From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265847AbUHRLRH (ORCPT ); Wed, 18 Aug 2004 07:17:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265317AbUHRLRH (ORCPT ); Wed, 18 Aug 2004 07:17:07 -0400 Received: from 216-54-166-5.gen.twtelecom.net ([216.54.166.5]:51671 "EHLO texas.encore.com") by vger.kernel.org with ESMTP id S265847AbUHRLQz (ORCPT ); Wed, 18 Aug 2004 07:16:55 -0400 Message-ID: <41233AA3.47834A14@compro.net> Date: Wed, 18 Aug 2004 07:16:51 -0400 From: Mark Hounschell Reply-To: markh@compro.net X-Mailer: Mozilla 4.8 [en] (X11; U; Linux 2.4.26-ert i686) X-Accept-Language: en MIME-Version: 1.0 To: William Lee Irwin III Cc: Brian McGrew , linux-kernel@vger.kernel.org Subject: Re: Help with mapping memory into kernel space? References: <20040818073141.GV11200@holomorphy.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org William Lee Irwin III wrote: > > On Tue, Aug 17, 2004 at 10:39:38PM -0700, Brian McGrew wrote: > > The overall problem is that the more system memory we install, > > the fewer IBB's we can use. For instance, 256MB lets us use > > four IBB's; 512MB lets us use three IBB's and so on. Basicly, > > the kernel blows up trying to map memory. Each IBB has two > > banks of 64MB of RAM on them which we try and memmap to system > > memory for speed of addressing. So essentaily, we're sending > > out four camera systems with only 256MB of memory which is only > > about one quarter of what we need. > > I can't think of any better way to explain it other than it's > > almost like adding system memory subtracts from kernel memory. > > Does that make any sense? We've tried building the kernel with > > the 4GB memory model and the 64GB memory model and had no success. > > You appear to be trying to ioremap() vast areas. ia32 has limited > address space, so you need to do one of two things: > (a) subdivide into portions mapped into different address spaces > (b) map portions on demand > > There is no support for (a) in Linux. > You might try the bigphysarea patch. We have basically the same problem with hardware not capabile of hardware scatter/gather in DMA mode. Bigphysarea was our solution. It does not appear to be available for the 2.6 kernel however Mark