Re: [PATCH v14 02/25] dt-bindings: Add binding for gunyah hypervisor

[Bjorn Andersson]

On Tue, Jun 13, 2023 at 10:20:30AM -0700, Elliot Berman wrote:
> When Linux is booted as a guest under the Gunyah hypervisor, the Gunyah

Is this unique to the case of booting Linux?

> Resource Manager applies a devicetree overlay describing the virtual
> platform configuration of the guest VM, such as the message queue
> capability IDs for communicating with the Resource Manager. This
> information is not otherwise discoverable by a VM: the Gunyah hypervisor
> core does not provide a direct interface to discover capability IDs nor
> a way to communicate with RM without having already known the
> corresponding message queue capability ID. Add the DT bindings that
> Gunyah adheres for the hypervisor node and message queues.
> 
> Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
> Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
> ---
>  .../bindings/firmware/gunyah-hypervisor.yaml  | 82 +++++++++++++++++++
>  1 file changed, 82 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
> 
> diff --git a/Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml b/Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
> new file mode 100644
> index 0000000000000..3fc0b043ac3cf
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
> @@ -0,0 +1,82 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/firmware/gunyah-hypervisor.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Gunyah Hypervisor
> +
> +maintainers:
> +  - Prakruthi Deepak Heragu <quic_pheragu@xxxxxxxxxxx>
> +  - Elliot Berman <quic_eberman@xxxxxxxxxxx>
> +
> +description: |+
> +  Gunyah virtual machines use this information to determine the capability IDs
> +  of the message queues used to communicate with the Gunyah Resource Manager.
> +  See also: https://github.com/quic/gunyah-resource-manager/blob/develop/src/vm_creation/dto_construct.c
> +
> +properties:
> +  compatible:
> +    const: gunyah-hypervisor
> +
> +  "#address-cells":
> +    description: Number of cells needed to represent 64-bit capability IDs.
> +    const: 2
> +
> +  "#size-cells":
> +    description: must be 0, because capability IDs are not memory address
> +                  ranges and do not have a size.
> +    const: 0
> +
> +patternProperties:
> +  "^gunyah-resource-mgr(@.*)?":
> +    type: object
> +    description:
> +      Resource Manager node which is required to communicate to Resource
> +      Manager VM using Gunyah Message Queues.
> +
> +    properties:
> +      compatible:
> +        const: gunyah-resource-manager
> +
> +      reg:
> +        items:
> +          - description: Gunyah capability ID of the TX message queue
> +          - description: Gunyah capability ID of the RX message queue
> +
> +      interrupts:
> +        items:
> +          - description: Interrupt for the TX message queue
> +          - description: Interrupt for the RX message queue
> +
> +    additionalProperties: false
> +
> +    required:
> +      - compatible
> +      - reg
> +      - interrupts
> +
> +additionalProperties: false
> +
> +required:
> +  - compatible
> +  - "#address-cells"
> +  - "#size-cells"
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +
> +    hypervisor {
> +        #address-cells = <2>;
> +        #size-cells = <0>;
> +        compatible = "gunyah-hypervisor";

It's typical to carry the compatible first among the properties.

Unrelated to the binding itself, I don't see any code that matches this
compatible, and as such will probe the resource manager. What am I
missing?

> +
> +        gunyah-resource-mgr@0 {
> +            compatible = "gunyah-resource-manager";
> +            interrupts = <GIC_SPI 3 IRQ_TYPE_EDGE_RISING>, /* TX full IRQ */

This is the "Tx no longer full IRQ", so the comment is misleading.

> +                         <GIC_SPI 4 IRQ_TYPE_EDGE_RISING>; /* RX empty IRQ */

And this irq seems to fire when there's data in the RX queue, not when
it's empty...

> +            reg = <0x00000000 0x00000000>, <0x00000000 0x00000001>;
> +                  /* TX, RX cap ids */

Wrapping this differently will make the comments more useful.

Regards,
Bjorn

> +        };
> +    };
> -- 
> 2.40.0
>