Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752680Ab1DUCcI (ORCPT ); Wed, 20 Apr 2011 22:32:08 -0400 Received: from smtp-out.google.com ([74.125.121.67]:44201 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752121Ab1DUCcG (ORCPT ); Wed, 20 Apr 2011 22:32:06 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=date:from:x-x-sender:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version:content-type; b=QXZD6f2bdkPSq1q2ItSwlHzj3Z6RlyFYYempIMC5cAn1owF+uPoI6OcP84p8w9194G uQEPCEYRFoshoeCv7lqA== Date: Wed, 20 Apr 2011 19:31:57 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: "H. Peter Anvin" cc: Clemens Ladisch , Ingo Molnar , Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [patch v2] x86: allow ZONE_DMA to be configurable In-Reply-To: <4DA8A5CE.2010004@zytor.com> Message-ID: References: <4DA82F33.7080403@ladisch.de> <4DA8A5CE.2010004@zytor.com> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2069 Lines: 50 On Fri, 15 Apr 2011, H. Peter Anvin wrote: > On 04/15/2011 04:42 AM, Clemens Ladisch wrote: > > David Rientjes wrote: > >> ZONE_DMA is unnecessary for a large number of machines that do not > >> require addressing in the lower 16MB of memory because they do not use > >> ISA devices with 16-bit address registers (plus one page byte register). > >> > >> This patch allows users to disable ZONE_DMA for x86 if they know they > >> will not be using such devices with their kernel. > >> ... > >> config ZONE_DMA > >> - def_bool y > >> + bool "DMA memory allocation support" if EXPERT > > > > Better call it "ISA/LPC DMA memory allocation support". > > > >> + default y > > > > Does it make sense to have this without CONFIG_ISA_DMA_API? > > > >> + help > >> + DMA memory allocation support allows old ISA devices with 16-bit > >> + address registers to allocate memory within the first 16MB of > >> + address space. Disable if no such devices will be used. > > > > "Old ISA devices" might be misleading because ISA does not imply actual > > ISA slots; please mention LPC devices like the floppy controller and the > > parallel port in ECP mode. > > > > This isn't really a very good edit, as ZONE_DMA isn't inherently limited > to ISA/LPC devices (and LPC devices which do LPC-native bus mastering > DMA are not affected.) ZONE_DMA is used even for some PCI devices which > have restrictions on the DMA address mask. > Peter, do you think we can merge this patch now? The discussion from October resulted in the decision to rename CONFIG_EMBEDDED to CONFIG_EXPERT and make CONFIG_GENERIC_ISA_DMA and CONFIG_ISA_DMA_API configurable for x86. That's all been done via the -mm tree and is in the latest git. We've run without ZONE_DMA for a few years without issues (and, obviously, this patch) on x86. -- 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/