netdev - Re: Ethernet not working on a different SoC with same eth HW

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Message-ID: <20161104151744.GG3600@lunn.ch>
Date:   Fri, 4 Nov 2016 16:17:44 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Måns Rullgård <mans@...sr.com>
Cc:     Mason <slash.tmp@...e.fr>, netdev <netdev@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Timur Tabi <timur@...eaurora.org>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        Zefir Kurtisi <zefir.kurtisi@...atec.com>,
        Martin Blumenstingl <martin.blumenstingl@...il.com>,
        Uwe Kleine-Konig <u.kleine-koenig@...gutronix.de>,
        Daniel Mack <zonque@...il.com>,
        Sebastian Frias <sf84@...oste.net>
Subject: Re: Ethernet not working on a different SoC with same eth HW

On Fri, Nov 04, 2016 at 03:05:00PM +0000, Måns Rullgård wrote:
> Andrew Lunn <andrew@...n.ch> writes:
> 
> >> > I agree with you. But fixing it is likely to break boards which
> >> > currently have "rgmii", but actually need the delay in order to work.
> >> 
> >> Does the internal delay here refer to the PHY or the MAC?  It's a
> >> property of the MAC node after all.
> >
> > It is the PHY which applies the delay.
> 
> Says who?

The source code.

>  Some MACs can do it too.

I'm sure they can. But look at the code. Nearly none do, and those
that do are potentially broken.
 
> There is also no way to specify the amount of delay required even though
> many devices support more than one value.

Those PHYs that which support variable delays add there own device
tree properties. See for example Micrel KSZ9021/KSZ9031 Gigabit Ethernet PHY

     Andrew