Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932859AbXLNEbc (ORCPT ); Thu, 13 Dec 2007 23:31:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756937AbXLNEbX (ORCPT ); Thu, 13 Dec 2007 23:31:23 -0500 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:56377 "EHLO ebiederm.dsl.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755754AbXLNEbW (ORCPT ); Thu, 13 Dec 2007 23:31:22 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: Roland Dreier Cc: venkatesh.pallipadi@intel.com, ak@muc.de, ebiederm@xmission.com, torvalds@linux-foundation.org, gregkh@suse.de, airlied@skynet.ie, davej@redhat.com, mingo@elte.hu, tglx@linutronix.de, hpa@zytor.com, akpm@linux-foundation.org, arjan@infradead.org, jesse.barnes@intel.com, linux-kernel@vger.kernel.org, Suresh Siddha Subject: Re: [RFC PATCH 06/12] PAT 64b: Add ioremap_wc support References: <20071213235543.568682000@intel.com> <20071213235712.339088000@intel.com> Date: Thu, 13 Dec 2007 21:28:23 -0700 In-Reply-To: (Roland Dreier's message of "Thu, 13 Dec 2007 20:17:14 -0800") Message-ID: User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1734 Lines: 43 Roland Dreier writes: > > --- linux-2.6.24-rc4.orig/include/asm-x86/io_64.h 2007-12-11 > 14:24:56.000000000 -0800 > > +++ linux-2.6.24-rc4/include/asm-x86/io_64.h 2007-12-11 15:49:52.000000000 > -0800 > > @@ -142,7 +142,8 @@ > > * it's useful if some control registers are in such an area and write > combining > > * or read caching is not desirable: > > */ > > -extern void __iomem * ioremap_nocache (unsigned long offset, unsigned long > size); > > +extern void __iomem * ioremap_nocache(unsigned long offset, unsigned long > size); > > +extern void __iomem * ioremap_wc(unsigned long offset, unsigned long size); > > I think ioremap_wc() needs to be available on all archs for this to be > really useful to drivers. It can be a fallback to ioremap_nocache() > everywhere except 64-bit x86, but it's not nice for every driver that > wants to use this to need an "#ifdef X86" or whatever. > > Also I didn't see anything like pgprot_wc() in the patchset (although pgprot_writcombined. > I just skimmed quickly for now). The use case I actually have would > be in a a driver's .mmap method, where I want to map device registers > into userspace with write-combining turned on: > > vma->vm_page_prot = pgprot_wc(vma->vm_page_prot); > io_remap_pfn_range(vma, vma->vm_start, pfn, PAGE_SIZE, > vma->vm_page_prot); > > where the pfn points into a PCI BAR (which will only be mapped once, > so no issues with conflicting PATs or anything like that). Eric -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/