Re: [PATCH v6 1/5] dt-bindings: arm: coresight-tnoc: Bind on platform bus instead of AMBA

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] The kernel has no platform driver configured to match the `qcom,coresight-tnoc` compatible string, leaving the device unbound on the platform bus.
- [Low] Restricting the 'compatible' property to a single string abruptly breaks schema validation for existing in-tree device trees that use the dual-string AMBA format.
--

--- Patch [1]: [PATCH v6 1/5] dt-bindings: arm: coresight-tnoc: Bind on platform bus instead of AMBA ---
commit 53696bf96bfa353e6c866bb916cba6363324a355
Author: Jie Gan <jie.gan@oss.qualcomm.com>

dt-bindings: arm: coresight-tnoc: Bind on platform bus instead of AMBA

The Aggregator TraceNoC hardware exposes CID registers, but the Component
ID value returned by the hardware is 0x00000000 instead of a valid AMBA
Component ID. As a result, the device cannot be identified on the AMBA
bus.

> Describe the Aggregator TraceNoC with a dedicated single
> "qcom,coresight-tnoc" compatible instead of the two-string AMBA form
> "qcom,coresight-tnoc", "arm,primecell". This creates the device on the
> platform bus so it is bound by the platform driver through its compatible
> string rather than as an AMBA device.

[Severity: High]
Does the platform driver have the correct compatible string to match this?

Looking at itnoc_of_match in drivers/hwtracing/coresight/coresight-tnoc.c:

static const struct of_device_id itnoc_of_match[] = {
	{ .compatible = "qcom,coresight-itnoc" },
	{}
};

Since "qcom,coresight-tnoc" is not in this match table, will the device
silently fail to probe at runtime on the platform bus?

> diff --git a/Documentation/devicetree/bindings/arm/qcom,coresight-tnoc.yaml b/Documentation/devicetree/bindings/arm/qcom,coresight-tnoc.yaml
> index ef648a15b8065..72fb1210e22e0 100644
> --- a/Documentation/devicetree/bindings/arm/qcom,coresight-tnoc.yaml
> +++ b/Documentation/devicetree/bindings/arm/qcom,coresight-tnoc.yaml

[ ... ]

> @@ -22,24 +22,12 @@ description: >
>  
>    Note this binding is specifically intended for Aggregator TNOC instances.
>  
> -# Need a custom select here or 'arm,primecell' will match on lots of nodes
> -select:
> -  properties:
> -    compatible:
> -      contains:
> -        enum:
> -          - qcom,coresight-tnoc
> -  required:
> -    - compatible
> -
>  properties:
>    $nodename:
>      pattern: "^tn(@[0-9a-f]+)$"
>  
>    compatible:
> -    items:
> -      - const: qcom,coresight-tnoc
> -      - const: arm,primecell
> +    const: qcom,coresight-tnoc

[Severity: Low]
Will this break schema validation for existing device trees?

Existing files like arch/arm64/boot/dts/qcom/sm8750.dtsi still use the dual
string format:

		tn@109ab000 {
			compatible = "qcom,coresight-tnoc", "arm,primecell";

Running make dtbs_check might produce validation errors until those device
trees are updated to match this new strict constraint.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260710-fix-tracenoc-probe-issue-v6-0-41eb36fef8d9@oss.qualcomm.com?part=1