Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755751AbZD0KQb (ORCPT ); Mon, 27 Apr 2009 06:16:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753115AbZD0KQV (ORCPT ); Mon, 27 Apr 2009 06:16:21 -0400 Received: from yw-out-2324.google.com ([74.125.46.29]:60424 "EHLO yw-out-2324.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752366AbZD0KQU (ORCPT ); Mon, 27 Apr 2009 06:16:20 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=KcnocDe6WPBF2N/39bCQG1qgoU+Vx3rCcGbQqJl8jluFTQCEl9OhY7U/AFznixfcuV 9NcFntdNTza3AINzNXsk4C9QGKLT+7RnkEewkaUEsXAOu6FvF3L6/Rm9JP4ViHRSGZwo nFN7U6B60bGC2YUYAZPeFCjS06G6x2jC80/Z8= MIME-Version: 1.0 In-Reply-To: References: <20090424183517.GB23140@ovro.caltech.edu> Date: Mon, 27 Apr 2009 18:16:19 +0800 X-Google-Sender-Auth: b4b39bf4bbd72578 Message-ID: <2a27d3730904270316u6c06eafeja75f6e9e5c83ed29@mail.gmail.com> Subject: Re: [PATCH] fsldma: use PCI Read Multiple command From: Li Yang To: Liu Dave-R63238 Cc: Ira Snyder , linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, Dan Williams Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1057 Lines: 25 On Mon, Apr 27, 2009 at 5:09 PM, Liu Dave-R63238 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. > > 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? I guess it's not reasonable to use DMA from non-prefetchable memory. So it's up to the driver which uses the DMA engine to prevent from using DMA API on non-prefetchable memory. - Leo -- 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/