[PATCH] ASoC: fsl_sai: Set SAI Channel Mode to Output Mode

[Shengjiu Wang]

Transmit data pins will output zero when slots are masked or channels
are disabled. In CHMOD TDM mode, transmit data pins are tri-stated when
slots are masked or channels are disabled. When data pins are tri-stated,
there is noise on some channels when FS clock value is high and data is
read while fsclk is transitioning from high to low.

Signed-off-by: Cosmin-Gabriel Samoila <cosmin.samoila@xxxxxxx>
Signed-off-by: Shengjiu Wang <shengjiu.wang@xxxxxxx>
---
 sound/soc/fsl/fsl_sai.c | 12 ++++++++++--
 sound/soc/fsl/fsl_sai.h |  2 ++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
index 62c5fdb678fc..33b194a5c1dc 100644
--- a/sound/soc/fsl/fsl_sai.c
+++ b/sound/soc/fsl/fsl_sai.c
@@ -486,6 +486,12 @@ static int fsl_sai_hw_params(struct snd_pcm_substream *substream,
 
 	val_cr4 |= FSL_SAI_CR4_FRSZ(slots);
 
+	/* Output Mode - data pins transmit 0 when slots are masked
+	 * or channels are disabled
+	 */
+	if (tx)
+		val_cr4 |= FSL_SAI_CR4_CHMOD;
+
 	/*
 	 * For SAI master mode, when Tx(Rx) sync with Rx(Tx) clock, Rx(Tx) will
 	 * generate bclk and frame clock for Tx(Rx), we should set RCR4(TCR4),
@@ -494,7 +500,8 @@ static int fsl_sai_hw_params(struct snd_pcm_substream *substream,
 
 	if (!sai->is_slave_mode && fsl_sai_dir_is_synced(sai, adir)) {
 		regmap_update_bits(sai->regmap, FSL_SAI_xCR4(!tx, ofs),
-				   FSL_SAI_CR4_SYWD_MASK | FSL_SAI_CR4_FRSZ_MASK,
+				   FSL_SAI_CR4_SYWD_MASK | FSL_SAI_CR4_FRSZ_MASK |
+				   FSL_SAI_CR4_CHMOD_MASK,
 				   val_cr4);
 		regmap_update_bits(sai->regmap, FSL_SAI_xCR5(!tx, ofs),
 				   FSL_SAI_CR5_WNW_MASK | FSL_SAI_CR5_W0W_MASK |
@@ -502,7 +509,8 @@ static int fsl_sai_hw_params(struct snd_pcm_substream *substream,
 	}
 
 	regmap_update_bits(sai->regmap, FSL_SAI_xCR4(tx, ofs),
-			   FSL_SAI_CR4_SYWD_MASK | FSL_SAI_CR4_FRSZ_MASK,
+			   FSL_SAI_CR4_SYWD_MASK | FSL_SAI_CR4_FRSZ_MASK |
+			   FSL_SAI_CR4_CHMOD_MASK,
 			   val_cr4);
 	regmap_update_bits(sai->regmap, FSL_SAI_xCR5(tx, ofs),
 			   FSL_SAI_CR5_WNW_MASK | FSL_SAI_CR5_W0W_MASK |
diff --git a/sound/soc/fsl/fsl_sai.h b/sound/soc/fsl/fsl_sai.h
index 6aba7d28f5f3..19cd4e1bbff9 100644
--- a/sound/soc/fsl/fsl_sai.h
+++ b/sound/soc/fsl/fsl_sai.h
@@ -119,6 +119,8 @@
 #define FSL_SAI_CR4_FRSZ_MASK	(0x1f << 16)
 #define FSL_SAI_CR4_SYWD(x)	(((x) - 1) << 8)
 #define FSL_SAI_CR4_SYWD_MASK	(0x1f << 8)
+#define FSL_SAI_CR4_CHMOD       BIT(5)
+#define FSL_SAI_CR4_CHMOD_MASK  BIT(5)
 #define FSL_SAI_CR4_MF		BIT(4)
 #define FSL_SAI_CR4_FSE		BIT(3)
 #define FSL_SAI_CR4_FSP		BIT(1)
-- 
2.27.0