From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gw01.mail.saunalahti.fi (gw01.mail.saunalahti.fi [195.197.172.115]) by ozlabs.org (Postfix) with ESMTP id 58C0C685CC for ; Wed, 19 Oct 2005 06:45:01 +1000 (EST) Message-ID: <435557A0.8090505@iki.fi> Date: Tue, 18 Oct 2005 23:14:24 +0300 From: Kalle Pokki MIME-Version: 1.0 To: dhlii@comcast.net References: <4354AC78.5080206@comcast.net> <4354B707.6060002@iki.fi> <435549C2.1000106@dlasys.net> In-Reply-To: <435549C2.1000106@dlasys.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: linuxppc-embedded Subject: Re: Need help Understanding initial memory conditions. List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , David H. Lynch Jr. wrote: > Kalle Pokki wrote: > >> 1. Put RAM to 0x0000000 and flash to some location it mirrors to your >> boot vector. Linux always expects your physical memory to be at zero. >> It is then mapped to virtual address 0xC0000000. > > In both this list and elsewhere I have seen several references to > the difficulty setting up Linux with a physical RAM base other than > 0x0. I was hoping that I could bypass that by re-arranging physical > memory using the BAT's or MMU. > I am gathering that while this is possible, that it not sufficient. > That if memory is re-arranged after power-on it has to be done by > something Linux is not aware of. I'm afraid you cannot fool Linux that way... it will take control of the BATs and MMU. Even as a concept, you cannot re-arrange physical memory with the MMU at all - it's virtual memory when you do the address translation. The only way to arrange physical memory is to program the memory controller. I don't know how flexible the OCM controller in ppc405 is, but I'd be surprised if one couldn't freely set the addresses to whatever suits best.