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: Cliff Cai <cliff.cai@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/soc/blackfin/bf5xx-ac97-pcm.c b/sound/soc/blackfin/bf5xx-ac97-pcm.c
index 51f4907..25e50d2 100644 (file)
--- a/sound/soc/blackfin/bf5xx-ac97-pcm.c
+++ b/sound/soc/blackfin/bf5xx-ac97-pcm.c
@@ -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,

diff --git a/sound/soc/blackfin/bf5xx-ac97.c b/sound/soc/blackfin/bf5xx-ac97.c
index c782e31..5e5aafb 100644 (file)
--- a/sound/soc/blackfin/bf5xx-ac97.c
+++ b/sound/soc/blackfin/bf5xx-ac97.c
@@ -129,7 +129,6 @@ static void enqueue_cmd(struct snd_ac97 *ac97, __u16 addr, __u16 data)
        struct ac97_frame *nextwrite;
 
        sport_incfrag(sport, &nextfrag, 1);
-       sport_incfrag(sport, &nextfrag, 1);
 
        nextwrite = (struct ac97_frame *)(sport->tx_buf + \
                        nextfrag * sport->tx_fragsize);

diff --git a/sound/soc/blackfin/bf5xx-sport.h b/sound/soc/blackfin/bf5xx-sport.h
index 4c16345..fcadcc0 100644 (file)
--- a/sound/soc/blackfin/bf5xx-sport.h
+++ b/sound/soc/blackfin/bf5xx-sport.h
@@ -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;
 };