fsl_sai: work around missing MCLK on i.mx 8m plus

Some audio codecs need the MCLK during setup of the codec, however
for the i.MX 8M Plus it is gated with the bce bit.
So enable the bit already in fsl_sai_hw_params() which is an
early state when initalizing sai and codec.
Notably the WM8904 codec on the Dahlia carrier board is affected.

Fixes a timeout on audio start:

root@verdin-imx8mp:~# aplay sound/Gong.wav
[ 1356.402716] wm8904 3-001a: DC servo timed out
[ 1362.410401] wm8904 3-001a: DC servo timed out
Playing WAVE 'sound/Gong.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo

Related-to: ELB-3554
Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>

3 files changed, 33 insertions, 6 deletions

diff --git a/arch/arm64/boot/dts/freescale/imx8mp.dtsi b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
index a0867c9feeb8..3a16d9d80a56 100644
--- a/arch/arm64/boot/dts/freescale/imx8mp.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
@@ -1167,7 +1167,7 @@
 				ranges;
 
 				sai1: sai@30c10000 {
-					compatible = "fsl,imx8mq-sai", "fsl,imx6sx-sai";
+					compatible = "fsl,imx8mp-sai", "fsl,imx6sx-sai";
 					reg = <0x30c10000 0x10000>;
 					interrupts = <GIC_SPI 95 IRQ_TYPE_LEVEL_HIGH>;
 					clocks = <&audiomix_clk IMX8MP_CLK_AUDIOMIX_SAI1_IPG>, <&clk IMX8MP_CLK_DUMMY>,
@@ -1183,7 +1183,7 @@
 				};
 
 				sai2: sai@30c20000 {
-					compatible = "fsl,imx8mq-sai", "fsl,imx6sx-sai";
+					compatible = "fsl,imx8mp-sai", "fsl,imx6sx-sai";
 					reg = <0x30c20000 0x10000>;
 					interrupts = <GIC_SPI 96 IRQ_TYPE_LEVEL_HIGH>;
 					clocks = <&audiomix_clk IMX8MP_CLK_AUDIOMIX_SAI2_IPG>, <&clk IMX8MP_CLK_DUMMY>,
@@ -1199,7 +1199,7 @@
 				};
 
 				sai3: sai@30c30000 {
-					compatible = "fsl,imx8mq-sai", "fsl,imx6sx-sai";
+					compatible = "fsl,imx8mp-sai", "fsl,imx6sx-sai";
 					reg = <0x30c30000 0x10000>;
 					interrupts = <GIC_SPI 50 IRQ_TYPE_LEVEL_HIGH>;
 					clocks = <&audiomix_clk IMX8MP_CLK_AUDIOMIX_SAI3_IPG>, <&clk IMX8MP_CLK_DUMMY>,
@@ -1215,7 +1215,7 @@
 				};
 
 				sai5: sai@30c50000 {
-					compatible = "fsl,imx8mq-sai", "fsl,imx6sx-sai";
+					compatible = "fsl,imx8mp-sai", "fsl,imx6sx-sai";
 					reg = <0x30c50000 0x10000>;
 					interrupts = <GIC_SPI 90 IRQ_TYPE_LEVEL_HIGH>;
 					clocks = <&audiomix_clk IMX8MP_CLK_AUDIOMIX_SAI5_IPG>, <&clk IMX8MP_CLK_DUMMY>,
@@ -1231,7 +1231,7 @@
 				};
 
 				sai6: sai@30c60000 {
-					compatible = "fsl,imx8mq-sai", "fsl,imx6sx-sai";
+					compatible = "fsl,imx8mp-sai", "fsl,imx6sx-sai";
 					reg = <0x30c60000 0x10000>;
 					interrupts = <GIC_SPI 90 IRQ_TYPE_LEVEL_HIGH>;
 					clocks = <&audiomix_clk IMX8MP_CLK_AUDIOMIX_SAI6_IPG>,
@@ -1248,7 +1248,7 @@
 				};
 
 				sai7: sai@30c80000 {
-					compatible = "fsl,imx8mq-sai", "fsl,imx6sx-sai";
+					compatible = "fsl,imx8mp-sai", "fsl,imx6sx-sai";
 					reg = <0x30c80000 0x10000>;
 					interrupts = <GIC_SPI 111 IRQ_TYPE_LEVEL_HIGH>;
 					clocks = <&audiomix_clk IMX8MP_CLK_AUDIOMIX_SAI7_IPG>, <&clk IMX8MP_CLK_DUMMY>,
diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
index d9958a52e871..ec572612bb50 100644
--- a/sound/soc/fsl/fsl_sai.c
+++ b/sound/soc/fsl/fsl_sai.c
@@ -73,6 +73,17 @@ static struct fsl_sai_soc_data fsl_sai_imx7ulp = {
 	.constrain_period_size = false,
 };
 
+static struct fsl_sai_soc_data fsl_sai_imx8mp = {
+	.imx = true,
+	.dataline = 0xff,
+	.fifos = 8,
+	.fifo_depth = 128,
+	.flags = 0,
+	.reg_offset = 8,
+	.constrain_period_size = false,
+	.mclk_gated_by_bce = true,
+};
+
 static struct fsl_sai_soc_data fsl_sai_imx8mq = {
 	.imx = true,
 	.dataline = 0xff,
@@ -782,6 +793,18 @@ static int fsl_sai_hw_params(struct snd_pcm_substream *substream,
 			   FSL_SAI_CR5_FBT_MASK, val_cr5);
 	regmap_write(sai->regmap, FSL_SAI_xMR(tx),
 			~0UL - ((1 << min(channels, slots)) - 1));
+
+	/*
+	 * Some audio codecs need the MCLK during setup of the codec, however
+	 * for the i.MX 8M Plus it is gated with the receiver/transmiter BCE
+	 * bit. So enable the bit already here.
+	 */
+	if (sai->soc->mclk_gated_by_bce) {
+		/* Switch on MCLK early */
+		regmap_update_bits(sai->regmap, FSL_SAI_xCSR(tx, offset),
+				   FSL_SAI_CSR_BCE, FSL_SAI_CSR_BCE);
+	}
+
 	return 0;
 }
 
@@ -1270,6 +1293,7 @@ static const struct of_device_id fsl_sai_ids[] = {
 	{ .compatible = "fsl,imx6sx-sai", .data = &fsl_sai_imx6sx },
 	{ .compatible = "fsl,imx6ul-sai", .data = &fsl_sai_imx6ul },
 	{ .compatible = "fsl,imx7ulp-sai", .data = &fsl_sai_imx7ulp },
+	{ .compatible = "fsl,imx8mp-sai", .data = &fsl_sai_imx8mp },
 	{ .compatible = "fsl,imx8mq-sai", .data = &fsl_sai_imx8mq },
 	{ .compatible = "fsl,imx8qm-sai", .data = &fsl_sai_imx8qm },
 	{ /* sentinel */ }
diff --git a/sound/soc/fsl/fsl_sai.h b/sound/soc/fsl/fsl_sai.h
index 8476cfffaa25..54e491182db8 100644
--- a/sound/soc/fsl/fsl_sai.h
+++ b/sound/soc/fsl/fsl_sai.h
@@ -89,6 +89,7 @@
 /* SAI Transmit/Receive Control Register */
 #define FSL_SAI_CSR_TERE	BIT(31)
 #define FSL_SAI_CSR_SE		BIT(30)
+#define FSL_SAI_CSR_BCE		BIT(28)
 #define FSL_SAI_CSR_FR		BIT(25)
 #define FSL_SAI_CSR_SR		BIT(24)
 #define FSL_SAI_CSR_xF_SHIFT	16
@@ -225,6 +226,8 @@ struct fsl_sai_soc_data {
 	bool imx;
 	/* True for EDMA because it needs period size multiple of maxburst */
 	bool constrain_period_size;
+	/* Set to true if the MCLK to the output pin is gated with bce */
+	bool mclk_gated_by_bce;
 };
 
 struct fsl_sai_verid {