ASoC: fsl_sai: Allow setting the SAI MCLK direction

On mx6ul the General Purpose Register 1 (GPR1) contains the following
bits for configuring the direction of the SAI MCLKs:
SAI1_MCLK_DIR, SAI2_MCLK_DIR, SAI3_MCLK_DIR

Introduce  the "fsl,sai-mclk-direction-output" optional property to allow
configuring the SAI_MCLK outputs.

Tested on a imx6ul-evk board.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/fsl-sai.txt

@@ -48,6 +48,11 @@ Required properties:
 			  receive data by following their own bit clocks and
 			  frame sync clocks separately.
 
+Optional properties (for mx6ul):
+
+  - fsl,sai-mclk-direction-output: This is a boolean property. If present,
+			 indicates that SAI will output the SAI MCLK clock.
+
 Note:
 - If both fsl,sai-asynchronous and fsl,sai-synchronous-rx are absent, the
   default synchronous mode (sync Rx with Tx) will be used, which means both

include/linux/mfd/syscon/imx6q-iomuxc-gpr.h

@@ -447,5 +447,11 @@
 #define IMX6UL_GPR1_ENET2_CLK_OUTPUT		(0x1 << 18)
 #define IMX6UL_GPR1_ENET_CLK_DIR		(0x3 << 17)
 #define IMX6UL_GPR1_ENET_CLK_OUTPUT		(0x3 << 17)
+#define IMX6UL_GPR1_SAI1_MCLK_DIR		(0x1 << 19)
+#define IMX6UL_GPR1_SAI2_MCLK_DIR		(0x1 << 20)
+#define IMX6UL_GPR1_SAI3_MCLK_DIR		(0x1 << 21)
+#define IMX6UL_GPR1_SAI_MCLK_MASK		(0x7 << 19)
+#define MCLK_DIR(x) (x == 1 ? IMX6UL_GPR1_SAI1_MCLK_DIR : x == 2 ? \
+		     IMX6UL_GPR1_SAI2_MCLK_DIR : IMX6UL_GPR1_SAI3_MCLK_DIR)
 
 #endif /* __LINUX_IMX6Q_IOMUXC_GPR_H */

sound/soc/fsl/fsl_sai.c

@@ -21,6 +21,8 @@
 #include <sound/core.h>
 #include <sound/dmaengine_pcm.h>
 #include <sound/pcm_params.h>
+#include <linux/mfd/syscon.h>
+#include <linux/mfd/syscon/imx6q-iomuxc-gpr.h>
 
 #include "fsl_sai.h"
 #include "imx-pcm.h"
@@ -786,10 +788,12 @@ static int fsl_sai_probe(struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
 	struct fsl_sai *sai;
+	struct regmap *gpr;
 	struct resource *res;
 	void __iomem *base;
 	char tmp[8];
 	int irq, ret, i;
+	int index;
 
 	sai = devm_kzalloc(&pdev->dev, sizeof(*sai), GFP_KERNEL);
 	if (!sai)
@@ -878,6 +882,22 @@ static int fsl_sai_probe(struct platform_device *pdev)
 		fsl_sai_dai.symmetric_samplebits = 0;
 	}
 
+	if (of_find_property(np, "fsl,sai-mclk-direction-output", NULL) &&
+	    of_device_is_compatible(pdev->dev.of_node, "fsl,imx6ul-sai")) {
+		gpr = syscon_regmap_lookup_by_compatible("fsl,imx6ul-iomuxc-gpr");
+		if (IS_ERR(gpr)) {
+			dev_err(&pdev->dev, "cannot find iomuxc registers\n");
+			return PTR_ERR(gpr);
+		}
+
+		index = of_alias_get_id(np, "sai");
+		if (index < 0)
+			return index;
+
+		regmap_update_bits(gpr, IOMUXC_GPR1, MCLK_DIR(index),
+				   MCLK_DIR(index));
+	}
+
 	sai->dma_params_rx.addr = res->start + FSL_SAI_RDR;
 	sai->dma_params_tx.addr = res->start + FSL_SAI_TDR;
 	sai->dma_params_rx.maxburst = FSL_SAI_MAXBURST_RX;