Annotation of prex/boot/arm/gba/head.S, Revision 1.1.1.1
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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