From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756351Ab0IUWQG (ORCPT ); Tue, 21 Sep 2010 18:16:06 -0400 Received: from digitaldans.com ([69.36.177.99]:54839 "EHLO digitaldans.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754098Ab0IUWQE (ORCPT ); Tue, 21 Sep 2010 18:16:04 -0400 X-Greylist: delayed 738 seconds by postgrey-1.27 at vger.kernel.org; Tue, 21 Sep 2010 18:16:04 EDT In-Reply-To: <20100921164944.164ed0af@udp111988uds.am.freescale.net> References: <1285066638-7473-1-git-send-email-leoli@freescale.com> <877FD0B5-19A7-4A16-831E-369B80B104EA@kernel.crashing.org> <20100921163456.7e2c9b32@udp111988uds.am.freescale.net> <20100921164944.164ed0af@udp111988uds.am.freescale.net> Mime-Version: 1.0 (Apple Message framework v753.1) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: <2C3F2C02-35B6-46AF-82DA-44ACCBFB8362@digitaldans.com> Cc: Timur Tabi , dan.j.williams@intel.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: 7bit From: Dan Malek Subject: Re: [PATCH] fsldma: add support to 36-bit physical address Date: Tue, 21 Sep 2010 15:05:05 -0700 To: Scott Wood X-Mailer: Apple Mail (2.753.1) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sep 21, 2010, at 2:49 PM, Scott Wood wrote: > > On Tue, 21 Sep 2010 16:43:12 -0500 > Timur Tabi wrote: > >> Since we don't DMA the descriptors themselves, I just don't see how >> this patch does anything. > > Look in dmaengine.c, there are calls to dma_map_single() and > dma_map_page(), using what I assume is that same device pointer -- > unless there's confusion between the channel and the controller. The DMA descriptors are accessed using DMA by the controller itself. The APIs need to ensure proper coherency between the CPU and the DMA controller for the descriptor access. The underlying implementation of the API will depend upon the hardware capabilities that ensure this coherency. -- Dan