init.s

嵌入式系统 EP93xx处理器

//*****************************************************************************
//
// INIT.S - Code which is loaded into the Cirrus Logic ARM processor via the
//          boot.S to SDRAM.
//
// Copyright (c) 2006 Cirrus Logic, Inc.
//
//*****************************************************************************

#include "asmdefs.h"

//*****************************************************************************
//
// The read-only code area.
//
//*****************************************************************************
    _TEXT_

    //
    // The C main entry.
    //
    _IMPORT_	main
    
    //
    // This is the entry point of the program.
    //
    _ENTRY_
    
    //
    // This is the interrupt vector table.
    // Relative address because of uncertain SDRAM base address.
    //
    add		pc, pc, _CONST_ 0x38
    ldr		pc, [pc, _CONST_ 0x18]
    ldr		pc, [pc, _CONST_ 0x18]
    ldr		pc, [pc, _CONST_ 0x18]
    ldr		pc, [pc, _CONST_ 0x18]
    ldr		pc, [pc, _CONST_ 0x18]
    ldr		pc, [pc, _CONST_ 0x18]
    ldr		pc, [pc, _CONST_ 0x18]
    
jump_table _LABEL_
    _WORD_	0x00000000
    _WORD_	0x00000000 + 0x04
    _WORD_	0x00000000 + 0x08
    _WORD_	0x00000000 + 0x0c
    _WORD_	0x00000000 + 0x10
    _WORD_	0x00000000 + 0x14
    _WORD_	0x00000000 + 0x18
    _WORD_	0x00000000 + 0x1c
    
//*****************************************************************************
//
// Builds the page table.
//
//*****************************************************************************
reset _LABEL_
    //
    // Set the stack pointer to 0x00600000
    //
    ldr     r13, =0x00600000

    //
    // Load a pointer to the page table.
    //
    mov     r11, pc
    and     r11, r11, _CONST_ 0xf0000000
    orr     r0, r11, _CONST_ 0x00004000

    //
    // Clear out the page table.
    //
    mov     r1, r0
    mov     r2, _CONST_ 0x00004000
    mov     r3, _CONST_ 0x00000000
clear _LABEL_
        str     r3, [r1], _CONST_ 4
        subs    r2, r2, _CONST_ 4
        bne     clear

    //
    // Create a non-cacheable/non-bufferable mapping of SDRAM
    // at 0x0000_0000, only map 8M for this program.
    //
    mov     r1, r0
    mov     r2, _CONST_ 0x00000020
    orr     r3, r11, _CONST_ 0x00000012
    orr     r3, r3, _CONST_ 0x00000c00
map_sdram _LABEL_
        str     r3, [r1], _CONST_ 4
        add     r3, r3, _CONST_ 0x00100000
        subs    r2, r2, _CONST_ 4
        bne     map_sdram
            
    //
    // Create a read-write mapping of FLASH nCS6
    // at virtual address 0x6000_0000.
    //
    add     r1, r0, _CONST_ 0x00001800
    mov     r2, _CONST_ 0x00000400
    ldr     r3, =0x60000c12
map_flash_6 _LABEL_
        str     r3, [r1], _CONST_ 4
        add     r3, r3, _CONST_ 0x00100000
        subs    r2, r2, _CONST_ 4
        bne     map_flash_6

    //
    // Create a read-write mapping of the hardware registers
    // at virtual address 0x8000_0000.
    //
    add     r1, r0, _CONST_ 0x00002000
    mov     r2, _CONST_ 0x00000400
    ldr     r3, =0x80000c12
map_hw _LABEL_
        str     r3, [r1], _CONST_ 4
        add     r3, r3, _CONST_ 0x00100000
        subs    r2, r2, _CONST_ 4
        bne     map_hw

    //
    // Setup the MMU.
    //
    orr     r0, r11, _CONST_ 0x00004000
    mcr     p15, 0, r0, c2, c0, 0
    mov     r0, _CONST_ 0x00000003
    mcr     p15, 0, r0, c3, c0, 0

    //
    // Enable the MMU and branch to our equivalent virtual address.
    //
    ldr     r0, =0xc0000079
    ldr     r1, =go_virtual
    mov     r2, r11
    sub     r1, r1, r2
    bic     r1, r1, _CONST_ 0xf0000000
    mcr     p15, 0, r0, c1, c0, 0
    mov     pc, r1
go_virtual _LABEL_
    nop
    
    //
    // Switch to C entry
    //    
    bl		main

    _END_