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. 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
