From mboxrd@z Thu Jan 1 00:00:00 1970 From: Larry Johnson Date: Fri, 28 Mar 2008 09:54:56 -0500 Subject: [U-Boot-Users] [PATCH v4] ppc: Add CFG_MEM_TOP_HIDE option to hide memory area that doesn't get "touched" In-Reply-To: <200803281105.33719.sr@denx.de> References: <1206523009-18011-1-git-send-email-sr@denx.de> <200803270655.10577.sr@denx.de> <47EBE8A9.1080806@acm.org> <200803281105.33719.sr@denx.de> Message-ID: <47ED06C0.7000306@acm.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Stefan Roese wrote: > 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. I'm not explaining it well, you can look at "http://en.wikipedia.org/wiki/English_relative_clauses" for a better explanation. What you have above should be technically correct, at worse it would be redundant. Best regards, Larry