Re: [PATCH v5 02/13] dt-bindings: Add binding for gunyah hypervisor

[Elliot Berman]

On 10/12/2022 8:56 AM, Rob Herring wrote:
> On Mon, Oct 10, 2022 at 05:08:29PM -0700, Elliot Berman wrote:
> > When Linux is booted as a guest under the Gunyah hypervisor, the Gunyah
> > 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.
> >
> > Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
> > ---
> >   .../bindings/firmware/gunyah-hypervisor.yaml  | 87 +++++++++++++++++++
> >   MAINTAINERS                                   |  1 +
> >   2 files changed, 88 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 000000000000..f0a14101e2fd
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
> > @@ -0,0 +1,87 @@
> > +# 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:
> > +  - Murali Nalajala <quic_mnalajal@xxxxxxxxxxx>
> > +  - Elliot Berman <quic_eberman@xxxxxxxxxxx>
> > +
> > +description: |+
> > +  On systems which support devicetree, Gunyah generates and overlays a deviceetree overlay which
>
> How you end up with the node (applying an overlay) is not relavent to
> the binding.
>
> > +  describes the basic configuration of the hypervisor. Virtual machines use this information to determine
> > +  the capability IDs of the message queues used to communicate with the Gunyah Resource Manager.
>
> Wrap at 80. That is the coding standard still though 100 is deemed
> allowed. And yamllint only complains at 110 because I didn't care to fix
> everyones lines over 100.
>
> > +  See also: https://github.com/quic/gunyah-resource-manager/blob/develop/src/vm_creation/dto_construct.c
> > +
> > +properties:
> > +  compatible:
> > +    items:
> > +      - const: gunyah-hypervisor-1.0
> > +      - const: gunyah-hypervisor
>
> 2 compatibles implies a difference between the 2. What's the difference?
> Where does '1.0' come from?

There's no difference. I thought the convention was to have 
device-specific compatible and the generic compatible. "device-specific" 
here would be specific to version of Gunyah since it's software.

We do similar for firmware in the qcom,scm bindings and following that 
principle.

> > +
> > +  "#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:
> > +        items:
> > +          - const: gunyah-resource-manager-1-0
> > +          - const: gunyah-resource-manager
>
> Same comment here.
>
> > +
> > +      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-1.0", "gunyah-hypervisor";
> > +
> > +        gunyah-resource-mgr@0 {
> > +            compatible = "gunyah-resource-manager-1-0", "gunyah-resource-manager";
> > +            interrupts = <GIC_SPI 3 IRQ_TYPE_EDGE_RISING>, /* TX full IRQ */
> > +                         <GIC_SPI 4 IRQ_TYPE_EDGE_RISING>; /* RX empty IRQ */
> > +            reg = <0x00000000 0x00000000>, <0x00000000 0x00000001>;
> > +                  /* TX, RX cap ids */
> > +        };
> > +    };
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 91d00b00d91c..ef6de7599d98 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -8884,6 +8884,7 @@ M:	Elliot Berman <quic_eberman@xxxxxxxxxxx>
> >   M:	Murali Nalajala <quic_mnalajal@xxxxxxxxxxx>
> >   L:	linux-arm-msm@xxxxxxxxxxxxxxx
> >   S:	Supported
> > +F:	Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
> >   F:	Documentation/virt/gunyah/
> >   
> >   HABANALABS PCI DRIVER
> > --
> > 2.25.1