И вот это можно попробовать:
bootcode_delay
The bootcode_delay command delays for a given number of seconds in bootcode.bin before loading start.elf: the default value is 0.
This is particularly useful to insert a delay before reading the EDID of the monitor, for example if the Pi and monitor are powered from the same source, but the monitor takes longer to start up than the Pi. Try setting this value if the display detection is wrong on initial boot, but is correct if you soft-reboot the Pi without removing power from the monitor.