From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938549AbcIFRVa (ORCPT ); Tue, 6 Sep 2016 13:21:30 -0400 Received: from mail-pf0-f193.google.com ([209.85.192.193]:36676 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933502AbcIFRV2 (ORCPT ); Tue, 6 Sep 2016 13:21:28 -0400 Date: Tue, 6 Sep 2016 10:21:28 -0700 From: Nicolin Chen To: Jon Hunter Cc: vinod.koul@intel.com, linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org, dmaengine@vger.kernel.org, gnurou@gmail.com, thierry.reding@gmail.com, swarren@wwwdotorg.org, ldewangan@nvidia.com Subject: Re: [PATCH v2 2/2] dmaengine: tegra210-adma: Add memcpy support Message-ID: <20160906172127.GA966@Asurada-Nvidia> References: <738e0f1560436d613d9a7dab2fd540abea9503d3.1472857934.git.nicoleotsuka@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 06, 2016 at 12:52:03PM +0100, Jon Hunter wrote: > > + /* TODO: ADMA should support up to 8 chunks or periods */ > > + desc->num_periods = 1; > > + desc->buf_len = buf_len; > > + desc->period_len = buf_len; > What would be the benefit of using 8 periods here? My understanding is > that you will get an interrupt per period and do you really want this > for memcpy? You are right about the interrupt. And it doesn't seem to be beneficial unless the period size is over the limitation of Transfer Count, which is rare but might theoretically exist? I admit the "TODO" word here is a bit misleading for memcpy. I can remove the word and write a more appropriate comments.