ASoC: ti: davinci-mcasp: Improve serializer handling in multi AXR setups

When multiple serializers are used we need to track the number of
serializers used by the other stream direction to avoid killing data lines
when the first stream used more serializers than the second would need.
We are still protected against the case when the second stream uses more
serializers which had affected the running stream as well.

To take advantage of the improved serializer logic we need to modify the
channel constraints rule as well to allow the use of multiple serializers
for the second stream as additional ones will not affect the FS/BCLK on
the bus.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20190725083432.7419-1-peter.ujfalusi@ti.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/ti/davinci-mcasp.c

@@ -109,6 +109,7 @@ struct davinci_mcasp {
 
 	/* Used for comstraint setting on the second stream */
 	u32	channels;
+	u8	active_serializers[2];
 
 #ifdef CONFIG_GPIOLIB
 	struct gpio_chip gpio_chip;
@@ -813,6 +814,7 @@ static int mcasp_common_hw_param(struct davinci_mcasp *mcasp, int stream,
 	u8 rx_ser = 0;
 	u8 slots = mcasp->tdm_slots;
 	u8 max_active_serializers = (channels + slots - 1) / slots;
+	u8 max_rx_serializers, max_tx_serializers;
 	int active_serializers, numevt;
 	u32 reg;
 	/* Default configuration */
@@ -822,22 +824,28 @@ static int mcasp_common_hw_param(struct davinci_mcasp *mcasp, int stream,
 	if (stream == SNDRV_PCM_STREAM_PLAYBACK) {
 		mcasp_set_reg(mcasp, DAVINCI_MCASP_TXSTAT_REG, 0xFFFFFFFF);
 		mcasp_clr_bits(mcasp, DAVINCI_MCASP_XEVTCTL_REG, TXDATADMADIS);
+		max_tx_serializers = max_active_serializers;
+		max_rx_serializers =
+			mcasp->active_serializers[SNDRV_PCM_STREAM_CAPTURE];
 	} else {
 		mcasp_set_reg(mcasp, DAVINCI_MCASP_RXSTAT_REG, 0xFFFFFFFF);
 		mcasp_clr_bits(mcasp, DAVINCI_MCASP_REVTCTL_REG, RXDATADMADIS);
+		max_tx_serializers =
+			mcasp->active_serializers[SNDRV_PCM_STREAM_PLAYBACK];
+		max_rx_serializers = max_active_serializers;
 	}
 
 	for (i = 0; i < mcasp->num_serializer; i++) {
 		mcasp_set_bits(mcasp, DAVINCI_MCASP_XRSRCTL_REG(i),
 			       mcasp->serial_dir[i]);
 		if (mcasp->serial_dir[i] == TX_MODE &&
-					tx_ser < max_active_serializers) {
+					tx_ser < max_tx_serializers) {
 			mcasp_mod_bits(mcasp, DAVINCI_MCASP_XRSRCTL_REG(i),
 				       mcasp->dismod, DISMOD_MASK);
 			set_bit(PIN_BIT_AXR(i), &mcasp->pdir);
 			tx_ser++;
 		} else if (mcasp->serial_dir[i] == RX_MODE &&
-					rx_ser < max_active_serializers) {
+					rx_ser < max_rx_serializers) {
 			clear_bit(PIN_BIT_AXR(i), &mcasp->pdir);
 			rx_ser++;
 		} else {
@@ -884,7 +892,8 @@ static int mcasp_common_hw_param(struct davinci_mcasp *mcasp, int stream,
 		} else {
 			dma_data->maxburst = 0;
 		}
-		return 0;
+
+		goto out;
 	}
 
 	if (period_words % active_serializers) {
@@ -914,6 +923,9 @@ static int mcasp_common_hw_param(struct davinci_mcasp *mcasp, int stream,
 		numevt = 0;
 	dma_data->maxburst = numevt;
 
+out:
+	mcasp->active_serializers[stream] = active_serializers;
+
 	return 0;
 }
 
@@ -1153,6 +1165,37 @@ static int davinci_mcasp_hw_params(struct snd_pcm_substream *substream,
 	int period_size = params_period_size(params);
 	int ret;
 
+	switch (params_format(params)) {
+	case SNDRV_PCM_FORMAT_U8:
+	case SNDRV_PCM_FORMAT_S8:
+		word_length = 8;
+		break;
+
+	case SNDRV_PCM_FORMAT_U16_LE:
+	case SNDRV_PCM_FORMAT_S16_LE:
+		word_length = 16;
+		break;
+
+	case SNDRV_PCM_FORMAT_U24_3LE:
+	case SNDRV_PCM_FORMAT_S24_3LE:
+		word_length = 24;
+		break;
+
+	case SNDRV_PCM_FORMAT_U24_LE:
+	case SNDRV_PCM_FORMAT_S24_LE:
+		word_length = 24;
+		break;
+
+	case SNDRV_PCM_FORMAT_U32_LE:
+	case SNDRV_PCM_FORMAT_S32_LE:
+		word_length = 32;
+		break;
+
+	default:
+		printk(KERN_WARNING "davinci-mcasp: unsupported PCM format");
+		return -EINVAL;
+	}
+
 	ret = davinci_mcasp_set_dai_fmt(cpu_dai, mcasp->dai_fmt);
 	if (ret)
 		return ret;
@@ -1187,37 +1230,6 @@ static int davinci_mcasp_hw_params(struct snd_pcm_substream *substream,
 	if (ret)
 		return ret;
 
-	switch (params_format(params)) {
-	case SNDRV_PCM_FORMAT_U8:
-	case SNDRV_PCM_FORMAT_S8:
-		word_length = 8;
-		break;
-
-	case SNDRV_PCM_FORMAT_U16_LE:
-	case SNDRV_PCM_FORMAT_S16_LE:
-		word_length = 16;
-		break;
-
-	case SNDRV_PCM_FORMAT_U24_3LE:
-	case SNDRV_PCM_FORMAT_S24_3LE:
-		word_length = 24;
-		break;
-
-	case SNDRV_PCM_FORMAT_U24_LE:
-	case SNDRV_PCM_FORMAT_S24_LE:
-		word_length = 24;
-		break;
-
-	case SNDRV_PCM_FORMAT_U32_LE:
-	case SNDRV_PCM_FORMAT_S32_LE:
-		word_length = 32;
-		break;
-
-	default:
-		printk(KERN_WARNING "davinci-mcasp: unsupported PCM format");
-		return -EINVAL;
-	}
-
 	davinci_config_channel_size(mcasp, word_length);
 
 	if (mcasp->op_mode == DAVINCI_MCASP_IIS_MODE)
@@ -1404,12 +1416,13 @@ static int davinci_mcasp_startup(struct snd_pcm_substream *substream,
 	max_channels *= tdm_slots;
 	/*
 	 * If the already active stream has less channels than the calculated
-	 * limnit based on the seirializers * tdm_slots, we need to use that as
-	 * a constraint for the second stream.
-	 * Otherwise (first stream or less allowed channels) we use the
-	 * calculated constraint.
+	 * limit based on the seirializers * tdm_slots, and only one serializer
+	 * is in use we need to use that as a constraint for the second stream.
+	 * Otherwise (first stream or less allowed channels or more than one
+	 * serializer in use) we use the calculated constraint.
 	 */
-	if (mcasp->channels && mcasp->channels < max_channels)
+	if (mcasp->channels && mcasp->channels < max_channels &&
+	    ruledata->serializers == 1)
 		max_channels = mcasp->channels;
 	/*
 	 * But we can always allow channels upto the amount of
@@ -1470,6 +1483,7 @@ static void davinci_mcasp_shutdown(struct snd_pcm_substream *substream,
 	struct davinci_mcasp *mcasp = snd_soc_dai_get_drvdata(cpu_dai);
 
 	mcasp->substreams[substream->stream] = NULL;
+	mcasp->active_serializers[substream->stream] = 0;
 
 	if (mcasp->op_mode == DAVINCI_MCASP_DIT_MODE)
 		return;