linux-kernel - Re: [PATCH v1 1/2] dt-bindings: ethernet: eswin: add clock sampling control

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Message-ID: <abf12a3f-9cdd-472d-a02e-af4da594b84f@gmail.com>
Date: Thu, 22 Jan 2026 23:39:29 -0800
From: Bo Gan <ganboing@...il.com>
To: Andrew Lunn <andrew@...n.ch>, 李志
 <lizhi2@...incomputing.com>
Cc: devicetree@...r.kernel.org, andrew+netdev@...n.ch, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, netdev@...r.kernel.org, pabeni@...hat.com,
 mcoquelin.stm32@...il.com, alexandre.torgue@...s.st.com,
 rmk+kernel@...linux.org.uk, linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 ningyu@...incomputing.com, linmin@...incomputing.com,
 pinkesh.vaghela@...fochips.com, weishangjuan@...incomputing.com
Subject: Re: [PATCH v1 1/2] dt-bindings: ethernet: eswin: add clock sampling
 control

Hi Andrew,

On 1/22/26 19:19, Andrew Lunn wrote:
>>> You say internal. So the skew is fixed, it is a property of the
>>> silicon? If so, why a DT property? Why not just hard code it in the
>>> driver? Since it is internal, different boards should not need it set
>>> differently?
>>>
>> Thanks for the question.
>>
>> EIC7700 has two Ethernet MACs. Only eth1 has this internal RXC/RXD skew,
>> eth0 does not.
>>
>> So this is not a chip-wide constant that can be hardcoded in the driver.
>> We need a way to distinguish the two MAC instances, which is why this is
>> described per-port in DTS.
> 
> I assume the address of the interface is fixed. So you can just key
> off that to distinguish the two instances.
> 
> Since this is an internal property, not a board property, it is not
> clear it actually belongs on DT.
> 
>      Andrew

IMO, they should be in DT to provide maximum flexibility. The SoC .dtsi
can provide some sane defaults, and the board vendor can later override
them if the mac/phy requires further tuning. Applying such tuning by
the address of MAC seems messy and it hides the parameters used behind
driver. Through DT, everything becomes really clear.

I assume this is not uncommon: E.g., starfive/jh7110:
https://lore.kernel.org/all/20230714104521.18751-3-samin.guo@starfivetech.com/

BTW, no need to worry about backward compat. ESWIN hasn't checked-in any
DT for eth yet. As you and Russell said, they need to do it, pronto.

Bo