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

Elliot Berman
2022-10-13T23:59:18Z

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@quicinc.com>
>> ---
>> .../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@quicinc.com>
>> + - Elliot Berman <quic_eberman@quicinc.com>
>> +
>> +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@quicinc.com>
>> M: Murali Nalajala <quic_mnalajal@quicinc.com>
>> L: linux-arm-msm@vger.kernel.org
>> S: Supported
>> +F: Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
>> F: Documentation/virt/gunyah/
>>
>> HABANALABS PCI DRIVER
>> --
>> 2.25.1
>>
>>