Thanks Eric, recovery mode works.
About a working mode suitable for running factory test commands, if "androidboot.mode=factory" not working on i.MX8M + Android 8.1, is there a proper mode you recommend?
Here are some descriptions of this mode:
1. Less than 10s quick boot time
2. ADB is enabled
3. Device drivers of Linux kernel are running, and peripherals such as LCD/Touch Panel/Camera can be tested in this mode
4. Unit can boot into Android normally after a power restart.
Thanks!
Terri