[U-Boot] [PATCH v2 5/9] AVR32: macb - Disable 100mbps if clock is slow

[Haavard Skinnemoen]

Jean-Christophe PLAGNIOL-VILLARD wrote:
> > On the EVK1100 board, the CPU (UC3A0512) is connected to the PHY via an
> > RMII bus. This requires the CPU clock to be at least 50 MHz.
> > Unfortunately, the chip on current EVK1100 boards may be unable to run
> > at more than 50 MHz, and with the oscillator on the board, the closest
> > frequency we can generate is 48 MHz.  
> IMHO It's a HW design error to not use the MII

Some people want to use the extra pins for other things...

Unfortunately, there are quite a few boards with early engineering
samples around, and they have various issues. The chips that are in
production are capable of running fast enough to support RMII.

> > This patch makes it possible to limit the macb to 10 MBit for this
> > case. We are open for suggestions for other solutions.  
> I guest you may need to disable the phy auto config mode and force him to be
> see as a 10Mbps phy evenif it's a 10/100

No need to disable autonegotiation -- you still want to select between
half an full duplex, for example. But you'll need to limit the
available options to the ones that actually work.

That said, I kind of like Ben's suggestion -- it's a more general
solution to all sorts of board/phy/chip/whatever limitations.

As for a better name, how about CONFIG_MACB_ADVERTISE?

Haavard