our board has intel skylake I3-6100U  CPU we use seabios (1.11.1. and 1.13.0) as payload of coreboot (be78775a9302f9526df6eb61f8a430f4298f0e97)  to boot Linux OS.

We can successfully boot Linux OS. boot menu shows on DP port screen.

 

 But we need use serial port for boot menu since DP port will be removed in production.

I can turn on serial debug port by using:

CONFIG_DEBUG_LEVEL=4

CONFIG_DEBUG_SERIAL_MMIO=y

CONFIG_DEBUG_SERIAL_MEM_ADDRESS=0xFE034000

CONFIG_DEBUG_COREBOOT=y

 

But I can't turn on the  sercon port for boot menu. Seems that address for sercon is u16, only take 16bit address. I use 16bit serial port address for coreboot 0x3e8, it is not working.

 

How to turn on MMIO serial console for boot menu?

 

Thanks,