From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (from majordomo@localhost) by oss.sgi.com (8.11.2/8.11.3) id fBJ34q827827 for linux-mips-outgoing; Tue, 18 Dec 2001 19:04:52 -0800 Received: from ns1.ltc.com (vsat-148-63-243-254.c3.sb4.mrt.starband.net [148.63.243.254]) by oss.sgi.com (8.11.2/8.11.3) with SMTP id fBJ34ho27821 for ; Tue, 18 Dec 2001 19:04:45 -0800 Received: from prefect (unknown [10.1.1.86]) by ns1.ltc.com (Postfix) with SMTP id B1627590A9; Tue, 18 Dec 2001 21:02:19 -0500 (EST) Message-ID: <056a01c18831$919daf90$5601010a@prefect> From: "Bradley D. LaRonde" To: "Maciej W. Rozycki" , "Jun Sun" Cc: , References: Subject: Re: ISA Date: Tue, 18 Dec 2001 21:05:01 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Sender: owner-linux-mips@oss.sgi.com Precedence: bulk ----- Original Message ----- From: "Maciej W. Rozycki" To: "Jun Sun" Cc: ; Sent: Tuesday, December 18, 2001 8:50 PM Subject: Re: ISA > On Tue, 18 Dec 2001, Jun Sun wrote: > > Now when people using ioremap/readb/writeb method to access ISA memory space, > > which lives in the lower range of the "bus memory space", it will collide with > > system ram under 1:1 mapping assumption. > > Hmm, I believe there should be no such problem. For systems equipped > with the PCI bus we may just assume the low 16MB of PCI memory address > space is reserved for ISA memory addresses (it's hardwired for many > platforms, so there should be no problem with it), i.e. avoid programming > BARs to point to that space and make ioremap() (or __ioremap(), actually) > act accordingly, i.e. assume a 1:1 mapping for addresses above 16MB and > perform an ISA mapping for ones below 16MB. That sounds like the simplest and best solution. Regards, Brad From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <056a01c18831$919daf90$5601010a@prefect> From: "Bradley D. LaRonde" References: Subject: Re: ISA Date: Tue, 18 Dec 2001 21:05:01 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mips@oss.sgi.com To: "Maciej W. Rozycki" , Jun Sun Cc: jim@jtan.com, linux-mips@oss.sgi.com Message-ID: <20011219020501.FTcLKyT1gmQ0NMl8xe14L0EtJ3EJTgpCUCLe6fHXZ30@z> ----- Original Message ----- From: "Maciej W. Rozycki" To: "Jun Sun" Cc: ; Sent: Tuesday, December 18, 2001 8:50 PM Subject: Re: ISA > On Tue, 18 Dec 2001, Jun Sun wrote: > > Now when people using ioremap/readb/writeb method to access ISA memory space, > > which lives in the lower range of the "bus memory space", it will collide with > > system ram under 1:1 mapping assumption. > > Hmm, I believe there should be no such problem. For systems equipped > with the PCI bus we may just assume the low 16MB of PCI memory address > space is reserved for ISA memory addresses (it's hardwired for many > platforms, so there should be no problem with it), i.e. avoid programming > BARs to point to that space and make ioremap() (or __ioremap(), actually) > act accordingly, i.e. assume a 1:1 mapping for addresses above 16MB and > perform an ISA mapping for ones below 16MB. That sounds like the simplest and best solution. Regards, Brad