u-boot/arch/x86/cpu/start.S
Simon Glass 60994a02a5 x86: Init the debug UART if enabled
If the debug UART is enabled, get it ready for use at the earliest possible
opportunity. This is not actually very early, but until we have a stack it
is difficult to make it work.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
2015-10-21 07:46:50 -06:00

221 lines
5.1 KiB
ArmAsm

/*
* U-Boot - x86 Startup Code
*
* (C) Copyright 2008-2011
* Graeme Russ, <graeme.russ@gmail.com>
*
* (C) Copyright 2002
* Daniel Engström, Omicron Ceti AB, <daniel@omicron.se>
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include <config.h>
#include <asm/global_data.h>
#include <asm/post.h>
#include <asm/processor.h>
#include <asm/processor-flags.h>
#include <generated/generic-asm-offsets.h>
#include <generated/asm-offsets.h>
.section .text
.code32
.globl _start
.type _start, @function
.globl _x86boot_start
_x86boot_start:
/*
* This is the fail-safe 32-bit bootstrap entry point.
*
* This code is used when booting from another boot loader like
* coreboot or EFI. So we repeat some of the same init found in
* start16.
*/
cli
cld
/* Turn off cache (this might require a 486-class CPU) */
movl %cr0, %eax
orl $(X86_CR0_NW | X86_CR0_CD), %eax
movl %eax, %cr0
wbinvd
/* Tell 32-bit code it is being entered from an in-RAM copy */
movl $GD_FLG_WARM_BOOT, %ebx
/*
* Zero the BIST (Built-In Self Test) value since we don't have it.
* It must be 0 or the previous loader would have reported an error.
*/
movl $0, %ebp
jmp 1f
/* Add a way for tools to discover the _start entry point */
.align 4
.long 0x12345678
_start:
/*
* This is the 32-bit cold-reset entry point, coming from start16.
* Set %ebx to GD_FLG_COLD_BOOT to indicate this.
*/
movl $GD_FLG_COLD_BOOT, %ebx
/* Save BIST */
movl %eax, %ebp
1:
/* Save table pointer */
movl %ecx, %esi
/* Load the segement registers to match the GDT loaded in start16.S */
movl $(X86_GDT_ENTRY_32BIT_DS * X86_GDT_ENTRY_SIZE), %eax
movw %ax, %fs
movw %ax, %ds
movw %ax, %gs
movw %ax, %es
movw %ax, %ss
/* Clear the interrupt vectors */
lidt blank_idt_ptr
/*
* Critical early platform init - generally not used, we prefer init
* to happen later when we have a console, in case something goes
* wrong.
*/
jmp early_board_init
.globl early_board_init_ret
early_board_init_ret:
post_code(POST_START)
/* Initialise Cache-As-RAM */
jmp car_init
.globl car_init_ret
car_init_ret:
#ifndef CONFIG_HAVE_FSP
/*
* We now have CONFIG_SYS_CAR_SIZE bytes of Cache-As-RAM (or SRAM,
* or fully initialised SDRAM - we really don't care which)
* starting at CONFIG_SYS_CAR_ADDR to be used as a temporary stack
* and early malloc() area. The MRC requires some space at the top.
*
* Stack grows down from top of CAR. We have:
*
* top-> CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE
* MRC area
* global_data with x86 global descriptor table
* early malloc area
* stack
* bottom-> CONFIG_SYS_CAR_ADDR
*/
movl $(CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE - 4), %esp
#ifdef CONFIG_DCACHE_RAM_MRC_VAR_SIZE
subl $CONFIG_DCACHE_RAM_MRC_VAR_SIZE, %esp
#endif
#else
/*
* U-Boot enters here twice. For the first time it comes from
* car_init_done() with esp points to a temporary stack and esi
* set to zero. For the second time it comes from fsp_init_done()
* with esi holding the HOB list address returned by the FSP.
*/
#endif
/* Set up global data */
mov %esp, %eax
call board_init_f_mem
mov %eax, %esp
#ifdef CONFIG_DEBUG_UART
call debug_uart_init
#endif
/* Get address of global_data */
mov %fs:0, %edx
#ifdef CONFIG_HAVE_FSP
/* Store the HOB list if we have one */
test %esi, %esi
jz skip_hob
movl %esi, GD_HOB_LIST(%edx)
/*
* After fsp_init() returns, the stack has already been switched to a
* place within system memory as defined by CONFIG_FSP_TEMP_RAM_ADDR.
* Enlarge the size of malloc() pool before relocation since we have
* plenty of memory now.
*/
subl $CONFIG_FSP_SYS_MALLOC_F_LEN, %esp
movl %esp, GD_MALLOC_BASE(%edx)
skip_hob:
#else
/* Store table pointer */
movl %esi, GD_TABLE(%edx)
#endif
/* Store BIST */
movl %ebp, GD_BIST(%edx)
/* Set parameter to board_init_f() to boot flags */
post_code(POST_START_DONE)
xorl %eax, %eax
/* Enter, U-Boot! */
call board_init_f
/* indicate (lack of) progress */
movw $0x85, %ax
jmp die
.globl board_init_f_r_trampoline
.type board_init_f_r_trampoline, @function
board_init_f_r_trampoline:
/*
* SDRAM has been initialised, U-Boot code has been copied into
* RAM, BSS has been cleared and relocation adjustments have been
* made. It is now time to jump into the in-RAM copy of U-Boot
*
* %eax = Address of top of new stack
*/
/* Stack grows down from top of SDRAM */
movl %eax, %esp
/* See if we need to disable CAR */
.weak car_uninit
movl $car_uninit, %eax
cmpl $0, %eax
jz 1f
call car_uninit
1:
/* Re-enter U-Boot by calling board_init_f_r() */
call board_init_f_r
die:
hlt
jmp die
hlt
blank_idt_ptr:
.word 0 /* limit */
.long 0 /* base */
.p2align 2 /* force 4-byte alignment */
/* Add a multiboot header so U-Boot can be loaded by GRUB2 */
multiboot_header:
/* magic */
.long 0x1badb002
/* flags */
.long (1 << 16)
/* checksum */
.long -0x1BADB002 - (1 << 16)
/* header addr */
.long multiboot_header - _x86boot_start + CONFIG_SYS_TEXT_BASE
/* load addr */
.long CONFIG_SYS_TEXT_BASE
/* load end addr */
.long 0
/* bss end addr */
.long 0
/* entry addr */
.long CONFIG_SYS_TEXT_BASE