Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752319AbZD0JJa (ORCPT ); Mon, 27 Apr 2009 05:09:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751764AbZD0JJU (ORCPT ); Mon, 27 Apr 2009 05:09:20 -0400 Received: from az33egw02.freescale.net ([192.88.158.103]:62412 "EHLO az33egw02.freescale.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751763AbZD0JJU convert rfc822-to-8bit (ORCPT ); Mon, 27 Apr 2009 05:09:20 -0400 X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 8BIT Subject: RE: [PATCH] fsldma: use PCI Read Multiple command Date: Mon, 27 Apr 2009 17:09:13 +0800 Message-ID: In-Reply-To: <20090424183517.GB23140@ovro.caltech.edu> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PATCH] fsldma: use PCI Read Multiple command Thread-Index: AcnFC64fztqaY+DAQ5aCj0/qmZUiqwCCrMqw References: <20090424183517.GB23140@ovro.caltech.edu> From: "Liu Dave-R63238" To: "Ira Snyder" , Cc: , "Dan Williams" , "Li Yang-R58472" , "Zhang Wei" X-Brightmail-Tracker: AAAAAQAAAWE= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1227 Lines: 29 > 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. IIRC, the default for 83xx DMA controller uses the PCI mem read command, not mem read line. You are assuming the PCI memory space is prefetchable( no side effect) for DMA. Is it possible that DMA is from non-prefetchable memory space? > 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. -- 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/