Re: [PATCH] dma: pl330: Add support for DMA_PAUSE command

Re: [PATCH] dma: pl330: Add support for DMA_PAUSE command

[Lars-Peter Clausen]

On 05/15/2014 02:01 PM, Tushar Behera wrote:
> On 14 May 2014 17:54, Lars-Peter Clausen <lars@metafoo.de> wrote:
>> On 05/14/2014 02:07 PM, Tushar Behera wrote:
>>>
>>> On 14 May 2014 17:29, Jassi Brar <jassisinghbrar@gmail.com> wrote:
>>>>
>>>> On Wed, May 14, 2014 at 8:53 AM, Tushar Behera <tushar.behera@linaro.org>
>>>> 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.

Are you seeing an actual issue that you are trying to fix with your patch?

- Lars

Re: [PATCH] dma: pl330: Add support for DMA_PAUSE command

[Takashi Iwai]

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@metafoo.de> wrote:
> >> On 05/14/2014 02:07 PM, Tushar Behera wrote:
> >>>
> >>> On 14 May 2014 17:29, Jassi Brar <jassisinghbrar@gmail.com> wrote:
> >>>>
> >>>> On Wed, May 14, 2014 at 8:53 AM, Tushar Behera <tushar.behera@linaro.org>
> >>>> 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

Re: [PATCH] dma: pl330: Add support for DMA_PAUSE command

[Lars-Peter Clausen]

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@metafoo.de> wrote:
>>>> On 05/14/2014 02:07 PM, Tushar Behera wrote:
>>>>>
>>>>> On 14 May 2014 17:29, Jassi Brar <jassisinghbrar@gmail.com> wrote:
>>>>>>
>>>>>> On Wed, May 14, 2014 at 8:53 AM, Tushar Behera <tushar.behera@linaro.org>
>>>>>> 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

Re: [alsa-devel] [PATCH] dma: pl330: Add support for DMA_PAUSE command

[Takashi Iwai]

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@metafoo.de> wrote:
> >>>> On 05/14/2014 02:07 PM, Tushar Behera wrote:
> >>>>>
> >>>>> On 14 May 2014 17:29, Jassi Brar <jassisinghbrar@gmail.com> wrote:
> >>>>>>
> >>>>>> On Wed, May 14, 2014 at 8:53 AM, Tushar Behera <tushar.behera@linaro.org>
> >>>>>> 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

Re: [alsa-devel] [PATCH] dma: pl330: Add support for DMA_PAUSE command

[Lars-Peter Clausen]

On 05/19/2014 10:37 AM, Takashi Iwai wrote:
> 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@metafoo.de> wrote:
>>>>>> On 05/14/2014 02:07 PM, Tushar Behera wrote:
>>>>>>>
>>>>>>> On 14 May 2014 17:29, Jassi Brar <jassisinghbrar@gmail.com> wrote:
>>>>>>>>
>>>>>>>> On Wed, May 14, 2014 at 8:53 AM, Tushar Behera <tushar.behera@linaro.org>
>>>>>>>> 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?

Uhm, yes, I was only looking at the code, but couldn't find the check that 
makes sure that the PAUSE_PUSH/PAUSE_RELEASE events are only triggered if 
SNDRV_PCM_INFO_PAUSE is set. Looks like I need a pair of glasses.

Thanks and sorry for the noise,
- Lars

Re: [PATCH] dma: pl330: Add support for DMA_PAUSE command

[Tushar Behera]

On 16 May 2014 00:51, Lars-Peter Clausen <lars@metafoo.de> wrote:
> On 05/15/2014 02:01 PM, Tushar Behera wrote:
>>
>> On 14 May 2014 17:54, Lars-Peter Clausen <lars@metafoo.de> wrote:
>>>
>>> On 05/14/2014 02:07 PM, Tushar Behera wrote:
>>>>
>>>>
>>>> On 14 May 2014 17:29, Jassi Brar <jassisinghbrar@gmail.com> wrote:
>>>>>
>>>>>
>>>>> On Wed, May 14, 2014 at 8:53 AM, Tushar Behera
>>>>> <tushar.behera@linaro.org>
>>>>> 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.
>
> Are you seeing an actual issue that you are trying to fix with your patch?
>
> - Lars
>

Without this patch applied, if audio is playing back while suspend is
triggered, it doesn't playback after resume. Stopping the stream and
replaying works.

-- 
Tushar Behera

Re: [PATCH] dma: pl330: Add support for DMA_PAUSE command

[Lars-Peter Clausen]

On 05/19/2014 05:10 AM, Tushar Behera wrote:
> On 16 May 2014 00:51, Lars-Peter Clausen <lars@metafoo.de> wrote:
>> On 05/15/2014 02:01 PM, Tushar Behera wrote:
>>>
>>> On 14 May 2014 17:54, Lars-Peter Clausen <lars@metafoo.de> wrote:
>>>>
>>>> On 05/14/2014 02:07 PM, Tushar Behera wrote:
>>>>>
>>>>>
>>>>> On 14 May 2014 17:29, Jassi Brar <jassisinghbrar@gmail.com> wrote:
>>>>>>
>>>>>>
>>>>>> On Wed, May 14, 2014 at 8:53 AM, Tushar Behera
>>>>>> <tushar.behera@linaro.org>
>>>>>> 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.
>>
>> Are you seeing an actual issue that you are trying to fix with your patch?
>>
>> - Lars
>>
>
> Without this patch applied, if audio is playing back while suspend is
> triggered, it doesn't playback after resume. Stopping the stream and
> replaying works.
>

Ok, I think your second suggestion was correct. Call 
dmaengine_terminate_all() instead of damengine_pause() in 
snd_dmaengine_pcm_trigger() if the dmaengine driver does not support pausing 
the transfer.

- Lars