Re: [RFC PATCH v3 10/12] dt-bindings: arm: Add virtio transport for SCMI

From: Rob Herring
Date: Mon May 17 2021 - 17:39:23 EST


On Tue, May 11, 2021 at 02:20:38AM +0200, Peter Hilber wrote:
> From: Igor Skalkin <igor.skalkin@xxxxxxxxxxxxxxx>
>
> 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
>
> Signed-off-by: Igor Skalkin <igor.skalkin@xxxxxxxxxxxxxxx>
> [ Peter: Adapted patch for submission to upstream. ]
> Co-developed-by: Peter Hilber <peter.hilber@xxxxxxxxxxxxxxx>
> Signed-off-by: Peter Hilber <peter.hilber@xxxxxxxxxxxxxxx>
> ---
> .../devicetree/bindings/arm/arm,scmi.txt | 35 +++++++++++++++++--
> 1 file changed, 33 insertions(+), 2 deletions(-)

Seems like it may not be perfectly clear what properties apply or not
for the different transports. Can you convert this to DT schema first.

>
> diff --git a/Documentation/devicetree/bindings/arm/arm,scmi.txt b/Documentation/devicetree/bindings/arm/arm,scmi.txt
> index 667d58e0a659..5d209ba666f6 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 +24,15 @@ 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".
> +
> +The virtio transport only supports a single device.
> +
> +Additional required properties:
> +
> - #address-cells : should be '1' if the device has sub-nodes, maps to
> protocol identifier for a given sub-node.
> - #size-cells : should be '0' as 'reg' property doesn't have any size
> @@ -50,7 +62,8 @@ Each protocol supported shall have a sub-node with corresponding compatible
> as described in the following sections. If the platform supports dedicated
> communication channel for a particular protocol, the 3 properties namely:
> mboxes, mbox-names and shmem shall be present in the sub-node corresponding
> -to that protocol.
> +to that protocol. The virtio transport does not support dedicated communication
> +channels.
>
> Clock/Performance bindings for the clocks/OPPs based on SCMI Message Protocol
> ------------------------------------------------------------
> @@ -129,7 +142,8 @@ Required sub-node properties:
> [5] Documentation/devicetree/bindings/reset/reset.txt
> [6] Documentation/devicetree/bindings/regulator/regulator.yaml
>
> -Example:
> +Example (mailbox transport):
> +----------------------------
>
> sram@50000000 {
> compatible = "mmio-sram";
> @@ -237,3 +251,20 @@ thermal-zones {
> ...
> };
> };
> +
> +Example (virtio transport):
> +---------------------------
> +
> +virtio_mmio@4b001000 {
> + compatible = "virtio,mmio";
> + ...
> +};
> +
> +firmware {
> + ...
> + scmi {
> + compatible = "arm,scmi-virtio";
> + ...
> +
> +The rest is similar to the mailbox transport example, when omitting the
> +mailbox/shmem-specific properties.
> --
> 2.25.1
>
>