[U-Boot] [PATCH 5/6] net: Kirkwood_egiga: forced interface speed config support

[Lennert Buytenhek <buytenh@marvell.com>]

On Tue, Jul 21, 2009 at 12:01:49PM -0700, Prafulla Wadaskar wrote:

> > >>> By default Auto Negotiation is enabled for interface speed but on 
> > >>> some platforms like RD6281A it does not work.
> > >>> If you want to forced program it to desired speed, this 
> > patch helps-
> > >>>
> > >>> Through this patch Auto negotiation can be disabled and desired 
> > >>> interface speed can be configured
> > >>>
> > >>> This patch is tested on RD6281A Kirkwood board
> > >>>
> > >>> Signed-off-by: Prafulla Wadaskar <prafulla@marvell.com>
> > >>> ---
> > >>>       
> > >> Applied to net repo.
> > >>     
> > >
> > > Please reconsider - see my previous comment. [Sorry it came 
> > so late.]
> > >
> > > Best regards,
> > >
> > > Wolfgang Denk
> > >
> > >   
> > No problem.  I assumed it was a chip erratum but should have 
> > looked closer.  Let's wait for Prafulla's response.
>
> Ideally auto negotiation must work, but :-(
> I don't think this is not for SoC/PHY erratum since both are working
> okay with other boards.
> Only the difference is on RD6281A the multichip mode is used,
> I am discovering why it is not working.

Isn't it just because on the RD6281A, the first ethernet MAC of the
CPU is connected to an ethernet switch chip instead of an ethernet PHY,
and therefore there is no negotiation to be done?  (The second MAC
is connected to a PHY directly, so that one should just use autoneg.)

Even on the RD6281Z, we should just force the ethernet MAC to a
fixed speed/duplex, since even though PHY polling might work there,
we'll be talking to the PHY corresponding to the first switch port,
which means that you might not be able to tftp from the second switch
port or so if there's nothing plugged into the first one.

FWIW, the linux kernel port also forces 1000/full on the CPU MACs where
a switch chip is connected.  On those CPU MACs where there is a switch
chip connected, the (R)(G)MII interface becomes purely a bus to
transport packets into and out of the crossbar, one that is always up.