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|
/**
* @file start.S
*
* RTEMS entry point.
*/
/*
* RTEMS GBA BSP
*
* Copyright (c) by Jeff Frohwein.
*
* Copyright (c) 2003, Jason Wilkins.
*
* Copyright (c) 2004 Markku Puro <markku.puro@kopteri.net>
* based on crt0.S v1.28 by Jeff Frohwein
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.org/license/LICENSE.
*/
/*****************************************************************************
* This source file is based on work by Jeff Frohwein and Jason Wilkins
*****************************************************************************
*****************************************************************************
* crt0.S v1.28 by Jeff Frohwein
* :
* This file is released into the public domain for commercial
* or non-commercial usage with no restrictions placed upon it.
*****************************************************************************
* Copyright 2003, Jason Wilkins. This source code is free for any use except
* that this copyright notice and the following disclaimers remain intact when
* the source is distributed. Object code and binary distributions may be made
* as if the code were in the public domain.
*
* THIS CODE WAS NOT MADE IN ASSOCIATION WITH NINTENDO AND DOES NOT MAKE USE
* OF ANY INTELLECTUAL PROPERTY CLAIMED BY NINTENDO.
*
* GAMEBOY ADVANCE IS A TRADEMARK OF NINTENDO.
*
* THIS CODE HAS BEEN PROVIDED "AS-IS" WITHOUT A WARRANTY OF ANY KIND, EITHER
* EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO IMPLIED WARRANTIES OF
* MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. THE ENTIRE RISK AS TO THE
* QUALITY OR PERFORMANCE OF THE CODE IS WITH YOU.
*
* IN NO EVENT, UNLESS AGREED TO IN WRITING, WILL ANY COPYRIGHT HOLDER, OR ANY
* OTHER PARTY, BE HELD LIABLE FOR ANY DAMAGES RESULTING FROM THE USE OR
* INABILITY TO USE THIS CODE.
*****************************************************************************/
#define __asm__
#include <rtems/asm.h>
#include <asm_macros.h>
#include <arm_mode_bits.h>
/* @cond INCLUDE_ASM */
#ifndef NINTENDO_LOGO
#define NINTENDO_LOGO 1
#endif
#ifndef GBA_MULTIBOOT
#define GBA_MULTIBOOT 1
#endif
#ifndef GAME_TITLE
#define GAME_TITLE "RTEMS-RTOS "
#endif
#ifdef GBA_MULTIBOOT
#ifndef GAME_CODE
#define GAME_CODE "MB "
#endif
#ifndef COMPLEMENT_CHECK
#define COMPLEMENT_CHECK 0xE2
#endif
#else
#ifndef GAME_CODE
#define GAME_CODE "GBA "
#endif
#ifndef COMPLEMENT_CHECK
#define COMPLEMENT_CHECK 0xC7
#endif
#endif
#ifndef MAKER_CODE
#define MAKER_CODE "00"
#endif
/**
* RTEMS entry point
* function void _start(void)
*
*/
/*****************************************************************************\
ROM Header
\*****************************************************************************/
.text
.align
.arm
/*---------------------------------------------------------------------------+
| Nintendo Header:
| A special header is required or the GBA will refuse to run your code.
|
| File offsets from 0x0200000 or 0x08000000.
+----------------------------------------------------------------------------*/
PUBLIC_ARM_FUNCTION(_start)
b SYM(_real_start) /* 0x00 Entry Point */
SYM(_gba_rom_header):
#if NINTENDO_LOGO /* 0x04 Nintendo Logo Character Data */
#include "logo.S"
#else
.fill 156, 1, 0 /* 0x04 Nintendo Logo Character Data */
#endif
.ascii GAME_TITLE /* 0xA0 Game Title */
.ascii GAME_CODE /* 0xAC Game Code */
.ascii MAKER_CODE /* 0xB0 Maker Code */
.byte 0x96 /* 0xB2 Fixed Value */
.byte 0 /* 0xB3 Main Unit Code */
.byte 0 /* 0xB4 Device Type */
.byte 0, 0, 0, 0, 0, 0, 0 /* 0xB5 Reserved (7 Bytes) */
.byte 0 /* 0xBC Software Version No. */
.byte COMPLEMENT_CHECK /* 0xBD Complement Check */
.byte 0, 0 /* 0xBE Reserved */
.Lheader_end:
#if GBA_MULTIBOOT
/*---------------------------------------------------------------------------+
| Multiboot Header:
| The following header is required if the code is meant for Multiboot.
|
| If the code has been downloaded through the serial port, then the GBA BIOS
| will set offset 0xC0 depending on the boot method:
| 1 = JoyBus, 3 = Multiboot
| It remains 0 for cartridges.
|
| offset 0xC4 will be set to the GBA's assigned slave number 1-3.
| This header also defines the symbols _boot_method and _slave_number for
| easy reference to these values. Some libraries may depend on them whether
| or not the code is meant for Multiboot.
|
+----------------------------------------------------------------------------*/
SYM(_gba_multiboot_start):
b SYM(_real_start) /* 0xC0 Multiboot Entry Point */
OBJECT(_boot_method)
.byte 0 /* 0xC4 Boot Method */
OBJECT(_slave_number)
.byte 0 /* 0xC5 Slave Number (1-3) */
.align
STATIC_OBJECT(_gba_mb_reserved)
.word 0, 0, 0, 0, 0, 0 /* 0xC8 Reserved (6 words) */
SYM(_gba_joybus_start):
b SYM(_real_start) /* 0xE0 JoyBus Entry Point */
.Lmultiboot_header_end:
#endif
/*---------------------------------------------------------------------------+
| Restore registers and stack from GBA bios IRQ frame and call ISR_Handler
+----------------------------------------------------------------------------*/
EXTERN(_ISR_Handler)
.align
PUBLIC_ARM_FUNCTION(_gba_ISR_handler)
ldmfd r13!,{r0-r3,r12,r14}
b _ARMV4_Exception_interrupt
LABEL_END(_gba_ISR_handler)
/*---------------------------------------------------------------------------+
| Code to initialize the low-level BSP environment
+----------------------------------------------------------------------------*/
SYM(_real_start):
/* Initialize IRQ and USR Stack Pointers */
SYM(_gba_init_stacks):
mov r0, #(Mode_IRQ | Int_Bits) /* No interrupts */
msr cpsr, r0 /* switch to IRQ mode */
ldr sp, =__sp_irq /* defined in linkcmds */
mov r0, #(ModePriv | Int_Bits) /* No interrupts */
msr cpsr, r0 /* switch to System Mode */
ldr sp, =__sp_usr /* defined in linkcmds */
/* Switch to Thumb Mode */
SYM(_gba_bx_thumb):
adr r0, .Lthumb + 1
bx r0
.thumb
.Lthumb:
/* Reduce gameboy waitstates */
SYM(_reduce_waitstates):
ldr r1, =0x4000204
ldrh r0, =0x4490
strh r0, [r1]
#if GBA_MULTIBOOT
/*---------------------------------------------------------------------------+
| Load Multiboot Image from ROM into RAM:
| Check to see if the image is meant for Multiboot or GamePak. If it is for
| Multiboot then check if it is currently running from EWRAM or from CARTROM.
| If it is running from CARTROM, then it needs to be copied to EWRAM and
| re-executed from the beginning.
|
| The reason for all this is to allow a program to be used "as-is" with a
| flash-cart, emulator, or MBV2-style Multiboot cable without rebuilding.
|
| NOTE: Any branchs used above this code need to be relative.
+----------------------------------------------------------------------------*/
STATIC_THUMB_FUNCTION(_gba_load_multiboot)
ldr r0, =_start /* 8000000h=GamePak 2000000h=Multiboot*/
ldr r1, =__gba_rom_start /* defined in linkcmds */
cmp r0, r1
beq SYM(_no_load_multiboot)/* skip if GamePak */
mov r3, pc
cmp r1, r3 /* check program counter */
bhi SYM(_no_load_multiboot)/* skip if already running from EWRAM */
sub r3, r1, r0 /* diff between _start and CARTROM */
ldr r2, =__load_stop_data /* defined in linkcmds */
add r2, r2, r3 /* adjust pointer into ROM */
bl SYM(gba_move_memory)
/* patch multiboot header */
ldr r0, =SYM(_boot_method)
mov r1, #3
str r1, [r0]
/* remember that multiboot image came from GamePak */
ldr r0, =SYM(_gba_flash_loaded_multiboot)
mov r1, #0
str r1, [r0]
ldr r0, =SYM(_start)
bx r0 /* restart */
LABEL_END(_gba_load_multiboot)
.align 4
OBJECT(_gba_flash_loaded_multiboot)
.word -1
LABEL_END(_gba_flash_loaded_multiboot)
SYM(_no_load_multiboot):
#endif
/* Initialize Standard Sections */
STATIC_THUMB_FUNCTION(_gba_init_std_sections)
/* Copy internal work ram (iwram section ROM to RAM)*/
ldr r0,=__iwram_start
ldr r1,=__load_start_iwram
ldr r2,=__load_stop_iwram
bl SYM(gba_move_memory)
/* Copy external work ram (ewram section ROM to RAM) */
ldr r0,=__ewram_start
ldr r1,=__load_start_ewram
ldr r2,=__load_stop_ewram
bl SYM(gba_move_memory)
/* load initial values of variables like 'int foo = 42' */
ldr r0, =__data_start /* defined in linkcmds */
ldr r1, =__load_start_data /* defined in linkcmds */
ldr r2, =__load_stop_data /* defined in linkcmds */
bl SYM(gba_move_memory)
/* zero the bss */
ldr r0, =__bss_start /* defined in linkcmds */
ldr r1, =__bss_end /* defined in linkcmds */
bl SYM(gba_zero_memory)
LABEL_END(_gba_init_std_sections)
/* Initialize Interrupt Vector */
STATIC_THUMB_FUNCTION(_gba_init_intr_vect)
ldr r1, =__irq_vector /* defined in linkcmds */
ldr r0, =SYM(_gba_ISR_handler)
str r0, [r1]
LABEL_END(_gba_init_intr_vect)
/* Enter the C code. If it returns, then restart */
STATIC_THUMB_FUNCTION(_gba_call_arm_boot_card)
adr r1, .Larm
bx r1
.arm
.Larm:
ldr r1, =boot_card
mov r0, #0
bl SYM(_gba_call_via_r1)
ldr r0, =SYM(_gba_reset)
SYM(_gba_call_via_r1):
bx r1
/* GBA Reset */
PUBLIC_ARM_FUNCTION(_gba_reset)
adr r0, .Lthumb2 + 1
bx r0
.thumb
.Lthumb2:
/* disable interrupts */
ldr r0, =0x04000208
mov r1, #0
strb r1, [r0]
/* reset stack, default free area */
ldr r0, =0x03007F00
mov sp, r0
#if GBA_MULTIBOOT
ldr r0, =SYM(_gba_flash_loaded_multiboot)
ldr r0, [r0]
cmp r0, #0
beq SYM(_reset)
#endif
ldr r0, =_start /* defined in linkcmds */
ldr r1, =__gba_rom_start /* defined in linkcmds */
sub r0, r0, r1
lsr r0, r0, #24
SYM(_reset):
/* soft reset (swi 0) parameter: where is _start */
ldr r1, =0x03007FFA
strb r0, [r1]
mov r0, #0xFE /* clear all but EWRAM */
swi 1
swi 0
LABEL_END(_gba_reset)
/*---------------------------------------------------------------------------+
| Library Functions
+----------------------------------------------------------------------------*/
/* gba_zero_memory */
PUBLIC_THUMB_FUNCTION(gba_zero_memory)
mov r2, #0
nop
LABEL_END(gba_zero_memory)
/* gba_set_memory */
PUBLIC_THUMB_FUNCTION(gba_set_memory)
cmp r0, r1
bcs .Lset_memory_return
.Lset_memory_loop:
stmia r0!, {r2}
cmp r0, r1
bcc .Lset_memory_loop
.Lset_memory_return:
bx lr
LABEL_END(gba_set_memory)
/* gba_move_memory */
.align
PUBLIC_THUMB_FUNCTION(gba_move_memory)
cmp r0, r1
bcc .Lforward_move /* if dst < src then forward copy */
bhi .Lreverse_move /* if dst > src then reverse copy */
bx lr /* else dst == src, nothing to do */
.Lforward_move:
cmp r1, r2
bcs .Lmove_memory_return
.Lforward_move_loop:
ldmia r1!, {r3}
stmia r0!, {r3}
cmp r1, r2
bcc .Lforward_move_loop
bx lr
.Lreverse_move:
cmp r2, r1
bls .Lmove_memory_return
sub r3, r2, r1
add r0, r0, r3
.Lreverse_move_loop:
sub r2, r2, #4
ldr r3, [r2]
sub r0, r0, #4
str r3, [r0]
cmp r2, r1
bhi .Lreverse_move_loop
.Lmove_memory_return:
bx lr
LABEL_END(gba_move_memory)
/* @todo FIXME: Remove unused handler needed by ../score/cpu_asm.S
*****************************************************************************/
.arm
.global SWI_Handler
SWI_Handler:
mov pc, lr
/* @endcond */
|
