From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 94F31DDE1F for ; Tue, 4 Dec 2007 06:07:44 +1100 (EST) Date: Mon, 3 Dec 2007 13:07:23 -0600 From: Matt Porter To: David Hawkins Subject: Re: Maximum ioremap size for ppc arch? Message-ID: <20071203190723.GB30746@gate.crashing.org> References: <36D7B34A3A79F84F82FA0C154F299F2505FE26D2@E03MVX1-UKDY.domain1.systemhost.net> <20071203153009.GA30746@gate.crashing.org> <475441DD.9030601@ovro.caltech.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <475441DD.9030601@ovro.caltech.edu> Cc: linuxppc-embedded@ozlabs.org List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, Dec 03, 2007 at 09:50:21AM -0800, David Hawkins wrote: > Could you comment on a similar problem I had/have. > > I have a CPU with 1GB memory, and I use about 20 cPCI boards that > I give 8MB windows in PCI space. When I was trying to load my > custom driver with these boards, it would give me ioremap failures. > On a CPU that had 512MB of memory it worked fine. My 'temporary hack' > (which is still in place) for the 1GB CPUs was to add mem=512M (or > whatever it is) to the kernel command line. That was a good > enough fix at the time :) > > I have figured I was running out of page table entries or something > like that and was going to investigate one of these days ... > > However, perhaps it was that I was running out of address space. > But 0xC0000000 is at 3GB, I can't see that I would be triggering > an address space issue: > > 1GB = 0x40000000 > 20 x 8MB = 160MB > > But, I figured I'd ask anyway :) Yes, same thing. There's N ways to fix it. But I see you're talking x86. > PS. The CPUs in this case are x86 based, while the PCI boards use > PLX-9054 bridges. I'm building new peripheral boards with MPC8349EAs > so this problem is going to rear its ugly head again soon, when > I work on the drivers for the new peripheral boards. You should be able to do something similar on x86 but the details are TBD. I would probably try to limit low memory to 512MB in the x86 case. -Matt