protecting and unprotecting of NOR flash

[Sergey Lapin]

hi, all!
I'm new to mtd kernel code base, where could I fond code, which
protects and unprotects my NOR
flash chip? it is AT49BV642D
u-boot is capable of protecting it with protect command, I need to
find where it is being
un-protected in Linux, because I can erase and write blocks which I
protected in u-boot before
I don't want for kernel to touch protection status
so I'd like to find which code to disable and protect/unprotect chip
using boot loader.

Thanks a lot,
S.