Re: [PATCH net-next 08/12] dt-bindings: net: toshiba,tc965x-dwmac: add TC956x Ethernet bridge

[Alex Elder]

On 5/7/26 9:12 AM, Bjorn Andersson wrote:
> On Fri, May 01, 2026 at 10:54:16AM -0500, Alex Elder wrote:
> > diff --git a/Documentation/devicetree/bindings/net/toshiba,tc956x-dwmac.yaml b/Documentation/devicetree/bindings/net/toshiba,tc956x-dwmac.yaml
> [..]
> > +
> > +  gpio-controller: true
>
> I don't have any concern with the use of a proper gpio driver to model
> the implementation, but if I understand correctly this relationship
> between gpio controller and gpio consumer is strictly internal to "the
> PCI device".

(I think you're already cool with this but I still wanted to respond.)

That is not correct.  These GPIO lines are used two ways for the
RB3gen2:
- drivers/pci/pwrctrl/pci-pwrctrl-tc9563.c uses GPIOs 2 and 3 to
  assert/deassert the reset lines associated with the two exposed
  downstream PCIe ports on the PCIe switch within the TC956x.

- Each of the Ethernet PHYs has a reset GPIO.  On the RB3gen2, the
  GPIOs used for the purpose come from the GPIO controller embedded
  in the TC9564 (00 and 01).

These are therefore "exposed" (they are *not* strictly internal).

> Is this connection variable or is the link merely expressed in
> DeviceTree to mitigate the fact that you choose to implement the
> responsibilities of the two parts split into two device drivers?

It is variable.  These resets might be implemented by other GPIO
controllers on other platforms.

> Are there other consumers of these TC956x gpios which would result in a
> board designer (and hence dts author) to ever reference this
> gpio-controller in a different way?

They could.  Nine of these GPIOs are exposed by the TC956x pins
(GPIO00-06, GPIO12, GPIO35 and GPIO36).  The RB3gen2 uses 00-03
(and possibly 04 but that's for a PHY we haven't tested yet).

					-Alex

> Regards,
> Bjorn