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

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

On 7/9/2026 3:59 PM, Krzysztof Kozlowski wrote:
> On Tue, Jul 07, 2026 at 05:08:49PM +0800, Jie Gan wrote:
>> 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, so the device is created on the platform bus and
>> bound by the platform driver through its compatible string.
> 
> I asked already: this is not a valid reason. References to Linux
> structures are not correct here. If this is your reason, then answer is:
> fix drivers, by renaming or doing whatever is necessary to platform bus
> to behave like amba bus.

The issue is that we are not allowed to introduce a DT property to 
bypass the AMBA bus validation, which reads the Component ID (CID) 
registers. Besides, I cannot fix this in the TraceNoC AMBA driver 
because the driver is only invoked after amba_match() succeeds. Since 
the device fails the AMBA match, the TraceNoC AMBA driver is never reached.

The solution proposed by the CoreSight maintainer, Suzuki, is to define 
a dedicated compatible string for the Aggregator TraceNoC device and 
have it probed by the existing platform driver. If the AMBA bus cannot 
identify the device as a valid AMBA device, we should not fake the 
hardware description to make it appear as one.

Thanks,
Jie

>>
>> Drop the custom select block as well. It was only needed to avoid
>> matching the "arm,primecell" string on unrelated nodes; with the single
>> "qcom,coresight-tnoc" compatible the schema's auto-generated select
>> already matches the right nodes.
> 
> Why are you describing the diff? It's obvious.
> 
> 
>>
>> Update the example node to use the standalone compatible form.
> 
> And here.
> 
> You got comments at v4, nothing improveed. Your commit msg tells useless
> things like what you did or you want different Linux behavior.
> 
> Best regards,
> Krzysztof
>