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

[Xilin Wu]

On 9/3/2026 10:40 PM, Konrad Dybcio wrote:
> 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?

Yeah I think so.

> Konrad


--
Best regards,
Xilin Wu <sophon@xxxxxxxxx>