[PATCH v2 2/2] arm64: dts: qcom: kaanapali: fix traceNoC probe issue

[Suzuki K Poulose]

On 24/06/2026 14:48, Jie Gan wrote:
> 
> 
> On 6/24/2026 9:27 PM, Konrad Dybcio wrote:
>> On 6/24/26 11:49 AM, Jie Gan wrote:
>>> The AMBA bus attempts to read the CID/PID of a device before invoking
>>> its probe function if the arm,primecell-periphid property is absent.
>>> This causes a deferred probe issue for the TraceNoC device, as the
>>> CID/PID cannot be read from the periphid register.
>>
>> Why does it probe defer?
>>
> 
> For an AMBA device, the periphid is mandatory for probing. In the 
> amba_match function, AMBA attempts to read the periphid from the CID/PID 
> registers if the arm,primecell-periphid property is absent in the device 
> tree. If this read fails, it returns -EPROBE_DEFER, and the probe 
> ultimately fails.

Why does it fail ? power management ? hw broken ? Is it really AMBA or 
do you pretend that to be an AMBA device by faking the CID/PID?

Suzuki


> Most AMBA devices expose valid CID/PID registers, so specifying 
> arm,primecell-periphid in the device tree is usually unnecessary. 
> However, for the TraceNoC device in this case, AMBA cannot reliably read 
> the periphid from the corresponding registers.
> 
>> And is this required for all TNOC devices?
> 
> So far, the TNOC device has been added to sm8750, Glymur, and Kaanapali 
> platforms, and all exhibit probe failures due to the same root cause.
> 
> I prefer to fix it on Kaanapali first.
> 
> Thanks,
> Jie
> 
>>
>> Konrad
>