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

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Date:   Thu, 24 Aug 2017 18:04:01 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Antoine Tenart <antoine.tenart@...e-electrons.com>,
        davem@...emloft.net, kishon@...com, jason@...edaemon.net,
        sebastian.hesselbarth@...il.com,
        gregory.clement@...e-electrons.com,
        thomas.petazzoni@...e-electrons.com, nadavh@...vell.com,
        linux-kernel@...r.kernel.org, mw@...ihalf.com, stefanc@...vell.com,
        miquel.raynal@...e-electrons.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 09/13] net: mvpp2: dynamic reconfiguration of
 the PHY mode

On Thu, Aug 24, 2017 at 06:57:43PM +0200, Andrew Lunn wrote:
> > 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 we need a hardware diagram...
> 
> How are the RJ45, copper PHY, SFP module connected to the SoC?
> 
> Somewhere there must be a mux, to select between copper and
> fibre. Where is that mux?

In the 88x3310 PHY:

                     .------- RJ45
MVPP2 ----- 88x3310 PHY
                     `------- SFP+

Here's the commentry I've provided at the very top of the 88x3310 driver
which describes all these modes:

 * There appears to be several different data paths through the PHY which
 * are automatically managed by the PHY.  The following has been determined
 * via observation and experimentation:
 *
 *       SGMII PHYXS -- BASE-T PCS -- 10G PMA -- AN -- Copper (for <= 1G)
 *  10GBASE-KR PHYXS -- BASE-T PCS -- 10G PMA -- AN -- Copper (for 10G)
 *  10GBASE-KR PHYXS -- BASE-R PCS -- Fiber
 *
 * If both the fiber and copper ports are connected, the first to gain
 * link takes priority and the other port is completely locked out.

It's not a copper-only PHY, it's just like most other PHYs out there
that support multiple connections, like the 88e151x series that support
both RJ45 and fibre and can auto-switch between them.

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