From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756237Ab2INHO2 (ORCPT ); Fri, 14 Sep 2012 03:14:28 -0400 Received: from na3sys009aog109.obsmtp.com ([74.125.149.201]:36229 "EHLO na3sys009aog109.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755071Ab2INHO0 (ORCPT ); Fri, 14 Sep 2012 03:14:26 -0400 Message-ID: <5052D979.3030901@ti.com> Date: Fri, 14 Sep 2012 10:15:05 +0300 From: Peter Ujfalusi User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120903 Thunderbird/15.0 MIME-Version: 1.0 To: Russell King - ARM Linux CC: Lars-Peter Clausen , Mark Brown , Liam Girdwood , Tony Lindgren , Vinod Koul , Dan Williams , Jarkko Nikula , alsa-devel@alsa-project.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Janusz Krzysztofik , Ricardo Neri Subject: Re: [PATCH v2 03/15] dmaengine: Add no_wakeup parameter to dmaengine_prep_dma_cyclic() References: <1347543485-339-1-git-send-email-peter.ujfalusi@ti.com> <1347543485-339-4-git-send-email-peter.ujfalusi@ti.com> <5051FB4D.3000009@metafoo.de> <20120913153824.GK28448@n2100.arm.linux.org.uk> In-Reply-To: <20120913153824.GK28448@n2100.arm.linux.org.uk> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/13/2012 06:38 PM, Russell King - ARM Linux wrote: > On Thu, Sep 13, 2012 at 05:27:09PM +0200, Lars-Peter Clausen wrote: >> Hm... Do you think it would work as well if we implement this by setting the >> callback for the descriptor to NULL? If the callback is NULL there is >> nothing to at the end of a transfer/period and the dma engine driver may >> choose to disable interrupts. This would also benefit non cyclic transfers >> where the callback is NULL and we do not need add the new parameter to >> dmaengine_prep_dma_cyclic. > > Actually, there's a way to do that already. DMA_PREP_INTERRUPT. > Unfortunately, most DMA engine slave API users don't set it when they > setup their transfer: > > * @DMA_PREP_INTERRUPT - trigger an interrupt (callback) upon completion of > * this transaction As I mentioned already to Vinod: the description of this flag is close enough for our needs (other than the notion of 'this transaction' is not really correct for cyclic mode). I will resend the series to add the flags as new parameter instead of the no_wakeup. > > if we fixed that, then we could use the lack of it to avoid the interrupt. > > However, cyclic transfers don't have the flags parameter used to pass this > bit. Yet another bit of yucky inconsistent design in DMA engine land... > -- Péter