Re: [PATCH v6 2/7] dt-bindings: net: amlogic,meson-dwmac: add amlogic,t7-dwmac

[Lucas Tanure]

On Tue, Nov 10, 2026 at 5:54 PM Rob Herring <robh@xxxxxxxxxx> wrote:
>
> On Thu, Nov 05, 2026 at 10:03:17AM +0000, Lucas Tanure wrote:
> > The T7 has the same ethernet glue as the G12A but needs two clocks of
> > its own. The controller reaches memory through a pipeline stage with
> > its own gate; nothing else claims it, so it is switched off as unused
> > and transfers never finish. The glue registers sit in a block clocked
> > together with the MDIO multiplexer, which probes after the controller
> > has programmed them: the writes are lost and the port keeps the
> > bootloader's delays.
> >
> > So the T7 gets its own clock list, without the timing adjustment clock
> > it never uses. Its delays follow ethernet-controller.yaml: the PHY adds
> > the 2ns, and only the receive delay line offers fine tuning, so only
> > rx-internal-delay-ps is valid here.
> >
> > Assisted-by: LLM
> > Signed-off-by: Lucas Tanure <tanure@xxxxxxxxx>
> > ---
> >  .../bindings/net/amlogic,meson-dwmac.yaml     | 49 +++++++++++++++++++
> >  1 file changed, 49 insertions(+)
>
> I tend to agree with the sashiko comment, but am fine either way. Once
> the if/then schemas are longer than the main schema, it's a sign to
> split.

In V7 I will split as I think it will be easier to review.

>
> >
> > diff --git a/Documentation/devicetree/bindings/net/amlogic,meson-dwmac.yaml b/Documentation/devicetree/bindings/net/amlogic,meson-dwmac.yaml
> > index e769c9bb70d8..ff5e50f65114 100644
> > --- a/Documentation/devicetree/bindings/net/amlogic,meson-dwmac.yaml
> > +++ b/Documentation/devicetree/bindings/net/amlogic,meson-dwmac.yaml
> > @@ -23,6 +23,7 @@ select:
> >            - amlogic,meson-gxbb-dwmac
> >            - amlogic,meson-axg-dwmac
> >            - amlogic,meson-g12a-dwmac
> > +          - amlogic,t7-dwmac
> >    required:
> >      - compatible
> >
> > @@ -84,6 +85,49 @@ allOf:
> >          rx-internal-delay-ps:
> >            default: 0
> >
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            const: amlogic,t7-dwmac
> > +    then:
> > +      properties:
> > +        clocks:
> > +          items:
> > +            - description: GMAC main clock
> > +            - description: First parent clock of the internal mux
> > +            - description: Second parent clock of the internal mux
> > +            - description:
> > +                clock of the pipeline stage inserted in the bus path between
> > +                the controller and the DRAM. Without it, the controller cannot
> > +                complete DMA transfers.
> > +            - description:
> > +                clock of the register block holding PRG_ETH0 and PRG_ETH1.
> > +                Without it, the block reads as zero and ignores writes.
> > +
> > +        clock-names:
> > +          items:
> > +            - const: stmmaceth
> > +            - const: clkin0
> > +            - const: clkin1
> > +            - const: pipeline
> > +            - const: pclk
> > +
> > +        # The PHY adds the 2ns RGMII delays, see ethernet-controller.yaml.
> > +        # The RX delay line of this glue is fine tuning in 200ps steps,
>
> Sounds like constraints:
>
> maximum: 2000
> multipleOf: 200

Yes, with maximum: 3000: the field is four bits, 0 to 15 steps of
200ps.
>
> > +        # added on top of what phy-mode describes. The TX side has no fine
> > +        # tuning: its only step is a quarter of the clock period, the full
> > +        # 2ns at 1Gbit/s, so the TX property is not accepted.
>
> Move this to tx-internal-delay-ps. You can (kind of ackwardly) do:
>
> tx-internal-delay-ps:
>   description: ...
>   not: {}

dt_binding_check does not accept "not" on a property under
properties: or in an allOf entry: cell.yaml allows only description,
deprecated, const, enum, minimum, maximum, multipleOf, default, $ref
and oneOf there. It passes only inside if/then, and the new file has
no if/then. So the property stays false, with the explanation as a
comment above it.

>
> (or "not: true")
>
> > +        rx-internal-delay-ps:
> > +          default: 0
> > +
> > +        tx-internal-delay-ps: false
> > +
> > +        # Deprecated: new SoCs use the standard *-internal-delay-ps
> > +        # properties instead.
> > +        amlogic,tx-delay-ns: false
> > +        amlogic,rx-delay-ns: false
> > +
> >    - if:
> >        properties:
> >          compatible:
> > @@ -106,6 +150,7 @@ allOf:
> >            contains:
> >              enum:
> >                - amlogic,meson-g12a-dwmac
> > +              - amlogic,t7-dwmac
> >      then:
> >        properties:
> >          rx-internal-delay-ps:
> > @@ -142,6 +187,10 @@ properties:
> >        - items:
> >            - const: amlogic,meson6-dwmac
> >            - const: snps,dwmac
> > +      - items:
> > +          - const: amlogic,t7-dwmac
> > +          - const: snps,dwmac-5.10a
> > +          - const: snps,dwmac
>
> I would drop either both or at least 'snps,dwmac'. They provide no value
> because there is nothing to use them. IOW, there's not s/w that works
> which only understands the last 2 and not amlogic,t7-dwmac. Correct me
> if I'm wrong. Maybe a bootloader with simple needs.
>
> Rob

Right, nothing uses them: the generic driver cannot enable the
pipeline clock, and no bootloader drives this port from the device
tree. v7 keeps "snps,dwmac-5.10a" for the core version and drops
"snps,dwmac".

Thanks,
Lucas