[U-Boot-Users] pci memory booting on ppc460

[ayman at austin.rr.com]

On Wed, Apr 23, 2008 at 10:26:51AM +0200, Stefan Roese wrote:

> Full ACK from me. I would always recommend to use a small NOR FLASH with a 
> full-blown U-Boot for booting from NOR with full DDR2 setup etc. All this 
> will be hard to implement with all the restrictions for booting from PCI 
> (even though I have never done this before, but I suspect that it will be 
> quite as limited as booting from NAND).
> 
> > But of course there may be 
> > reasons to want to boot over PCI ...
> 
> Yes, what is the main reason you want to do this? As mentioned above, I 
> recommend to boot from a small NOR FLASH (512kB) and "wait" in U-Boot for the 
> PCI host to provide the OS/application image via PCI.

Ok, here is what I want to do.  I have a board that has several PPC460s
on it.  Each has its own DDR2.  One of them is the master and boots up
normally today with uboot, launches linux, etc.  What I want to do is
have that master load the flash binary image into memory and then lock
that memory down (via whatever kernel calls are required).  Then I want
to configure each slaves PCI bar registers to be able to read from this
main memory and then tell them to go.  So my thought was that it would
appear to the slaves that they are just loading from a regular flash
and this image would contain uboot, kernel, root filesystem.  Basically
everything a flash normally would have.  It sounded reasonable at the
time.   The reason to avoid a flash on every one is so that we don't
have to reflash that many CPUs every time and because it will take up
more board space.  Thanks 

- ame