linux-kernel - [PATCH] ASoC: fsl_sai: Enable BCI bit if SAI works on synchronous mode with BYP asserted

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Date:   Tue, 30 May 2023 18:30:12 +0800
From:   Chancel Liu <chancel.liu@....com>
To:     lgirdwood@...il.com, broonie@...nel.org, perex@...ex.cz,
        tiwai@...e.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        shengjiu.wang@...il.com, Xiubo.Lee@...il.com, festevam@...il.com,
        nicoleotsuka@...il.com
Cc:     Chancel Liu <chancel.liu@....com>
Subject: [PATCH] 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@....com>
---
 sound/soc/fsl/fsl_sai.c | 11 +++++++++--
 sound/soc/fsl/fsl_sai.h |  1 +
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
index d9344025dc16..5e09f634c61b 100644
--- a/sound/soc/fsl/fsl_sai.c
+++ b/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 */
diff --git a/sound/soc/fsl/fsl_sai.h b/sound/soc/fsl/fsl_sai.h
index 3eb994aef36a..8254c3547b87 100644
--- a/sound/soc/fsl/fsl_sai.h
+++ b/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)
-- 
2.25.1