[Skiboot] Question about PCIe slots in device-tree

Oliver oohall at gmail.com
Thu Dec 6 15:00:01 AEDT 2018

On Wed, Dec 5, 2018 at 11:28 PM Илья Кузнецов <ilya at yadro.com> wrote:
> Hello,
> I'm wondering what is the reason to register only PCIe downstream port of the
> switch directly connected to CPU? What if I would like to see third or fourth
> switch in chain in the device-tree?
> https://github.com/open-power/skiboot/blob/10497d05169fe6e05cecb762a35c63c164469819/core/pcie-slot.c#L551
> My question relates to pnv_php kernel driver which checks for capabilities
> through the device-tree.

I don't think there was ever a really good reason for it. The best
explanation I can think of is that a lot of systems have dubiously
configured PCIe switches that advertise downstream ports as hotplug
capable even though the physical form factor of the slot is not
hotplug capable. I don't really see that as a major issue since we can
work around it in skiboot if necessary.

If you want to change that behaviour then you're welcome to.


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