Re: [PATCH 1/6] PCI: of: Avoid config reads for disabled bridge nodes

[Konrad Dybcio]

On 9/2/26 11:31 AM, Xilin Wu wrote:
> On 9/2/2026 4:43 PM, Konrad Dybcio wrote:
>> On 9/1/26 10:47 AM, Xilin Wu wrote:
>>> The TC9563 PCI power-control driver powers off external downstream ports
>>> whose device tree nodes have status = "disabled".
>>>
>>> On the Radxa Dragon Q8B, reading the Vendor ID from one of these
>>> powered-off port functions during PCI enumeration raises an Arm SError
>>> instead of returning an all-ones PCI error response. This prevents the
>>> board from completing boot.
>>
>> I agree with the premise of the patch, but I'd like to understand why
>> that happens - do you have any details?
> 
> Unfortunately, I don't have further details. The downstream kernel also includes a similar workaround, so I suspect it's related to how the TC9563 chip is designed.

I'm curious in why the port is still advertised on the bus if
the i2c interface writes some magic bits to "disable" it on the IC
side.. but perhaps that's just how that IC behaves and we can't
do anything about it?

Konrad