[U-Boot-Users] [PATCH v2] PPC405EX(r) ECC and SDRAM Initialization Clean-ups

[kenneth johansson]

On Mon, 2008-04-28 at 14:47 -0700, Grant Erickson wrote:
> On 4/28/08 2:27 PM, Wolfgang Denk wrote:
> > In message <1209401636-9846-1-git-send-email-gerickson at nuovations.com> you
> > wrote:
> >> The primary goal of these changes is to unify some of the low-level
> >> SDRAM and ECC initialization code for the PPC4xx processors that use a
> >> common DDR2 SDRAM controller.
> >> 
> >> In particular, in the case of the 405EX[r], it must initialize SDRAM
> >> before a primordial stack is available since OCM doesn't exist and the
> >> data cache does not work for such a purpose. As a consequence, the ECC
> >> (and SDRAM) initialization code must be stack-free.
> > 
> > Stefan already asked this... I would also like to understand why the
> > data cache cannot be used for initial RAM as we do on so many other
> > systems?
> 
> Agreed. The changes were based on the comments in the Kilauea and Makalu
> board ports indicating that this had been attempted--twice--and didn't work.
> 
> I am escalating with AMCC to find out if this is a processor errata, board
> issue or just a programming issue that needs to be investigated further.

The cache trick works fine on 405CR/405GP. Is the cache redesigned for
405EX. Why would they still call it a 405 if the core was redesigned?