linux-kernel - Re: [net-next RFC PATCH 03/14] dt-bindings: net: document ethernet PHY package nodes

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Message-ID: <ZWC+PbNjir7rT4MK@shell.armlinux.org.uk>
Date:   Fri, 24 Nov 2023 15:16:13 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Jie Luo <quic_luoj@...cinc.com>,
        Christian Marangi <ansuelsmth@...il.com>,
        Rob Herring <robh@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Florian Fainelli <florian.fainelli@...adcom.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Daniel Golle <daniel@...rotopia.org>,
        Qingfang Deng <dqfext@...il.com>,
        SkyLake Huang <SkyLake.Huang@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        David Epping <david.epping@...singlinkelectronics.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Harini Katakam <harini.katakam@....com>,
        Simon Horman <horms@...nel.org>,
        Robert Marko <robert.marko@...tura.hr>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [net-next RFC PATCH 03/14] dt-bindings: net: document ethernet
 PHY package nodes

On Fri, Nov 24, 2023 at 03:44:20PM +0100, Andrew Lunn wrote:
> > 		First Serdes mode	Second Serdes mode
> > Option 1	PSGMII for copper	Disabled
> > 		ports 0-4
> > Option 2	PSGMII for copper	1000BASE-X / 100BASE-FX
> > 		ports 0-4
> > Option 3	QSGMII for copper	SGMII for
> > 		ports 0-3		copper port 4
> 
> With option 2, can the second SERDES also do SGMII? You are likely to
> need that when a Copper SFP module is inserted into the cage.

The document states "The fiber port supports 1000BASE-X/100BASE-FX".

The same is true of Marvell 88x3310's fiber port - it supports only
fiber not SGMII. This is actually something else that - when the
patches for stacked PHYs mature - will need to be addressed. If we
have a 1G copper SFP plugged into an interface that only supports
1000base-X then we need a way to switch the PHY on the SFP module
to 1000base-X if it's in SGMII mode.

Some copper SFPs come up in 1000base-X mode, and we currently rely
on the 88e1111 driver to switch them to SGMII mode. Others do want
SGMII mode (like Mikrotik RJ01 where the PHY is inaccessible and
thus can't be reconfigured.)

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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