Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752618AbXFCWY7 (ORCPT ); Sun, 3 Jun 2007 18:24:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751277AbXFCWYx (ORCPT ); Sun, 3 Jun 2007 18:24:53 -0400 Received: from caramon.arm.linux.org.uk ([217.147.92.249]:4200 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751095AbXFCWYw (ORCPT ); Sun, 3 Jun 2007 18:24:52 -0400 Date: Sun, 3 Jun 2007 23:24:39 +0100 From: Russell King To: Christoph Lameter Cc: Paul Mackerras , KAMEZAWA Hiroyuki , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, jens.axboe@oracle.com Subject: Re: Define CONFIG_BOUNCE to avoid useless inclusion of bounce buffer logic. Message-ID: <20070603222439.GA16422@flint.arm.linux.org.uk> Mail-Followup-To: Christoph Lameter , Paul Mackerras , KAMEZAWA Hiroyuki , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, jens.axboe@oracle.com References: <20070522133906.ae9c362a.kamezawa.hiroyu@jp.fujitsu.com> <20070523140702.GA16972@flint.arm.linux.org.uk> <18005.2746.374990.29287@cargo.ozlabs.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1208 Lines: 25 On Wed, May 23, 2007 at 09:03:02PM -0700, Christoph Lameter wrote: > On Thu, 24 May 2007, Paul Mackerras wrote: > > Also there is the problem that some drivers use ZONE_DMA allocations > > because their device can only generate addresses below some limit, but > > on a platform with an IOMMU there is in fact no restriction on what > > memory the device can access. > > That problem is to some extend addressed by switching ZONE_DMA off which > results in GFP_DMA becoming meaningless. And if GFP_DMA and ZONE_DMA is > gone from a platform then the MAX_DMA_ADDRESS inconsistencies are solved > since the cause of the inconsistencies has evaporated. Suffice it to say then that with this approach ARM will _never_ be able to have ZONE_DMA turned off, even on platforms where there are no DMA restrictions. I guess that's something we'll just have to live with. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: - 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/