From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (from majordomo@localhost) by oss.sgi.com (8.11.3/8.11.3) id f4AMTbJ17225 for linux-mips-outgoing; Thu, 10 May 2001 15:29:37 -0700 Received: from dea.waldorf-gmbh.de (IDENT:root@localhost [127.0.0.1]) by oss.sgi.com (8.11.3/8.11.3) with ESMTP id f4AMTYF17222 for ; Thu, 10 May 2001 15:29:35 -0700 Received: (from ralf@localhost) by dea.waldorf-gmbh.de (8.11.1/8.11.1) id f4AKKIj06232; Thu, 10 May 2001 17:20:18 -0300 Date: Thu, 10 May 2001 17:20:18 -0300 From: Ralf Baechle To: Jun Sun Cc: "Maciej W. Rozycki" , linux-mips@oss.sgi.com Subject: Re: lift the ioport_resource limit ... Message-ID: <20010510172018.A6188@bacchus.dhis.org> References: <3AFAD9E8.EC4D6D80@mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <3AFAD9E8.EC4D6D80@mvista.com>; from jsun@mvista.com on Thu, May 10, 2001 at 11:11:53AM -0700 X-Accept-Language: de,en,fr Sender: owner-linux-mips@oss.sgi.com Precedence: bulk On Thu, May 10, 2001 at 11:11:53AM -0700, Jun Sun wrote: > I would not normally assign IO space above 0xffff either. But recently I > found multiple PCI buses, especially dual PCI buses, are getting popular, as > examplified by two Gallelio chips and the new NEC Vrc5477 chips. > > Since all drivers share the same mips_io_port_base, - even though the devices > may be on different PCI buses - we need to assign the PCI IO windows > contiguously so that drivers can share the same base address. In most such > setups, you will get more than 0xffff IO ranges. After some discussion with some of the Linux PCI guys I think we should try to avoid extend the per-bus I/O address space beyond 64k ports. This is not a very strong ``should avoid'', though. The primary concern is a number of broken peripheral chips which apparently are floating around out there in good numbers. Another reason to not extend the PCI-bus address range to 4g ports is the size of the available physical address space in the main processor's address space itself. Limited by the 32-bit address space we can only address a limited number via in/out anyway, so we better shouldn't fake what we ain't got (cited freely after Seymoure Cray), so 4g ports is silly anyway. Ralf