x86BIOS and the ISA bus and low memory in general...

[Jung-uk Kim]

On Thursday 15 October 2009 04:37 pm, Marcel Moolenaar wrote:
> On Oct 15, 2009, at 12:45 PM, M. Warner Losh wrote:
> > [[ redirected to arch@ ]]
> >
> > In message: <200910151431.53236.jkim at FreeBSD.org>
> >            Jung-uk Kim <jkim at FreeBSD.org> writes:
> > <snip>
> >
> > : This is actually very interesting discussion for me because one
> > : of
> >
> > my
> >
> > : pet projects is extending x86bios to support non-PC
> > : architectures. If anyone is interested, the current source
> > : tarball is here:
> > :
> > : http://people.freebsd.org/~jkim/x86bios-20091015.tar.bz2
> > :
> > : Especially, please see the code around #ifdef
> > : X86BIOS_COMPAT_ARCH. Basically, mapping I/O ports and orm(4) is
> > : missing.  We don't have
> >
> > to
> >
> > : implement I/O ports but orm(4) vs. bus_space(9) is critical to
> > : make it a reality.  Please consider it as a real practical
> > : example for orm, not just a blackhole driver. :-)
> >
> > I thought that most video cards had I/O ports as well as video
> > RAM that needed to be mapped...  Am I crazy?
>
> It depends on the platform. On an Itanium machine I have the
> VGA frame buffer is at physical address 0xA0000-0xC0000.

The address is the same, then. :-)

> The only requirement is that you use non-cached I/O, otherwise
> you get a machine check. This can mean a non-identity mapping
> or not. It all depends...

I couldn't find a way to manipulate memory attribute directly on ia64, 
i.e., mem_range_attr_{get,set}() and pmap_mapdev_attr() only exist on 
amd64 and i386.  Does pmap_mapdev() set the attribute as UC?

> I/O ports don't exist and there's a memory region for generating
> I/O port accesses, but the translation is not linear, so you
> can't work with a single base and port offset to get this to work.
> See ia64_ioport_address() in sys/ia64/ia64/machdep.c

It seems there are PC-compatible inline functions {in,out}[bwl] in 
sys/ia64/include/cpufunc.h.  Will they work as I expect?

Thanks,

Jung-uk Kim