Looks like your driver is already working on Kernel mode by default. I would give a try to this:
https://wiki.manjaro.org/index.php?title=Configure_Graphics_Cards
If that doesn’t help, the problem might be the timing in which the driver is being loaded in the boot sequence. Most likely, lightdm is starting up before the video driver is ready.
You might want to play around with Early KMS as explained in the Arch Wiki.
Hope the above helps! 