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

[Takashi Iwai]

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?


thanks,

Takashi