linux-kernel - Re: [PATCH v5 3/6] net: phy: at803x: add QCA8084 ethernet phy support

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Message-ID: <1eb60a08-f095-421a-bec6-96f39db31c09@lunn.ch>
Date:   Sat, 18 Nov 2023 16:51:42 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Luo Jie <quic_luoj@...cinc.com>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        hkallweit1@...il.com, linux@...linux.org.uk, corbet@....net,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v5 3/6] net: phy: at803x: add QCA8084 ethernet phy support

On Sat, Nov 18, 2023 at 02:27:51PM +0800, Luo Jie wrote:
> Add qca8084 PHY support, which is four-port PHY with maximum
> link capability 2.5G, the features of each port is almost same
> as QCA8081 and slave seed config is not needed.
> 
> Three kind of interface modes supported by qca8084.
> PHY_INTERFACE_MODE_10G_QXGMII, PHY_INTERFACE_MODE_2500BASEX and
> PHY_INTERFACE_MODE_SGMII.

Sorry for joining the conversation late.

I'm trying to get my head around QXGMII. Let me describe what i think
is happening, and then you can correct me....

You have 4 MACs, probably in a switch. The MII interfaces from these
MACs go into a multiplexer, and out comes QXGMII? You then have a
SERDES interface out of the switch and into the PHY package. Inside
the PHY package there is a demultiplexor, giving you four MII
interfaces, one to each PHY in the package.

If you have the PHY SERDES running in 2500BaseX, you have a single
MAC, no mux/demux, and only one PHY is used? The other three are idle.
Same from SGMII?

So the interface mode QXGMII is a property of the package. It is not
really a property of one PHY. Having one PHY using QXGMII and another
SGMII does not work?

     Andrew