Re: [PATCH v4 1/5] dt-bindings: arm: coresight-tnoc: Add standalone qcom,coresight-agtnoc compatible

[Jie Gan <jie.gan@oss.qualcomm.com>]

On 7/1/2026 2:57 PM, Krzysztof Kozlowski wrote:
> On Wed, Jul 01, 2026 at 09:53:41AM +0800, Jie Gan wrote:
>> The TNOC compatible previously only allowed the two-string AMBA form
>> "qcom,coresight-tnoc", "arm,primecell", which forces the device onto the
>> AMBA bus.
>>
>> Convert the compatible to a oneOf and add a standalone
>> "qcom,coresight-agtnoc" compatible alongside the existing AMBA form. The
>> standalone string carries no "arm,primecell" entry, so the device is
>> created on the platform bus instead of the AMBA bus.
> 
> That's a Linux driver specific reason, so not a valid one.
> 
> Describe the hardware instead.
> 
> Also, you do not get other compatible for the same device.

The device is intended to be discovered and probed via the AMBA bus. 
However, due to a hardware issue, AMBA probing does not work correctly. 
While adding the arm,primecell-periphid property would allow the 
existing AMBA driver to bind, but I think that's a temp WA. As 
Suzuki/Leo pointed out, we should not add the property to pretend the 
device as an AMBA device.

Instead, I introduced a dedicated compatible string so the device can be 
handled by the existing platform driver without relying on the missing 
AMBA primecell identification. The purpose of the new compatible is to 
clearly distinguish this platform-specific case from the standard 
AMBA-based implementation. Or shall I re-use the existing compatible 
"qcom,coresight-tnoc" as platform standalone compatible?

We already have a similar pattern for the interconnect TraceNoC device, 
which uses the platform-specific compatible string qcom,coresight-itnoc.

Thanks,
Jie

> 
> Best regards,
> Krzysztof
>