linux-kernel - RE: [EXT] Re: [PATCH 2/5] dt-bindings: net: add schema for NXP S32CC dwmac glue driver

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Message-ID: <AM9PR04MB85066636DE2D99C8F2A9F4CDE23E9@AM9PR04MB8506.eurprd04.prod.outlook.com>
Date:   Wed, 9 Nov 2022 22:55:11 +0000
From:   Jan Petrous <jan.petrous@....com>
To:     Chester Lin <clin@...e.com>, Andrew Lunn <andrew@...n.ch>
CC:     Andreas Färber <afaerber@...e.de>,
        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>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        dl-S32 <S32@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Matthias Brugger <mbrugger@...e.com>
Subject: RE: [EXT] Re: [PATCH 2/5] dt-bindings: net: add schema for NXP S32CC
 dwmac glue driver

Hi Chester,
 
> Hi Andrew and Andreas,
> 
> On Thu, Nov 03, 2022 at 11:05:30PM +0100, Andrew Lunn wrote:
> > > > > +      - description: Main GMAC clock
> > > > > +      - description: Peripheral registers clock
> > > > > +      - description: Transmit SGMII clock
> > > > > +      - description: Transmit RGMII clock
> > > > > +      - description: Transmit RMII clock
> > > > > +      - description: Transmit MII clock
> > > > > +      - description: Receive SGMII clock
> > > > > +      - description: Receive RGMII clock
> > > > > +      - description: Receive RMII clock
> > > > > +      - description: Receive MII clock
> > > > > +      - description:
> > > > > +          PTP reference clock. This clock is used for programming the
> > > > > +          Timestamp Addend Register. If not passed then the system
> > > > > +          clock will be used.
> >
> > > Not clear to me has been whether the PHY mode can be switched at
> runtime
> > > (like DPAA2 on Layerscape allows for SFPs) or whether this is fixed by
> board
> > > design.
> >
> > Does the hardware support 1000BaseX? Often the hardware implementing
> > SGMII can also do 1000BaseX, since SGMII is an extended/hacked up
> > 1000BaseX.
> >
> > If you have an SFP connected to the SERDES, a fibre module will want
> > 1000BaseX and a copper module will want SGMII. phylink will tell you
> > what phy-mode you need to use depending on what module is in the
> > socket. This however might be a mute point, since both of these are
> > probably using the SGMII clocks.
> >
> > Of the other MII modes listed, it is very unlikely a runtime swap will
> > occur.
> >
> >       Andrew
> 
> Here I just focus on GMAC since there are other LAN interfaces that S32
> family
> uses [e.g. PFE]. According to the public GMACSUBSYS ref manual rev2[1]
> provided
> on NXP website, theoretically GMAC can run SGMII in 1000Mbps and
> 2500Mbps so I
> assume that supporting 1000BASE-X could be achievable. I'm not sure if any
> S32
> board variant might have SFP ports but RJ-45 [1000BASE-T] should be the
> major
> type used on S32G-EVB and S32G-RDB2.
> 
> @NXP, please feel free to correct me if anything wrong.
> 

NXP eval boards (EVB or RDB) have also 2.5G PHYs, so together with SerDes
driver we support 100M/1G/2.5G on such copper PHYs. 

/Jan

--
NXP Czechia, AP Ethernet