I'm new to the i.MX8M family and I have a problem running an RPMsg-lite example under the kernel 5.4 and Debian Buster, using an i.MX8M Mini EVK (8MMINILPD4-EVK).
The rpmsg_lite_str_echo_rtos_imxcm4 (MCUXPresso SDK 2.8) example runs well with the imx_4.19.35_1.1.0 kernel branch from CodeAurora. I'm kicking off the CM4 binary in u-boot, and after Linux has booted, the ttyRPMSG30 appears and allows communication with the Cortex M4. The dtb I'm using here is fsl-imx8mm-evk-m4.dtb and the imx_rpmsg_tty module tells me at startup that it found the M4 endpoint.
But when I update to the imx_5.4.24_2.1.0 kernel branch, the imx_rpmsg_tty kernel module is still loaded, but does not recognize the rpmsg-lite endpoint of the CM4 - no tty appears and there is no message in the log that the connection is established. The CM4 binary is running and prints its start message on the console.
Probably the issue is an inappropriate device tree for kernel 5.4? Neither imx8mm-evk.dtb nor imx8mm-evk-rpmsg.dtb works. Taking the respective parts from the working 4.19 device tree (fsl-imx8mm-evk-m4) does not help either.
I'm also experiencing this with linux-imx 5.4.24-2.1.0 kernel. Has there been any development on the matter or is it time for me to "roll up my sleeves" and get to work?