Could You share a Linkit _defconfig with early serial debug enabled? I'm decidedly missing something as, even enabling
CONFIG_DEBUG_UART=y CONFIG_DEBUG_UART_BASE=0x10000e00 CONFIG_DEBUG_UART_CLOCK=20 CONFIG_DEBUG_UART_SHIFT=2 CONFIG_DEBUG_UART_ANNOUNCE=y
I still have plenty of errors:
/home/mcon/vocore/__V2__/Buildroot/recov/host/bin/mipsel-linux-ld.bfd: arch/mips/cpu/start.o: in function `wr_done': (.text+0x650): undefined reference to `debug_uart_init' /home/mcon/vocore/__V2__/Buildroot/recov/host/bin/mipsel-linux-ld.bfd: (.text+0x654): undefined reference to `debug_uart_init' /home/mcon/vocore/__V2__/Buildroot/recov/host/bin/mipsel-linux-ld.bfd: board/vocore/vocore2/built-in.o: in function `board_early_init_f': (.text.board_early_init_f+0x10): undefined reference to `printhex8' /home/mcon/vocore/__V2__/Buildroot/recov/host/bin/mipsel-linux-ld.bfd: common/built-in.o: in function `putc': (.text.putc+0x18): undefined reference to `printch' /home/mcon/vocore/__V2__/Buildroot/recov/host/bin/mipsel-linux-ld.bfd: common/built-in.o: in function `puts': (.text.puts+0x2c): undefined reference to `printch'
You need to pick a debug uart driver, e.g. CONFIG_DEBUG_UART_NS16550.