From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from an-out-0708.google.com (an-out-0708.google.com [209.85.132.242]) by ozlabs.org (Postfix) with ESMTP id 7C925DDDF6 for ; Mon, 27 Apr 2009 17:48:24 +1000 (EST) Received: by an-out-0708.google.com with SMTP id c2so1283402anc.39 for ; Mon, 27 Apr 2009 00:48:21 -0700 (PDT) MIME-Version: 1.0 Sender: pku.leo@gmail.com In-Reply-To: <20090424183517.GB23140@ovro.caltech.edu> References: <20090424183517.GB23140@ovro.caltech.edu> Date: Mon, 27 Apr 2009 15:48:21 +0800 Message-ID: <2a27d3730904270048g1e247797s6a25f9e28d664214@mail.gmail.com> Subject: Re: [PATCH] fsldma: use PCI Read Multiple command From: Li Yang To: Ira Snyder Content-Type: text/plain; charset=UTF-8 Cc: linuxppc-dev@ozlabs.org, Dan Williams , linux-kernel@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sat, Apr 25, 2009 at 2:35 AM, Ira Snyder wrote: > By default, the Freescale 83xx DMA controller uses the PCI Read Line > command when reading data over the PCI bus. Setting the controller to use > the PCI Read Multiple command instead allows the controller to read much > larger bursts of data, which provides a drastic speed increase. > > The slowdown due to using PCI Read Line was only observed when a PCI-to-PCI > bridge was between the devices trying to communicate. > > A simple test driver showed an increase from 4MB/sec to 116MB/sec when > performing DMA over the PCI bus. Using DMA to transfer between blocks of > local SDRAM showed no change in performance with this patch. The dmatest > driver was also used to verify the correctness of the transfers, and showed > no errors. > > Signed-off-by: Ira W. Snyder Acked-by: Li Yang Thanks, Leo