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>
Acked-by: Nicolin Chen <nicoleotsuka@xxxxxxxxx>
---
changes in v2
- update note
- add acked-by Nicolin
sound/soc/fsl/fsl_sai.c | 10 ++++++++--
sound/soc/fsl/fsl_sai.h | 2 ++
2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
index 38c7bcbb361d..b2d65e53dbc4 100644
--- a/sound/soc/fsl/fsl_sai.c
+++ b/sound/soc/fsl/fsl_sai.c
@@ -489,6 +489,10 @@ static int fsl_sai_hw_params(struct snd_pcm_substream *substream,
val_cr4 |= FSL_SAI_CR4_FRSZ(slots);
+ /* Set to output mode to avoid tri-stated data pins */
+ 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),
@@ -497,7 +501,8 @@ 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 |
@@ -508,7 +513,8 @@ static int fsl_sai_hw_params(struct snd_pcm_substream *substream,
FSL_SAI_CR3_TRCE_MASK,
FSL_SAI_CR3_TRCE((1 << pins) - 1));
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 5f630be74853..736a437450c8 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
