From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Tue, 11 Jan 2005 22:12:08 +0000 Subject: Re: pgprot_writecombine & shub 1.x Message-Id: <16868.20280.382146.632034@napali.hpl.hp.com> List-Id: References: <200501111200.02504.jbarnes@sgi.com> In-Reply-To: <200501111200.02504.jbarnes@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Tue, 11 Jan 2005 12:00:02 -0800, Jesse Barnes 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