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

Jean-Christophe PLAGNIOL-VILLARD
2009-01-28T23:13:47Z

On 22:42 Wed 28 Jan , Haavard Skinnemoen wrote:
> 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...
make sense
so I'll put a 10Mpbs phy personnaly instead or a 10/100 that can be put in a
10 mode instead to avoid to manage it in the code
>
> 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.
I do not mean the autoneg but to specify to the phy, if possible, to never
accept the 100Mps instead of do it in the code
>
> 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?
why not

Best Regards,
J.