U-boot version: 2016.05
The top-level makefile definition generates SPL:
The origin of variables such as BOARD,CPU required for generating SPL:
The top-level makefile contains the. config
The. config contains the configured CPU, board-level information
The top layer makefile contains the CONFIG.MK,
Arch/arm/makefile is also included in the arch/arm/makefile definition of head-y: arch/arm/makefile:73:head-y: = arch/arm/cpu/$ (CPU)/START.O
CONFIG.MK converts the CPU and board-level information defined by the. config to variables such as CPU SOC board, which the top-level makefile export
Variables defined by config.mk
Top level makefile Export these variables
SPL Generation rule:
SPL specific build process defined in SCRIPTS/MAKEFILE.SPL
The MAKEFILE.SPL build target is all:
${spl_bin}.bin = U-boot-spl.bin
U-boot-spl.bin relies on U-BOOT-SPL,U-BOOT-SPL to generate rules:
U-boot-spl-init U-boot-spl-main defines the source code that SPL contains:
HEAD-Y is defined in Arch/arm/makefile and MAKEFILE.SPL contains this file:
Head-y = arch/arm/makefile:73:head-y: = arch/arm/cpu/$ (CPU)/START.O = ARCH/ARM/ARMV7/START.O,
can see start. S is the code that u-boot-spl.bin the first execution.
Arch/arm/makefile also defines the libs-y, which defines the source code for SPL compilation.
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