netdev - Re: [PATCH net-next v4 0/5] dpaa2-eth: add MAC/PHY support through phylink

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Date:   Fri, 22 Nov 2019 00:06:31 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Ioana Ciornei <ioana.ciornei@....com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        laurentiu.tudor@....com, andrew@...n.ch, f.fainelli@...il.com
Subject: Re: [PATCH net-next v4 0/5] dpaa2-eth: add MAC/PHY support through
 phylink

On Sun, Nov 17, 2019 at 04:49:24PM +0000, Russell King - ARM Linux admin wrote:
> On Thu, Oct 31, 2019 at 01:18:27AM +0200, Ioana Ciornei wrote:
> > The dpaa2-eth driver now has support for connecting to its associated PHY
> > device found through standard OF bindings. The PHY interraction is handled
> > by PHYLINK and even though, at the moment, only RGMII_* phy modes are
> > supported by the driver, this is just the first step into adding the
> > necessary changes to support the entire spectrum of capabilities.
> 
> Hi,
> 
> You mention that one of the aims here is to eventually support SFPs.
> Do you have a plan to solve the current problem with the DPAA2
> structure, where the physical network interfaces are configured at
> boot time by RCW for their operating mode?
> 
> If you want full SFP support, then you will need to dynamically
> reconfigure the network interfaces.  For example, 10G NBASE-T SFP+
> modules will dynamically switch between 10GBASE-R (XFI), 5000BASE-X,
> 2500BASE-X, and SGMII depending on the copper side link speed.  The
> PHY may also support UXSGMII but it doesn't power up that way and it
> is not known whether it is possible or how to change the interface
> mode to UXSGMII.
> 
> Then there's the whole issue of SGMII vs 1000BASE-X SFPs, and fiber
> channel SFPs that can operate at 2500BASE-X.

The last thing to be aware of WRT SFPs is that not all of those which
use SGMII send the 16-bit configuration word.  There's at least SFP
out there that I have at the moment where the PHY chip on it is not
capable of doing so, due to the way the chip vendor designed the
device - yet it expects to link to a MAC using SGMII at 1G and 100M
rates by forcing the rates on the MAC side.

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