[PATCH v4 01/11] ASoC: jz4740-i2s: Handle independent FIFO flush bits

[Aidan MacDonald <aidanmacdonald.0x0@xxxxxxxxx>]

On the JZ4740, there is a single bit that flushes (empties) both
the transmit and receive FIFO. Later SoCs have independent flush
bits for each FIFO, which allows us to flush the right FIFO when
starting up a stream.

This also fixes a bug: since we were only setting the JZ4740's
flush bit, which corresponds to the TX FIFO flush bit on other
SoCs, other SoCs were not having their RX FIFO flushed at all.

Fixes: 967beb2e8777 ("ASoC: jz4740: Add jz4780 support")
Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@xxxxxxxxx>
---
 sound/soc/jz4740/jz4740-i2s.c | 33 ++++++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/sound/soc/jz4740/jz4740-i2s.c b/sound/soc/jz4740/jz4740-i2s.c
index ecd8df70d39c..576f31f9d734 100644
--- a/sound/soc/jz4740/jz4740-i2s.c
+++ b/sound/soc/jz4740/jz4740-i2s.c
@@ -64,6 +64,9 @@
 #define JZ_AIC_CTRL_ENABLE_PLAYBACK BIT(1)
 #define JZ_AIC_CTRL_ENABLE_CAPTURE BIT(0)
 
+#define JZ4760_AIC_CTRL_TFLUSH BIT(8)
+#define JZ4760_AIC_CTRL_RFLUSH BIT(7)
+
 #define JZ_AIC_CTRL_OUTPUT_SAMPLE_SIZE_OFFSET 19
 #define JZ_AIC_CTRL_INPUT_SAMPLE_SIZE_OFFSET  16
 
@@ -90,6 +93,8 @@ enum jz47xx_i2s_version {
 struct i2s_soc_info {
 	enum jz47xx_i2s_version version;
 	struct snd_soc_dai_driver *dai;
+
+	bool shared_fifo_flush;
 };
 
 struct jz4740_i2s {
@@ -124,12 +129,33 @@ static int jz4740_i2s_startup(struct snd_pcm_substream *substream,
 	uint32_t conf, ctrl;
 	int ret;
 
+	/*
+	 * When we can flush FIFOs independently, only flush the
+	 * FIFO that is starting up.
+	 */
+	if (!i2s->soc_info->shared_fifo_flush) {
+		ctrl = jz4740_i2s_read(i2s, JZ_REG_AIC_CTRL);
+
+		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+			ctrl |= JZ4760_AIC_CTRL_TFLUSH;
+		else
+			ctrl |= JZ4760_AIC_CTRL_RFLUSH;
+
+		jz4740_i2s_write(i2s, JZ_REG_AIC_CTRL, ctrl);
+	}
+
 	if (snd_soc_dai_active(dai))
 		return 0;
 
-	ctrl = jz4740_i2s_read(i2s, JZ_REG_AIC_CTRL);
-	ctrl |= JZ_AIC_CTRL_FLUSH;
-	jz4740_i2s_write(i2s, JZ_REG_AIC_CTRL, ctrl);
+	/*
+	 * When there is a shared flush bit for both FIFOs we can
+	 * only flush the FIFOs if no other stream has started.
+	 */
+	if (i2s->soc_info->shared_fifo_flush) {
+		ctrl = jz4740_i2s_read(i2s, JZ_REG_AIC_CTRL);
+		ctrl |= JZ_AIC_CTRL_FLUSH;
+		jz4740_i2s_write(i2s, JZ_REG_AIC_CTRL, ctrl);
+	}
 
 	ret = clk_prepare_enable(i2s->clk_i2s);
 	if (ret)
@@ -444,6 +470,7 @@ static struct snd_soc_dai_driver jz4740_i2s_dai = {
 static const struct i2s_soc_info jz4740_i2s_soc_info = {
 	.version = JZ_I2S_JZ4740,
 	.dai = &jz4740_i2s_dai,
+	.shared_fifo_flush = true,
 };
 
 static const struct i2s_soc_info jz4760_i2s_soc_info = {
-- 
2.35.1