From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758952Ab2AMTmb (ORCPT ); Fri, 13 Jan 2012 14:42:31 -0500 Received: from mail-bk0-f46.google.com ([209.85.214.46]:34459 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932383Ab2AMTmV (ORCPT ); Fri, 13 Jan 2012 14:42:21 -0500 Message-ID: <4F1096E9.4020501@mvista.com> Date: Fri, 13 Jan 2012 23:41:13 +0300 From: Sergei Shtylyov User-Agent: Mozilla/5.0 (X11; Linux i686; rv:6.0) Gecko/20110812 Thunderbird/6.0 MIME-Version: 1.0 To: "Gupta, Ajay Kumar" CC: "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: RFC: usb: musb: Adding CPPI4.1 DMA driver under drivers/dma References: <201201120753.00667.oneukum@suse.de> <20120112215014.GC5735@xanatos> <20120112215459.GA1161@kroah.com> <20120112222947.GD5735@xanatos> <20120112223513.GA2925@kroah.com> <20120113061144.GA30569@suse.cz> <47CEF8C4B26E8C44B22B028A650E0EA9317A6B8B@DBDE01.ent.ti.com> In-Reply-To: <47CEF8C4B26E8C44B22B028A650E0EA9317A6B8B@DBDE01.ent.ti.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello. On 01/13/2012 01:40 PM, Gupta, Ajay Kumar wrote: > CPPI4.1 (Communication Port Programming Interface) is a TI specific DMA > controller used in multiple TI platform such as AM33x, DA8x, AM35x, TI81x. > The DMA engine is mainly used by musb controller on above platform. There are (at least out of tree) platforms using CPPI 4.1 for Ethernet. > Earlier version of the driver was submitted by Sergei Shtylyov at [1] but > was not merged due to disagreement on the location of driver in kernel. To be precise, TI requested pulling out already queued (to arch/arm/common/) CPPI 4.1 driver from RMK's patch system without even notifying me. At least that was RMK's version... > Refer the discussions at [1] for more details. > [1] http://marc.info/?l=linux-usb&m=125087318308323 Unfortunately, that's not all of the discussion of interest. > The new implementation of the CPPI4.1 DMA slave driver will be in the > drivers/dma folder, complying to dmaengine framework. Has there been any work in this direction done yet? > It would involve changes in existing musb driver also for which current > plan is to maintain the compatibility of non-CPPI4.1 DMA in musb driver. I didn't quite understand this part... > The task is planned to be spitted into below subtasks. > (1) Post RFC on the API details, changes envisaged in musb driver and other > challenges First of all, I foresee changes in drivers/dma/ to cope with the entity in CPPI 4.1 called the queue manager (there's also buffer manager but it wasn't implemented on DA8xx, so I didn't design any API for it). > (2) Implement and post RFC for the CPPI4.1 DMA driver and changes needed in > musb driver. > Let me know if you have any thoughts/comments on this. > Regards, > Ajay WBR, Sergei