[alsa-devel] [PATCH 1/2] ALSA: hda - Add fixed codec delay to runtime delay.

[Takashi Iwai]

At Wed,  3 Apr 2013 08:30:03 -0700,
Dylan Reid wrote:
> 
> Allow a codec to specify a delay in addition to the delay before
> samples are passed through DMA.  Some codecs have large processing
> delays because of built-in DSPs that require codec-side buffers of
> many milliseconds.  Default to zero delay if the codec doesn't specify
> a callback to get the processing delay.
> 
> Signed-off-by: Dylan Reid <dgreid at chromium.org>
> ---
>  sound/pci/hda/hda_codec.c | 17 +++++++++++++++++
>  sound/pci/hda/hda_codec.h |  4 ++++
>  sound/pci/hda/hda_intel.c |  2 ++
>  3 files changed, 23 insertions(+)
> 
> diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
> index 17286b3..1d792dd 100644
> --- a/sound/pci/hda/hda_codec.c
> +++ b/sound/pci/hda/hda_codec.c
> @@ -3724,6 +3724,23 @@ void snd_hda_codec_set_power_to_all(struct hda_codec *codec, hda_nid_t fg,
>  }
>  EXPORT_SYMBOL_HDA(snd_hda_codec_set_power_to_all);
>  
> +/**
> + * snd_hda_codec_processing_delay - get the fixed delay through the codec
> + * @codec: HD-audio codec
> + * @stream: playback or capture
> + *
> + * This is needed for codecs that contain DSPs that cause long delays.
> + */
> +unsigned int snd_hda_codec_processing_delay(struct hda_codec *codec,
> +					    unsigned int stream)
> +{
> +	if (codec->patch_ops.get_processing_delay)
> +		return codec->patch_ops.get_processing_delay(codec, stream);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_HDA(snd_hda_codec_processing_delay);

In the second thought, it would fit more better to pcm_ops than codec
patch_ops.  That is, the change would be like below.


Takashi

---
diff --git a/sound/pci/hda/hda_codec.h b/sound/pci/hda/hda_codec.h
index 23ca172..c93f902 100644
--- a/sound/pci/hda/hda_codec.h
+++ b/sound/pci/hda/hda_codec.h
@@ -757,6 +757,9 @@ struct hda_pcm_ops {
 		       struct snd_pcm_substream *substream);
 	int (*cleanup)(struct hda_pcm_stream *info, struct hda_codec *codec,
 		       struct snd_pcm_substream *substream);
+	unsigned int (*get_delay)(struct hda_pcm_stream *info,
+				  struct hda_codec *codec,
+				  struct snd_pcm_substream *substream);
 };
 
 /* PCM information for each substream */
diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index 418bfc0..a88f016 100644
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -2349,8 +2349,11 @@ static unsigned int azx_get_position(struct azx *chip,
 				     struct azx_dev *azx_dev,
 				     bool with_check)
 {
+	struct snd_pcm_substream *substream = azx_dev->substream;
+	struct azx_pcm *apcm = snd_pcm_substream_chip(substream);
 	unsigned int pos;
-	int stream = azx_dev->substream->stream;
+	int stream = substream->stream;
+	struct hda_pcm_stream *hinfo = apcm->hinfo[stream];
 	int delay = 0;
 
 	switch (chip->position_fix[stream]) {
@@ -2399,9 +2402,13 @@ static unsigned int azx_get_position(struct azx *chip,
 			delay = 0;
 			chip->driver_caps &= ~AZX_DCAPS_COUNT_LPIB_DELAY;
 		}
-		azx_dev->substream->runtime->delay =
-			bytes_to_frames(azx_dev->substream->runtime, delay);
+		delay = bytes_to_frames(azx_dev->substream->runtime, delay);
 	}
+
+	if (hinfo->ops.get_delay)
+		delay += hinfo->ops.get_delay(hinfo, apcm->codec, substream);
+	azx_dev->substream->runtime->delay = delay;
+
 	trace_azx_get_position(chip, azx_dev, pos, delay);
 	return pos;
 }