[U-Boot-Users] MII / RMII

[Ben Warren]

Stefan Roese wrote:
> On Tuesday 08 January 2008, Andy Fleming wrote:
>   
>>> I think that if you use an Ethernet and need to differentiate
>>> between MII and RMII they should be mutually exclusive.
>>> You either define CONFIG_RMII OR CONFIG_MII but not both.
>>> If you have a PHY on the chip, then you do not define any of the two.
>>> MII uses more pins and maybe different pins, so a port for a CPU
>>> should differentiate.
>>>       
>> I'm a little late to this, but I feel I should make sure people are aware
>> that CONFIG_MII and CONFIG_RMII are not, in this case, two different
>> options for the same concept.  CONFIG_MII is the option you enable to allow
>> MII Management operations to be done.  It should *probably* be called
>> CONFIG_MDIO.
>>     
>
> Yes, this would be good. Anyone interested in fixing up a patch for this?
>   
I think it's a noble idea, but probably a can of worms in practice. The 
use of the term 'MII' is rampant, for example we have 'mii' commands, 
and 'bbmii' commands. These both really concern MDIO, but I doubt we 
want to change them.

The real culprit is RMII. As Andy has pointed out, RMII is a data plane 
alternative to MII, but shares the MDIO control plane. RMII is a 
hardware configuration, and as such is 'set and forget' and highly 
implementation-specific. Having a global CONFIG_RMII makes no sense. If 
anything, CONFIG_RMII should be changed to stuff like CONFIG_TSEC_RMII_2 
etc. (a quickly made-up example with no grounding in reality), where the 
hardware binding is obvious.

regards,
Ben