Re: [PATCH 07/13] ASoC: ti: davinci-i2s: Add TDM support

On 15/03/2024 13:27, Bastien Curutchet wrote:

TDM is not supported by the McBSP driver. The McBSP datasheet does not name explicitly TDM as a supported format but it is possible to configure the McBSP to do TDM if all slots are used by McBSP.

Add TDM support. It uses single-phase frame. Slot width is used to compute the McBSP's word length.

Implement the set_tdm_slot() hook of snd_soc_dai_ops struct. It only supports TDM if all slots are used by McBSP.

The snd_soc_dai_driver's capture.channels_max is updated from 2 to 128. 128 is the maximum frame length when using single-phase frame. playback.channels_max has not been updated as I could not test TDM on playbacks with my hardware.

This was tested on platform designed off of DAVINCI/OMAP_L138 with BP_FC format so this is only supported format for TDM yet. A check is done in davinci_i2s_set_dai_fmt() to prevent TDM to be used with other formats

Signed-off-by: Bastien Curutchet bastien.curutchet@bootlin.com

sound/soc/ti/davinci-i2s.c | 81 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 77 insertions(+), 4 deletions(-)

diff --git a/sound/soc/ti/davinci-i2s.c b/sound/soc/ti/davinci-i2s.c index f4514d4dff07..4adaed010700 100644 --- a/sound/soc/ti/davinci-i2s.c +++ b/sound/soc/ti/davinci-i2s.c @@ -160,6 +160,9 @@ struct davinci_mcbsp_dev { unsigned int fmt; int clk_div; bool i2s_accurate_sck;

• int tdm_slots;
• int slot_width;

};

static inline void davinci_mcbsp_write_reg(struct davinci_mcbsp_dev *dev, @@ -213,6 +216,57 @@ static void davinci_mcbsp_stop(struct davinci_mcbsp_dev *dev, int playback) toggle_clock(dev, playback); }

+static int davinci_i2s_tdm_word_length(int tdm_slot_width) +{

• switch (tdm_slot_width) {
• case 8:

• return DAVINCI_MCBSP_WORD_8;
  

• case 12:

• return DAVINCI_MCBSP_WORD_12;
  

• case 16:

• return DAVINCI_MCBSP_WORD_16;
  

• case 20:

• return DAVINCI_MCBSP_WORD_20;
  

• case 24:

• return DAVINCI_MCBSP_WORD_24;
  

• case 32:

• return DAVINCI_MCBSP_WORD_32;
  

• default:

• return -EINVAL;
  

• }

+}

+static int davinci_i2s_set_tdm_slot(struct snd_soc_dai *cpu_dai,

• 		    unsigned int tx_mask,
  

• 		    unsigned int rx_mask,
  

• 		    int slots, int slot_width)
  

+{

• struct davinci_mcbsp_dev *dev = snd_soc_dai_get_drvdata(cpu_dai);
• dev_dbg(dev->dev, "%s - slots %d, slot_width %d\n", __func__, slots, slot_width);

The __func__ can be ommited, it is better to leave it for dynamic debugging by adding "dyndbg=+pmf" module parameter if needed.

• if (slots > 128 || !slots) {

• dev_err(dev->dev, "Invalid number of slots\n");
  

• return -EINVAL;
  

• }
• if (rx_mask != (1 << slots) - 1) {

• dev_err(dev->dev, "Invalid RX mask (0x%08x) : all slots must be used by McBSP\n",
  

• 	rx_mask);
  

• return -EINVAL;
  

This is only a restriction for RX?

• }
• if (davinci_i2s_tdm_word_length(slot_width) < 0) {

• dev_err(dev->dev, "%s: Unsupported slot_width %d\n", __func__, slot_width);
  

• return -EINVAL;
  

• }
• dev->tdm_slots = slots;
• dev->slot_width = slot_width;
• return 0;

+}

#define DEFAULT_BITPERSAMPLE 16

static int davinci_i2s_set_dai_fmt(struct snd_soc_dai *cpu_dai, @@ -228,6 +282,13 @@ static int davinci_i2s_set_dai_fmt(struct snd_soc_dai *cpu_dai, DAVINCI_MCBSP_SRGR_FWID(DEFAULT_BITPERSAMPLE - 1);

dev->fmt = fmt;

• if ((dev->tdm_slots || dev->slot_width) &&

•    ((fmt & SND_SOC_DAIFMT_CLOCK_PROVIDER_MASK) != SND_SOC_DAIFMT_BP_FC)) {
  

• dev_err(dev->dev, "TDM is only supported for BP_FC format\n");
  

• return -EINVAL;
  

I think this is not a valid statement, Fsync can be generated internally or coming from external source in TDM mode also.

• }
• /* set master/slave audio interface */ switch (fmt & SND_SOC_DAIFMT_CLOCK_PROVIDER_MASK) { case SND_SOC_DAIFMT_BP_FP:

@@ -383,7 +444,13 @@ static int davinci_i2s_hw_params(struct snd_pcm_substream *substream,

master = dev->fmt & SND_SOC_DAIFMT_CLOCK_PROVIDER_MASK; fmt = params_format(params);

• mcbsp_word_length = asp_word_length[fmt];

• if (dev->slot_width)

• mcbsp_word_length = davinci_i2s_tdm_word_length(dev->slot_width);
  

• else

• mcbsp_word_length = asp_word_length[fmt];
  

• if (mcbsp_word_length < 0)

• return mcbsp_word_length;
  
  

  switch (master) { case SND_SOC_DAIFMT_BP_FP:

@@ -483,8 +550,13 @@ static int davinci_i2s_hw_params(struct snd_pcm_substream *substream, switch (master) { case SND_SOC_DAIFMT_BP_FP: case SND_SOC_DAIFMT_BP_FC:

• rcr |= DAVINCI_MCBSP_RCR_RFRLEN1(0);
  

• xcr |= DAVINCI_MCBSP_XCR_XFRLEN1(0);
  

• if (dev->tdm_slots > 0) {
  

• 	rcr |= DAVINCI_MCBSP_RCR_RFRLEN1(dev->tdm_slots - 1);
  

• 	xcr |= DAVINCI_MCBSP_XCR_XFRLEN1(dev->tdm_slots - 1);
  

• } else {
  

• 	rcr |= DAVINCI_MCBSP_RCR_RFRLEN1(0);
  

• 	xcr |= DAVINCI_MCBSP_XCR_XFRLEN1(0);
  

• }
  

  break; case SND_SOC_DAIFMT_BC_FC: case SND_SOC_DAIFMT_BC_FP:

@@ -609,6 +681,7 @@ static const struct snd_soc_dai_ops davinci_i2s_dai_ops = { .hw_params = davinci_i2s_hw_params, .set_fmt = davinci_i2s_set_dai_fmt, .set_clkdiv = davinci_i2s_dai_set_clkdiv,

• .set_tdm_slot = davinci_i2s_set_tdm_slot,

};

@@ -621,7 +694,7 @@ static struct snd_soc_dai_driver davinci_i2s_dai = { }, .capture = { .channels_min = 2,

• .channels_max = 2,
  

• .channels_max = 128,
  

  .rates = DAVINCI_I2S_RATES, .formats = DAVINCI_I2S_FORMATS, },