[U-Boot-Users] [PATCH] Add support for Generic PHY in macb

[Haavard Skinnemoen]

On Fri, 22 Feb 2008 16:05:34 +0100
Michael Schwingen <rincewind at discworld.dascon.de> wrote:

> Haavard Skinnemoen wrote:
> > All MII-capable PHYs should have a working PHYSID1 register. If it
> > doesn't, something is broken.
> >   
> It depends - I am not sure if there are PHYs which simply do not 
> implement MDIO, but at least for ethernet switches, such chips do exist.

Right. We might need to add support for such PHYs, but just disabling
the sanity check is far from enough.

In any case, the dm9161a PHY in question does implement MDIO, so it
really should work without any modifications.

> > So I think the CONFIG_GENERIC_PHY name is misleading -- the test is
> > generic enough as is. CONFIG_BROKEN_PHY would be better, if there's
> > really no way to get your PHY to behave.
> >   
> Right. Or CONFIG_PHY_NO_MDIO or something like that. This is in the 
> direction of CONFIG_MII_ETHSWITCH which is used eg. by AcTux-2 for this 
> purpose.

I think U-Boot needs a common PHY layer like Linux has. IIRC someone
suggested the same thing some time ago. There's no point going around
adding the same special-case code to every ethernet driver in the
tree...

> > But note that if MDIO communication isn't working, autonegotiation
> > won't work, and the speed and duplex settings will most likely be
> > wrong. So I don't think simply #ifdefing out that sanity check is
> > really going to solve any problems.
> >   
> The chip may do autonegotiation by default, however, the MAC driver 
> still needs to know about the negotiated speed/duplex, so unless there 
> is some board-specific way to read those (eg. by GPIO pins), only one 
> speed/duplex will work and all other modes will be broken. This is 
> different from the case with the hardwired ethernet switch - in case of 
> the switch, we know that the MII port is always running at 100Mbps, 
> full-duplex.

Hmm...most switches support autonegotiation don't they? If not, what
happens if you plug in in an old computer with a 10Mbps ethernet board?

But I guess we need something equivalent to CONFIG_FIXED_PHY in Linux...

Haavard