[PATCH v3 8/8] dt-bindings: net: ethernet-controller: tabulate who adds the RGMII delays

[Jerome Brunet]

On sam. 10 oct. 2026 at 11:59, Lucas Tanure <tanure at linux.com> wrote:

> The informative section explains in prose how phy-mode, the delay
> properties in the MAC node and the mode handed to the PHY fit together,
> and says itself that developers often get this wrong. A reader has to
> work through several paragraphs before answering the one question they
> usually have: for this phy-mode and these properties, which part adds
> which delay.
>
> Add a table that answers it at a glance, with one row for every
> combination the properties allow.
>
> Assisted-by: LLM
> Signed-off-by: Lucas Tanure <tanure at linux.com>
> ---
>  .../bindings/net/ethernet-controller.yaml      | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/net/ethernet-controller.yaml b/Documentation/devicetree/bindings/net/ethernet-controller.yaml
> index 1bafd687dcb1..bba27a9feb61 100644
> --- a/Documentation/devicetree/bindings/net/ethernet-controller.yaml
> +++ b/Documentation/devicetree/bindings/net/ethernet-controller.yaml
> @@ -339,6 +339,24 @@ additionalProperties: true
>  # has added. Failure to remove the delay will result in a
>  # non-functioning link.
>  #
> +# Put together, with the two properties in the MAC node, this is who
> +# adds each delay:
> +#
> +#   phy-mode    tx-internal-delay-ps  rx-internal-delay-ps  TX delay    RX delay
> +#   rgmii       -                     -                     PCB trace   PCB trace
> +#   rgmii-id    -                     -                     PHY         PHY
> +#   rgmii-id    present               -                     MAC         PHY
> +#   rgmii-id    -                     present               PHY         MAC
> +#   rgmii-id    present               present               MAC         MAC
> +#   rgmii-txid  -                     -                     PHY         PCB trace
> +#   rgmii-txid  present               -                     MAC         PCB trace
> +#   rgmii-rxid  -                     -                     PCB trace   PHY
> +#   rgmii-rxid  -                     present               PCB trace   MAC
> +#

That would match how the HW is working on the A733 Allwinner too but I'm
not entirely sure this is what Andrew had in mind from our previous
discussion [1]. Adding him to the thread

[1]: https://lore.kernel.org/linux-sunxi/491f043e-6dc6-4936-a490-31a3362c5b6e@lunn.ch/

> +# A property for a clock the PCB already delays is not in this table.
> +# It is either the fine tuning described next, or a mistake the MAC
> +# should report as a fatal error.
> +#
>  # Sometimes there is a need to fine tune the delays. Often the MAC or
>  # PHY can perform this fine tuning. In the MAC node, the Device Tree
>  # properties 'rx-internal-delay-ps' and 'tx-internal-delay-ps' should

Acked-by: Jerome Brunet <jbrunet at baylibre.com>

> -- 
> 2.56.0
>

-- 
Jerome