[PATCH v1] ASoC: codecs: ntp8918: calculate bclk using tdm params

[Ilias Izmaylov]

Use a function snd_soc_tdm_params_to_bclk instead of snd_soc_params_to_bclk
to calculate bclk frequency correctly using frame size, channel period
and a number of channels

Since in NTP8918 the word clock and bit clock frequencies are both 64
bits per period and given that the device has only 2 channels it means
that the period per channel is equal to 32 bits. Thus to calculate bit
clock frequency the only other non-constant value that we need is frame
size (or sample rate)

Also implemented a set_tdm_slot dai ops callback for ntp8918 codec that will
ensure that tdm slot width and slot num are set to 32 and 2
respectively because ntp8918 can only operate in that configuration

Signed-off-by: Ilias Izmaylov <ikizmaylov@xxxxxxxxxxxxxxxxx>
---
 sound/soc/codecs/ntp8918.c | 43 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/sound/soc/codecs/ntp8918.c b/sound/soc/codecs/ntp8918.c
index cc672fd93def4..c37bd5b53ed8a 100644
--- a/sound/soc/codecs/ntp8918.c
+++ b/sound/soc/codecs/ntp8918.c
@@ -32,6 +32,15 @@
 			     SNDRV_PCM_FMTBIT_S24_LE | \
 			     SNDRV_PCM_FMTBIT_S32_LE)
 
+/*
+ * The NTP8918 word clock (WCK) period is fixed at 64 bits,
+ * and the bit clock (BCK) period is equal to the word clock period.
+ * The interface has only 2 channels, meaning the number of ticks
+ * for both word and bit clocks per channel is 64 / 2 = 32.
+ */
+#define NTP8918_BCK_CHANNEL_PERIOD		32
+#define NTP8918_NR_CHANNELS			2
+
 #define NTP8918_INPUT_FMT			0x0
 #define  NTP8918_INPUT_FMT_MASTER_MODE		BIT(0)
 #define  NTP8918_INPUT_FMT_GSA_MODE		BIT(1)
@@ -215,7 +224,17 @@ static int ntp8918_hw_params(struct snd_pcm_substream *substream,
 	int bclk;
 	int ret;
 
-	bclk = snd_soc_params_to_bclk(params);
+	/*
+	 * When calculating bit clock frequency the only non-constant
+	 * input that's needed is sample rate which then needs to be
+	 * multiplied by constant values of BCK channel period and
+	 * number of channels.
+	 */
+	bclk = snd_soc_tdm_params_to_bclk(params,
+					  NTP8918_BCK_CHANNEL_PERIOD,
+					  NTP8918_NR_CHANNELS,
+					  0);
+
 	switch (bclk) {
 	case 3072000:
 	case 2822400:
@@ -313,10 +332,32 @@ static int ntp8918_digital_mute(struct snd_soc_dai *dai, int mute, int stream)
 	return ret < 0 ? ret : 0;
 }
 
+static int ntp8918_set_tdm_slot(struct snd_soc_dai *dai, unsigned int tx_mask,
+				unsigned int rx_mask, int slots,
+				int slot_width)
+{
+	if (slots != NTP8918_NR_CHANNELS) {
+		dev_err(dai->component->dev,
+			"Unsupported number of TDM slots %d, should be %d\n",
+			slots, NTP8918_NR_CHANNELS);
+		return -EINVAL;
+	}
+
+	if (slot_width != NTP8918_BCK_CHANNEL_PERIOD) {
+		dev_err(dai->component->dev,
+			"Unsupported TDM slot width %d, should be %d\n",
+			slot_width, NTP8918_BCK_CHANNEL_PERIOD);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static const struct snd_soc_dai_ops ntp8918_dai_ops = {
 	.hw_params = ntp8918_hw_params,
 	.set_fmt = ntp8918_set_fmt,
 	.mute_stream = ntp8918_digital_mute,
+	.set_tdm_slot = ntp8918_set_tdm_slot,
 };
 
 static struct snd_soc_dai_driver ntp8918_dai = {
-- 
2.47.3