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wdenk2262cfe2002-11-18 00:14:45 +00001/*
wdenk8bde7f72003-06-27 21:31:46 +00002 * U-boot - i386 Startup Code
wdenk2262cfe2002-11-18 00:14:45 +00003 *
wdenk7a8e9bed2003-05-31 18:35:21 +00004 * Copyright (c) 2002, 2003 Omicron Ceti AB, Daniel Engström <denaiel@omicron.se>
wdenk2262cfe2002-11-18 00:14:45 +00005 *
6 * See file CREDITS for list of people who contributed to this
7 * project.
8 *
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License as
11 * published by the Free Software Foundation; either version 2 of
12 * the License, or (at your option) any later version.
13 *
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
22 * MA 02111-1307 USA
23 */
24
25
26#define BOOT_SEG 0xffff0000 /* linear segment of boot code */
27#define a32 .byte 0x67;
28#define o32 .byte 0x66;
29
30.section .start16, "ax"
31.code16
32.globl start16
wdenk8bde7f72003-06-27 21:31:46 +000033start16:
wdenk2262cfe2002-11-18 00:14:45 +000034 /* First we let the BSP do some early initialization
35 * this code have to map the flash to its final position
36 */
37 mov $board_init16_ret, %bp
38 jmp board_init16
wdenk8bde7f72003-06-27 21:31:46 +000039board_init16_ret:
40
wdenk2262cfe2002-11-18 00:14:45 +000041 /* Turn of cache (this might require a 486-class CPU) */
Wolfgang Denk53677ef2008-05-20 16:00:29 +020042 movl %cr0, %eax
43 orl $0x60000000,%eax
44 movl %eax, %cr0
wdenk8bde7f72003-06-27 21:31:46 +000045 wbinvd
46
wdenk2262cfe2002-11-18 00:14:45 +000047 /* load the descriptor tables */
48o32 cs lidt idt_ptr
Wolfgang Denk53677ef2008-05-20 16:00:29 +020049o32 cs lgdt gdt_ptr
wdenk2262cfe2002-11-18 00:14:45 +000050
51
52 /* Now, we enter protected mode */
Wolfgang Denk53677ef2008-05-20 16:00:29 +020053 movl %cr0, %eax
54 orl $1,%eax
55 movl %eax, %cr0
wdenk8bde7f72003-06-27 21:31:46 +000056
wdenk2262cfe2002-11-18 00:14:45 +000057 /* Flush the prefetch queue */
Wolfgang Denk53677ef2008-05-20 16:00:29 +020058 jmp ff
wdenk2262cfe2002-11-18 00:14:45 +000059ff:
60
61 /* Finally jump to the 32bit initialization code */
wdenk8bde7f72003-06-27 21:31:46 +000062 movw $code32start, %ax
Wolfgang Denk53677ef2008-05-20 16:00:29 +020063 movw %ax,%bp
wdenk2262cfe2002-11-18 00:14:45 +000064o32 cs ljmp *(%bp)
65
66 /* 48-bit far pointer */
67code32start:
Wolfgang Denk53677ef2008-05-20 16:00:29 +020068 .long _start /* offset */
69 .word 0x10 /* segment */
wdenk2262cfe2002-11-18 00:14:45 +000070
71idt_ptr:
Wolfgang Denk53677ef2008-05-20 16:00:29 +020072 .word 0 /* limit */
73 .long 0 /* base */
wdenk8bde7f72003-06-27 21:31:46 +000074
wdenk2262cfe2002-11-18 00:14:45 +000075gdt_ptr:
Wolfgang Denk53677ef2008-05-20 16:00:29 +020076 .word 0x30 /* limit (48 bytes = 6 GDT entries) */
77 .long BOOT_SEG + gdt /* base */
wdenk2262cfe2002-11-18 00:14:45 +000078
wdenk8bde7f72003-06-27 21:31:46 +000079 /* The GDT table ...
wdenk2262cfe2002-11-18 00:14:45 +000080 *
Wolfgang Denk53677ef2008-05-20 16:00:29 +020081 * Selector Type
82 * 0x00 NULL
83 * 0x08 Unused
wdenk8bde7f72003-06-27 21:31:46 +000084 * 0x10 32bit code
wdenk2262cfe2002-11-18 00:14:45 +000085 * 0x18 32bit data/stack
86 * 0x20 16bit code
Wolfgang Denk53677ef2008-05-20 16:00:29 +020087 * 0x28 16bit data/stack
wdenk2262cfe2002-11-18 00:14:45 +000088 */
89
90gdt:
Wolfgang Denk53677ef2008-05-20 16:00:29 +020091 .word 0, 0, 0, 0 /* NULL */
92 .word 0, 0, 0, 0 /* unused */
wdenk2262cfe2002-11-18 00:14:45 +000093
Wolfgang Denk53677ef2008-05-20 16:00:29 +020094 .word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */
95 .word 0 /* base address = 0 */
96 .word 0x9B00 /* code read/exec */
97 .word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */
wdenk2262cfe2002-11-18 00:14:45 +000098
Wolfgang Denk53677ef2008-05-20 16:00:29 +020099 .word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */
100 .word 0x0 /* base address = 0 */
101 .word 0x9300 /* data read/write */
102 .word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */
wdenk8bde7f72003-06-27 21:31:46 +0000103
Wolfgang Denk53677ef2008-05-20 16:00:29 +0200104 .word 0xFFFF /* 64kb */
105 .word 0 /* base address = 0 */
106 .word 0x9b00 /* data read/write */
107 .word 0x0010 /* granularity = 1 (+5th nibble of limit) */
wdenk8bde7f72003-06-27 21:31:46 +0000108
Wolfgang Denk53677ef2008-05-20 16:00:29 +0200109 .word 0xFFFF /* 64kb */
110 .word 0 /* base address = 0 */
111 .word 0x9300 /* data read/write */
112 .word 0x0010 /* granularity = 1 (+5th nibble of limit) */