The Design And Implementation Of SPI Based Serial Debug Port On EDK ?

The UEFI(Unified Extensible Firmware Interface)BIOS(Basic Input Output System)has gradually replaced the traditional BIOS firmware in x86 system,and is standard firmware since the launch of UEFI specification.In traditional compter system,the serial port debugging function is achieved via LPC(Low Pin Count)bus connection to serial port controller.In Intel new announced mobile chip,considering low power consumption and low out pin count,LPC bus would be removed,so in Intel mobile platform,need to research and design a new interface to implement the serial port debugging function.Firstly,from hardware and software perspective this paper analyzes Intel mobile chip,which is lack of LPC bus,serial debugging is the system demand function,by studying three kinds of peripheral interface:UART,I~2C and SPI in Intel mobile chip,gets the conclusion that choose Intel mobile chip internal general SPI bus to implement the serial port debugging function.This paper,then puts forward the hardware SPI to debug serial port design using the Intel mobile processor built-in general SPI controller to connect adapter chip MAX3100,desings and implements SPI bus controller's configuration and resource allocation in EDK II,implements the serial port class instance based on SPI bus,and follows the UEFI model driver,refers to the I2C driver model in EDK II,implements the SPI bus,controller and device the three layer UEFI driver,creates the ACPI DBG2 description table to support Windows operating system serial debugging function,creates a serial port ACPI device based on SPI bus to support Android operating system serial debugging function.Finally,on Intel Apollo Lake mobile platform,the serial port debugging function based on SPI bus is verified in UEFI BIOS startup process and operation system serial port debugging.Through the analysis of the results,it is proved that the serial port debugging function based on SPI bus implements all the functions of serial debugging based on LPC bus,and achieves two times the transmission baud rate.