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-rw-r--r--README21
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diff --git a/README b/README
index 5cbe7c1..46e6a33 100644
--- a/README
+++ b/README
@@ -1929,6 +1929,27 @@ Configuration Settings:
Scratch address used by the alternate memory test
You only need to set this if address zero isn't writeable
+- CFG_MEM_TOP_HIDE (PPC only):
+ 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 option can be used as a workaround for the 440EPx/GRx
+ CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
+ be touched.
+
+ WARNING: Please make sure that this value is a multiple of
+ the Linux page size (normally 4k). If this is not the case,
+ then the end address of the Linux memory will be located at a
+ non page size aligned address and this could cause major
+ problems.
+
- CFG_TFTP_LOADADDR:
Default load address for network file downloads