According to the answer on that question How to disable HDMI when board is booted I tried to disable HDMI on my custom board based on the iMX6 cpu.
I added in the bootargs the following options: 'video=mxcfb0:off video=mxcfb1:off video=mxcfb2:off ' and as a result kernel hangs without any errors, oops and etc.
I get the same behavior when I disable frame buffer support in the kernel.
My kernel version is 3.14.28
What can be a reason of that?