linux-kernel - Re: [PATCH v1 2/2] dt-bindings: arm: Add remote etm driver

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Message-ID: <d2c4e571-fbc4-4c3b-b382-1dabb88fbcb9@linaro.org>
Date:   Tue, 7 Nov 2023 16:30:31 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Mao Jinlong <quic_jinlmao@...cinc.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        James Clark <james.clark@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>
Cc:     linux-kernel@...r.kernel.org, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>,
        Tao Zhang <quic_taozha@...cinc.com>
Subject: Re: [PATCH v1 2/2] dt-bindings: arm: Add remote etm driver

On 07/11/2023 07:09, Mao Jinlong wrote:
> Add new coresight-remote-etm.yaml file describing the bindings required
> to define coresight remote etm in the device trees.

Subject: drop driver. Bindings are about hardware, not drivers.

> 
> Signed-off-by: Mao Jinlong <quic_jinlmao@...cinc.com>
> ---
>  .../arm/qcom,coresight-remote-etm.yaml        | 59 +++++++++++++++++++
>  1 file changed, 59 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/qcom,coresight-remote-etm.yaml
> 
> diff --git a/Documentation/devicetree/bindings/arm/qcom,coresight-remote-etm.yaml b/Documentation/devicetree/bindings/arm/qcom,coresight-remote-etm.yaml
> new file mode 100644
> index 000000000000..04bb57b48d96
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/qcom,coresight-remote-etm.yaml
> @@ -0,0 +1,59 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/arm/qcom,coresight-remote-etm.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Qualcomm Coresight Remote ETM

What is ETM?

> +
> +maintainers:
> +  - Jinlong Mao <quic_jinlmao@...cinc.com>
> +  - Tao Zhang <quic_taozha@...cinc.com>
> +
> +description: |

Do not need '|' unless you need to preserve formatting.

> +  Support for ETM trace collection on remote processor using coresight
> +  framework. Enabling this will allow turning on ETM tracing on remote
> +  processor via sysfs and collecting the trace via TMC sinks.
> +
> +properties:
> +  compatible:
> +    items:
> +      - const: qcom,coresight-remote-etm
> +
> +  qcom,inst-id:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      Instance id of remote etm.

It's the first time this property appears... Why do you need to
hard-code it and why would it differ between each board? If you want to
use existing, accepted property, then you must use exactly the same.

> +
> +  out-ports:
> +    $ref: /schemas/graph.yaml#/properties/ports
> +    additionalProperties: false
> +
> +    properties:
> +      port:
> +        description: Output connection to the CoreSight Trace bus.
> +        $ref: /schemas/graph.yaml#/properties/port
> +
> +required:
> +  - compatible
> +  - qcom,inst-id
> +  - out-ports
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    modem_etm0 {

Node names should be generic. See also an explanation and list of
examples (not exhaustive) in DT specification:
https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation

Underscores are not allowed.

> +        compatible = "qcom,coresight-remote-etm";
> +        qcom,inst-id = <2>;
> +
> +        out-ports {
> +            port {
> +                modem_etm0_out_funnel_modem: endpoint {
> +                remote-endpoint =
> +                    <&funnel_modem_in_modem_etm0>;

Fix wrapping.

> +                };
> +            };
> +        };
> +    };
> +...

Best regards,
Krzysztof