Hello !
What is "Dirty Regions functionality"?
I provided you a link in the Coreelec 8.90.1 thread: [8.90.1] CoreELEC for S905/S912 devices
Did you follow the links in the original post of wrxtasy ? Additional information regarding dirty regions is available there. For your convenience:
HOW-TO:Modify dirty regions - Official Kodi Wiki
and
Working with dirty regions | Kodi | Open Source Home Theater Software