I just finished building from HEAD for bf527-ezkit_defconfig and I get an error.
.../drivers/usb/musb/blackfin.h:51:3: error: #error "Please use PIO mode in MUSB driver on bf52x chip v0.0 and v0.1"
You might try the 2013R1-RC1 tag instead of HEAD.
Also, look into the source to see the context of that #error. It seems clear that some developer believes it's important not to use whatever settings are currently in bf527-ezkit_defconfig. I'm working with BF51x (BF516), so I'm not really familiar with your processors details. I'm also working on a custom board, so I have my own defconfig tailored to my Blackfin proc and hardware. Unless you're specifically using the BF527 EZ-KIT and not your own custom board, I'd suggest creating your own defconfig. Even if you are using the BF527 EZ-KIT, you might have to make a few changes to get it working with the current uClinux sources. Perhaps someone from Analog Devices can check into whether the BF527 EZ-KIT is up to date in the git source repository.