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

[Cosmin-Gabriel Samoila]

Looks good to me!

Best regards,
Cosmin

On Sat, 2019-08-31 at 01:55 +0300, Daniel Baluta wrote:
> From SAI datasheet:
> 
> CHMOD, configures if transmit data pins are configured for TDM mode
> or Output mode.
> 	* (0) TDM mode, transmit data pins are tri-stated when slots
> are
> 	masked or channels are disabled.
> 	* (1) Output mode, transmit data pins are never tri-stated and
> 	will output zero 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.
> 
> Fix this by setting CHMOD to Output Mode so that pins will output
> zero
> when slots are masked or channels are disabled.
> 
> Cc: NXP Linux Team <linux-imx at nxp.com>
> Signed-off-by: Cosmin-Gabriel Samoila <cosmin.samoila at nxp.com>
> Signed-off-by: Daniel Baluta <daniel.baluta at nxp.com>
> ---
>  sound/soc/fsl/fsl_sai.c | 15 ++++++++++++---
>  sound/soc/fsl/fsl_sai.h |  2 ++
>  2 files changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
> index e896b577b1f7..b9daab0eb6eb 100644
> --- a/sound/soc/fsl/fsl_sai.c
> +++ b/sound/soc/fsl/fsl_sai.c
> @@ -467,6 +467,12 @@ static int fsl_sai_hw_params(struct
> snd_pcm_substream *substream,
>  
>  	val_cr4 |= FSL_SAI_CR4_FRSZ(slots);
>  
> +	/*
> +	 * set CHMOD to Output Mode so that transmit data pins will
> +	 * output zero when slots are masked or channels are disabled
> +	 */
> +	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),
> @@ -477,7 +483,8 @@ static int fsl_sai_hw_params(struct
> snd_pcm_substream *substream,
>  	if (!sai->is_slave_mode) {
>  		if (!sai->synchronous[TX] && sai->synchronous[RX] &&
> !tx) {
>  			regmap_update_bits(sai->regmap,
> FSL_SAI_TCR4(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_TCR5(ofs),
>  				FSL_SAI_CR5_WNW_MASK |
> FSL_SAI_CR5_W0W_MASK |
> @@ -486,7 +493,8 @@ static int fsl_sai_hw_params(struct
> snd_pcm_substream *substream,
>  				~0UL - ((1 << channels) - 1));
>  		} else if (!sai->synchronous[RX] && sai-
> >synchronous[TX] && tx) {
>  			regmap_update_bits(sai->regmap,
> FSL_SAI_RCR4(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_RCR5(ofs),
>  				FSL_SAI_CR5_WNW_MASK |
> FSL_SAI_CR5_W0W_MASK |
> @@ -497,7 +505,8 @@ 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 f96f8d97489d..1e3b4a6889a8 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	GENMASK(5, 5)
>  #define FSL_SAI_CR4_MF		BIT(4)
>  #define FSL_SAI_CR4_FSE		BIT(3)
>  #define FSL_SAI_CR4_FSP		BIT(1)