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Commit | Line | Data |
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2262cfee | 1 | /* |
fea25720 | 2 | * U-boot - x86 Startup Code |
2262cfee | 3 | * |
dbf7115a GR |
4 | * (C) Copyright 2008-2011 |
5 | * Graeme Russ, <graeme.russ@gmail.com> | |
6 | * | |
7 | * (C) Copyright 2002,2003 | |
fa82f871 | 8 | * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se> |
2262cfee | 9 | * |
1a459660 | 10 | * SPDX-License-Identifier: GPL-2.0+ |
2262cfee WD |
11 | */ |
12 | ||
c81b26be | 13 | #include <asm/global_data.h> |
0c24c9cc | 14 | #include <asm/processor-flags.h> |
2262cfee WD |
15 | |
16 | #define BOOT_SEG 0xffff0000 /* linear segment of boot code */ | |
17 | #define a32 .byte 0x67; | |
18 | #define o32 .byte 0x66; | |
19 | ||
20 | .section .start16, "ax" | |
21 | .code16 | |
22 | .globl start16 | |
8bde7f77 | 23 | start16: |
91d82a29 GB |
24 | /* Set the Cold Boot / Hard Reset flag */ |
25 | movl $GD_FLG_COLD_BOOT, %ebx | |
26 | ||
8ffb2e8f GR |
27 | /* |
28 | * First we let the BSP do some early initialization | |
2262cfee WD |
29 | * this code have to map the flash to its final position |
30 | */ | |
2262cfee | 31 | jmp board_init16 |
88fa0a6e | 32 | .globl board_init16_ret |
8bde7f77 WD |
33 | board_init16_ret: |
34 | ||
2262cfee | 35 | /* Turn of cache (this might require a 486-class CPU) */ |
53677ef1 | 36 | movl %cr0, %eax |
7b3d5380 | 37 | orl $(X86_CR0_NW | X86_CR0_CD), %eax |
53677ef1 | 38 | movl %eax, %cr0 |
8bde7f77 WD |
39 | wbinvd |
40 | ||
c14a3669 | 41 | /* load the temporary Global Descriptor Table */ |
797960fd | 42 | o32 cs lidt idt_ptr |
53677ef1 | 43 | o32 cs lgdt gdt_ptr |
2262cfee | 44 | |
2262cfee | 45 | /* Now, we enter protected mode */ |
53677ef1 | 46 | movl %cr0, %eax |
0c24c9cc | 47 | orl $X86_CR0_PE, %eax |
53677ef1 | 48 | movl %eax, %cr0 |
8bde7f77 | 49 | |
2262cfee | 50 | /* Flush the prefetch queue */ |
53677ef1 | 51 | jmp ff |
2262cfee | 52 | ff: |
2262cfee | 53 | /* Finally jump to the 32bit initialization code */ |
8bde7f77 | 54 | movw $code32start, %ax |
8ffb2e8f | 55 | movw %ax, %bp |
2262cfee WD |
56 | o32 cs ljmp *(%bp) |
57 | ||
58 | /* 48-bit far pointer */ | |
59 | code32start: | |
53677ef1 WD |
60 | .long _start /* offset */ |
61 | .word 0x10 /* segment */ | |
2262cfee | 62 | |
797960fd GR |
63 | idt_ptr: |
64 | .word 0 /* limit */ | |
65 | .long 0 /* base */ | |
66 | ||
c14a3669 GR |
67 | /* |
68 | * The following Global Descriptor Table is just enough to get us into | |
69 | * 'Flat Protected Mode' - It will be discarded as soon as the final | |
70 | * GDT is setup in a safe location in RAM | |
71 | */ | |
2262cfee | 72 | gdt_ptr: |
c14a3669 | 73 | .word 0x20 /* limit (32 bytes = 4 GDT entries) */ |
53677ef1 | 74 | .long BOOT_SEG + gdt /* base */ |
2262cfee | 75 | |
58c7a675 GR |
76 | /* Some CPUs are picky about GDT alignment... */ |
77 | .align 16 | |
78 | gdt: | |
79 | /* | |
80 | * The GDT table ... | |
2262cfee | 81 | * |
53677ef1 WD |
82 | * Selector Type |
83 | * 0x00 NULL | |
84 | * 0x08 Unused | |
8bde7f77 | 85 | * 0x10 32bit code |
2262cfee | 86 | * 0x18 32bit data/stack |
2262cfee | 87 | */ |
58c7a675 GR |
88 | /* The NULL Desciptor - Mandatory */ |
89 | .word 0x0000 /* limit_low */ | |
90 | .word 0x0000 /* base_low */ | |
91 | .byte 0x00 /* base_middle */ | |
92 | .byte 0x00 /* access */ | |
93 | .byte 0x00 /* flags + limit_high */ | |
94 | .byte 0x00 /* base_high */ | |
2262cfee | 95 | |
58c7a675 GR |
96 | /* Unused Desciptor - (matches Linux) */ |
97 | .word 0x0000 /* limit_low */ | |
98 | .word 0x0000 /* base_low */ | |
99 | .byte 0x00 /* base_middle */ | |
100 | .byte 0x00 /* access */ | |
101 | .byte 0x00 /* flags + limit_high */ | |
102 | .byte 0x00 /* base_high */ | |
53677ef1 | 103 | |
58c7a675 GR |
104 | /* |
105 | * The Code Segment Descriptor: | |
106 | * - Base = 0x00000000 | |
107 | * - Size = 4GB | |
108 | * - Access = Present, Ring 0, Exec (Code), Readable | |
109 | * - Flags = 4kB Granularity, 32-bit | |
110 | */ | |
111 | .word 0xffff /* limit_low */ | |
112 | .word 0x0000 /* base_low */ | |
113 | .byte 0x00 /* base_middle */ | |
114 | .byte 0x9b /* access */ | |
115 | .byte 0xcf /* flags + limit_high */ | |
116 | .byte 0x00 /* base_high */ | |
53677ef1 | 117 | |
58c7a675 GR |
118 | /* |
119 | * The Data Segment Descriptor: | |
120 | * - Base = 0x00000000 | |
121 | * - Size = 4GB | |
122 | * - Access = Present, Ring 0, Non-Exec (Data), Writable | |
123 | * - Flags = 4kB Granularity, 32-bit | |
124 | */ | |
125 | .word 0xffff /* limit_low */ | |
126 | .word 0x0000 /* base_low */ | |
127 | .byte 0x00 /* base_middle */ | |
128 | .byte 0x93 /* access */ | |
129 | .byte 0xcf /* flags + limit_high */ | |
130 | .byte 0x00 /* base_high */ |