netdev - Re: [PATCH 1/2] dt-bindings: net: motorcomm: Add chip mode cfg

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Message-ID: <6f630ae9-60a3-437e-973e-7743f8dd6352@motor-comm.com>
Date: Sun, 11 Aug 2024 05:45:45 -0700
From: "Frank.Sae" <Frank.Sae@...or-comm.com>
To: Andrew Lunn <andrew@...n.ch>, Krzysztof Kozlowski <krzk@...nel.org>
Cc: hkallweit1@...il.com, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, linux@...linux.org.uk, netdev@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 yuanlai.cui@...or-comm.com, hua.sun@...or-comm.com,
 xiaoyong.li@...or-comm.com, suting.hu@...or-comm.com, jie.han@...or-comm.com
Subject: Re: [PATCH 1/2] dt-bindings: net: motorcomm: Add chip mode cfg


On 7/27/24 04:07, Andrew Lunn wrote:
> On Sat, Jul 27, 2024 at 11:25:25AM +0200, Krzysztof Kozlowski wrote:
>> On 27/07/2024 11:20, Frank.Sae wrote:
>>>   The motorcomm phy (yt8821) supports the ability to
>>>   config the chip mode of serdes.
>>>   The yt8821 serdes could be set to AUTO_BX2500_SGMII or
>>>   FORCE_BX2500.
>>>   In AUTO_BX2500_SGMII mode, SerDes
>>>   speed is determined by UTP, if UTP link up
>>>   at 2.5GBASE-T, SerDes will work as
>>>   2500BASE-X, if UTP link up at
>>>   1000BASE-T/100BASE-Tx/10BASE-T, SerDes will work
>>>   as SGMII.
>>>   In FORCE_BX2500, SerDes always works
>>>   as 2500BASE-X.
> When the SERDES is forced to 2500BaseX, does it perform rate
> adaptation? e.g. does it insert pause frames to slow down the MAC?
>
> Maybe look at air_en8811h.c.
>
>        Andrew

Yes, when the serdes is forced to 2500base-x, it inserts pause frames to
perform rate adaptation to slow down the MAC.