Annotation of prex/boot/arm/gba/head.S, Revision 1.1
1.1 ! nbrk 1: /*-
! 2: * Copyright (c) 2005, Kohsuke Ohtani
! 3: * All rights reserved.
! 4: *
! 5: * Redistribution and use in source and binary forms, with or without
! 6: * modification, are permitted provided that the following conditions
! 7: * are met:
! 8: * 1. Redistributions of source code must retain the above copyright
! 9: * notice, this list of conditions and the following disclaimer.
! 10: * 2. Redistributions in binary form must reproduce the above copyright
! 11: * notice, this list of conditions and the following disclaimer in the
! 12: * documentation and/or other materials provided with the distribution.
! 13: * 3. Neither the name of the author nor the names of any co-contributors
! 14: * may be used to endorse or promote products derived from this software
! 15: * without specific prior written permission.
! 16: *
! 17: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
! 18: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
! 19: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
! 20: * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
! 21: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
! 22: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
! 23: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
! 24: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
! 25: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
! 26: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
! 27: * SUCH DAMAGE.
! 28: */
! 29:
! 30: /*
! 31: * head.S - low level platform support
! 32: *
! 33: * This file contains the code from crt0.S which is released under
! 34: * public domain by Jeff Frohwein.
! 35: */
! 36:
! 37: /*-
! 38: * Memory usage:
! 39: *
! 40: * 0x02000000 - 0x0203ffff : EWRAM (256K)
! 41: * 0x03000000 - 0x03007fff : IWRAM (32K)
! 42: * 0x04000000 - 0x040003ff : I/O Register (1K)
! 43: * 0x05000000 - 0x050003ff : Palette RAM (1K)
! 44: * 0x06000000 - 0x06017fff : VRAM (96K)
! 45: *
! 46: * Note:
! 47: * 0x03007f00 - 0x03007fff is reserved by GBA BIOS.
! 48: */
! 49:
! 50: #include <conf/config.h>
! 51: #include <platform.h>
! 52:
! 53: #define ENTRY(x) .global x; .align; x##:
! 54:
! 55: .section ".text","ax"
! 56: .code 32
! 57: /*
! 58: * Kernel start point
! 59: */
! 60: ENTRY(boot_entry)
! 61: b rom_header_end
! 62:
! 63: /*
! 64: * GBA ROM header
! 65: */
! 66:
! 67: /* Nintendo Logo Character Data (8000004h) */
! 68: .fill 156,1,0
! 69:
! 70: /* Game Title (80000A0h) */
! 71: .byte 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
! 72: .byte 0x00,0x00,0x00,0x00
! 73:
! 74: /* Game Code (80000ACh) */
! 75: .byte 0x00,0x00,0x00,0x00
! 76:
! 77: /* Maker Code (80000B0h) */
! 78: .byte 0x30,0x31
! 79:
! 80: /* Fixed Value (80000B2h) */
! 81: .byte 0x96
! 82:
! 83: /* Main Unit Code (80000B3h) */
! 84: .byte 0x00
! 85:
! 86: /* Device Type (80000B4h) */
! 87: .byte 0x00
! 88:
! 89: /* Unused Data (7Byte) (80000B5h) */
! 90: .byte 0x00,0x00,0x00,0x00,0x00,0x00,0x00
! 91:
! 92: /* Software Version No (80000BCh) */
! 93: .byte 0x00
! 94:
! 95: /* Complement Check (80000BDh) */
! 96: .byte 0xf0
! 97:
! 98: /* Checksum (80000BEh) */
! 99: .byte 0x00,0x00
! 100:
! 101: .align
! 102: .code 32
! 103:
! 104: rom_header_end:
! 105: b start_vector
! 106:
! 107: .global __boot_method, __slave_number
! 108:
! 109: __boot_method:
! 110: .byte 0 /* boot method (0=ROM boot, 3=Multiplay boot) */
! 111: __slave_number:
! 112: .byte 0 /* slave # (1=slave#1, 2=slave#2, 3=slave#3) */
! 113:
! 114: .byte 0
! 115: .byte 0
! 116: .word 0
! 117: .word 0
! 118: .word 0
! 119: .word 0
! 120: .word 0
! 121: .word 0
! 122:
! 123: .align
! 124: .code 32
! 125: stack_end: .word BOOT_STACK+0xf00
! 126:
! 127: start_vector:
! 128: mov r0, #0xd3 /* Enter SVC mode, Disable IRQ,FIQ */
! 129: msr cpsr_c, r0
! 130: ldr sp, stack_end
! 131:
! 132: adr r0, thumb_mode + 1
! 133: bx r0
! 134: .code 16
! 135: thumb_mode:
! 136:
! 137: /*
! 138: * Relocate the loader code
! 139: */
! 140: mov r3, #0x40
! 141: lsl r3, #7 /* r3 = 0x2000 (8K) */
! 142: mov r2, #3
! 143: lsl r2, #24 /* r2 = 0x3000000 */
! 144: lsl r1, r3, #14 /* r1 = 0x8000000 */
! 145:
! 146: copy_loop:
! 147: ldmia r1!, {r0}
! 148: stmia r2!, {r0}
! 149: sub r3, #4
! 150: bne copy_loop
! 151:
! 152: ldr r0, =loader_main
! 153: bx r0 /* Change to ARM mode */
! 154:
! 155: .code 32
! 156:
! 157: /*
! 158: * Start kernel
! 159: */
! 160: ENTRY(start_kernel)
! 161: bx r0
! 162:
! 163: /*
! 164: * Put one character to Visual Boy Advance (VBA) emulator console.
! 165: *
! 166: * Important:
! 167: * This BIOS call is not supported by actual GBA BIOS. So, you must
! 168: * disable this function when you run it on actual GBA H/W.
! 169: * Otherwise, it will hang.
! 170: */
! 171: putbuf:
! 172: .long 0
! 173:
! 174: ENTRY(putchar)
! 175: #if defined(DEBUG) && defined(CONFIG_DIAG_VBA)
! 176: ldr r1, =putbuf
! 177: str r0, [r1]
! 178: mov r0, r1
! 179: swi $0xff0000
! 180: #endif
! 181: mov pc, lr
! 182: /*
! 183: * Panic handler
! 184: */
! 185: ENTRY(machine_panic)
! 186: stop:
! 187: b stop
! 188:
! 189: .section .tail,"ax"
! 190: dummy:
! 191: .byte 0xff
! 192:
! 193: .end
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