[U-Boot-Users] [PATCH v4] ppc: Add CFG_MEM_TOP_HIDE option to hide memory area that doesn't get "touched"

[Kumar Gala]

On Mar 26, 2008, at 4:16 AM, Stefan Roese wrote:
> If CFG_MEM_TOP_HIDE is defined in the board config header, this  
> specified
> memory area will get subtracted from the top (end) of ram and won't  
> get
> "touched" at all by U-Boot. By fixing up gd->ram_size the Linux kernel
> should gets passed the now "corrected" memory size and won't touch it
> either. This should work for arch/ppc and arch/powerpc. Only Linux  
> board
> ports in arch/powerpc with bootwrapper support, that recalculate the
> memory size from the SDRAM controller setup will have to get fixed.
>
> This patch enables this config option on some PPC440EPx boards as a  
> workaround
> for the CHIP 11 errata. Here the description from the AMCC  
> documentation:

If you reduce the memory size this way does the 44x kernel have issues  
with the TLBs that are used to mapped pin kernel lowmem?

I know on 85xx this would be a bad thing and rather than changing gd- 
 >ram_size, i'd add a memreserve in the device tree that the kernel  
got passed.

- k