Re: [PATCH net-next v4 4/8] dt-bindings: mfd: Add SoC-e SWIP parent

[Rob Herring <robh@kernel.org>]

On Tue, Nov 10, 2026 at 05:10:15PM +0100, Vasilij Strassheim wrote:
> On Fri, 2026-11-06 at 22:51 +0100, Vasilij Strassheim wrote:
> > On Fri, 2026-11-06 at 12:13 +0100, Krzysztof Kozlowski wrote:
> > > On Thu, Nov 05, 2026 at 03:16:48PM +0100, Vasilij Strassheim wrote:
> > > > Add a binding for the SoC-e SWIP multifunction FPGA IP core.
> > > > 
> > > > Describe the shared MMIO address space and address translation for
> > > > the required Ethernet switch child and the optional integrated MDIO
> > > > controller and MMIO-controlled MDIO multiplexer.
> > > > 
> > > > Signed-off-by: Vasilij Strassheim <v.strassheim@linutronix.de>
> > > > ---
> > > >  .../devicetree/bindings/mfd/soce,swip.yaml         | 137 +++++++++++++++++++++
> > > >  1 file changed, 137 insertions(+)
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/mfd/soce,swip.yaml b/Documentation/devicetree/bindings/mfd/soce,swip.yaml
> > > > new file mode 100644
> > > > index 000000000000..625be299e262
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/mfd/soce,swip.yaml
> > > > @@ -0,0 +1,137 @@
> > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > > +%YAML 1.2
> > > > +---
> > > > +$id: http://devicetree.org/schemas/mfd/soce,swip.yaml#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +
> > > > +title: SoC-e SWIP multifunction Ethernet switch FPGA IP core
> > > > +
> > > > +maintainers:
> > > > +  - Vasilij Strassheim <v.strassheim@linutronix.de>
> > > > +
> > > > +description:
> > > > +  SoC-e Switch IP (SWIP) cores integrate Ethernet switching logic, an
> > > > +  MDIO controller, and an MDIO bus multiplexer in one memory-mapped device.
> > > > +  The MDIO bus multiplexer is wired to the integrated MDIO controller.
> > > > +
> > > > +properties:
> > > > +  compatible:
> > > > +    const: soce,swip
> > > > +
> > > > +  reg:
> > > > +    maxItems: 1
> > > > +
> > > > +  '#address-cells':
> > > > +    const: 1
> > > > +
> > > > +  '#size-cells':
> > > > +    const: 1
> > > > +
> > > > +  ranges: true
> > > > +
> > > > +  mdio@204:
> > > > +    $ref: /schemas/net/soce,swip-mdio.yaml#
> > > > +    unevaluatedProperties: false
> > > > +
> > > > +  mdio-mux@202:
> > > > +    $ref: /schemas/net/mdio-mux-mmioreg.yaml#
> > > > +    unevaluatedProperties: false

Given the MDIO bus and mux registers are adjacent, I don't know that 
putting the mux into its own node and driver really buys you anything. 
Can't your MDIO driver handle the muxing directly? mdio-mux-mmioreg was 
created for when you have mux registers in some completely unrelated 
block.

> > > > +
> > > > +  ethernet-switch:
> > > 
> > > Why are you mixing children with and without bus addresses? This is
> > > discouraged and shows that device is not correctly represented, e.g. if
> > > the ethernet-switch does not have resources, then THIS device is the
> > > ethernet switch.
> > > 
> > 
> > There is no hardware reason for leaving the switch child unaddressed.
> > Just an error that occurred while converting the binding to the MFD
> > model.
> > I will describe the switch function as an ethernet-switch@0 child node
> > with a reg property for it's register resources, like the ocelot MFD
> > binding.
> 
> It looks like I need a different name for the MFD parent to avoid a
> naming collision with the ethernet-switch@0 child. I checked other
> bindings but could not find a suitable example.
> 
> I would appreciate any suggestions for a suitable name for the parent
> node representing the FPGA IP core. It mainly acts as a container for
> its child devices. I am considering "bus", "ip-core" or "shell".

Krzysztof's point was combine the child and parent nodes into the 
parent. This is not really an MFD. Almost every ethernet MAC has an MDIO 
controller in it and none of those bindings are MFDs.

Rob