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Commit 6b58a821 authored by Cliff Cai's avatar Cliff Cai Committed by Takashi Iwai
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ALSA: ASoC Blackfin: fix bug - Audio Latency on AD1981 with MMAP enabled 



With MMAP enabled (DMA mode) on the AD1981, there is +/- 250ms of delay between
writing data to alsa and audio starts coming out of the AD1981.

Copy more data to local buffer before starting DMA

Signed-off-by: default avatarCliff Cai <cliff.cai@analog.com>
Signed-off-by: default avatarBryan Wu <cooloney@kernel.org>
Signed-off-by: default avatarMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 5564b14b

sound/soc/blackfin/bf5xx-ac97-pcm.c

+35 −7
Original line number Diff line number Diff line
@@ -56,6 +56,7 @@ static void bf5xx_mmap_copy(struct snd_pcm_substream *substream, 
		sport->tx_pos += runtime->period_size;

		if (sport->tx_pos >= runtime->buffer_size)

			sport->tx_pos %= runtime->buffer_size;

		sport->tx_delay_pos = sport->tx_pos;

	} else {

		bf5xx_ac97_to_pcm(

			(struct ac97_frame *)sport->rx_dma_buf + sport->rx_pos,
@@ -72,7 +73,15 @@ static void bf5xx_dma_irq(void *data) 
	struct snd_pcm_substream *pcm = data;

#if defined(CONFIG_SND_MMAP_SUPPORT)

	struct snd_pcm_runtime *runtime = pcm->runtime;

	struct sport_device *sport = runtime->private_data;

	bf5xx_mmap_copy(pcm, runtime->period_size);

	if (pcm->stream == SNDRV_PCM_STREAM_PLAYBACK) {

		if (sport->once == 0) {

			snd_pcm_period_elapsed(pcm);

			bf5xx_mmap_copy(pcm, runtime->period_size);

			sport->once = 1;

		}

	}

#endif

	snd_pcm_period_elapsed(pcm);

}
@@ -114,6 +123,10 @@ static int bf5xx_pcm_hw_params(struct snd_pcm_substream *substream, 


static int bf5xx_pcm_hw_free(struct snd_pcm_substream *substream)

{

	struct snd_pcm_runtime *runtime = substream->runtime;



	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)

	memset(runtime->dma_area, 0, runtime->buffer_size);

	snd_pcm_lib_free_pages(substream);

	return 0;

}
@@ -127,16 +140,11 @@ static int bf5xx_pcm_prepare(struct snd_pcm_substream *substream) 
	 * SPORT working in TMD mode(include AC97).

	 */

#if defined(CONFIG_SND_MMAP_SUPPORT)

	size_t size = bf5xx_pcm_hardware.buffer_bytes_max

			* sizeof(struct ac97_frame) / 4;

	/*clean up intermediate buffer*/

	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {

		memset(sport->tx_dma_buf, 0, size);

		sport_set_tx_callback(sport, bf5xx_dma_irq, substream);

		sport_config_tx_dma(sport, sport->tx_dma_buf, runtime->periods,

			runtime->period_size * sizeof(struct ac97_frame));

	} else {

		memset(sport->rx_dma_buf, 0, size);

		sport_set_rx_callback(sport, bf5xx_dma_irq, substream);

		sport_config_rx_dma(sport, sport->rx_dma_buf, runtime->periods,

			runtime->period_size * sizeof(struct ac97_frame));
@@ -164,8 +172,12 @@ static int bf5xx_pcm_trigger(struct snd_pcm_substream *substream, int cmd) 
	pr_debug("%s enter\n", __func__);

	switch (cmd) {

	case SNDRV_PCM_TRIGGER_START:

		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)

		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {

			bf5xx_mmap_copy(substream, runtime->period_size);

			snd_pcm_period_elapsed(substream);

			sport->tx_delay_pos = 0;

			sport_tx_start(sport);

		}

		else

			sport_rx_start(sport);

		break;
@@ -198,7 +210,7 @@ static snd_pcm_uframes_t bf5xx_pcm_pointer(struct snd_pcm_substream *substream) 


#if defined(CONFIG_SND_MMAP_SUPPORT)

	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)

		curr = sport->tx_pos;

		curr = sport->tx_delay_pos;

	else

		curr = sport->rx_pos;

#else
@@ -237,6 +249,21 @@ static int bf5xx_pcm_open(struct snd_pcm_substream *substream) 
	return ret;

}



static int bf5xx_pcm_close(struct snd_pcm_substream *substream)

{

	struct snd_pcm_runtime *runtime = substream->runtime;

	struct sport_device *sport = runtime->private_data;



	pr_debug("%s enter\n", __func__);

	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {

		sport->once = 0;

		memset(sport->tx_dma_buf, 0, runtime->buffer_size * sizeof(struct ac97_frame));

	} else

		memset(sport->rx_dma_buf, 0, runtime->buffer_size * sizeof(struct ac97_frame));



	return 0;

}



#ifdef CONFIG_SND_MMAP_SUPPORT

static int bf5xx_pcm_mmap(struct snd_pcm_substream *substream,

	struct vm_area_struct *vma)
@@ -272,6 +299,7 @@ static int bf5xx_pcm_copy(struct snd_pcm_substream *substream, int channel, 


struct snd_pcm_ops bf5xx_pcm_ac97_ops = {

	.open		= bf5xx_pcm_open,

	.close		= bf5xx_pcm_close,

	.ioctl		= snd_pcm_lib_ioctl,

	.hw_params	= bf5xx_pcm_hw_params,

	.hw_free	= bf5xx_pcm_hw_free,

sound/soc/blackfin/bf5xx-ac97.c

+0 −1
Original line number Diff line number Diff line
@@ -128,7 +128,6 @@ static void enqueue_cmd(struct snd_ac97 *ac97, __u16 addr, __u16 data) 
	int nextfrag = sport_tx_curr_frag(sport);

	struct ac97_frame *nextwrite;



	sport_incfrag(sport, &nextfrag, 1);

	sport_incfrag(sport, &nextfrag, 1);



	nextwrite = (struct ac97_frame *)(sport->tx_buf + \

sound/soc/blackfin/bf5xx-sport.h

+2 −0
Original line number Diff line number Diff line
@@ -123,6 +123,8 @@ struct sport_device { 
	int rx_pos;

	unsigned int tx_buffer_size;

	unsigned int rx_buffer_size;

	int tx_delay_pos;

	int once;

#endif

	void *private_data;

};