----- Original Message ----- From: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl> To: "Jun Sun" <jsun@mvista.com> Cc: <jim@jtan.com>; <linux-mips@oss.sgi.com> 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
