ASoC: OMAP: Use McBSP threshold to playback and capture

This patch changes the way DMA is done in omap-pcm.c
in order to reduce power consumption. There is no need
to have so much SW control in order to have DMA in idle
state during audio streaming. Configuring McBSP threshold value
and DMA to FRAME_SYNC are sufficient.

Signed-off-by: Eduardo Valentin <eduardo.valentin@nokia.com>
Acked-by: Jarkko Nikula <jhnikula@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/omap/omap-mcbsp.c

@@ -139,28 +139,59 @@ static const unsigned long omap34xx_mcbsp_port[][2] = {
 static const unsigned long omap34xx_mcbsp_port[][2] = {};
 #endif
 
+static void omap_mcbsp_set_threshold(struct snd_pcm_substream *substream)
+{
+	struct snd_soc_pcm_runtime *rtd = substream->private_data;
+	struct snd_soc_dai *cpu_dai = rtd->dai->cpu_dai;
+	struct omap_mcbsp_data *mcbsp_data = to_mcbsp(cpu_dai->private_data);
+	int samples = snd_pcm_lib_period_bytes(substream) >> 1;
+
+	/* Configure McBSP internal buffer usage */
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+		omap_mcbsp_set_tx_threshold(mcbsp_data->bus_id, samples - 1);
+	else
+		omap_mcbsp_set_rx_threshold(mcbsp_data->bus_id, samples - 1);
+}
+
 static int omap_mcbsp_dai_startup(struct snd_pcm_substream *substream,
 				  struct snd_soc_dai *dai)
 {
 	struct snd_soc_pcm_runtime *rtd = substream->private_data;
 	struct snd_soc_dai *cpu_dai = rtd->dai->cpu_dai;
 	struct omap_mcbsp_data *mcbsp_data = to_mcbsp(cpu_dai->private_data);
+	int bus_id = mcbsp_data->bus_id;
 	int err = 0;
 
-	if (cpu_is_omap343x() && mcbsp_data->bus_id == 1) {
+	if (!cpu_dai->active)
+		err = omap_mcbsp_request(bus_id);
+
+	if (cpu_is_omap343x()) {
+		int max_period;
+
 		/*
 		 * McBSP2 in OMAP3 has 1024 * 32-bit internal audio buffer.
 		 * Set constraint for minimum buffer size to the same than FIFO
 		 * size in order to avoid underruns in playback startup because
 		 * HW is keeping the DMA request active until FIFO is filled.
 		 */
+		if (bus_id == 1)
+			snd_pcm_hw_constraint_minmax(substream->runtime,
+					SNDRV_PCM_HW_PARAM_BUFFER_BYTES,
+					4096, UINT_MAX);
+
+		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+			max_period = omap_mcbsp_get_max_tx_threshold(bus_id);
+		else
+			max_period = omap_mcbsp_get_max_rx_threshold(bus_id);
+
+		max_period++;
+		max_period <<= 1;
+
 		snd_pcm_hw_constraint_minmax(substream->runtime,
-			SNDRV_PCM_HW_PARAM_BUFFER_BYTES, 4096, UINT_MAX);
+						SNDRV_PCM_HW_PARAM_PERIOD_BYTES,
+						32, max_period);
 	}
 
-	if (!cpu_dai->active)
-		err = omap_mcbsp_request(mcbsp_data->bus_id);
-
 	return err;
 }
 
@@ -220,7 +251,7 @@ static int omap_mcbsp_dai_hw_params(struct snd_pcm_substream *substream,
 	struct omap_mcbsp_data *mcbsp_data = to_mcbsp(cpu_dai->private_data);
 	struct omap_mcbsp_reg_cfg *regs = &mcbsp_data->regs;
 	int dma, bus_id = mcbsp_data->bus_id, id = cpu_dai->id;
-	int wlen, channels, wpf;
+	int wlen, channels, wpf, sync_mode = OMAP_DMA_SYNC_ELEMENT;
 	unsigned long port;
 	unsigned int format;
 
@@ -236,13 +267,17 @@ static int omap_mcbsp_dai_hw_params(struct snd_pcm_substream *substream,
 	} else if (cpu_is_omap343x()) {
 		dma = omap24xx_dma_reqs[bus_id][substream->stream];
 		port = omap34xx_mcbsp_port[bus_id][substream->stream];
+		omap_mcbsp_dai_dma_params[id][substream->stream].set_threshold =
+						omap_mcbsp_set_threshold;
+		sync_mode = OMAP_DMA_SYNC_FRAME;
 	} else {
 		return -ENODEV;
 	}
 	omap_mcbsp_dai_dma_params[id][substream->stream].name =
 		substream->stream ? "Audio Capture" : "Audio Playback";
 	omap_mcbsp_dai_dma_params[id][substream->stream].dma_req = dma;
 	omap_mcbsp_dai_dma_params[id][substream->stream].port_addr = port;
+	omap_mcbsp_dai_dma_params[id][substream->stream].sync_mode = sync_mode;
 	cpu_dai->dma_data = &omap_mcbsp_dai_dma_params[id][substream->stream];
 
 	if (mcbsp_data->configured) {

sound/soc/omap/omap-pcm.c

@@ -162,7 +162,7 @@ static int omap_pcm_prepare(struct snd_pcm_substream *substream)
 	 */
 	dma_params.data_type			= OMAP_DMA_DATA_TYPE_S16;
 	dma_params.trigger			= dma_data->dma_req;
-	dma_params.sync_mode			= OMAP_DMA_SYNC_ELEMENT;
+	dma_params.sync_mode			= dma_data->sync_mode;
 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
 		dma_params.src_amode		= OMAP_DMA_AMODE_POST_INC;
 		dma_params.dst_amode		= OMAP_DMA_AMODE_CONSTANT;
@@ -205,6 +205,7 @@ static int omap_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct omap_runtime_data *prtd = runtime->private_data;
+	struct omap_pcm_dma_data *dma_data = prtd->dma_data;
 	unsigned long flags;
 	int ret = 0;
 
@@ -214,6 +215,10 @@ static int omap_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
 	case SNDRV_PCM_TRIGGER_RESUME:
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
 		prtd->period_index = 0;
+		/* Configure McBSP internal buffer usage */
+		if (dma_data->set_threshold)
+			dma_data->set_threshold(substream);
+
 		omap_start_dma(prtd->dma_ch);
 		break;
 

sound/soc/omap/omap-pcm.h

@@ -29,6 +29,8 @@ struct omap_pcm_dma_data {
 	char		*name;		/* stream identifier */
 	int		dma_req;	/* DMA request line */
 	unsigned long	port_addr;	/* transmit/receive register */
+	int		sync_mode;	/* DMA sync mode */
+	void (*set_threshold)(struct snd_pcm_substream *substream);
 };
 
 extern struct snd_soc_platform omap_soc_platform;