[PATCH RFC v1 2/2] ASoC: meson: aiu: Move AIU_I2S_MISC hold setting to aiu-fifo-i2s

[Martin Blumenstingl]

The out-of-tree vendor driver uses the following approach to set the
AIU_I2S_MISC register:
1) write AIU_MEM_I2S_START_PTR and AIU_MEM_I2S_RD_PTR
2) configure AIU_I2S_MUTE_SWAP[15:0]
3) write AIU_MEM_I2S_END_PTR
4) set AIU_I2S_MISC[2] to 1 (documented as: "put I2S interface in hold
   mode")
5) set AIU_I2S_MISC[4] to 1 (depending on the driver revision it always
   stays at 1 while for older drivers this bit is unset in step 4)
6) set AIU_I2S_MISC[2] to 0
7) write AIU_MEM_I2S_MASKS
8) toggle AIU_MEM_I2S_CONTROL[0]
9) toggle AIU_MEM_I2S_BUF_CNTL[0]

Additional testing shows that when AIU_I2S_MISC[2] is set to 1 then no
interrupts are generated anymore. The way this bit is managed by the
vendor driver as well as not getting any interrupts can mean that it's
related to the FIFO and not the encoder.

Move setting the AIU_I2S_MISC[2] bit to aiu_fifo_i2s_hw_params() so it
closer resembles the flow in the vendor kernel. While here also
configure AIU_I2S_MISC[4] (documented as: "force each audio data to
left or right according to the bit attached with the audio data")
similar to how the vendor driver does this. This fixes the infamous and
long-standing "machine gun noise" issue (a buffer underrun issue).

Fixes: 6ae9ca9ce986bf ("ASoC: meson: aiu: add i2s and spdif support")
Reported-by: Christian Hewitt <christianshewitt at gmail.com>
Reported-by: Geraldo Nascimento <geraldogabriel at gmail.com>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl at googlemail.com>
---
 sound/soc/meson/aiu-encoder-i2s.c | 33 -------------------------------
 sound/soc/meson/aiu-fifo-i2s.c    | 12 +++++++++++
 2 files changed, 12 insertions(+), 33 deletions(-)

diff --git a/sound/soc/meson/aiu-encoder-i2s.c b/sound/soc/meson/aiu-encoder-i2s.c
index 932224552146..67729de41a73 100644
--- a/sound/soc/meson/aiu-encoder-i2s.c
+++ b/sound/soc/meson/aiu-encoder-i2s.c
@@ -18,7 +18,6 @@
 #define AIU_RST_SOFT_I2S_FAST		BIT(0)
 
 #define AIU_I2S_DAC_CFG_MSB_FIRST	BIT(2)
-#define AIU_I2S_MISC_HOLD_EN		BIT(2)
 #define AIU_CLK_CTRL_I2S_DIV_EN		BIT(0)
 #define AIU_CLK_CTRL_I2S_DIV		GENMASK(3, 2)
 #define AIU_CLK_CTRL_AOCLK_INVERT	BIT(6)
@@ -36,37 +35,6 @@ static void aiu_encoder_i2s_divider_enable(struct snd_soc_component *component,
 				      enable ? AIU_CLK_CTRL_I2S_DIV_EN : 0);
 }
 
-static void aiu_encoder_i2s_hold(struct snd_soc_component *component,
-				 bool enable)
-{
-	snd_soc_component_update_bits(component, AIU_I2S_MISC,
-				      AIU_I2S_MISC_HOLD_EN,
-				      enable ? AIU_I2S_MISC_HOLD_EN : 0);
-}
-
-static int aiu_encoder_i2s_trigger(struct snd_pcm_substream *substream, int cmd,
-				   struct snd_soc_dai *dai)
-{
-	struct snd_soc_component *component = dai->component;
-
-	switch (cmd) {
-	case SNDRV_PCM_TRIGGER_START:
-	case SNDRV_PCM_TRIGGER_RESUME:
-	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
-		aiu_encoder_i2s_hold(component, false);
-		return 0;
-
-	case SNDRV_PCM_TRIGGER_STOP:
-	case SNDRV_PCM_TRIGGER_SUSPEND:
-	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
-		aiu_encoder_i2s_hold(component, true);
-		return 0;
-
-	default:
-		return -EINVAL;
-	}
-}
-
 static int aiu_encoder_i2s_setup_desc(struct snd_soc_component *component,
 				      struct snd_pcm_hw_params *params)
 {
@@ -353,7 +321,6 @@ static void aiu_encoder_i2s_shutdown(struct snd_pcm_substream *substream,
 }
 
 const struct snd_soc_dai_ops aiu_encoder_i2s_dai_ops = {
-	.trigger	= aiu_encoder_i2s_trigger,
 	.hw_params	= aiu_encoder_i2s_hw_params,
 	.hw_free	= aiu_encoder_i2s_hw_free,
 	.set_fmt	= aiu_encoder_i2s_set_fmt,
diff --git a/sound/soc/meson/aiu-fifo-i2s.c b/sound/soc/meson/aiu-fifo-i2s.c
index 2388a2d0b3a6..d0a1090d6465 100644
--- a/sound/soc/meson/aiu-fifo-i2s.c
+++ b/sound/soc/meson/aiu-fifo-i2s.c
@@ -20,6 +20,8 @@
 #define AIU_MEM_I2S_CONTROL_MODE_16BIT	BIT(6)
 #define AIU_MEM_I2S_BUF_CNTL_INIT	BIT(0)
 #define AIU_RST_SOFT_I2S_FAST		BIT(0)
+#define AIU_I2S_MISC_HOLD_EN		BIT(2)
+#define AIU_I2S_MISC_FORCE_LEFT_RIGHT	BIT(4)
 
 #define AIU_FIFO_I2S_BLOCK		256
 
@@ -90,6 +92,10 @@ static int aiu_fifo_i2s_hw_params(struct snd_pcm_substream *substream,
 	unsigned int val;
 	int ret;
 
+	snd_soc_component_update_bits(component, AIU_I2S_MISC,
+				      AIU_I2S_MISC_HOLD_EN,
+				      AIU_I2S_MISC_HOLD_EN);
+
 	ret = aiu_fifo_hw_params(substream, params, dai);
 	if (ret)
 		return ret;
@@ -117,6 +123,12 @@ static int aiu_fifo_i2s_hw_params(struct snd_pcm_substream *substream,
 	snd_soc_component_update_bits(component, AIU_MEM_I2S_MASKS,
 				      AIU_MEM_I2S_MASKS_IRQ_BLOCK, val);
 
+	snd_soc_component_update_bits(component, AIU_I2S_MISC,
+				      AIU_I2S_MISC_FORCE_LEFT_RIGHT,
+				      AIU_I2S_MISC_FORCE_LEFT_RIGHT);
+	snd_soc_component_update_bits(component, AIU_I2S_MISC,
+				      AIU_I2S_MISC_HOLD_EN, 0);
+
 	return 0;
 }
 
-- 
2.34.1