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

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Date:   Thu, 10 Nov 2022 14:04:09 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Jan Petrous <jan.petrous@....com>
Cc:     Chester Lin <clin@...e.com>,
        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

On Thu, Nov 10, 2022 at 08:51:43AM +0000, Jan Petrous wrote:
> Hi 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.
> > 
> > Hi Jan
> > 
> > Does the SERDES clock need to change when going between 1000BaseX and
> > 2500BaseX?
> > 
> > If so, it sounds like Linux not having control of that clock is going
> > to limit what can be supported.
> 
> No, the SerDes clock remains the same, the change is done internally, without
> any necessity of clock change intervention by GMAC driver.

Hi Jan

Thanks for the information. So this binding should work.

The only suggestion i have is that the binding does not call is SGMII
clock, because it is used for more than SGMII, also 1000base-X, and
2500Base-X. So PCS clock might be better.

	Andrew