Re: [PATCH v2 2/3] dt-bindings: arm: Add Coresight Dummy Trace YAML schema

[Rob Herring]

On Fri, Mar 24, 2023 at 02:16:07PM +0800, Hao Zhang wrote:
> Add new coresight-dummy.yaml file describing the bindings required
> to define coresight dummy trace in the device trees.

The diff tells me all this. Please explain why this is needed and needs 
to be in DT here.

> 
> Signed-off-by: Hao Zhang <quic_hazha@xxxxxxxxxxx>
> ---
>  .../bindings/arm/qcom,coresight-dummy.yaml    | 118 ++++++++++++++++++
>  1 file changed, 118 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/qcom,coresight-dummy.yaml
> 
> diff --git a/Documentation/devicetree/bindings/arm/qcom,coresight-dummy.yaml b/Documentation/devicetree/bindings/arm/qcom,coresight-dummy.yaml
> new file mode 100644
> index 000000000000..7b719b084d72
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/qcom,coresight-dummy.yaml
> @@ -0,0 +1,118 @@
> +# SPDX-License-Identifier: GPL-2.0-only or BSD-2-Clause
> +# Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved.
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/arm/qcom,coresight-dummy.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: QCOM Coresight Dummy component
> +
> +description: |
> +  The Coresight Dummy component is for the specific devices that HLOS don't have
> +  permission to access or configure. Such as Coresight sink EUD, some TPDMs etc.

EUD? TPDM?

I don't really love 'dummy' used here. Maybe the OS still wants/needs to 
know where the sink goes to even if not configurable.

You *can* have multiple compatibles for a single generic driver if those 
compatibles might be useful some day.

> +  So there need driver to register dummy devices as Coresight devices. Provide
> +  Coresight API for dummy device operations, such as enabling and disabling
> +  dummy devices. Build the Coresight path for dummy sink or dummy source for
> +  debugging.
> +
> +  The primary use case of the coresight dummy is to build path for dummy sink or
> +  dummy source.
> +
> +maintainers:
> +  - Mao Jinlong <quic_jinlmao@xxxxxxxxxxx>
> +  - Tao Zhang <quic_taozha@xxxxxxxxxxx>
> +  - Hao Zhang <quic_hazha@xxxxxxxxxxx>
> +
> +select:
> +  properties:
> +    compatible:
> +      contains:
> +        enum:
> +          - qcom,coresight-dummy
> +  required:
> +    - compatible
> +
> +properties:
> +  $nodename:
> +    pattern: "^dummy_.*(sink|source)_[0-9]+.*$"

Don't use '_' in node names.

Convention for multiple instances without 'reg' is '-[0-9]+' on the end, 
but you are allowing anything after that.

> +  compatible:
> +    items:
> +      - const: qcom,coresight-dummy
> +
> +  qcom,dummy-sink:
> +    type: boolean
> +    description:
> +      Indicates that the type of this coresight node is dummy sink.
> +
> +  qcom,dummy-source:

Incorporate source or sink into the compatible strings.

It's also somewhat redundant with 'in-ports' vs. 'out-ports'.

> +    type: boolean
> +    description:
> +      Indicates that the type of this coresight node is dummy source.
> +
> +  out-ports:
> +    description: |

Don't need '|' unless you need to preserve formatting.

> +      Output connections from the dummy source to Coresight Trace bus.
> +    $ref: /schemas/graph.yaml#/properties/ports
> +
> +    properties:
> +      port:
> +        description: Output connection from the dummy source to Coresight
> +            Trace bus.
> +        $ref: /schemas/graph.yaml#/properties/port
> +
> +  in-ports:
> +    description: |
> +      Input connections from the CoreSight Trace bus to dummy sink.
> +    $ref: /schemas/graph.yaml#/properties/ports
> +
> +    properties:
> +      port:
> +        description: Input connection from the Coresight Trace bus to
> +            dummy sink.
> +        $ref: /schemas/graph.yaml#/properties/port
> +
> +required:
> +  - compatible
> +
> +additionalProperties: false
> +
> +oneOf:
> +  - required:
> +      - qcom,dummy-sink
> +  - required:
> +      - qcom,dummy-source
> +
> +examples:
> +  # minimum dummy sink definition. dummy sink connect to coresight replicator.
> +  - |
> +    dummy_sink_1 {
> +      compatible = "qcom,coresight-dummy";
> +      qcom,dummy-sink;
> +
> +      in-ports {
> +        port {
> +          eud_in_replicator_swao: endpoint {
> +            remote-endpoint =
> +              <&replicator_swao_out_eud>;
> +          };
> +        };
> +      };
> +    };
> +
> +  # minimum dummy source definition. dummy source connect to coresight funnel.
> +  - |
> +    dummy_source_1 {
> +      compatible = "qcom,coresight-dummy";
> +      qcom,dummy-source;
> +
> +      out-ports {
> +        port {
> +          dummy_riscv_out_funnel_swao: endpoint {
> +            remote-endpoint =
> +              <&funnel_swao_in_dummy_riscv>;
> +          };
> +        };
> +      };
> +    };
> +
> +...
> -- 
> 2.17.1
>