
> +
> +- compatible : shall be "arm,scmi-virtio".
> +- virtio_transport : phandle of the virtio device. This device must support one
> +                     virtqueue for transmitting commands ("tx", cmdq), and,
> +		     optionally, one more virtqueue for receiving notifications
> +		     and delayed responses ("rx", eventq).

Isn't what the virtio device provides discoverable? We don't have virtio 
protocols in DT for anything else. Why is SCMI special?

Rob