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 f4AINU109917 for linux-mips-outgoing; Thu, 10 May 2001 11:23:30 -0700 Received: from hermes.mvista.com (gateway-1237.mvista.com [12.44.186.158]) by oss.sgi.com (8.11.3/8.11.3) with ESMTP id f4AINQF09912; Thu, 10 May 2001 11:23:26 -0700 Received: from mvista.com (IDENT:jsun@orion.mvista.com [10.0.0.75]) by hermes.mvista.com (8.11.0/8.11.0) with ESMTP id f4AIBQ016225; Thu, 10 May 2001 11:11:26 -0700 Message-ID: <3AFAD9E8.EC4D6D80@mvista.com> Date: Thu, 10 May 2001 11:11:53 -0700 From: Jun Sun X-Mailer: Mozilla 4.72 [en] (X11; U; Linux 2.2.18 i686) X-Accept-Language: en MIME-Version: 1.0 To: "Maciej W. Rozycki" CC: Ralf Baechle , linux-mips@oss.sgi.com Subject: Re: lift the ioport_resource limit ... References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mips@oss.sgi.com Precedence: bulk "Maciej W. Rozycki" wrote: > > On Wed, 9 May 2001, Jun Sun wrote: > > > The PCI IO space essentially extends the ISA bus, which effectively removes > > the 0xffff limits. > > Note that while there is usually no problem with using addresses beyond > 64kB in the PCI I/O space, certain PCI-to-PCI bridges may not pass such > accesses across. So it's best to avoid assigning and using them. That's > why Linux remaps "high" I/O space resources on Alpha, which get set up for > some systems by the SRM console (firmware), e.g. in the system I was using > a few years ago, SRM used to assign addresses around 0x11000 and 0x12000 > for the onboard network and SCSI devices, IIRC. > 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. Jun