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

[Michael Schwingen <rincewind@discworld.dascon.de>]

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.
> 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.
> 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.

cu
Michael