From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Tue, 12 Apr 2005 12:43:19 +0100 (BST) Received: from extgw-uk.mips.com ([IPv6:::ffff:62.254.210.129]:45083 "EHLO bacchus.net.dhis.org") by linux-mips.org with ESMTP id ; Tue, 12 Apr 2005 12:43:04 +0100 Received: from dea.linux-mips.net (localhost.localdomain [127.0.0.1]) by bacchus.net.dhis.org (8.13.1/8.13.1) with ESMTP id j3CBgqqQ021323; Tue, 12 Apr 2005 12:42:52 +0100 Received: (from ralf@localhost) by dea.linux-mips.net (8.13.1/8.13.1/Submit) id j3CBgqH8021322; Tue, 12 Apr 2005 12:42:52 +0100 Date: Tue, 12 Apr 2005 12:42:52 +0100 From: Ralf Baechle To: "Maciej W. Rozycki" Cc: Paul Chapman , linux-mips@linux-mips.org Subject: Re: ip27 PCI devices Message-ID: <20050412114252.GE5573@linux-mips.org> References: <1113251422.21580.33.camel@paul.dev.brocku.ca> <20050412105815.GC5573@linux-mips.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 7701 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: ralf@linux-mips.org Precedence: bulk X-list: linux-mips On Tue, Apr 12, 2005 at 12:18:15PM +0100, Maciej W. Rozycki wrote: > > > I've been experimenting with trying various PCI cards I have lying > > > around in my Origin 200, to see if I can make any of them work. > > > > The current Linux implementation limits IP27 to cards with 64-bit > > addressing capability. > > Do we have a problem with our implementation of PCI DMA masks or is the > low 4GB of PCI address space already consumed on this system? The problem > is most 32-bit PCI cards unfortunately do not support DAC. 32-bit devices can only address a tiny fraction of the address space on IP27. To make matters more interesting, there is no memory at all in the low 4GB of the crosstalk address space, so 32-bit PCI has to rely on the yet non-existing support for the IOMMU. SGI trying to save a little too much money on the external SRAM for the IOMMU in the Origin 200 finally made it a hard to use in an OS, deadlock prone thing. Ralf