Do you insert the TF card before the system booting up ?
CM3 doesn’t support dynamic detection of the SDcard after the system boots up on RPI CM4 IO board.
The Raspberry Pi CM4 IO board, and the other fork of the CM4 IO board design, don’t have the sd_detect signal, so the SD card must persist before power on.
When working with Radxa CM3, it’s a headache for us, we need to support SD card hotplug on regular condition(Radxa CM3 IO board), we also have to support these none sd_detect IO boards.
The above example is for ‘b15’, but the operation method is the same for ‘b25’, only the version number is different.
b15: ‘5.10.160-19-rk356x’
b25: ‘5.10.160-18-rk356x’
Also, you should know that the above changes will be rewritten if you update the kernel.
For example, ‘apt upgrade’ or ‘rsetup’ … etc.