u-boot/arch/x86/cpu/start_from_tpl.S
Simon Glass 08deb6d36f x86: Add more comments to the start-up code
The full start-up sequence (TPL->SPL->U-Boot) can be a bit confusing since
each phase has its own 'start' file. Add comments to explain this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
2019-10-08 13:57:36 +08:00

50 lines
958 B
ArmAsm

/* SPDX-License-Identifier: GPL-2.0+ */
/*
* 32-bit x86 Startup Code when running from TPL. This is the startup code in
* SPL, when TPL is used.
*
* Copyright 2018 Google, Inc
* Written by Simon Glass <sjg@chromium.org>
*/
#include <config.h>
.section .text.start
.code32
.globl _start
.type _start, @function
_start:
/* Set up memory using the existing stack */
mov %esp, %eax
call board_init_f_alloc_reserve
mov %eax, %esp
call board_init_f_init_reserve
xorl %eax, %eax
call board_init_f
call board_init_f_r
/* Should not return here */
jmp .
.globl board_init_f_r_trampoline
.type board_init_f_r_trampoline, @function
board_init_f_r_trampoline:
/*
* TPL has been executed: SDRAM has been initialised, BSS has been
* cleared.
*
* %eax = Address of top of new stack
*/
/* Stack grows down from top of SDRAM */
movl %eax, %esp
/* Re-enter SPL by calling board_init_f_r() */
call board_init_f_r
die:
hlt
jmp die
hlt