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