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gerrit.devboardsforandroid.linaro.org / platform / external / u-boot / b0e3adf669d5c245bf64d0445285fdd1ba0628d0 / . / arch / x86 / cpu / start16.S
blob: 5eb17f15c906f8a085f43161163a0668508c6745 [file] [log] [blame]
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]1/*
Bin Mengfea1c472015-01-20 11:25:44 +0800[diff] [blame]2 * U-Boot - x86 Startup Code
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]3 *
Graeme Russdbf71152011-04-13 19:43:26 +1000[diff] [blame]4 * (C) Copyright 2008-2011
5 * Graeme Russ, <graeme.russ@gmail.com>
6 *
7 * (C) Copyright 2002,2003
Albert ARIBAUDfa82f872011-08-04 18:45:45 +0200[diff] [blame]8 * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se>
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]9 *
Wolfgang Denk1a459662013-07-08 09:37:19 +0200[diff] [blame]10 * SPDX-License-Identifier: GPL-2.0+
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]11 */
12
Graeme Russc81b26b2010-10-07 20:03:30 +1100[diff] [blame]13#include <asm/global_data.h>
Graeme Russ0c24c9c2011-02-12 15:11:32 +1100[diff] [blame]14#include <asm/processor-flags.h>
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]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
wdenk8bde7f72003-06-27 21:31:46 +0000[diff] [blame]23start16:
Simon Glassf67cd512014-11-06 13:20:10 -0700[diff] [blame]24 /* Save BIST */
25 movl %eax, %ecx
26
Gabe Black91d82a22012-11-03 11:41:28 +0000[diff] [blame]27 /* Set the Cold Boot / Hard Reset flag */
28 movl $GD_FLG_COLD_BOOT, %ebx
29
Simon Glass3c006952014-11-06 13:20:03 -0700[diff] [blame]30 xorl %eax, %eax
Bin Mengfea1c472015-01-20 11:25:44 +0800[diff] [blame]31 movl %eax, %cr3 /* Invalidate TLB */
Simon Glass3c006952014-11-06 13:20:03 -0700[diff] [blame]32
Simon Glass85d87322014-11-06 13:20:01 -0700[diff] [blame]33 /* Turn off cache (this might require a 486-class CPU) */
Wolfgang Denk53677ef2008-05-20 16:00:29 +0200[diff] [blame]34 movl %cr0, %eax
Ondrej Kupka7b3d5382011-09-30 21:05:11 +1100[diff] [blame]35 orl $(X86_CR0_NW | X86_CR0_CD), %eax
Wolfgang Denk53677ef2008-05-20 16:00:29 +0200[diff] [blame]36 movl %eax, %cr0
wdenk8bde7f72003-06-27 21:31:46 +0000[diff] [blame]37 wbinvd
38
Graeme Russc14a3662010-04-24 00:05:43 +1000[diff] [blame]39 /* load the temporary Global Descriptor Table */
Graeme Russ797960f2010-08-22 16:25:59 +1000[diff] [blame]40o32 cs lidt idt_ptr
Wolfgang Denk53677ef2008-05-20 16:00:29 +0200[diff] [blame]41o32 cs lgdt gdt_ptr
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]42
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]43 /* Now, we enter protected mode */
Wolfgang Denk53677ef2008-05-20 16:00:29 +0200[diff] [blame]44 movl %cr0, %eax
Graeme Russ0c24c9c2011-02-12 15:11:32 +1100[diff] [blame]45 orl $X86_CR0_PE, %eax
Wolfgang Denk53677ef2008-05-20 16:00:29 +0200[diff] [blame]46 movl %eax, %cr0
wdenk8bde7f72003-06-27 21:31:46 +0000[diff] [blame]47
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]48 /* Flush the prefetch queue */
Wolfgang Denk53677ef2008-05-20 16:00:29 +0200[diff] [blame]49 jmp ff
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]50ff:
Simon Glassf67cd512014-11-06 13:20:10 -0700[diff] [blame]51
Bin Mengfea1c472015-01-20 11:25:44 +0800[diff] [blame]52 /* Finally restore BIST and jump to the 32-bit initialization code */
wdenk8bde7f72003-06-27 21:31:46 +0000[diff] [blame]53 movw $code32start, %ax
Graeme Russ8ffb2e82010-10-07 20:03:21 +1100[diff] [blame]54 movw %ax, %bp
Simon Glassf67cd512014-11-06 13:20:10 -0700[diff] [blame]55 movl %ecx, %eax
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]56o32 cs ljmp *(%bp)
57
58 /* 48-bit far pointer */
59code32start:
Wolfgang Denk53677ef2008-05-20 16:00:29 +0200[diff] [blame]60 .long _start /* offset */
61 .word 0x10 /* segment */
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]62
Graeme Russ797960f2010-08-22 16:25:59 +1000[diff] [blame]63idt_ptr:
64 .word 0 /* limit */
65 .long 0 /* base */
66
Bin Mengfea1c472015-01-20 11:25:44 +0800[diff] [blame]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 */
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]72gdt_ptr:
Bin Meng35d4fed2014-10-16 22:58:35 +0800[diff] [blame]73 .word 0x1f /* limit (31 bytes = 4 GDT entries - 1) */
Bin Meng002610f2015-06-07 11:33:13 +0800[diff] [blame]74 .long BOOT_SEG + gdt_rom /* base */
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]75
Bin Mengfea1c472015-01-20 11:25:44 +0800[diff] [blame]76 /* Some CPUs are picky about GDT alignment... */
77 .align 16
Bin Meng002610f2015-06-07 11:33:13 +0800[diff] [blame]78.globl gdt_rom
79gdt_rom:
Graeme Russ58c7a672011-12-19 14:26:18 +1100[diff] [blame]80 /*
81 * The GDT table ...
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]82 *
Wolfgang Denk53677ef2008-05-20 16:00:29 +0200[diff] [blame]83 * Selector Type
84 * 0x00 NULL
85 * 0x08 Unused
wdenk8bde7f72003-06-27 21:31:46 +0000[diff] [blame]86 * 0x10 32bit code
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]87 * 0x18 32bit data/stack
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]88 */
Graeme Russ58c7a672011-12-19 14:26:18 +1100[diff] [blame]89 /* The NULL Desciptor - Mandatory */
90 .word 0x0000 /* limit_low */
91 .word 0x0000 /* base_low */
92 .byte 0x00 /* base_middle */
93 .byte 0x00 /* access */
94 .byte 0x00 /* flags + limit_high */
95 .byte 0x00 /* base_high */
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]96
Graeme Russ58c7a672011-12-19 14:26:18 +1100[diff] [blame]97 /* Unused Desciptor - (matches Linux) */
98 .word 0x0000 /* limit_low */
99 .word 0x0000 /* base_low */
100 .byte 0x00 /* base_middle */
101 .byte 0x00 /* access */
102 .byte 0x00 /* flags + limit_high */
103 .byte 0x00 /* base_high */
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]104
Graeme Russ58c7a672011-12-19 14:26:18 +1100[diff] [blame]105 /*
106 * The Code Segment Descriptor:
107 * - Base = 0x00000000
108 * - Size = 4GB
109 * - Access = Present, Ring 0, Exec (Code), Readable
110 * - Flags = 4kB Granularity, 32-bit
111 */
112 .word 0xffff /* limit_low */
113 .word 0x0000 /* base_low */
114 .byte 0x00 /* base_middle */
115 .byte 0x9b /* access */
116 .byte 0xcf /* flags + limit_high */
117 .byte 0x00 /* base_high */
wdenk2262cfe2002-11-18 00:14:45 +0000[diff] [blame]118
Graeme Russ58c7a672011-12-19 14:26:18 +1100[diff] [blame]119 /*
120 * The Data Segment Descriptor:
121 * - Base = 0x00000000
122 * - Size = 4GB
123 * - Access = Present, Ring 0, Non-Exec (Data), Writable
124 * - Flags = 4kB Granularity, 32-bit
125 */
126 .word 0xffff /* limit_low */
127 .word 0x0000 /* base_low */
128 .byte 0x00 /* base_middle */
129 .byte 0x93 /* access */
130 .byte 0xcf /* flags + limit_high */
131 .byte 0x00 /* base_high */