Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752455AbYCPMU2 (ORCPT ); Sun, 16 Mar 2008 08:20:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751718AbYCPMUT (ORCPT ); Sun, 16 Mar 2008 08:20:19 -0400 Received: from www.tglx.de ([62.245.132.106]:41199 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751706AbYCPMUS (ORCPT ); Sun, 16 Mar 2008 08:20:18 -0400 Date: Sun, 16 Mar 2008 13:20:08 +0100 From: "Hans J. Koch" To: "Leon Woestenberg" Cc: "Jean-Samuel Chenard" , "Thomas Gleixner" , LKML , "Greg KH" , grant.likely@secretlab.ca, "Juergen Beisert" Subject: Re: Linux UIO driver cache problem in PowerPC (fix) Message-ID: <20080316132008.5050153d@bluebox.local> In-Reply-To: References: <169c03cb0803121222h5fca9cdal5af873cd2a700f4d@mail.gmail.com> <20080313081932.4edee290@dilbert.local> <20080314113336.63af1e7a@bluebox.local> Organization: Linutronix GmbH X-Mailer: Claws Mail 3.0.1 (GTK+ 2.12.0; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1345 Lines: 41 Am Sun, 16 Mar 2008 03:51:10 +0100 schrieb "Leon Woestenberg" : > Hello, > > On Fri, Mar 14, 2008 at 11:33 AM, Hans J. Koch > wrote: > > I investigated a bit and found your patch to be correct. I cleaned > > it up a bit and sent it to Greg and LKML. I added you as author > > and also took the freedom to add your Signed-off-by. > > > Could you elaborate why exactly this is needed, maybe even as a > comment in the patch? As far as I understood, the VM_IO flag simply means that the page is used for IO. On some architectures this automatically means that the page is not cached, but this is not guaranteed. That's why pgprot_noncached() exists. If I misunderstood something or somebody can explain it better, please let me know. > > It seemed non-trivial enough to rectify adding a comment. It _is_ trivial. It's just something you don't need every day, and therefore it's not known to everybody (including me) or not obvious. But if you look at it: VM_IO means IO pgprot_noncached means noncached What could be more trivial? Thanks, Hans -- 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/