Steward has updated pcsx4all below brings huge improvments download below or it can be downloaded from the ownloads section here.
Finally, it can write framebuffer into DMA directly for RetroGame.
This method is adopted from GP2X Wiz (notaz used long time ago)
The speed is good for pcsx4all emulator on RetroGame device now.
Kindly help to test it.
pcsx4all for testing:
https://github.com/steward-fu/gh_retrogame_binary/blob/master/PCSX4ALL/int_sd/emus/pcsx4all/pcsx4all
I should optimize all of emulator by using DMA method to speed up, soon.