From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756101AbcIFNqR (ORCPT ); Tue, 6 Sep 2016 09:46:17 -0400 Received: from hqemgate15.nvidia.com ([216.228.121.64]:14784 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753534AbcIFNqO (ORCPT ); Tue, 6 Sep 2016 09:46:14 -0400 X-PGP-Universal: processed; by hqnvupgp07.nvidia.com on Tue, 06 Sep 2016 06:41:25 -0700 Subject: Re: [PATCH v2 0/2] Add memcpy support for tegra210-adma To: Dmitry Osipenko , Nicolin Chen , References: <319ca097-4b10-83b9-841c-52adccbb48ad@nvidia.com> <5db4d7db-b1f4-c6af-de56-e8bb13ebc465@gmail.com> <6f45ff6e-5fa7-7aca-154c-85cf235aa62f@nvidia.com> CC: , , , , , , From: Jon Hunter Message-ID: Date: Tue, 6 Sep 2016 14:46:01 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <6f45ff6e-5fa7-7aca-154c-85cf235aa62f@nvidia.com> X-Originating-IP: [10.21.132.106] X-ClientProxiedBy: DRUKMAIL101.nvidia.com (10.25.59.19) To UKMAIL101.nvidia.com (10.26.138.13) Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/09/16 14:04, Jon Hunter wrote: > > On 06/09/16 13:03, Dmitry Osipenko wrote: >> On 06.09.2016 14:33, Jon Hunter wrote: >>> >>> On 03/09/16 01:32, Nicolin Chen wrote: >>>> This series of patches add memcpy support for tegra210 ADMA engine. >>> >>> Thanks. Any reason you choose this DMA and not the APB DMA? The APB DMA >>> is more of a generic DMA and so for memcpy it would seem to be a good >>> choice and it is available on all Tegras not just Tegra210. >>> >> >> Just a small clarification: >> >> If I'm not mistaken, APB DMA is mem-to-device, while AHB DMA is mem-to-mem. So, >> you probably meant AHB and not the APB. > > Description from the Tegra TRM: > > "The APB DMA Controller is placed between the AHB Bus and the APB Bus > and is a master on both buses. > > The APB DMA Controller is used for block data transfers from a source > location to the destination location. The source may be > DRAM or IRAM, and the destination location could be devices placed on > APB Bus; or vice versa." Sorry this appears to be a completely worthless response :-( I had made the assumption that if the DMA can transfer from APB-to-AHB and AHB-to-APB, it could also do AHB to AHB. However, now I look closely at the registers I see that it cannot and therefore, cannot support memcpy at all! Ok, so ignore my comment here, as it appears only the ADMA can support memcpy. Weird. Jon -- nvpublic