linux-kernel - Re: [RFC net-next 6/8] net: phylink: Configure MAC/PCS when link is up without PHY

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Message-ID: <20200127140038.GD13647@lunn.ch>
Date:   Mon, 27 Jan 2020 15:00:38 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     Jose Abreu <Jose.Abreu@...opsys.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC net-next 6/8] net: phylink: Configure MAC/PCS when link is
 up without PHY

> Yes, I realise that, but it comes with the expense of potentially
> breaking mvneta and mvpp2, where the settings are automatically
> passed between the PCS and MAC in hardware. I also believe DSA
> works around this, and I need to look at that.

Hi Russell

The mv88e6xxx driver has code for when SGMII is used. It transfers the
negotiated speed from the PCS to the MAC.

But it recently turned out something like this is also needed for
other link modes involving the SERDES. It used to work, i think
because Phylink would initially configure the MAC approximately right,
or the mv88e6xxx driver was looking at phylink state it should not.
But it no longer works.

I would like to see a generic solution, and would be happy to remove
the current SGMII code when you have something to replace it.

    Andrew