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

[Krzysztof Kozlowski <krzk@kernel.org>]

On 01/07/2026 09:16, Jie Gan wrote:
> 
> 
> 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 

If this is not AMBA bus device, then drop primecell compatible.

> 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 

As I said, that's a Linux driver specific reason, so not a valid one.

Fix your drivers if you insist on that.

> 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.
I do not see there a fake, duplicated compatible for the same device.
Can you elaborate how is that relevant?

Best regards,
Krzysztof