At Fri, 16 May 2014 12:51:51 +0200, Lars-Peter Clausen wrote: > > 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 <lars@xxxxxxxxxx> wrote: > >>>> On 05/14/2014 02:07 PM, Tushar Behera wrote: > >>>>> > >>>>> On 14 May 2014 17:29, Jassi Brar <jassisinghbrar@xxxxxxxxx> wrote: > >>>>>> > >>>>>> On Wed, May 14, 2014 at 8:53 AM, Tushar Behera <tushar.behera@xxxxxxxxxx> > >>>>>> 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? That's weird. We have already a check in snd_pcm_pre_pause() in pcm_native.c to filter only for substreams with SNDRV_PCM_INFO_PAUSE flag. Could you check in which code path it is triggered? thanks, Takashi -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
