[U-Boot] Question: Information regarding MII and PHY

[Graeme Russ]

Hello again,

On Thu, Sep 22, 2011 at 11:20 AM, Graeme Russ <graeme.russ at gmail.com> wrote:
> I'm looking at adding a new Gigabit Ethernet driver (Realtek
> RTL8211CL) to U-Boot. The datasheet, in addition to register

OK, the RTL8211CL is just the transceiver (PHY?) - The MAC is actually part
of an Intel PCH (Platform Controller Hub). From what I can gather MII is
the standard interface between the MAC (Intel PCH) and the transceiver/PHY
(RTL8211CL) (they actually communicate using RGMII - Reduced Gigabit Media
Independent Interface)

> descriptions, mentions MII/GMII and PHY support (but not much on the
> specifics). Now in U-Boot there appears to be a common set of code
> relating to PHY and MII. There appears to be a mix of Ethernet drivers
> that use MII/PHY and drivers that do not, but I cannot seems to quite
> get me head around it all. One weird thing is that there does not
> appear to be any granular inclusion of PHY drivers -
> /include/config_phylib_all_drivers.h defines them all when
> CONFIG_PHYLIB is defined, but I could not find any boards that defined
> just one PHY driver. I also cannot find how MII/PHY functions interact
> with PCI for PCI based cards.

I now see why there is no relationship between MII/PHY and PCI as they are
not connected to the PCI bus - Communication with the PHY is done through
the MAC. So is it the case that 'PHY Drivers' in U-Boot provide access
to the PHY (Transceiver) _through_ the MAC and in order to use the PHY
drivers, the MAC driver (i.e. the Ethernet driver) needs to provide hooks
to pass PHY requests from U-Boot over the (RG)MII interface?

Or am I even more confused?

> In short, I'm very confused - Can anyone give me any pointers to how
> it all fits together

Thanks,

Graeme