From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753139Ab0BTBKL (ORCPT ); Fri, 19 Feb 2010 20:10:11 -0500 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:43638 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751326Ab0BTBKI (ORCPT ); Fri, 19 Feb 2010 20:10:08 -0500 Date: Fri, 19 Feb 2010 17:10:25 -0800 (PST) Message-Id: <20100219.171025.09226171.davem@davemloft.net> To: hancockrwd@gmail.com Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, romieu@fr.zoreil.com Subject: Re: [PATCH 2.6.34] r8169: enable 64-bit DMA by default for PCI Express devices (v2) From: David Miller In-Reply-To: <4B7F343E.4040409@gmail.com> References: <4B7CAEC1.6090408@gmail.com> <20100219.131718.115496278.davem@davemloft.net> <4B7F343E.4040409@gmail.com> X-Mailer: Mew version 6.3 on Emacs 23.1 / Mule 6.0 (HANACHIRUSATO) 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 From: Robert Hancock Date: Fri, 19 Feb 2010 19:00:46 -0600 > Currently use of 64-bit DMA is disabled in r8169 unless the user passes the > use_dac module option. This is reasonable for conventional PCI devices where > broken chipsets may not handle dual-address-cycle transfers properly for > 32-bit slots and so this may not be safe. However, PCI Express should not have > this problem and not using 64-bit DMA results in DMA transfers needlessly using > the IOMMU or SWIOTLB. Set the use_dac module parameter to a new default value of > -1 which results in 64-bit DMA being enabled by default for PCI Express devices > only. > > Signed-off-by: Robert Hancock Applied, thanks Robert.