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

[Jung-uk Kim]

On Friday 16 October 2009 02:25 pm, M. Warner Losh wrote:
> In message: <200910161400.00564.jkim at FreeBSD.org>
>
>             Jung-uk Kim <jkim at FreeBSD.org> writes:
> : On Friday 16 October 2009 01:46 pm, Jung-uk Kim wrote:
> : > 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?
> :
> : It seems pmap_mapdev() on ia64 uses IA64_PHYS_TO_RR6() macro.  If
> : I read the source correctly, then it is gives UC mapped "view" of
> : the physical address, right?  If so, orm(4) can simply do
> : pmap_mapdev()/pmap_unmapdev() around bus_space_read_region_1(). 
> : Am I right?
>
> I don't think that's the right solution here.  The pmap_mapdev
> stuff should happen when the resource is activated...

For that, I guess we need another resource flag, e.g., RF_DEVICE, 
maybe?

Jung-uk Kim