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