ADV7511 related kernel/buildroot configuration is documented here: docs.blackfin.uclinux.org/doku.php?id=linux-kernel:drivers:v4l2_blackfin_display&s[]=adv7511
I used to follow this document to do the HDMI display correctly, make sure you are using a clean version of the ADI 2012R2(or 2012R1) release of code. Please check if you have missed something on 1)improper configuration 2) you are not working on a clean ADI release version.