From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932288AbaEPKwK (ORCPT ); Fri, 16 May 2014 06:52:10 -0400 Received: from smtp-out-194.synserver.de ([212.40.185.194]:1105 "EHLO smtp-out-123.synserver.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757042AbaEPKv5 (ORCPT ); Fri, 16 May 2014 06:51:57 -0400 X-SynServer-TrustedSrc: 1 X-SynServer-AuthUser: lars@metafoo.de X-SynServer-PPID: 19250 Message-ID: <5375EDC7.5070105@metafoo.de> Date: Fri, 16 May 2014 12:51:51 +0200 From: Lars-Peter Clausen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131103 Icedove/17.0.10 MIME-Version: 1.0 To: Takashi Iwai CC: Linux-ALSA , Vinod Koul , Jassi Brar , Linux Kernel Mailing List , dmaengine@vger.kernel.org, Dan Williams , Tushar Behera Subject: Re: [alsa-devel] [PATCH] dma: pl330: Add support for DMA_PAUSE command References: <1400037830-21211-1-git-send-email-tushar.behera@linaro.org> <5373607D.2000200@metafoo.de> <537513A8.701@metafoo.de> In-Reply-To: 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 On 05/16/2014 07:49 AM, Takashi Iwai wrote: > At Thu, 15 May 2014 21:21:12 +0200, > Lars-Peter Clausen wrote: >> >> On 05/15/2014 02:01 PM, Tushar Behera wrote: >>> On 14 May 2014 17:54, Lars-Peter Clausen wrote: >>>> On 05/14/2014 02:07 PM, Tushar Behera wrote: >>>>> >>>>> On 14 May 2014 17:29, Jassi Brar wrote: >>>>>> >>>>>> On Wed, May 14, 2014 at 8:53 AM, Tushar Behera >>>>>> wrote: >>>>>>> >>>>>>> While playing back audio, pmc_dmaengine requests the DMA channel to >>>>>>> stop DMA transmission through DMA_PAUSE command. >>>>>>> >>>>>>> Currently PL330 driver doesn't support DMA pause command, leaving >>>>>>> the DMA state inconsistent when the system resumes. Instead, it would >>>>>>> be better to terminate the DMA transfer during suspend and restart >>>>>>> again during resume. >>>>>>> >>>>>>> Tested with audio playback across a suspend-resume cycle. >>>>>>> >>>>>> What is pmc_dmaengine? How does DMA_PAUSE help, when there is no >>>>>> DMA_RESUME? >>>>>> >>>>> >>>>> Sorry, it is a typo. >>>>> >>>>> sound/core/pcm_dmaengine.c:snd_dmaengine_pcm_trigger() --> >>>>> dmaengine_pause() is called during system suspend. >>>> >>>> >>>> It is only called if the DMA driver has support for pausing and resuming DMA >>>> transfers. Or at least that is the intention. >>>> >>>> - Lars >>> >>> During suspend, snd_dmaengine_pcm_trigger():SNDRV_PCM_TRIGGER_SUSPEND >>> is called which unconditionally calls dmaengine_pause(). Should we >>> update snd_dmaengine_pcm_trigger() to check for DMA pause/resume >>> support and call dmaengine_pause() or dmaengine_terminate_all() >>> accordingly? >> >> As far as I understand it we do not have to do anything for TRIGGER_SUSPEND >> if we do not set the SNDRV_PCM_INFO_RESUME flag. It looks like >> TRIGGER_SUSPEND is called unconditionally during suspend. But since the >> error code is ignored it should be fine if we just call dmaengine_pause() >> and that return -ENOSYS or similar. > > Well, TRIGGER_SUSPEND is issued by PCM core no matter whether > SNDRV_PCM_INFO_RESUME flag is set or not. The resume behavior depends > on the flag (SNDRV_PCM_TRIGGER_RESUME is issued if the flag is set, > otherwise the normal setup is done by alsa-lib at resume), but the > suspend is always triggered in the same way. > > So, PCM core assumes that the driver stops the stream somehow by > SNDRV_PCM_TRIGGER_SUSPEND. Ok, so we should call terminate_all() when we get a SNDRV_PCM_TRIGGER_SUSPEND if the dmaengine driver does not support pauseing the transfer. Thanks for the clarification. On a related note it seems like it is still possible to get PAUSE_PUSH/PAUSE_RELEASE events even if SNDRV_PCM_INFO_PAUSE is not set. Do you have an idea what should be the right thing to do in such a case? Return -ENOSYS? - Lars