[PATCH v4 1/7] ASoC: rockchip: Add support for rv1126 pdm

[Michael Riesch]

Hi Sugar Zhang,

Sorry to dig out this old thread, but I have two questions. Please see
below:

On 9/3/21 15:23, Sugar Zhang wrote:
> This patch adds support for rv1126 pdm controller which
> redesign cic filiter for better performance.
> 
> Signed-off-by: Sugar Zhang <sugar.zhang at rock-chips.com>
> ---
> 
> Changes in v4: None
> Changes in v3: None
> Changes in v2: None
> 
>  sound/soc/rockchip/rockchip_pdm.c | 76 +++++++++++++++++++++++++++++++++++----
>  sound/soc/rockchip/rockchip_pdm.h |  3 ++
>  2 files changed, 73 insertions(+), 6 deletions(-)
> 
> diff --git a/sound/soc/rockchip/rockchip_pdm.c b/sound/soc/rockchip/rockchip_pdm.c
> index 38bd603..67634d1 100644
> --- a/sound/soc/rockchip/rockchip_pdm.c
> +++ b/sound/soc/rockchip/rockchip_pdm.c
> @@ -24,6 +24,7 @@
>  enum rk_pdm_version {
>  	RK_PDM_RK3229,
>  	RK_PDM_RK3308,
> +	RK_PDM_RV1126,
>  };
>  
>  struct rk_pdm_dev {
> @@ -121,6 +122,55 @@ static unsigned int get_pdm_ds_ratio(unsigned int sr)
>  	return ratio;
>  }
>  
> +static unsigned int get_pdm_cic_ratio(unsigned int clk)
> +{
> +	switch (clk) {
> +	case 4096000:
> +	case 5644800:
> +	case 6144000:
> +		return 0;
> +	case 2048000:
> +	case 2822400:
> +	case 3072000:
> +		return 1;
> +	case 1024000:
> +	case 1411200:
> +	case 1536000:
> +		return 2;
> +	default:
> +		return 1;
> +	}
> +}
> +
> +static unsigned int samplerate_to_bit(unsigned int samplerate)
> +{
> +	switch (samplerate) {
> +	case 8000:
> +	case 11025:
> +	case 12000:
> +		return 0;
> +	case 16000:
> +	case 22050:
> +	case 24000:
> +		return 1;
> +	case 32000:
> +		return 2;
> +	case 44100:
> +	case 48000:
> +		return 3;
> +	case 64000:
> +	case 88200:
> +	case 96000:
> +		return 4;
> +	case 128000:
> +	case 176400:
> +	case 192000:
> +		return 5;
> +	default:
> +		return 1;
> +	}
> +}
> +
>  static inline struct rk_pdm_dev *to_info(struct snd_soc_dai *dai)
>  {
>  	return snd_soc_dai_get_drvdata(dai);
> @@ -166,7 +216,8 @@ static int rockchip_pdm_hw_params(struct snd_pcm_substream *substream,
>  	if (ret)
>  		return -EINVAL;
>  
> -	if (pdm->version == RK_PDM_RK3308) {
> +	if (pdm->version == RK_PDM_RK3308 ||
> +	    pdm->version == RK_PDM_RV1126) {
>  		rational_best_approximation(clk_out, clk_src,
>  					    GENMASK(16 - 1, 0),
>  					    GENMASK(16 - 1, 0),
> @@ -194,8 +245,18 @@ static int rockchip_pdm_hw_params(struct snd_pcm_substream *substream,
>  				   PDM_CLK_FD_RATIO_MSK,
>  				   val);
>  	}
> -	val = get_pdm_ds_ratio(samplerate);
> -	regmap_update_bits(pdm->regmap, PDM_CLK_CTRL, PDM_DS_RATIO_MSK, val);
> +
> +	if (pdm->version == RK_PDM_RV1126) {
> +		val = get_pdm_cic_ratio(clk_out);
> +		regmap_update_bits(pdm->regmap, PDM_CLK_CTRL, PDM_CIC_RATIO_MSK, val);
> +		val = samplerate_to_bit(samplerate);
> +		regmap_update_bits(pdm->regmap, PDM_CTRL0,
> +				   PDM_SAMPLERATE_MSK, PDM_SAMPLERATE(val));
> +	} else {
> +		val = get_pdm_ds_ratio(samplerate);
> +		regmap_update_bits(pdm->regmap, PDM_CLK_CTRL, PDM_DS_RATIO_MSK, val);
> +	}
> +
>  	regmap_update_bits(pdm->regmap, PDM_HPF_CTRL,
>  			   PDM_HPF_CF_MSK, PDM_HPF_60HZ);
>  	regmap_update_bits(pdm->regmap, PDM_HPF_CTRL,
> @@ -441,9 +502,10 @@ static bool rockchip_pdm_precious_reg(struct device *dev, unsigned int reg)
>  }
>  
>  static const struct reg_default rockchip_pdm_reg_defaults[] = {
> -	{0x04, 0x78000017},
> -	{0x08, 0x0bb8ea60},
> -	{0x18, 0x0000001f},
> +	{ PDM_CTRL0, 0x78000017 },
> +	{ PDM_CTRL1, 0x0bb8ea60 },
> +	{ PDM_CLK_CTRL, 0x0000e401 },
> +	{ PDM_DMA_CTRL, 0x0000001f },
>  };
>  
>  static const struct regmap_config rockchip_pdm_regmap_config = {
> @@ -469,6 +531,8 @@ static const struct of_device_id rockchip_pdm_match[] __maybe_unused = {
>  	  .data = (void *)RK_PDM_RK3308 },
>  	{ .compatible = "rockchip,rk3308-pdm",
>  	  .data = (void *)RK_PDM_RK3308 },
> +	{ .compatible = "rockchip,rv1126-pdm",
> +	  .data = (void *)RK_PDM_RV1126 },
>  	{},
>  };
>  MODULE_DEVICE_TABLE(of, rockchip_pdm_match);
> diff --git a/sound/soc/rockchip/rockchip_pdm.h b/sound/soc/rockchip/rockchip_pdm.h
> index 8e5bbaf..13bfbc2 100644
> --- a/sound/soc/rockchip/rockchip_pdm.h
> +++ b/sound/soc/rockchip/rockchip_pdm.h
> @@ -41,6 +41,8 @@
>  #define PDM_PATH1_EN		BIT(28)
>  #define PDM_PATH0_EN		BIT(27)
>  #define PDM_HWT_EN		BIT(26)
> +#define PDM_SAMPLERATE_MSK	GENMASK(7, 5)
> +#define PDM_SAMPLERATE(x)	((x) << 5)
>  #define PDM_VDW_MSK		(0x1f << 0)
>  #define PDM_VDW(X)		((X - 1) << 0)

The TRM of RV1126 and RK3568 both state that sample resolutions from 16
up to 24 bits are supported. However, I don't see anything in this patch
that restricts the capture formats accordingly. In fact, the driver
offers SNDRV_PCM_FMTBIT_S32_LE in my setup and via this PDM_VDW macro 31
is written to PDM_CTRL0, which is undefined behavior according to the TRM.

Are 32 bit samples supported by the RK3568/RV1126 PDM block?

> @@ -66,6 +68,7 @@
>  #define PDM_CLK_1280FS		(0x2 << 0)
>  #define PDM_CLK_2560FS		(0x3 << 0)
>  #define PDM_CLK_5120FS		(0x4 << 0)
> +#define PDM_CIC_RATIO_MSK	(0x3 << 0)
>  
>  /* PDM HPF CTRL */
>  #define PDM_HPF_LE		BIT(3)

Also, I noticed that the number of channels must be an even number.
Shouldn't it be possible to use a single mono PDM microphone with this
PDM block (i.e., having one channel)?

Thanks a lot and best regards,
Michael