new u-boot source code doesn't work in my C4 board

I just built u-boot codes from git://git.denx.de/u-boot.git and
git://gitorious.org/u-boot-omap3/mainline.git. I got blank screen. It
shows no signal. But it works with pre-built binaries. I see some
discussion about C4 patch of one month ago. I tried the patches, but
no joy.