Re: [PATCH v5 1/5] dt-bindings: arm: coresight-tnoc: Drop arm,primecell to bind on platform bus

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] Changing the compatible schema to strictly require only 'qcom,coresight-tnoc' breaks validation for existing device trees, and removing the custom select block prevents safe restoration of backward compatibility.
- [High] The platform driver is not configured to match the 'qcom,coresight-tnoc' compatible string, causing devices to fail probing if they conform to the new binding.
--

--- Patch [1]: [PATCH v5 1/5] dt-bindings: arm: coresight-tnoc: Drop arm,primecell to bind on platform bus ---
commit 04928b8d12a8ec737b7aeaf2dab2136838ce0ddd
Author: Jie Gan <jie.gan@oss.qualcomm.com>

dt-bindings: arm: coresight-tnoc: Drop arm,primecell to bind on platform bus

The TNOC compatible previously required the two-string AMBA form
"qcom,coresight-tnoc", "arm,primecell", which forces the device onto the
AMBA bus. Change the compatible to a single "qcom,coresight-tnoc" string
with no "arm,primecell" entry.

> 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: High]
Does this change break schema validation for existing device trees?

There are existing in-tree nodes, such as in 
arch/arm64/boot/dts/qcom/sm8750.dtsi, that still use the older fallback:

	compatible = "qcom,coresight-tnoc", "arm,primecell";

If this schema is updated to strictly require only qcom,coresight-tnoc,
validation for those existing device trees will fail.

Additionally, by removing the custom select block, if the arm,primecell
fallback is restored to maintain backward compatibility, won't dtschema
auto-generate a select that matches any node with arm,primecell and
erroneously apply this schema to unrelated AMBA devices across the system?

[Severity: High]
Will devices conforming to this new binding fail to probe?

Looking at the platform driver in 
drivers/hwtracing/coresight/coresight-tnoc.c, the OF match table lacks the 
required string:

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

Since the schema drops arm,primecell, the device will be instantiated
on the platform bus. Without qcom,coresight-tnoc in the platform driver's
match table, won't this result in a complete probe failure?

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260707-fix-tracenoc-probe-issue-v5-0-bf733ed9ebd0@oss.qualcomm.com?part=1