linux-kernel - Re: [PATCH V3 06/14] dts: bindings: Document device tree bindings for ETE

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Date:   Tue, 9 Feb 2021 13:00:31 -0600
From:   Rob Herring <robh@...nel.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, coresight@...ts.linaro.org,
        mathieu.poirier@...aro.org, suzuki.poulose@....com,
        mike.leach@...aro.org, lcherian@...vell.com,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH V3 06/14] dts: bindings: Document device tree bindings
 for ETE

On Wed, Jan 27, 2021 at 02:25:30PM +0530, Anshuman Khandual wrote:
> From: Suzuki K Poulose <suzuki.poulose@....com>
> 
> Document the device tree bindings for Embedded Trace Extensions.
> ETE can be connected to legacy coresight components and thus
> could optionally contain a connection graph as described by
> the CoreSight bindings.
> 
> Cc: devicetree@...r.kernel.org
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Cc: Mike Leach <mike.leach@...aro.org>
> Cc: Rob Herring <robh@...nel.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
> Changes in V3:
> 
> - Fixed all DT yaml semantics problems
> 
>  Documentation/devicetree/bindings/arm/ete.yaml | 74 ++++++++++++++++++++++++++
>  1 file changed, 74 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/ete.yaml
> 
> diff --git a/Documentation/devicetree/bindings/arm/ete.yaml b/Documentation/devicetree/bindings/arm/ete.yaml
> new file mode 100644
> index 0000000..edc1fe2
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/ete.yaml
> @@ -0,0 +1,74 @@
> +# SPDX-License-Identifier: GPL-2.0-only or BSD-2-Clause
> +# Copyright 2021, Arm Ltd
> +%YAML 1.2
> +---
> +$id: "http://devicetree.org/schemas/arm/ete.yaml#"
> +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> +
> +title: ARM Embedded Trace Extensions
> +
> +maintainers:
> +  - Suzuki K Poulose <suzuki.poulose@....com>
> +  - Mathieu Poirier <mathieu.poirier@...aro.org>
> +
> +description: |
> +  Arm Embedded Trace Extension(ETE) is a per CPU trace component that
> +  allows tracing the CPU execution. It overlaps with the CoreSight ETMv4
> +  architecture and has extended support for future architecture changes.
> +  The trace generated by the ETE could be stored via legacy CoreSight
> +  components (e.g, TMC-ETR) or other means (e.g, using a per CPU buffer
> +  Arm Trace Buffer Extension (TRBE)). Since the ETE can be connected to
> +  legacy CoreSight components, a node must be listed per instance, along
> +  with any optional connection graph as per the coresight bindings.
> +  See bindings/arm/coresight.txt.
> +
> +properties:
> +  $nodename:
> +    pattern: "^ete([0-9a-f]+)$"
> +  compatible:
> +    items:
> +      - const: arm,embedded-trace-extension
> +
> +  cpu:

We've already established 'cpus' for this purpose.

> +    description: |
> +      Handle to the cpu this ETE is bound to.
> +    $ref: /schemas/types.yaml#/definitions/phandle
> +
> +  out-ports:
> +    type: object

Replace with: $ref: /schemas/graph.yaml#/properties/ports

> +    description: |
> +      Output connections from the ETE to legacy CoreSight trace bus.
> +    properties:
> +      port:
> +        $ref: /schemas/graph.yaml#/properties/port

Actually, if only 1 port ever, you can drop 'out-ports' and just have 
'port'. Not sure though if the coresight stuff depends on 'out-ports'.

> +
> +required:
> +  - compatible
> +  - cpu
> +
> +additionalProperties: false
> +
> +examples:
> +
> +# An ETE node without legacy CoreSight connections
> +  - |
> +    ete0 {
> +      compatible = "arm,embedded-trace-extension";
> +      cpu = <&cpu_0>;
> +    };
> +# An ETE node with legacy CoreSight connections
> +  - |
> +   ete1 {
> +      compatible = "arm,embedded-trace-extension";
> +      cpu = <&cpu_1>;
> +
> +      out-ports {        /* legacy coresight connection */
> +         port {
> +             ete1_out_port: endpoint {
> +                remote-endpoint = <&funnel_in_port0>;
> +             };
> +         };
> +      };
> +   };
> +
> +...
> -- 
> 2.7.4
>