netdev - Re: [RFC/PATCH] net: nixge: Add PHYLINK support

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Date:   Thu, 6 Sep 2018 09:36:23 -0700
From:   Moritz Fischer <moritz.fischer@...us.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Alex Williams <alex.williams@...com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC/PATCH] net: nixge: Add PHYLINK support

Andrew,

On Wed, Sep 5, 2018 at 5:31 AM, Andrew Lunn <andrew@...n.ch> wrote:
>> Let me check, it seems there is a register that indicates whether the MAC can
>> do either 1G or 10G. I might be able to use that for some of the above, but
>> there is not really much in terms of writable registers there.
>
> Can the MAC do 10 or 100? At the moment, you don't have anything
> stopping the PHY anto-neg'ing 10Half. If the MAC does not fully
> implement standard Ethernet, you need to tell the PHY driver about
> this. That is what the validate call is about. phylink and phylib
> knows what the PHY supports. It passes that list to the validate
> call. You need to then remove all the modes the MAC does not support.

Makes sense, thanks for clarifying. I'll do some more research on this.
>
>> It's like a DMA engine with a bit of MDIO on the side. Let me see if
>> I can make it look less weird with that. If not I'll go with a
>> comment explaining that there isn't much to do for the MLO_AN_PHY
>> case and the MLO_FIXED cases?
>
> You again need to configure the MAC to the selected speed, duplex,
> etc. If the link is down, you want to disable the MAC. You need this
> for both MLO_AN_PHY and MLO_FIXED, because both specify speeds,
> duplex, etc.

I'll look into it.

Moritz