[coreboot] 4.9: FSP debug level (0-3)

Helllo, I'm porting core boot to a bay trail board. I noticed that starting from version 4.9, I can set the debug level of FSP. I downloaded FSP for Bay trail and used Intel's BCT to modify it. But coreboot hangs after calling to the FSP binary. How can I use the "FSP debug level" ? Thank you, Zvika