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scoutos / prex-0.9.0 / bsp / boot / arm / gba / head.S @ 03e9c04a

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/*-
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 * Copyright (c) 2005, Kohsuke Ohtani
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 * 3. Neither the name of the author nor the names of any co-contributors
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 *    may be used to endorse or promote products derived from this software
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 *    without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 */
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/*
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 * head.S - low level platform support
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 *
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 * This file contains the code from crt0.S which is released under
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 * public domain by Jeff Frohwein.
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 */
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/*-
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 * Memory usage:
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 *
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 * 0x02000000 - 0x0203ffff : EWRAM (256K)
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 * 0x03000000 - 0x03007fff : IWRAM (32K)
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 * 0x04000000 - 0x040003ff : I/O Register (1K)
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 * 0x05000000 - 0x050003ff : Palette RAM (1K)
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 * 0x06000000 - 0x06017fff : VRAM (96K)
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 *
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 * Note:
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 * 0x03007f00 - 0x03007fff is reserved by GBA BIOS.
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 */
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#include <conf/config.h>
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#include <machine/memory.h>
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#include <machine/syspage.h>
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#define ENTRY(x) .global x; .align; x##:
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	.section ".text","ax"
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	.code 32
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/*
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 * Loader start point
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 */
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ENTRY(boot_entry)
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	b	rom_header_end
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	/*
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	 * GBA ROM header
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	 */
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	/* Nintendo Logo Character Data (8000004h) */
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	.fill	156,1,0
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	/* Game Title (80000A0h) */
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	.byte	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
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	.byte	0x00,0x00,0x00,0x00
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	/* Game Code (80000ACh) */
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	.byte	0x00,0x00,0x00,0x00
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	/* Maker Code (80000B0h) */
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	.byte	0x30,0x31
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	/* Fixed Value (80000B2h) */
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	.byte	0x96
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	/* Main Unit Code (80000B3h) */
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	.byte	0x00
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	/* Device Type (80000B4h) */
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	.byte	0x00
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	/* Unused Data (7Byte) (80000B5h) */
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	.byte	0x00,0x00,0x00,0x00,0x00,0x00,0x00
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	/* Software Version No (80000BCh) */
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	.byte	0x00
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	/* Complement Check (80000BDh) */
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	.byte	0xf0
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	/* Checksum (80000BEh) */
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	.byte	0x00,0x00
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	.align
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	.code 32
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rom_header_end:
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	b	start_vector
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	.global __boot_method, __slave_number
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__boot_method:
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	.byte	0	/* boot method (0=ROM boot, 3=Multiplay boot) */
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__slave_number:
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	.byte	0	/* slave # (1=slave#1, 2=slave#2, 3=slave#3) */
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	.byte	0
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	.byte	0
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	.word	0
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	.word	0
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	.word	0
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	.word	0
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	.word	0
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	.word	0
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	.align
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	.code 32
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stack_top:	.word	(BOOTSTKTOP - KERNBASE)
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start_vector:
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	mov	r0, #0xd3		/* Enter SVC mode, Disable IRQ,FIQ */
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	msr	cpsr_c, r0
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	ldr	sp, stack_top
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	adr	r0, thumb_mode + 1
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	bx	r0
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	.code 16
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thumb_mode:
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/*
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 * Relocate the loader code
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 */
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	mov	r3, #0x40
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	lsl	r3, r3, #7  /* r3 = 0x2000 (8K) */
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	mov	r2, #3
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	lsl	r2, r2, #24 /* r2 = 0x3000000 */
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	lsl	r1, r3, #14 /* r1 = 0x8000000 */
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copy_loop:
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	ldmia	r1!, {r0}
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	stmia	r2!, {r0}
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	sub	r3, r3, #4
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	bne	copy_loop
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	ldr	r0, =main
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	bx	r0		/* Change to ARM mode */
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	.code 32
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#if defined(DEBUG) && defined(CONFIG_DIAG_VBA)
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/*
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 * Put one character to Visual Boy Advance (VBA) emulator console.
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 *
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 * Important:
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 * This BIOS call is not supported by actual GBA BIOS. So, you must
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 * disable this function when you run it on actual GBA H/W.
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 * Otherwise, it will hang.
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 */
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putbuf:
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	.long	0
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ENTRY(vba_putc)
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	ldr	r1, =putbuf
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	str	r0, [r1]
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	mov	r0, r1
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	swi	$0xff0000
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	mov	pc, lr
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#endif
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	.section .tail,"ax"
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dummy:
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	.byte	0xff
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.end