From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from digitaldans.com (digitaldans.com [69.36.177.99]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 0B224B70DF for ; Wed, 22 Sep 2010 08:16:03 +1000 (EST) 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> 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 Cc: Timur Tabi , linuxppc-dev@lists.ozlabs.org, dan.j.williams@intel.com, linux-kernel@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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