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

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Date:   Fri, 04 Nov 2016 15:22:15 +0000
From:   Måns Rullgård <mans@...sr.com>
To:     Andrew Lunn <andrew@...n.ch>
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

Andrew Lunn <andrew@...n.ch> writes:

> 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.

There's source code that disagrees with that.  The Broadcom GENET
driver, for instance.

>>  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.

Those few drivers that do anything differently based on these values
enable clock delay in the MAC.  That's why I wrote the NB8800 driver the
way I did.

-- 
Måns Rullgård