netdev - Re: [PATCH net-next 1/2] net: phylink: explicitly configure in-band autoneg for PHYs that support it

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Message-ID: <YCgFc0sK1BYtAo4d@lunn.ch>
Date:   Sat, 13 Feb 2021 17:59:31 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Michael Walle <michael@...le.cc>
Cc:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Antoine Tenart <atenart@...nel.org>,
        Quentin Schulz <quentin.schulz@...tlin.com>,
        netdev@...r.kernel.org, Heiner Kallweit <hkallweit1@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Maxim Kochetkov <fido_max@...ox.ru>,
        Bjarni Jonasson <bjarni.jonasson@...rochip.com>,
        Steen Hegelund <steen.hegelund@...rochip.com>,
        UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH net-next 1/2] net: phylink: explicitly configure in-band
 autoneg for PHYs that support it

> Thanks, but I'm not sure I understand the difference between "rate
> adaption" and symbol repetition. The SGMII link is always 1.25Gb,
> right? If the media side is 100Mbit it will repeat the symbol 10
> times or 100 times in case of 10Mbit. What is "rate adaption" then?

Hi Michael

Some multiG PHYs fix their host side interface to say 10Gbps,
independent of what the media side is doing. The PHY adapts the 10Gbps
stream it gets from the host down to 10Mbps etc as needed, dropping
frames if its internal buffers overflow.

       Andrew