1*4882a593Smuzhiyun/* 2*4882a593Smuzhiyun * U-Boot - x86 Startup Code 3*4882a593Smuzhiyun * 4*4882a593Smuzhiyun * (C) Copyright 2008-2011 5*4882a593Smuzhiyun * Graeme Russ, <graeme.russ@gmail.com> 6*4882a593Smuzhiyun * 7*4882a593Smuzhiyun * (C) Copyright 2002,2003 8*4882a593Smuzhiyun * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se> 9*4882a593Smuzhiyun * 10*4882a593Smuzhiyun * SPDX-License-Identifier: GPL-2.0+ 11*4882a593Smuzhiyun */ 12*4882a593Smuzhiyun 13*4882a593Smuzhiyun#include <asm/global_data.h> 14*4882a593Smuzhiyun#include <asm/processor-flags.h> 15*4882a593Smuzhiyun 16*4882a593Smuzhiyun#define BOOT_SEG 0xffff0000 /* linear segment of boot code */ 17*4882a593Smuzhiyun#define a32 .byte 0x67; 18*4882a593Smuzhiyun#define o32 .byte 0x66; 19*4882a593Smuzhiyun 20*4882a593Smuzhiyun.section .start16, "ax" 21*4882a593Smuzhiyun.code16 22*4882a593Smuzhiyun.globl start16 23*4882a593Smuzhiyunstart16: 24*4882a593Smuzhiyun /* Save BIST */ 25*4882a593Smuzhiyun movl %eax, %ecx 26*4882a593Smuzhiyun 27*4882a593Smuzhiyun /* Set the Cold Boot / Hard Reset flag */ 28*4882a593Smuzhiyun movl $GD_FLG_COLD_BOOT, %ebx 29*4882a593Smuzhiyun 30*4882a593Smuzhiyun xorl %eax, %eax 31*4882a593Smuzhiyun movl %eax, %cr3 /* Invalidate TLB */ 32*4882a593Smuzhiyun 33*4882a593Smuzhiyun /* Turn off cache (this might require a 486-class CPU) */ 34*4882a593Smuzhiyun movl %cr0, %eax 35*4882a593Smuzhiyun orl $(X86_CR0_NW | X86_CR0_CD), %eax 36*4882a593Smuzhiyun movl %eax, %cr0 37*4882a593Smuzhiyun wbinvd 38*4882a593Smuzhiyun 39*4882a593Smuzhiyun /* load the temporary Global Descriptor Table */ 40*4882a593Smuzhiyuno32 cs lidt idt_ptr 41*4882a593Smuzhiyuno32 cs lgdt gdt_ptr 42*4882a593Smuzhiyun 43*4882a593Smuzhiyun /* Now, we enter protected mode */ 44*4882a593Smuzhiyun movl %cr0, %eax 45*4882a593Smuzhiyun orl $X86_CR0_PE, %eax 46*4882a593Smuzhiyun movl %eax, %cr0 47*4882a593Smuzhiyun 48*4882a593Smuzhiyun /* Flush the prefetch queue */ 49*4882a593Smuzhiyun jmp ff 50*4882a593Smuzhiyunff: 51*4882a593Smuzhiyun 52*4882a593Smuzhiyun /* Finally restore BIST and jump to the 32-bit initialization code */ 53*4882a593Smuzhiyun movw $code32start, %ax 54*4882a593Smuzhiyun movw %ax, %bp 55*4882a593Smuzhiyun movl %ecx, %eax 56*4882a593Smuzhiyuno32 cs ljmp *(%bp) 57*4882a593Smuzhiyun 58*4882a593Smuzhiyun /* 48-bit far pointer */ 59*4882a593Smuzhiyuncode32start: 60*4882a593Smuzhiyun .long _start /* offset */ 61*4882a593Smuzhiyun .word 0x10 /* segment */ 62*4882a593Smuzhiyun 63*4882a593Smuzhiyunidt_ptr: 64*4882a593Smuzhiyun .word 0 /* limit */ 65*4882a593Smuzhiyun .long 0 /* base */ 66*4882a593Smuzhiyun 67*4882a593Smuzhiyun /* 68*4882a593Smuzhiyun * The following Global Descriptor Table is just enough to get us into 69*4882a593Smuzhiyun * 'Flat Protected Mode' - It will be discarded as soon as the final 70*4882a593Smuzhiyun * GDT is setup in a safe location in RAM 71*4882a593Smuzhiyun */ 72*4882a593Smuzhiyungdt_ptr: 73*4882a593Smuzhiyun .word 0x1f /* limit (31 bytes = 4 GDT entries - 1) */ 74*4882a593Smuzhiyun .long BOOT_SEG + gdt_rom /* base */ 75*4882a593Smuzhiyun 76*4882a593Smuzhiyun /* Some CPUs are picky about GDT alignment... */ 77*4882a593Smuzhiyun .align 16 78*4882a593Smuzhiyun.globl gdt_rom 79*4882a593Smuzhiyungdt_rom: 80*4882a593Smuzhiyun /* 81*4882a593Smuzhiyun * The GDT table ... 82*4882a593Smuzhiyun * 83*4882a593Smuzhiyun * Selector Type 84*4882a593Smuzhiyun * 0x00 NULL 85*4882a593Smuzhiyun * 0x08 Unused 86*4882a593Smuzhiyun * 0x10 32bit code 87*4882a593Smuzhiyun * 0x18 32bit data/stack 88*4882a593Smuzhiyun */ 89*4882a593Smuzhiyun /* The NULL Desciptor - Mandatory */ 90*4882a593Smuzhiyun .word 0x0000 /* limit_low */ 91*4882a593Smuzhiyun .word 0x0000 /* base_low */ 92*4882a593Smuzhiyun .byte 0x00 /* base_middle */ 93*4882a593Smuzhiyun .byte 0x00 /* access */ 94*4882a593Smuzhiyun .byte 0x00 /* flags + limit_high */ 95*4882a593Smuzhiyun .byte 0x00 /* base_high */ 96*4882a593Smuzhiyun 97*4882a593Smuzhiyun /* Unused Desciptor - (matches Linux) */ 98*4882a593Smuzhiyun .word 0x0000 /* limit_low */ 99*4882a593Smuzhiyun .word 0x0000 /* base_low */ 100*4882a593Smuzhiyun .byte 0x00 /* base_middle */ 101*4882a593Smuzhiyun .byte 0x00 /* access */ 102*4882a593Smuzhiyun .byte 0x00 /* flags + limit_high */ 103*4882a593Smuzhiyun .byte 0x00 /* base_high */ 104*4882a593Smuzhiyun 105*4882a593Smuzhiyun /* 106*4882a593Smuzhiyun * The Code Segment Descriptor: 107*4882a593Smuzhiyun * - Base = 0x00000000 108*4882a593Smuzhiyun * - Size = 4GB 109*4882a593Smuzhiyun * - Access = Present, Ring 0, Exec (Code), Readable 110*4882a593Smuzhiyun * - Flags = 4kB Granularity, 32-bit 111*4882a593Smuzhiyun */ 112*4882a593Smuzhiyun .word 0xffff /* limit_low */ 113*4882a593Smuzhiyun .word 0x0000 /* base_low */ 114*4882a593Smuzhiyun .byte 0x00 /* base_middle */ 115*4882a593Smuzhiyun .byte 0x9b /* access */ 116*4882a593Smuzhiyun .byte 0xcf /* flags + limit_high */ 117*4882a593Smuzhiyun .byte 0x00 /* base_high */ 118*4882a593Smuzhiyun 119*4882a593Smuzhiyun /* 120*4882a593Smuzhiyun * The Data Segment Descriptor: 121*4882a593Smuzhiyun * - Base = 0x00000000 122*4882a593Smuzhiyun * - Size = 4GB 123*4882a593Smuzhiyun * - Access = Present, Ring 0, Non-Exec (Data), Writable 124*4882a593Smuzhiyun * - Flags = 4kB Granularity, 32-bit 125*4882a593Smuzhiyun */ 126*4882a593Smuzhiyun .word 0xffff /* limit_low */ 127*4882a593Smuzhiyun .word 0x0000 /* base_low */ 128*4882a593Smuzhiyun .byte 0x00 /* base_middle */ 129*4882a593Smuzhiyun .byte 0x93 /* access */ 130*4882a593Smuzhiyun .byte 0xcf /* flags + limit_high */ 131*4882a593Smuzhiyun .byte 0x00 /* base_high */ 132