Re: pgprot_writecombine & shub 1.x

From: David Mosberger <davidm_at_napali.hpl.hp.com>
Date: 2005-01-12 09:12:08
>>>>> 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
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Received on Tue Jan 11 17:16:04 2005

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