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

[Lucas Tanure <tanure@linux.com>]

On 10/10/2026 23:37, Martin Blumenstingl wrote:
> Hi Andrew, Hi Lucas,
> 
> On Sat, Oct 10, 2026 at 12:59 PM Lucas Tanure <tanure@linux.com> wrote:
> [...]
>> +#   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
> We have some boards where the PCB traces result in part (1200ps) of
> the delay needed for RGMII (2000ps).
> The remainder (800ps) has to be added by either PHY or MAC: the
> (RTL8211F) PHY can only generate 0 or 2000ps delay so the MAC has to
> take over.
> For the three boards I have in mind, please see $ git grep
> rx-internal-delay-ps arch/arm64/boot/dts/amlogic/
> 
>> +# A property for a clock the PCB already delays is not in this table.
> Can you please explain this sentence (I'm not a native English speaker)?
> How I interpret the sentence: The PCB may add delays but those are
> implicit and not part of the {rx,tx}-internal-delay-ps properties. If
> the delays added by the PCB don't cover the full 2ns requirement then
> either MAC or PHY need to add the remainder, see fine-tuning below.
> 
>> +# It is either the fine tuning described next, or a mistake the MAC
>> +# should report as a fatal error.
> How can I differentiate between "fine tuning" and "mistake"?
> 
> 
> Best regards,
> Martin
The patch is wrong. It assumes a present property moves the 2ns from
the PHY to the MAC, and Andrew's reply on patch 4 says it does not.
I am dropping it in v4.

thanks
Lucas