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

[Lucas Tanure <tanure@linux.com>]

On 13/10/2026 08:14, Jerome Brunet wrote:
> On sam. 10 oct. 2026 at 11:59, Lucas Tanure <tanure@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@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@baylibre.com>
> 

Thanks, But I will drop this as it is wrong.
Lucas

>> -- 
>> 2.56.0
>>
> 


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