openwrt/target/linux/bcm27xx/patches-6.6/950-0752-ASoC-dwc-Fix-full-duplex-mode.patch

From 69fb23bb184ac6f17054b2233d22c1f0188f001a Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Tue, 28 Nov 2023 12:14:03 +0000
Subject: [PATCH 0752/1085] ASoC: dwc: Fix full-duplex mode

Configuration of the DMA register was carelessly zeroing bits that may
used by a stream in the other direction. Preserve them instead.

See: https://github.com/raspberrypi/linux/issues/5741

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
 sound/soc/dwc/dwc-i2s.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

--- a/sound/soc/dwc/dwc-i2s.c
+++ b/sound/soc/dwc/dwc-i2s.c
@@ -235,10 +235,17 @@ static void dw_i2s_config(struct dw_i2s_
 {
 	u32 ch_reg;
 	struct i2s_clk_config_data *config = &dev->config;
-	u32 dmacr = 0;
+	u32 dmacr;
 
 	i2s_disable_channels(dev, stream);
 
+	dmacr = i2s_read_reg(dev->i2s_base, I2S_DMACR);
+
+	if (stream == SNDRV_PCM_STREAM_PLAYBACK)
+		dmacr &= ~(DMACR_DMAEN_TXCH0 * 0xf);
+	else
+		dmacr &= ~(DMACR_DMAEN_RXCH0 * 0xf);
+
 	for (ch_reg = 0; ch_reg < (config->chan_nr / 2); ch_reg++) {
 		if (stream == SNDRV_PCM_STREAM_PLAYBACK) {
 			i2s_write_reg(dev->i2s_base, TCR(ch_reg),
@@ -258,10 +265,6 @@ static void dw_i2s_config(struct dw_i2s_
 			dmacr |= (DMACR_DMAEN_RXCH0 << ch_reg);
 		}
 	}
-	if (stream == SNDRV_PCM_STREAM_PLAYBACK)
-		dmacr |= DMACR_DMAEN_TX;
-	else if (stream == SNDRV_PCM_STREAM_CAPTURE)
-		dmacr |= DMACR_DMAEN_RX;
 
 	i2s_write_reg(dev->i2s_base, I2S_DMACR, dmacr);
 }
@@ -370,10 +373,13 @@ static int dw_i2s_startup(struct snd_pcm
 
 	dw_i2s_config(dev, substream->stream);
 	dmacr = i2s_read_reg(dev->i2s_base, I2S_DMACR);
-	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
 		dma_data = &dev->play_dma_data;
-	else if (substream->stream == SNDRV_PCM_STREAM_CAPTURE)
+		dmacr |= DMACR_DMAEN_TX;
+	} else if (substream->stream == SNDRV_PCM_STREAM_CAPTURE) {
 		dma_data = &dev->capture_dma_data;
+		dmacr |= DMACR_DMAEN_RX;
+	}
 
 	snd_soc_dai_set_dma_data(cpu_dai, substream, (void *)dma_data);
 	i2s_write_reg(dev->i2s_base, I2S_DMACR, dmacr);