minimal working example, still fails shutdown

.gitignore

@@ -0,0 +1,3 @@
+.cache
+.vscode
+build

CMakeLists.txt

@@ -0,0 +1,10 @@
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+
+project(beagle-mcu-hello-world C CXX)
+
+set(CMAKE_BUILD_TYPE Debug)
+target_compile_options(app PRIVATE -O0 -g)
+
+add_subdirectory(src)

boards/beagleplay_am6254_m4.overlay

@@ -0,0 +1,11 @@
+/ {
+    chosen {
+        mikrobus,uart = &main_uart5;
+        zephyr,console = "";
+    };
+};
+
+&main_uart5 {
+    status = "okay";
+    current-speed = <115200>;
+};

config.yaml

@@ -0,0 +1,17 @@
+sample:
+  description: Hello World
+  name: beagleplay_mcu_hello_world
+common:
+  min_ram: 1
+  min_flash: 4
+  tags: rproc
+  integration_platforms:
+    - beagleplay/am6254/m4
+  harness: console
+  harness_config:
+    type: one_line
+    regex:
+      - "Hello World! (.*)"
+tests:
+  sample.basic.helloworld:
+    tags: introduction

prj.conf

@@ -0,0 +1,37 @@
+# c version
+CONFIG_MAIN_STACK_SIZE=8192
+
+# logging
+CONFIG_LOG=n
+CONFIG_CONSOLE=n
+CONFIG_EARLY_CONSOLE=n
+CONFIG_PRINTK=n
+
+# gpio support
+CONFIG_GPIO=y
+
+# uart
+CONFIG_SERIAL=y
+CONFIG_UART_INTERRUPT_DRIVEN=n
+CONFIG_UART_NS16550=y
+
+# i2c
+CONFIG_I2C=y
+
+# OpenAMP support
+CONFIG_OPENAMP=y
+CONFIG_OPENAMP_RSC_TABLE=y
+
+# IPC/Mailbox
+CONFIG_IPM=y
+CONFIG_MBOX=y
+
+# Optional: RPMsg for communication
+CONFIG_RPMSG_SERVICE=y
+
+# build
+CONFIG_NO_OPTIMIZATIONS=n
+CONFIG_SIZE_OPTIMIZATIONS=n
+CONFIG_SPEED_OPTIMIZATIONS=n
+CONFIG_DEBUG_OPTIMIZATIONS=y
+CONFIG_DEBUG_THREAD_INFO=y

src/CMakeLists.txt

@@ -0,0 +1,7 @@
+cmake_minimum_required(VERSION 3.20.0)
+
+target_include_directories(app PRIVATE ./)
+
+target_sources(app PRIVATE
+    main.cpp
+)

src/main.cpp

@@ -0,0 +1,26 @@
+#include <zephyr/kernel.h>
+#include <zephyr/device.h>
+#include <zephyr/drivers/uart.h>
+#include <string.h>
+#include <openamp/open_amp.h>
+
+const struct device *uart_dev = DEVICE_DT_GET(DT_CHOSEN(mikrobus_uart));
+
+int main(void) {
+	const char *message = "Hello World from mikroBUS UART!\r\n";
+    int msg_len = strlen(message);
+
+    if (!device_is_ready(uart_dev)) {
+		return -1;
+	} 
+
+    while (1) {
+		k_sleep(K_SECONDS(1));
+		
+		for (int i = 0; i < msg_len; i++) {
+			uart_poll_out(uart_dev, message[i]);
+		}
+	}
+
+    return 0;
+}