[U-Boot-Users] debugging u-boot

[Lei Sun]

Hi ben:
  Thanks!
  Lession learned, Follow the SDK! clearly our hardware guy didn't.
Right now our board is full of wite wire :-) . We even have to bring
32 wires out of the SDRAM to make it works!

On 10/20/06, Ben Warren <bwarren at qstreams.com> wrote:
> On Fri, 2006-10-20 at 13:19 -0400, Lei Sun wrote:
> > Hi Ben:
> >   Thanks for the tips!
> >   We didn't use local bus interface to flash, but used 60x bus
> > instead. I looked at the schematic and did found some difference
> > between SDK (PQ2FADS-VR) and our board. We used JS28T256P30N95 flash,
> > and connect all address pins to CPU's ADD pins, but the SDK use
> > BADDR[27-29] to connect to flash's A[2] - A[0].
> > According to the mpc82xx manul, that should be the right way.
> >   That's so weird, because i was able to read the correct content out
> > of the flash, after manually initialized the BR/OR register through
> > JTAG.  It shouldn't be working at all if the flash connection was
> > wrong somehow.
>
> We made the same mistake on our first board, which is why I'm familiar
> with the topic.  Luckily, as you've noticed, your wiring will work for
> general purpose flash access, just not the reading of RCW values.  From
> what I've read, things are done this way because at initialization the
> CPU doesn't know the flash chip's data bus width so it does some tricks
> to get the data from any width device.  If you look at the first several
> words of your U-boot image, you'll see that each byte of your RCW is
> repeated 8 times.
>
> Anyway, hopefully you can either white-wire or load your RCW from
> another source.  In our case, we were lucky enough to have an I2C EEPROM
> device at the right address.  Your CPU manual probably mentions several
> options.
>
> regards,
> Ben
>
>