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rockbox/firmware/target/arm/tcc77x/crt0.S

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ArmAsm
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/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2002 by Linus Nielsen Feltzing
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
/* Arm bootloader and startup code based on startup.s from the iPodLinux loader
*
* Copyright (c) 2003, Daniel Palffy (dpalffy (at) rainstorm.org)
* Copyright (c) 2005, Bernard Leach <leachbj@bouncycastle.org>
*
*/
#include "config.h"
#include "cpu.h"
.section .init.text,"ax",%progbits
.extern irq
.extern fiq
.extern UIE
.extern main
.global start
/* Telechips firmware files start with a 32-byte header, as part of the code. */
start:
#ifdef TCCBOOT
/* Add -DTCCBOOT to EXTRA_DEFINES in the bootloader Makefile to
enable building the bootloader to be appended to the end of the
original firmware, dual-booting based on a key-press.
The following two values are filled in by mktccboot.
*/
.word 0 /* Saved entrypoint of original firmware*/
.word 0 /* Location in RAM of the start of our bootloader */
#else
// ldr pc, =start_loc /* jump to the main entry point */
b start_loc
.word 0xffff0601 /* Unknown magic */
.word 0x3a726556 /* "Ver:" */
.word 0x31373030 /* "0071" */
.word 0 /* First CRC32 */
.word 0 /* Unknown - always 0 */
.word 0 /* Second CRC32 */
.word 0 /* length of firmware file */
#ifdef LOGIK_DAX
/* Some original firmwares have 0x40 bytes of zeroes here - we
don't know why, but err on the side of caution and include it
here. */
.space 0x40
#endif
#endif
start_loc:
#ifdef BOOTLOADER
/*
If we are appended to the OF (i.e. dual-booting), do a simple GPIO
button check, and branch to the OF's entry point (saved by mktccboot)
if not active
*/
#ifdef TCCBOOT
mov r0, #0x80000000
#if defined(LOGIK_DAX)
ldr r0, [r0, #0x300] /* Hold button is GPIO A, pin 0x2 */
tst r0, #0x2
#elif defined(SANSA_M200)
ldr r0, [r0, #0x310] /* Hold button is GPIO B, pin 0x200 */
tst r0, #0x200
#elif defined(IAUDIO_7)
ldr r0, [r0, #0x300] /* Hold button is !GPIO A, pin 0x2 */
tst r0, #0x2
#else
#error No bootup key detection implemented for this target
#endif
ldrne pc, [pc, #-28] /* Jump to OF if HOLD button not pressed */
#endif /* TCCBOOT */
/* We are now definitely executing the bootloader, so we relocate to the
linked address (see boot.lds) - 1MB from the end of DRAM.
*/
#ifdef TCCBOOT
ldr r0, [pc, #-28] /* mktccboot fills in the load address */
#else
mov r0, #0x20000000 /* Otherwise, load address is the start of DRAM */
#endif
mov r1, #0x20000000 /* Destination: 1MB from end of DRAM */
add r1, r1, #((MEM - 1) * 0x100000)
ldr r2, =_dataend
1:
cmp r2, r1
ldrhi r3, [r0], #4
strhi r3, [r1], #4
bhi 1b
ldr pc, =copied_start /* jump to the relocated start_loc: */
copied_start:
#endif /* BOOTLOADER */
/* Set up stack for IRQ mode */
mov r0,#0xd2
msr cpsr, r0
ldr sp, =irq_stack
/* Set up stack for FIQ mode */
mov r0,#0xd1
msr cpsr, r0
ldr sp, =fiq_stack
/* Let abort and undefined modes use IRQ stack */
mov r0,#0xd7
msr cpsr, r0
ldr sp, =irq_stack
mov r0,#0xdb
msr cpsr, r0
ldr sp, =irq_stack
/* Switch to supervisor mode */
mov r0,#0xd3
msr cpsr, r0
ldr sp, =stackend
/* Copy exception handler code to address 0 */
mov r2, #0x0
ldr r3, =vectors_start
ldr r4, =vectors_end
1:
cmp r4, r3
ldrhi r5, [r3], #4
strhi r5, [r2], #4
bhi 1b
/* Initialise bss section to zero */
ldr r2, =_edata
ldr r3, =_end
mov r4, #0
1:
cmp r3, r2
strhi r4, [r2], #4
bhi 1b
/* Set up some stack and munge it with 0xdeadbeef */
ldr sp, =stackend
mov r3, sp
ldr r2, =stackbegin
ldr r4, =0xdeadbeef
1:
cmp r3, r2
strhi r4, [r2], #4
bhi 1b
bl main
/* main() should never return */
/* Exception handlers. Will be copied to address 0 after memory remapping */
vectors_start:
ldr pc, [pc, #24]
ldr pc, [pc, #24]
ldr pc, [pc, #24]
ldr pc, [pc, #24]
ldr pc, [pc, #24]
ldr pc, [pc, #24]
ldr pc, [pc, #24]
ldr pc, [pc, #24]
/* Exception vectors */
.global vectors
vectors:
.word start
.word undef_instr_handler
.word software_int_handler
.word prefetch_abort_handler
.word data_abort_handler
.word reserved_handler
.word irq_handler
.word fiq_handler
vectors_end:
.text
/* All illegal exceptions call into UIE with exception address as first
parameter. This is calculated differently depending on which exception
we're in. Second parameter is exception number, used for a string lookup
in UIE.
*/
undef_instr_handler:
mov r0, lr
mov r1, #0
b UIE
/* We run supervisor mode most of the time, and should never see a software
exception being thrown. Perhaps make it illegal and call UIE?
*/
software_int_handler:
reserved_handler:
movs pc, lr
prefetch_abort_handler:
sub r0, lr, #4
mov r1, #1
b UIE
data_abort_handler:
sub r0, lr, #8
mov r1, #2
b UIE
irq_handler:
stmfd sp!, {r0-r3, r12, lr}
bl irq
ldmfd sp!, {r0-r3, r12, lr}
subs pc, lr, #4
/* Align stacks to cache line boundary */
.balign 16
/* 256 words of IRQ stack */
.space 256*4
irq_stack:
/* 256 words of FIQ stack */
.space 256*4
fiq_stack:
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