CONFIG_DEBUG_LL is not available for thedefaultarchitecture x86.
Result is shown for architecture unicore32

Kernel low-level debugging functions

modulename: debug.ko

and/or

lluart.ko

configname: CONFIG_DEBUG_LL

Linux Kernel Configuration
└─>Kernel hacking
└─>Kernel low-level debugging functions
In linux kernel since version 2.6.12  
Say Y here to include definitions of printascii, printch, printhex
in the kernel. This is helpful if you are debugging code that
executes before the console is initialized.

source code: