[alsa-devel] [PATCH 7/7] ALSA: x86: hdmi: continue playback even when display resolution changes

[Anand, Jerome]

> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai at suse.de]
> Sent: Wednesday, December 14, 2016 6:31 PM
> To: Anand, Jerome <jerome.anand at intel.com>
> Cc: intel-gfx at lists.freedesktop.org; alsa-devel at alsa-project.org;
> ville.syrjala at linux.intel.com; broonie at kernel.org; pierre-
> louis.bossart at linux.intel.com; Ughreja, Rakesh A
> <rakesh.a.ughreja at intel.com>
> Subject: Re: [PATCH 7/7] ALSA: x86: hdmi: continue playback even when
> display resolution changes
> 
> On Mon, 12 Dec 2016 19:10:43 +0100,
> Jerome Anand wrote:
> >
> > When the display resolution changes, the drm disables the display
> > pipes due to which audio rendering stops. At this time, we need to
> > ensure the existing audio pointers and buffers are cleared out so that
> > the playback can restarted once the display pipe is enabled with a
> > different N/CTS values
> >
> > Signed-off-by: Pierre-Louis Bossart
> > <pierre-louis.bossart at linux.intel.com>
> > Signed-off-by: Jerome Anand <jerome.anand at intel.com>
> > ---
> >  sound/x86/intel_hdmi_audio.c | 21 ++++++++++++++++++---
> >  1 file changed, 18 insertions(+), 3 deletions(-)
> >
> > diff --git a/sound/x86/intel_hdmi_audio.c
> > b/sound/x86/intel_hdmi_audio.c index 9249521..d6fd638 100644
> > --- a/sound/x86/intel_hdmi_audio.c
> > +++ b/sound/x86/intel_hdmi_audio.c
> > @@ -43,6 +43,7 @@ static DEFINE_MUTEX(had_mutex);  static int
> > hdmi_card_index = SNDRV_DEFAULT_IDX1;  static char *hdmi_card_id =
> > SNDRV_DEFAULT_STR1;  static struct snd_intelhad *had_data;
> > +static int underrun_count;
> >
> >  module_param(hdmi_card_index, int, 0444);
> > MODULE_PARM_DESC(hdmi_card_index, @@ -1114,6 +1115,7 @@ static
> int
> > snd_intelhad_open(struct snd_pcm_substream *substream)
> >  	intelhaddata = snd_pcm_substream_chip(substream);
> >  	had_stream = intelhaddata->private_data;
> >  	runtime = substream->runtime;
> > +	underrun_count = 0;
> >
> >  	pm_runtime_get(intelhaddata->dev);
> >
> > @@ -1506,10 +1508,23 @@ static snd_pcm_uframes_t
> > snd_intelhad_pcm_pointer(
> >
> >  	buf_id = intelhaddata->curr_buf % 4;
> >  	had_read_register(AUD_BUF_A_LENGTH + (buf_id *
> HAD_REG_WIDTH), &t);
> > -	if (t == 0) {
> > -		pr_debug("discovered buffer done for buf %d\n", buf_id);
> > -		/* had_process_buffer_done(intelhaddata); */
> > +
> > +	if ((t == 0) || (t == ((u32)-1L))) {
> > +		underrun_count++;
> > +		pr_debug("discovered buffer done for buf %d, count =
> %d\n",
> > +			buf_id, underrun_count);
> > +
> > +		if (underrun_count > (HAD_MIN_PERIODS/2)) {
> > +			pr_debug("assume audio_codec_reset, underrun =
> %d - do xrun\n",
> > +				underrun_count);
> > +			underrun_count = 0;
> > +			return SNDRV_PCM_POS_XRUN;
> > +		}
> > +	} else {
> > +		/* Reset Counter */
> > +		underrun_count = 0;
> >  	}
> > +
> >  	t = intelhaddata->buf_info[buf_id].buf_size - t;
> >
> >  	if (intelhaddata->stream_info.buffer_rendered)
> 
> This change itself is OK, but this made me wonder about the driver
> implementation: the current MAX_PB=1 is the hardware limitation or the
> soft limitation?  That is, can't we play back two streams when we connect
> two HDMI monitors?
> 

Two streams was never validated from hardware per se. So setting the limitation in software.

> 
> thanks,
> 
> Takashi