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

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Message-ID: <CA+HBbNHkAxnTLo2N_-LtMCPhZLsqPAjpYUKBNoRqKc1qmbg=GQ@mail.gmail.com>
Date:   Fri, 24 Nov 2023 17:59:15 +0100
From:   Robert Marko <robert.marko@...tura.hr>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Andrew Lunn <andrew@...n.ch>, 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>, 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 4:16 PM Russell King (Oracle)
<linux@...linux.org.uk> wrote:
>
> 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.)

I can confirm that SGMII mode doesn't work with Option 2, I have tested this
a while ago with Mikrotik RJ01 (I think it has AR803x, but its not accessible as
you pointed out) and it was somewhat working but in half duplex only
and dropping
packets.
Currently, SFP mode is checked and only 1000Base-X and 100Base-FX are
accepted, otherwise the module insert will return and error for unsupported
mode.

Regards,
Robert

>
> --
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!



-- 
Robert Marko
Staff Embedded Linux Engineer
Sartura Ltd.
Lendavska ulica 16a
10000 Zagreb, Croatia
Email: robert.marko@...tura.hr
Web: www.sartura.hr