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

From: Lucas Tanure <tanure@linux.com>
To: Conor Dooley <conor@kernel.org>
Cc: xianwei.zhao@amlogic.com, Andrew Lunn <andrew+netdev@lunn.ch>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@kernel.org>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Neil Armstrong <neil.armstrong@linaro.org>,
	Kevin Hilman <khilman@baylibre.com>,
	Jerome Brunet <jbrunet@baylibre.com>,
	Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
	Maxime Chevallier <maxime.chevallier@bootlin.com>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	netdev@vger.kernel.org, devicetree@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 8/8] dt-bindings: net: ethernet-controller: tabulate who adds the RGMII delays
Date: Thu, 22 Oct 2026 18:49:32 +0100	[thread overview]
Message-ID: <a23b3a53-9cdf-4e32-8ca8-a80d927d65e2@linux.com> (raw)
In-Reply-To: <20261012-suds-karaoke-efc4acf056af@spud>

On 12/10/2026 20:18, Conor Dooley wrote:
> On Sat, Oct 10, 2026 at 11:59:00AM +0100, Lucas Tanure 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>
> 
> If the net guys think this is valuable,
> Acked-by: Conor Dooley <conor.dooley@microchip.com>
> 
Thanks, but I will drop this patch as is wrong.> (although for something 
like this, us acking probably ain't needed,
> ehh?)
> 
>> ---
>>   .../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
>> +#
>> +# 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
>> -- 
>> 2.56.0
>>


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