Had a stack of trouble getting the 12.1" panel to stay on in retro-pie. Eventually hdmi_safe=1 seemed to solve it, so then iterating through the config params that this sets by default it seems that the following two lines magically made it work…
I have the 12.1" screen. Isn’t the native resolution 1024x768 ? The screen provided EDID info seems to be wrong anyway as it started up in the wrong resolution, so on my 12.1" screen I did