From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753985AbYIWOEE (ORCPT ); Tue, 23 Sep 2008 10:04:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751103AbYIWODv (ORCPT ); Tue, 23 Sep 2008 10:03:51 -0400 Received: from de01egw01.freescale.net ([192.88.165.102]:45224 "EHLO de01egw01.freescale.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751036AbYIWODv (ORCPT ); Tue, 23 Sep 2008 10:03:51 -0400 Message-ID: <48D8F73A.4050004@freescale.com> Date: Tue, 23 Sep 2008 09:03:38 -0500 From: Timur Tabi User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv:1.8.1.16) Gecko/20080702 SeaMonkey/1.1.11 MIME-Version: 1.0 To: Ira Snyder CC: Dan Williams , linux-kernel@vger.kernel.org, maciej.sosnowski@intel.com, leoli@freescale.com, zw@zh-kernel.org, Kumar Gala Subject: Re: Problems with Freescale DMA driver References: <20080825165133.GA20446@ovro.caltech.edu> <48D2D00B.3010001@freescale.com> <20080922230435.GA20825@ovro.caltech.edu> In-Reply-To: <20080922230435.GA20825@ovro.caltech.edu> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ira Snyder wrote: > When your patch makes it in, you should probably add the cell-index to > all of the dts files that are missing them. Ah, I see that Kumar added a bunch of DMA nodes back in June and forgot the cell-index properties. > I was not able to cause the DMA controller to copy bad data. Perhaps the > kernel just had a bug at the time. It was still relatively early on in > the development cycle. dmatest runs all the time, so it's possible that it's eating up DMA resources. Try running your tests without CONFIG_DMATEST. > In a related note, I've been somewhat following the discussion on LKML > about creating an API for requesting a single DMA channel. This would be > great in a driver I've written for PCI communication over a backplane. > (I have a test board running in PCI Agent mode. It creates a virtual > ethernet interface that passes data over the PCI bus.) PCI devices should not be using generic DMA resources, so I don't see how this would apply. > Also, are there any plans to support the external start feature on the > 83XX parts? (According to my datasheet, it is supported.) I will be > using this feature in a driver I will be starting fairly soon. External start is very device-specific, so I don't see how a generic DMA driver, which is intended only for memory-to-memory DMA operations, can coordinate with an external master. -- Timur Tabi Linux kernel developer at Freescale