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,
26 #define BOOT_SEG 0xffff0000 /* linear segment of boot code */
27 #define a32 .byte 0x67;
28 #define o32 .byte 0x66;
30 .section .start16, "ax"
35 * First we let the BSP do some early initialization
36 * this code have to map the flash to its final position
39 .globl board_init16_ret
42 /* Turn of cache (this might require a 486-class CPU) */
48 /* load the temporary Global Descriptor Table */
52 /* Now, we enter protected mode */
57 /* Flush the prefetch queue */
60 /* Tell 32-bit code it is being entered from hard-reset */
63 /* Finally jump to the 32bit initialization code */
64 movw $code32start, %ax
68 /* 48-bit far pointer */
70 .long _start /* offset */
71 .word 0x10 /* segment */
78 * The following Global Descriptor Table is just enough to get us into
79 * 'Flat Protected Mode' - It will be discarded as soon as the final
80 * GDT is setup in a safe location in RAM
83 .word 0x20 /* limit (32 bytes = 4 GDT entries) */
84 .long BOOT_SEG + gdt /* base */
92 * 0x18 32bit data/stack
96 .word 0, 0, 0, 0 /* NULL */
97 .word 0, 0, 0, 0 /* unused */
99 .word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */
100 .word 0 /* base address = 0 */
101 .word 0x9B00 /* code read/exec */
102 .word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */
104 .word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */
105 .word 0x0 /* base address = 0 */
106 .word 0x9300 /* data read/write */
107 .word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */