exactly as you described, the sleep of death. ive got it narrowed down to 3 lines in the vibrator/tspdrv.c but never achieved what i needed,
Use what you need, i still have to re do a bunch of sh** because of the ov5693 camera in newer models, have to use jb blobs vs kitkat
however, another dev on my team has built kitkat for the f3, and i dare say hes better than i.
Device:
https://github.com/phenomx4/android_device_lge_fx3
Kernel:
https://github.com/phenomx4/android_kernel_lge_fx3