summaryrefslogtreecommitdiff
path: root/arch/x86/cpu/start.S
blob: 1b738f9916708c41ef176aaf79e2fa87f51e2aa0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
/*
 *  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 <version.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>

.section .text
.code32
.globl _start
.type _start, @function
.globl _x86boot_start
_x86boot_start:
	/*
	 * This is the fail safe 32-bit bootstrap entry point. The
	 * following code is not executed from a cold-reset (actually, a
	 * lot of it is, but from real-mode after cold reset. It is
	 * repeated here to put the board into a state as close to cold
	 * reset as necessary)
	 */
	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 */
	movw	$GD_FLG_WARM_BOOT, %bx
	jmp	1f
_start:
	/*
	 * This is the 32-bit cold-reset entry point. Initialize %bx to 0
	 * in case we're preceeded by some sort of boot stub.
	 */
	movw	$GD_FLG_COLD_BOOT, %bx
1:
	/* Save BIST */
	movl	%eax, %ebp

	/* Load the segement registes 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

	/* Early platform init (setup gpio, etc ) */
	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:
	/*
	 * 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.
	 *
	 * Stack grows down from top of CAR. We have:
	 *
	 * top-> CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE
	 *	global_data
	 *	x86 global descriptor table
	 *	early malloc area
	 *	stack
	 * bottom-> CONFIG_SYS_CAR_ADDR
	 */

	/* Stack grows down from top of CAR */
	movl	$(CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE), %esp

	/* Reserve space on stack for global data */
	subl	$GENERATED_GBL_DATA_SIZE, %esp

	/* Align global data to 16-byte boundary */
	andl	$0xfffffff0, %esp
	post_code(POST_START_STACK)

	/* Zero the global data since it won't happen later */
	xorl	%eax, %eax
	movl	$GENERATED_GBL_DATA_SIZE, %ecx
	movl	%esp, %edi
	rep	stosb

	/* Setup first parameter to setup_gdt, pointer to global_data */
	movl	%esp, %eax

	/* Reserve space for global descriptor table */
	subl	$X86_GDT_SIZE, %esp

	/* Align temporary global descriptor table to 16-byte boundary */
	andl	$0xfffffff0, %esp
	movl	%esp, %ecx

#if defined(CONFIG_SYS_MALLOC_F_LEN)
	subl	$CONFIG_SYS_MALLOC_F_LEN, %esp
	movl	%eax, %edx
	addl	$GD_MALLOC_BASE, %edx
	movl	%esp, (%edx)
#endif
	/* Store BIST */
	movl	%eax, %edx
	addl	$GD_BIST, %edx
	movl	%ebp, (%edx)

	/* Set second parameter to setup_gdt */
	movl	%ecx, %edx

	/* Setup global descriptor table so gd->xyz works */
	call	setup_gdt

	/* 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

	/* Reserve space on stack for global data */
	subl	$GENERATED_GBL_DATA_SIZE, %esp

	/* Align global data to 16-byte boundary */
	andl	$0xfffffff0, %esp

	/* Setup first parameter to memcpy (and setup_gdt) */
	movl	%esp, %eax

	/* Setup second parameter to memcpy */
	fs movl 0, %edx

	/* Set third parameter to memcpy */
	movl	$GENERATED_GBL_DATA_SIZE, %ecx

	/* Copy global data from CAR to SDRAM stack */
	call	memcpy

	/* Reserve space for global descriptor table */
	subl	$X86_GDT_SIZE, %esp

	/* Align global descriptor table to 16-byte boundary */
	andl	$0xfffffff0, %esp

	/* Set second parameter to setup_gdt */
	movl	%esp, %edx

	/* Setup global descriptor table so gd->xyz works */
	call	setup_gdt

	/* 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 */

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