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

[Stefan Roese]

On Thursday 27 March 2008, Larry Johnson wrote:
> It's clear now, but unfortunately I don't know enough to tell whether it
> is also correct :-( .  The statement as now written implies that the
> statement without the clause, i.e., "Only Linux board ports in
> arch/powerpc with bootwrapper support will have to get fixed in Linux
> additionally", is also true.  If this is not correct (because boards
> that do not recalculate their memory size do not need to be fixed in
> Linux), then you would write: "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 in Linux additionally."

Now I'm confused. :) 

Here is the current version I now have in my "master" branch (with your last 
sentense):

- 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 in Linux additionally.

		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.

Please send a patch to change this description if necessary.

Thanks.

Best regards,
Stefan

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