Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760273AbZD0UXA (ORCPT ); Mon, 27 Apr 2009 16:23:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759804AbZD0UWu (ORCPT ); Mon, 27 Apr 2009 16:22:50 -0400 Received: from ovro.ovro.caltech.edu ([192.100.16.2]:47116 "EHLO ovro.ovro.caltech.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759714AbZD0UWt (ORCPT ); Mon, 27 Apr 2009 16:22:49 -0400 Message-ID: <49F61416.8040501@ovro.caltech.edu> Date: Mon, 27 Apr 2009 13:22:46 -0700 From: David Hawkins User-Agent: Thunderbird 2.0.0.21 (Windows/20090302) MIME-Version: 1.0 To: Timur Tabi CC: Liu Dave-R63238 , Ira Snyder , linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, Dan Williams Subject: Re: [PATCH] fsldma: use PCI Read Multiple command References: <20090424183517.GB23140@ovro.caltech.edu> <49F608B7.9080409@ovro.caltech.edu> <49F60A3A.4060402@freescale.com> In-Reply-To: <49F60A3A.4060402@freescale.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (ovro.ovro.caltech.edu); Mon, 27 Apr 2009 13:22:49 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1268 Lines: 37 Hi Timur, >> Would you like some sort of summary of this info for a commit >> message? > > That's probably overkill. I just want a sentence or two that tells > someone looking at the code casually that the behavior of reading PCI > memory might be different than what they expect. Could you help us with the wording you'd like to see in the code. Did you want to see something in the header comments, or something near the register settings? How about something like this in place of the existing PCI_RM comment: PRC_RM - PCI read multiple The default PCI read command used by the DMA controller is PCI Read (PCI command 6h). When the burst length is 32-bytes or longer, PCI Read Line (PCI command Eh) is used (undocumented feature of the controller). Using PCI read multiple (PCI command Ch) results in high-performance across PCI bridges. DMA transfers to non-prefetchable PCI registers should not result in prefetched reads, even when using the PCI read multiple command. Cheers, Dave -- 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/