openwrt/target/linux/bcm27xx/patches-6.1/950-0894-ASOC-dwc-Improve-DMA-shutdown.patch

From e6baee4502c0228c79408b047096a1259a84353f Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Mon, 3 Jul 2023 10:14:43 +0100
Subject: [PATCH] ASOC: dwc: Improve DMA shutdown

Disabling the I2S interface with outstanding transfers prevents the
DMAC from shutting down, so keep it partially active after a stop.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
 sound/soc/dwc/dwc-i2s.c | 72 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 64 insertions(+), 8 deletions(-)

--- a/sound/soc/dwc/dwc-i2s.c
+++ b/sound/soc/dwc/dwc-i2s.c
@@ -165,24 +165,26 @@ static void i2s_start(struct dw_i2s_dev
 	i2s_write_reg(dev->i2s_base, CER, 1);
 }
 
-static void i2s_stop(struct dw_i2s_dev *dev,
-		struct snd_pcm_substream *substream)
+static void i2s_pause(struct dw_i2s_dev *dev, struct snd_pcm_substream *substream)
 {
 
 	i2s_clear_irqs(dev, substream->stream);
-	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
-		i2s_write_reg(dev->i2s_base, ITER, 0);
-	else
-		i2s_write_reg(dev->i2s_base, IRER, 0);
 
 	i2s_disable_irqs(dev, substream->stream, 8);
 
 	if (!dev->active) {
 		i2s_write_reg(dev->i2s_base, CER, 0);
-		i2s_write_reg(dev->i2s_base, IER, 0);
+		/* Keep the device enabled until the shutdown - do not clear IER */
 	}
 }
 
+static void i2s_stop(struct dw_i2s_dev *dev, struct snd_pcm_substream *substream)
+{
+	i2s_clear_irqs(dev, substream->stream);
+
+	i2s_disable_irqs(dev, substream->stream, 8);
+}
+
 static void dw_i2s_config(struct dw_i2s_dev *dev, int stream)
 {
 	struct i2s_clk_config_data *config = &dev->config;
@@ -288,6 +290,55 @@ static int dw_i2s_hw_params(struct snd_p
 	return 0;
 }
 
+static int dw_i2s_startup(struct snd_pcm_substream *substream,
+			  struct snd_soc_dai *cpu_dai)
+{
+	struct dw_i2s_dev *dev = snd_soc_dai_get_drvdata(cpu_dai);
+	union dw_i2s_snd_dma_data *dma_data = NULL;
+	u32 dmacr;
+
+	dev_dbg(dev->dev, "%s(%s)\n", __func__, substream->name);
+	if (!(dev->capability & DWC_I2S_RECORD) &&
+	    substream->stream == SNDRV_PCM_STREAM_CAPTURE)
+		return -EINVAL;
+
+	if (!(dev->capability & DWC_I2S_PLAY) &&
+	    substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+		return -EINVAL;
+
+	dw_i2s_config(dev, substream->stream);
+	dmacr = i2s_read_reg(dev->i2s_base, DMACR);
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+		dma_data = &dev->play_dma_data;
+	else if (substream->stream == SNDRV_PCM_STREAM_CAPTURE)
+		dma_data = &dev->capture_dma_data;
+
+	snd_soc_dai_set_dma_data(cpu_dai, substream, (void *)dma_data);
+	i2s_write_reg(dev->i2s_base, DMACR, dmacr);
+
+	return 0;
+}
+
+static void dw_i2s_shutdown(struct snd_pcm_substream *substream,
+			    struct snd_soc_dai *dai)
+{
+	struct dw_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);
+
+	dev_dbg(dev->dev, "%s(%s)\n", __func__, substream->name);
+	i2s_disable_channels(dev, substream->stream);
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+		i2s_write_reg(dev->i2s_base, ITER, 0);
+	else
+		i2s_write_reg(dev->i2s_base, IRER, 0);
+
+	i2s_disable_irqs(dev, substream->stream, 8);
+
+	if (!dev->active) {
+		i2s_write_reg(dev->i2s_base, CER, 0);
+		i2s_write_reg(dev->i2s_base, IER, 0);
+	}
+}
+
 static int dw_i2s_prepare(struct snd_pcm_substream *substream,
 			  struct snd_soc_dai *dai)
 {
@@ -315,9 +366,12 @@ static int dw_i2s_trigger(struct snd_pcm
 		i2s_start(dev, substream);
 		break;
 
+	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
+		dev->active--;
+		i2s_pause(dev, substream);
+		break;
 	case SNDRV_PCM_TRIGGER_STOP:
 	case SNDRV_PCM_TRIGGER_SUSPEND:
-	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 		dev->active--;
 		i2s_stop(dev, substream);
 		break;
@@ -394,6 +448,8 @@ static int dw_i2s_set_bclk_ratio(struct
 
 static const struct snd_soc_dai_ops dw_i2s_dai_ops = {
 	.hw_params	= dw_i2s_hw_params,
+	.startup	= dw_i2s_startup,
+	.shutdown	= dw_i2s_shutdown,
 	.prepare	= dw_i2s_prepare,
 	.trigger	= dw_i2s_trigger,
 	.set_fmt	= dw_i2s_set_fmt,