Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758185AbZD1Bbk (ORCPT ); Mon, 27 Apr 2009 21:31:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755331AbZD1Bba (ORCPT ); Mon, 27 Apr 2009 21:31:30 -0400 Received: from az33egw02.freescale.net ([192.88.158.103]:54244 "EHLO az33egw02.freescale.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754458AbZD1Bb3 convert rfc822-to-8bit (ORCPT ); Mon, 27 Apr 2009 21:31:29 -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: Tue, 28 Apr 2009 09:31:08 +0800 Message-ID: In-Reply-To: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PATCH] fsldma: use PCI Read Multiple command Thread-Index: AcnHRPdBWwGiOijVTWu5E4TWalmxaAAW+Frg References: <20090424183517.GB23140@ovro.caltech.edu> From: "Liu Dave-R63238" To: "Tabi Timur-B04825" Cc: "Ira Snyder" , , , "Dan Williams" , "Li Yang-R58472" X-Brightmail-Tracker: AAAAAQAAAWE= X-Brightmail-Tracker: AAAAAQAAAWE= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 836 Lines: 18 > > 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? > > This should be a safe assumption for this driver. Remember, this > driver just does offload memcpy, from one region to another. So the > PCI memory that you are reading from should be just a buffer of data, > and there should be side-effect of reading it. > > However, I would like to see a comment at the top of the file warning > people that copying from PCI memory will result in prefetched reads. How about FIFO RAM case? -- 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/