uname -a
Linux am62xx-evm 6.1.119-ti-ge4e8b16e66f5 #1 SMP PREEMPT Sat Dec  7 07:14:10 UTC 2024 aarch64 GNU/Linux


dmesg | grep rpmsg
[    3.738902] virtio_rpmsg_bus virtio0: rpmsg host is online
[    3.773832] virtio_rpmsg_bus virtio0: creating channel rpmsg_chrdev addr 0x1
[    3.829193] virtio_rpmsg_bus virtio1: rpmsg host is online


dmesg | grep remoteproc
[    3.566622] k3-m4-rproc 5000000.m4fss: configured M4 for remoteproc mode
[    3.580849] remoteproc remoteproc0: 5000000.m4fss is available
[    3.709686] remoteproc remoteproc0: powering up 5000000.m4fss
[    3.715889] remoteproc remoteproc0: Booting fw image am62-mcu-m4f0_0-fw, size 2400160
[    3.751410] remoteproc remoteproc0: remote processor 5000000.m4fss is now up
[    3.803573] remoteproc remoteproc1: 78000000.r5f is available
[    3.809608] remoteproc remoteproc1: attaching to 78000000.r5f
[    3.843133] remoteproc remoteproc1: remote processor 78000000.r5f is now attached
[    3.947905] remoteproc remoteproc2: 30074000.pru is available
[    3.954315] remoteproc remoteproc3: 30078000.pru is available


lsmod | grep rpmsg
rpmsg_ctrl 16384 0 - Live 0xffff800001281000
rpmsg_char 16384 1 rpmsg_ctrl, Live 0xffff80000122a000
virtio_rpmsg_bus 20480 0 - Live 0xffff800001171000
rpmsg_ns 16384 1 virtio_rpmsg_bus, Live 0xffff800001119000


cat /sys/class/remoteproc/remoteproc0/name
5000000.m4fss


cat /sys/class/remoteproc/remoteproc0/state
running


ls /sys/class/rpmsg/
rpmsg0       rpmsg_ctrl0  rpmsg_ctrl1


cat /sys/class/rpmsg/rpmsg0/name
rpmsg_chrdev


ls -l /dev | grep rpmsg
<no output, should be rpmsg0, rpmsg1, rpmsg_ctrl0, rpmsg_ctrl1>


Searched menuconfig for "rpmsg":
# CONFIG_RPMSG_TTY is not set
# CONFIG_SND_SOC_FSL_RPMSG is not set
# CONFIG_SND_SOC_IMX_RPMSG is not set
# CONFIG_CROS_EC_RPMSG is not set
# Rpmsg drivers
CONFIG_RPMSG=y
CONFIG_RPMSG_CHAR=m
CONFIG_RPMSG_CTRL=m
CONFIG_RPMSG_NS=m
CONFIG_RPMSG_MTK_SCP=m
CONFIG_RPMSG_QCOM_GLINK=y
CONFIG_RPMSG_QCOM_GLINK_RPM=y
CONFIG_RPMSG_QCOM_GLINK_SMEM=m
CONFIG_RPMSG_QCOM_SMD=y
CONFIG_RPMSG_VIRTIO=m
CONFIG_RPMSG_PRU=m
# end of Rpmsg drivers
# Rpmsg virtual device drivers
CONFIG_RPMSG_KDRV=y
# CONFIG_RPMSG_KDRV_DEMO is not set
# CONFIG_RPMSG_KDRV_DISPLAY is not set
CONFIG_RPMSG_KDRV_ETH_SWITCH=y
# end of Rpmsg virtual device drivers
CONFIG_SAMPLE_RPMSG_CLIENT=m


Searched menuconfig for "mailbox":
CONFIG_ARM_SCMI_TRANSPORT_MAILBOX=y
CONFIG_MAILBOX=y
CONFIG_APPLE_MAILBOX=y
# CONFIG_MAILBOX_TEST is not set


Device tree M4F node:
			m4fss@5000000 {
				compatible = "ti,am64-m4fss";
				reg = <0x00 0x5000000 0x00 0x30000 0x00 0x5040000 0x00 0x10000>;
				reg-names = "iram\0dram";
				ti,sci = <0x05>;
				ti,sci-dev-id = <0x09>;
				ti,sci-proc-ids = <0x18 0xff>;
				resets = <0x07 0x09 0x01>;
				firmware-name = "am62-mcu-m4f0_0-fw";
				wakeup-source;
				mboxes = <0x08 0x09>;
				memory-region = <0x0a 0x0b>;
				phandle = <0x66>;
			};


Device tree mailbox nodes and more:
			mailbox@4d000000 {
				compatible = "ti,am654-secure-proxy";
				#mbox-cells = <0x01>;
				reg-names = "target_data\0rt\0scfg";
				reg = <0x00 0x4d000000 0x00 0x80000 0x00 0x4a600000 0x00 0x80000 0x00 0x4a400000 0x00 0x80000>;
				interrupt-names = "rx_012";
				interrupts = <0x00 0x22 0x04>;
				phandle = <0x12>;
			};
...
		mailbox@43600000 {
			compatible = "ti,am654-secure-proxy";
			#mbox-cells = <0x01>;
			reg-names = "target_data\0rt\0scfg";
			reg = <0x00 0x43600000 0x00 0x10000 0x00 0x44880000 0x00 0x20000 0x00 0x44860000 0x00 0x20000>;
			status = "disabled";
			phandle = <0x76>;
		};
...
		mailbox@29000000 {
			compatible = "ti,am64-mailbox";
			reg = <0x00 0x29000000 0x00 0x200>;
			interrupts = <0x00 0x4c 0x04 0x00 0x4d 0x04>;
			#mbox-cells = <0x01>;
			ti,mbox-num-users = <0x04>;
			ti,mbox-num-fifos = <0x10>;
			phandle = <0x08>;

			mbox-m4-0 {
				ti,mbox-rx = <0x00 0x00 0x00>;
				ti,mbox-tx = <0x01 0x00 0x00>;
				phandle = <0x09>;
			};

			mbox-r5-0 {
				ti,mbox-rx = <0x02 0x00 0x00>;
				ti,mbox-tx = <0x03 0x00 0x00>;
				phandle = <0x0c>;
			};
		};
...
		mailbox0_cluster0 = "/bus@f0000/mailbox@29000000";
		mbox_m4_0 = "/bus@f0000/mailbox@29000000/mbox-m4-0";
		mbox_r5_0 = "/bus@f0000/mailbox@29000000/mbox-r5-0";


Code on the MCU M4F: I am using the following function calls:
RPMessage_waitForLinuxReady(SystemP_WAIT_FOREVER);
RPMessage_announce(ID_A53_0, localEndpt, "rpmsg_chrdev");

The debugger shows that both functions are called and return with success. The exact same MCU firmware also worked on Phytec's Linux. The SDK version is 09.01.00.39.