Re: pgprot_writecombine & shub 1.x

David Mosberger
2005-01-11T22:12:08Z

>>>>> On Tue, 11 Jan 2005 12:00:02 -0800, Jesse Barnes <jbarnes@sgi.com> said:

Jesse> SGI sn2 systems based on SHub 1.x chipsets don't support the
Jesse> write combine attribute on PIO space, only regular memory
Jesse> space. This is a problem because drivers often expect to map
Jesse> PIO space with certain memory attributes (e.g. the PCI mmap
Jesse> code, drm, fbmem, acorn video). None of the calls to
Jesse> pgprot_writecombine are in performance critical paths, so
Jesse> would making pgprot_writecombine into a machine vector would
Jesse> be ok? Comments?

This seems wrong to me. pgprot_writecombine() should do what it says,
no more and no less.

The EFI memory-map has already all the info needed to determine
whether write-combine mapping is supported, so perhaps the code should
be changed to take that into consideration instead?

--david