board: mimxrt685_evk/mimxrt685s/hifi4: Add init code

Add initialisation code for the HiFi 4 DSP domain of the mimxrt685_evk
board. Responsible for setting up signal sharing between Flexcomm zephyrproject-rtos#1 and
Flexcomm zephyrproject-rtos#3 peripherals both in the I2S mode (simultaneous audio
playback and capture).

Signed-off-by: Vit Stanicek <vit.stanicek@nxp.com>

boards/nxp/mimxrt685_evk/CMakeLists.txt

@@ -11,6 +11,7 @@ endif()
 
 if(CONFIG_BOARD_MIMXRT685_EVK_MIMXRT685S_HIFI4)
 zephyr_library()
+zephyr_library_sources(hifi4/init.c)
 endif()
 
 if(CONFIG_NXP_IMXRT_BOOT_HEADER)

boards/nxp/mimxrt685_evk/hifi4/init.c

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2020-2024 NXP
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/init.h>
+#include <zephyr/devicetree.h>
+#include <fsl_device_registers.h>
+
+static int mimxrt685_evk_hifi4_init(void)
+{
+/* flexcomm1 and flexcomm3 are configured to loopback the TX signal to RX */
+#if (DT_NODE_HAS_COMPAT_STATUS(DT_NODELABEL(flexcomm1), nxp_lpc_i2s, okay)) && \
+	(DT_NODE_HAS_COMPAT_STATUS(DT_NODELABEL(flexcomm3), nxp_lpc_i2s, okay)) && \
+	CONFIG_I2S
+
+	/* Set shared signal set 0 SCK, WS from Transmit I2S - Flexcomm3 */
+	SYSCTL1->SHAREDCTRLSET[0] = SYSCTL1_SHAREDCTRLSET_SHAREDSCKSEL(3) |
+				SYSCTL1_SHAREDCTRLSET_SHAREDWSSEL(3);
+
+#ifdef CONFIG_I2S_TEST_SEPARATE_DEVICES
+	/* Select Data in from Transmit I2S - Flexcomm 3 */
+	SYSCTL1->SHAREDCTRLSET[0] |= SYSCTL1_SHAREDCTRLSET_SHAREDDATASEL(3);
+	/* Enable Transmit I2S - Flexcomm 3 for Shared Data Out */
+	SYSCTL1->SHAREDCTRLSET[0] |= SYSCTL1_SHAREDCTRLSET_FC3DATAOUTEN(1);
+#endif
+
+	/* Set Receive I2S - Flexcomm 1 SCK, WS from shared signal set 0 */
+	SYSCTL1->FCCTRLSEL[1] = SYSCTL1_FCCTRLSEL_SCKINSEL(1) |
+				SYSCTL1_FCCTRLSEL_WSINSEL(1);
+
+	/* Set Transmit I2S - Flexcomm 3 SCK, WS from shared signal set 0 */
+	SYSCTL1->FCCTRLSEL[3] = SYSCTL1_FCCTRLSEL_SCKINSEL(1) |
+				SYSCTL1_FCCTRLSEL_WSINSEL(1);
+
+#ifdef CONFIG_I2S_TEST_SEPARATE_DEVICES
+	/* Select Receive I2S - Flexcomm 1 Data in from shared signal set 0 */
+	SYSCTL1->FCCTRLSEL[1] |= SYSCTL1_FCCTRLSEL_DATAINSEL(1);
+	/* Select Transmit I2S - Flexcomm 3 Data out to shared signal set 0 */
+	SYSCTL1->FCCTRLSEL[3] |= SYSCTL1_FCCTRLSEL_DATAOUTSEL(1);
+#endif
+
+#endif
+
+    return 0;
+}
+
+SYS_INIT(mimxrt685_evk_hifi4_init, PRE_KERNEL_1, 0);