ASoC: fsl_sai: Enable BCI bit if SAI works on synchronous mode with BYP asserted

There's an issue on SAI synchronous mode that TX/RX side can't get BCLK
from RX/TX it sync with if BYP bit is asserted. It's a workaround to
fix it that enable SION of IOMUX pad control and assert BCI.

For example if TX sync with RX which means both TX and RX are using clk
form RX and BYP=1. TX can get BCLK only if the following two conditions
are valid:
1. SION of RX BCLK IOMUX pad is set to 1
2. BCI of TX is set to 1

Signed-off-by: Chancel Liu <chancel.liu@nxp.com>
Acked-by: Shengjiu Wang <shengjiu.wang@gmail.com>
Link: https://lore.kernel.org/r/20230530103012.3448838-1-chancel.liu@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Chancel Liu

sound/soc/fsl/fsl_sai.c

@@ -491,14 +491,21 @@ static int fsl_sai_set_bclk(struct snd_soc_dai *dai, bool tx, u32 freq)
 	regmap_update_bits(sai->regmap, reg, FSL_SAI_CR2_MSEL_MASK,
 			   FSL_SAI_CR2_MSEL(sai->mclk_id[tx]));
 
-	if (savediv == 1)
+	if (savediv == 1) {
 		regmap_update_bits(sai->regmap, reg,
 				   FSL_SAI_CR2_DIV_MASK | FSL_SAI_CR2_BYP,
 				   FSL_SAI_CR2_BYP);
-	else
+		if (fsl_sai_dir_is_synced(sai, adir))
+			regmap_update_bits(sai->regmap, FSL_SAI_xCR2(tx, ofs),
+					   FSL_SAI_CR2_BCI, FSL_SAI_CR2_BCI);
+		else
+			regmap_update_bits(sai->regmap, FSL_SAI_xCR2(tx, ofs),
+					   FSL_SAI_CR2_BCI, 0);
+	} else {
 		regmap_update_bits(sai->regmap, reg,
 				   FSL_SAI_CR2_DIV_MASK | FSL_SAI_CR2_BYP,
 				   savediv / 2 - 1);
+	}
 
 	if (sai->soc_data->max_register >= FSL_SAI_MCTL) {
 		/* SAI is in master mode at this point, so enable MCLK */

sound/soc/fsl/fsl_sai.h

@@ -116,6 +116,7 @@
 
 /* SAI Transmit and Receive Configuration 2 Register */
 #define FSL_SAI_CR2_SYNC	BIT(30)
+#define FSL_SAI_CR2_BCI		BIT(28)
 #define FSL_SAI_CR2_MSEL_MASK	(0x3 << 26)
 #define FSL_SAI_CR2_MSEL_BUS	0
 #define FSL_SAI_CR2_MSEL_MCLK1	BIT(26)