RE: [PATCH V13 02/12] PCI: host-generic: Add common helpers for parsing Root Port properties

[Sherry Sun]

> On Thu, Apr 16, 2026 at 07:14:12PM +0800, Sherry Sun wrote:
> > Introduce generic helper functions to parse Root Port device tree
> > nodes and extract common properties like reset GPIOs. This allows
> > multiple PCI host controller drivers to share the same parsing logic.
> >
> > Define struct pci_host_port to hold common Root Port properties
> > (currently only reset GPIO descriptor) and add
> > pci_host_common_parse_ports() to parse Root Port nodes from device
> tree.
> 
> Are the Root Port and the RC the only possible places for 'reset' GPIO
> descriptions in DT?  I think PERST# routing is outside the PCIe spec, so it
> seems like a system could provide a PERST# GPIO routed to any Switch
> Upstream Port or Endpoint (I assume a PERST# connected to a switch would
> apply to both the upstream port and the downstream ports).

Hi Bjorn,

Thanks for the feedback. You're right that PERST# routing could theoretically be
connected to any device in the hierarchy. However, for this patch series, I've focused
on the most common use case in practice: use Root Port level PERST# instead of the
legacy Root Complex level PERST#.

Root Port level PERST# - This is the primary target, where each Root Port has individual
control over devices connected to it.
RC level PERST# - Legacy binding support, where a single GPIO controls all ports.

We can extend this framework later if real hardware emerges that needs Switch or
EP-level PERST# control. I can add a comment documenting this limitation if needed.

BTW, Mani and Rob had some great discussions in dt-schema about PERST# and WAKE#
sideband signals settings.
You can check here:
https://github.com/devicetree-org/dt-schema/issues/168
https://github.com/devicetree-org/dt-schema/pull/126
https://github.com/devicetree-org/dt-schema/pull/170

Best Regards
Sherry