[U-Boot] u-boot for Snow problem

Hello,

I changed the SYS_START to work around the bug in the manufacturer firmware, applied snow_defconfig, built u-boot.bin, packed it into kernel uimage, signed it, copied it to a kernel partition, bumped priority of the partition, and rebooted.

I get black screen with backlight on.

So

1) is u-boot supposed to have graphics console output? If so where is that output? LCD/HDMI/what HDMI mode?

The only display related option in menuconfig seems to be some SPI display bridge.

2) is u-boot supposed to have serial console output? If so where is that console? There is supposed to be some 'servo' connector somewhere but I did not find any information on the pinout.

3) how do I tell if u-boot is even running?

Thanks

Michal