2 * U-boot - i386 Startup Code
4 * Copyright (c) 2002, 2003 Omicron Ceti AB, Daniel Engström <denaiel@omicron.se>
6 * See file CREDITS for list of people who contributed to this
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.
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.
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,
25 #include <asm/global_data.h>
27 #define BOOT_SEG 0xffff0000 /* linear segment of boot code */
28 #define a32 .byte 0x67;
29 #define o32 .byte 0x66;
31 .section .start16, "ax"
35 /* Set the Cold Boot / Hard Reset flag */
36 movl $GD_FLG_COLD_BOOT, %ebx
39 * First we let the BSP do some early initialization
40 * this code have to map the flash to its final position
43 .globl board_init16_ret
46 /* Turn of cache (this might require a 486-class CPU) */
52 /* load the temporary Global Descriptor Table */
56 /* Now, we enter protected mode */
61 /* Flush the prefetch queue */
64 /* Finally jump to the 32bit initialization code */
65 movw $code32start, %ax
69 /* 48-bit far pointer */
71 .long _start /* offset */
72 .word 0x10 /* segment */
79 * The following Global Descriptor Table is just enough to get us into
80 * 'Flat Protected Mode' - It will be discarded as soon as the final
81 * GDT is setup in a safe location in RAM
84 .word 0x20 /* limit (32 bytes = 4 GDT entries) */
85 .long BOOT_SEG + gdt /* base */
93 * 0x18 32bit data/stack
97 .word 0, 0, 0, 0 /* NULL */
98 .word 0, 0, 0, 0 /* unused */
100 .word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */
101 .word 0 /* base address = 0 */
102 .word 0x9B00 /* code read/exec */
103 .word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */
105 .word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */
106 .word 0x0 /* base address = 0 */
107 .word 0x9300 /* data read/write */
108 .word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */