Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753930AbYKJWHX (ORCPT ); Mon, 10 Nov 2008 17:07:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751463AbYKJWHJ (ORCPT ); Mon, 10 Nov 2008 17:07:09 -0500 Received: from nlpi025.sbcis.sbc.com ([207.115.36.54]:47642 "EHLO nlpi025.prodigy.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750875AbYKJWHG (ORCPT ); Mon, 10 Nov 2008 17:07:06 -0500 Date: Mon, 10 Nov 2008 16:06:52 -0600 (CST) From: Christoph Lameter X-X-Sender: cl@quilx.com To: Yasunori Goto cc: "Luck, Tony" , FUJITA Tomonori , linux-ia64@vger.kernel.org, Linux Kernel ML , Joerg Roedel Subject: Re: [Q] Why does dma_alloc_coherent() of ia64 GFP_DMA? In-Reply-To: <20081110121123.F82A.E1E9C6FF@jp.fujitsu.com> Message-ID: References: <20081110121123.F82A.E1E9C6FF@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Spam-Score: -2.6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 717 Lines: 23 On Mon, 10 Nov 2008, Yasunori Goto wrote: > Even if a device allows over 4G access and the driver doesn't specify > GFP_DMA, dma_alloc_coherent() returns under 4G area. GFP_DMA can become 0 for configurations that have !CONFIG_ZONE_DMA. Then all of memory is available. The call is subarch specific. So f.e. Altix sn_dma_alloc_coherent does not set __GFP_DMA. If you have an IA64 arch that only support 32bit I/O then __GFP_DMA in dma_alloc_coherent makes sense. -- 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/