【u-boot-2018.11】源码分析之lowlevel_init.S

最新推荐文章于 2021-11-18 23:48:28 发布

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本文详细介绍了ARMv7架构下低级初始化过程。主要包括临时堆栈设置、全局数据配置及非常早期初始化函数调用等内容。对于使用特定配置进行初始化的场景提供了深入解析。

arch/arm/cpu/armv7/lowlevel_init.S：

#include <asm-offsets.h>
#include <config.h>
#include <linux/linkage.h>

.pushsection .text.s_init, "ax"
WEAK(s_init)
	bx	lr
ENDPROC(s_init)
.popsection

.pushsection .text.lowlevel_init, "ax"
WEAK(lowlevel_init)
	/*
	 * Setup a temporary stack. Global data is not available yet.
	 */
#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
	ldr	sp, =CONFIG_SPL_STACK
#else
	ldr	sp, =CONFIG_SYS_INIT_SP_ADDR
#endif
	bic	sp, sp, #7 /* 8-byte alignment for ABI compliance */
#ifdef CONFIG_SPL_DM
	mov	r9, #0
#else
	/*
	 * Set up global data for boards that still need it. This will be
	 * removed soon.
	 */
#ifdef CONFIG_SPL_BUILD
	ldr	r9, =gdata
#else
	sub	sp, sp, #GD_SIZE
	bic	sp, sp, #7
	mov	r9, sp
#endif
#endif
	/*
	 * Save the old lr(passed in ip) and the current lr to stack
	 */
	push	{ip, lr}

	/*
	 * Call the very early init function. This should do only the
	 * absolute bare minimum to get started. It should not:
	 *
	 * - set up DRAM
	 * - use global_data
	 * - clear BSS
	 * - try to start a console
	 *
	 * For boards with SPL this should be empty since SPL can do all of
	 * this init in the SPL board_init_f() function which is called
	 * immediately after this.
	 */
	bl	s_init
	pop	{ip, pc}
ENDPROC(lowlevel_init)
.popsection