[alsa-devel] [PATCH v5 05/14] ASoC: SOF: Add PCM operations support

[Ranjani Sridharan]

On Thu, 2019-04-04 at 12:37 +0200, Takashi Iwai wrote:
> On Thu, 21 Mar 2019 17:10:07 +0100,
> Pierre-Louis Bossart wrote:
> > 
> > +/* this may get called several times by oss emulation */
> > +static int sof_pcm_hw_params(struct snd_pcm_substream *substream,
> > +			     struct snd_pcm_hw_params *params)
> > +{
> 
> ....
> > +	/* container size */
> > +	switch (params_width(params)) {
> > +	case 16:
> > +		pcm.params.sample_container_bytes = 2;
> > +		break;
> > +	case 24:
> > +		pcm.params.sample_container_bytes = 4;
> > +		break;
> > +	case 32:
> > +		pcm.params.sample_container_bytes = 4;
> > +		break;
> > +	default:
> > +		return -EINVAL;
> > +	}
> 
> This can be simply snd_pcm_format_physical_width() / 8.
> 
> > +static int sof_pcm_open(struct snd_pcm_substream *substream)
> > +{
> 
> ....
> > +	/* set any runtime constraints based on topology */
> > +	snd_pcm_hw_constraint_step(substream->runtime, 0,
> > +				   SNDRV_PCM_HW_PARAM_BUFFER_SIZE,
> > +				   le32_to_cpu(caps->period_size_min));
> > +	snd_pcm_hw_constraint_step(substream->runtime, 0,
> > +				   SNDRV_PCM_HW_PARAM_PERIOD_SIZE,
> > +				   le32_to_cpu(caps->period_size_min));
> 
> Is period_size_min in frames or in bytes?  The code below refers as
> byte size while this refers as frames, so they look inconsistent.
> 
> > +
> > +	/* set runtime config */
> > +	runtime->hw.info = SNDRV_PCM_INFO_MMAP |
> > +			  SNDRV_PCM_INFO_MMAP_VALID |
> > +			  SNDRV_PCM_INFO_INTERLEAVED |
> > +			  SNDRV_PCM_INFO_PAUSE |
> > +			  SNDRV_PCM_INFO_RESUME |
> > +			  SNDRV_PCM_INFO_NO_PERIOD_WAKEUP;
> 
> Does SOF support the full resume?  That is, the stream gets resumed
> at
> the exact position that was suspended.  Most devices can't, hence
> they
> don't set *_INFO_RESUME flag and let user-space restarting.
Hi Takashi,

Thanks for your comment. The SOF driver definitely cannot guarantee to
resume from the exact same position due to the fact that triggers for
the host dma and link dma are not synchronized and also IPC scheduling
will affect this. So we should remove INOF_RESUME from hw.info.

I do one follow up question for you. When a stream resumes/restarts
after suspend, we have the need for restoring the hw_params in the SOF
driver prior to handling the START trigger. I noticed that the
legacy/skylake driver does not seem to do this though. Do you have any
insights on what we might be missing in the SOF driver?

Thanks,
Ranjani

> 
> > +	runtime->hw.period_bytes_min = le32_to_cpu(caps-
> > >period_size_min);
> > +	runtime->hw.period_bytes_max = le32_to_cpu(caps-
> > >period_size_max);
> > +	runtime->hw.periods_min = le32_to_cpu(caps->periods_min);
> > +	runtime->hw.periods_max = le32_to_cpu(caps->periods_max);
> > +	runtime->hw.buffer_bytes_max = le32_to_cpu(caps-
> > >buffer_size_max);
> 
> These refer as bytes...
> 
> 
> thanks,
> 
> Takashi
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