netdev - Re: [EXT] Re: [PATCH net-next 09/13] net: mvpp2: dynamic reconfiguration of the PHY mode

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Date:   Fri, 25 Aug 2017 09:19:55 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Antoine Tenart <antoine.tenart@...e-electrons.com>
Cc:     Stefan Chulski <stefanc@...vell.com>, Andrew Lunn <andrew@...n.ch>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kishon@...com" <kishon@...com>,
        "jason@...edaemon.net" <jason@...edaemon.net>,
        "sebastian.hesselbarth@...il.com" <sebastian.hesselbarth@...il.com>,
        "gregory.clement@...e-electrons.com" 
        <gregory.clement@...e-electrons.com>,
        "thomas.petazzoni@...e-electrons.com" 
        <thomas.petazzoni@...e-electrons.com>,
        Nadav Haklai <nadavh@...vell.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mw@...ihalf.com" <mw@...ihalf.com>,
        "miquel.raynal@...e-electrons.com" <miquel.raynal@...e-electrons.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [EXT] Re: [PATCH net-next 09/13] net: mvpp2: dynamic
 reconfiguration of the PHY mode

On Thu, Aug 24, 2017 at 07:14:18PM +0200, Antoine Tenart wrote:
> On Thu, Aug 24, 2017 at 05:08:29PM +0000, Stefan Chulski wrote:
> > > > Imagine phylib is using the copper Ethernet PHY, but the MAC is using
> > > > the SFP port. Somebody pulls out the copper cable, phylib says the
> > > > link is down, turns the carrier off and calls the callback. Not good,
> > > > since your SFP cable is still plugged in...  Ethtool is
> > > > returning/setting stuff in the Copper Ethernet PHY, when in fact you
> > > > intend to be setting SFP settings.
> > > 
> > > I see what could be the issue but I do not understand one aspect though:
> > > how could we switch from one PHY to another, as there's only one output
> > > between the SoC (and so a given GoP#) and the board. So if a given PHY can
> > > handle multiple modes I see, but in the other case a muxing somewhere would
> > > be needed? Or did I miss something?
> > 
> > I think PHY name and PHY mode struct that describe here both MAC to
> > PHY and PHY to PHY connection create confusion...  Serdes IP lane
> > doesn't care if connector is SFP, RJ45 or direct attached cable.
> > mvpp22_comphy_init only configures MAC to PHY
> > connection. SFI for 10G(KR in mainline), SGMII for 1G and HS_SGMII for
> > 2.5G.
> 
> So maybe one confusion was to name them PHY_MODE_10GKR and
> PHY_MODE_SGMII. It could be PHY_MODE_10G and PHY_MODE_1G instead.

SGMII mode supports 100M and 10M as well using data repetition, so 1G
makes it look like those speeds are not supported.

-- 
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