Krawall GBA modplayer on GitHub

[sebk]

Hello everyone!

I've finally gotten around to putting Krawall on GitHub: http://knzl.de/krawall/
I've updated it to work with the latest version of devkitARM.

Cheers,
Seb.

[andy]

Hi.

Is there any chance to put things together so Krawall can be used with devkitARM?

Actually there are some people like myself, who jump to GBA developement from tim to time.

[WinterMute]

I had the impression this was devkitARM ready although I see there appear to be a lack of binaries available.

I just had a quick look at the sources in github and I have a couple of observations.

There's a note in the TODO that says "Look into devkitPro's crt0 and make sure that a) multiple interrupts are possible and b) IRQ_TIMER1 is not interrupted by any other interrupt (Otherwise, there may be audible clicks). The devkitARM crt0 used for GBA doesn't have anything to do with interrupts - I have a particular dislike for end users messing with startup code as a general rule. The devkitAdvance way of doing things there basically meant that every GBA project had it's own crt0 with some horrendous number of potential variations which obviously has it's issues. With devkitARM we use a standard crt0 which copies sections to RAM as needed, clears BSS and initialises global constructors before jumping to main.

Code: Select all

	.section	".init"
	.global     _start
	.align
	.arm
@---------------------------------------------------------------------------------
_start:
@---------------------------------------------------------------------------------
	b	rom_header_end

	.fill   156,1,0			@ Nintendo Logo Character Data (8000004h)
	.fill	16,1,0			@ Game Title
	.byte   0x30,0x31		@ Maker Code (80000B0h)
	.byte   0x96			@ Fixed Value (80000B2h)
	.byte   0x00			@ Main Unit Code (80000B3h)
	.byte   0x00			@ Device Type (80000B4h)
	.fill	7,1,0			@ unused
	.byte	0x00			@ Software Version No (80000BCh)
	.byte	0xf0			@ Complement Check (80000BDh)
	.byte	0x00,0x00    		@ Checksum (80000BEh)

@---------------------------------------------------------------------------------
rom_header_end:
@---------------------------------------------------------------------------------
	b	start_vector			@ This branch must be here for proper
						@ positioning of the following header.

	.GLOBAL	__boot_method, __slave_number
@---------------------------------------------------------------------------------
__boot_method:
@---------------------------------------------------------------------------------
	.byte   0				@ boot method (0=ROM boot, 3=Multiplay boot)
@---------------------------------------------------------------------------------
__slave_number:
@---------------------------------------------------------------------------------
	.byte   0				@ slave # (1=slave#1, 2=slave#2, 3=slave#3)

	.byte   0 				@ reserved
	.byte   0 				@ reserved
	.word   0    				@ reserved
	.word   0				@ reserved
	.word   0    				@ reserved
	.word   0    				@ reserved
	.word   0    				@ reserved
	.word   0    				@ reserved

    .global     start_vector
    .align
@---------------------------------------------------------------------------------
start_vector:
@---------------------------------------------------------------------------------
	mov	r0, #0x4000000			@ REG_BASE
	str	r0, [r0, #0x208]

	mov	r0, #0x12			@ Switch to IRQ Mode
	msr	cpsr, r0
	ldr	sp, =__sp_irq			@ Set IRQ stack
	mov	r0, #0x1f			@ Switch to System Mode
	msr	cpsr, r0
	ldr	sp, =__sp_usr			@ Set user stack

@---------------------------------------------------------------------------------
@ Enter Thumb mode
@---------------------------------------------------------------------------------
	add	r0, pc, #1
	bx	r0

	.thumb

	ldr	r0, =__text_start
	lsl	r0, #5				@ Was code compiled at 0x08000000 or higher?
	bcs     DoEWRAMClear			@ yes, you can not run it in external WRAM

	mov     r0, pc
	lsl     r0, #5				@ Are we running from ROM (0x8000000 or higher) ?
	bcc     SkipEWRAMClear			@ No, so no need to do a copy.

@---------------------------------------------------------------------------------
@ We were started in ROM, silly emulators. :P
@ So we need to copy to ExWRAM.
@---------------------------------------------------------------------------------
	mov	r2, #2
	lsl	r2, r2, #24			@ r2= 0x02000000
	ldr	r3, =__end__			@ last ewram address
	sub	r3, r2				@ r3= actual binary size
	mov	r6, r2				@ r6= 0x02000000
	lsl	r1, r2, #2			@ r1= 0x08000000

	bl	CopyMem

	bx	r6				@ Jump to the code to execute

@---------------------------------------------------------------------------------
DoEWRAMClear:					@ Clear External WRAM to 0x00
@---------------------------------------------------------------------------------
	mov	r1, #0x40
	lsl	r1, #12				@ r1 = 0x40000
	lsl	r0, r1, #7			@ r0 = 0x2000000
	bl	ClearMem

@---------------------------------------------------------------------------------
SkipEWRAMClear:					@ Clear Internal WRAM to 0x00
@---------------------------------------------------------------------------------

@---------------------------------------------------------------------------------
@ Clear BSS section to 0x00
@---------------------------------------------------------------------------------
	ldr	r0, =__bss_start__
	ldr	r1, =__bss_end__
	sub	r1, r0
	bl	ClearMem

@---------------------------------------------------------------------------------
@ Clear SBSS section to 0x00
@---------------------------------------------------------------------------------
	ldr	r0, =__sbss_start__
	ldr	r1, =__sbss_end__
	sub	r1, r0
	bl	ClearMem

@---------------------------------------------------------------------------------
@ Copy initialized data (data section) from LMA to VMA (ROM to RAM)
@---------------------------------------------------------------------------------
	ldr	r1, =__data_lma
	ldr	r2, =__data_start__
	ldr	r4, =__data_end__
	bl	CopyMemChk

@---------------------------------------------------------------------------------
@ Copy internal work ram (iwram section) from LMA to VMA (ROM to RAM)
@---------------------------------------------------------------------------------
	ldr	r1,= __iwram_lma
	ldr	r2,= __iwram_start__
	ldr	r4,= __iwram_end__
	bl	CopyMemChk

@---------------------------------------------------------------------------------
@ Copy internal work ram overlay 0 (iwram0 section) from LMA to VMA (ROM to RAM)
@---------------------------------------------------------------------------------
	ldr	r2,= __load_stop_iwram0
	ldr	r1,= __load_start_iwram0
	sub	r3, r2, r1			@ Is there any data to copy?
	beq	CIW0Skip			@ no

	ldr	r2,= __iwram_overlay_start
	bl	CopyMem
@---------------------------------------------------------------------------------
CIW0Skip:
@---------------------------------------------------------------------------------
@ Copy external work ram (ewram section) from LMA to VMA (ROM to RAM)
@---------------------------------------------------------------------------------
	ldr	r1, =__ewram_lma
	ldr	r2, =__ewram_start
	ldr	r4, =__ewram_end
	bl	CopyMemChk

@---------------------------------------------------------------------------------
CEW0Skip:
@---------------------------------------------------------------------------------
@ set heap end
@---------------------------------------------------------------------------------
	ldr	r1, =fake_heap_end
	ldr	r0, =__eheap_end
	str	r0, [r1]
@---------------------------------------------------------------------------------
@ global constructors
@---------------------------------------------------------------------------------
	ldr	r3, =__libc_init_array
	bl	_blx_r3_stub
@---------------------------------------------------------------------------------
@ Jump to user code
@---------------------------------------------------------------------------------
	mov	r0, #0				@ int argc
	mov	r1, #0				@ char	*argv[]
	ldr	r3, =main
	bl	_blx_r3_stub
@---------------------------------------------------------------------------------
@ Clear memory to 0x00 if length != 0
@---------------------------------------------------------------------------------
@ r0 = Start Address
@ r1 = Length
@---------------------------------------------------------------------------------
ClearMem:
@---------------------------------------------------------------------------------
	mov	r2,#3				@ These	commands are used in cases where
	add	r1,r2				@ the length is	not a multiple of 4,
	bic	r1,r2				@ even though it should be.

	beq	ClearMX				@ Length is zero so exit

	mov	r2,#0
@---------------------------------------------------------------------------------
ClrLoop:
@---------------------------------------------------------------------------------
	stmia	r0!, {r2}
	sub	r1,#4
	bne	ClrLoop
@---------------------------------------------------------------------------------
ClearMX:
@---------------------------------------------------------------------------------
	bx	lr

@---------------------------------------------------------------------------------
_blx_r3_stub:
@---------------------------------------------------------------------------------
	bx	r3

@---------------------------------------------------------------------------------
@ Copy memory if length	!= 0
@---------------------------------------------------------------------------------
@ r1 = Source Address
@ r2 = Dest Address
@ r4 = Dest Address + Length
@---------------------------------------------------------------------------------
CopyMemChk:
@---------------------------------------------------------------------------------
	sub	r3, r4, r2			@ Is there any data to copy?
@---------------------------------------------------------------------------------
@ Copy memory
@---------------------------------------------------------------------------------
@ r1 = Source Address
@ r2 = Dest Address
@ r3 = Length
@---------------------------------------------------------------------------------
CopyMem:
@---------------------------------------------------------------------------------
	mov	r0, #3				@ These commands are used in cases where
	add	r3, r0				@ the length is not a multiple	of 4,
	bic	r3, r0				@ even	though it should be.
	beq	CIDExit				@ Length is zero so exit

@---------------------------------------------------------------------------------
CIDLoop:
@---------------------------------------------------------------------------------
	ldmia	r1!, {r0}
	stmia	r2!, {r0}
	sub	r3, #4
	bne	CIDLoop
@---------------------------------------------------------------------------------
CIDExit:
@---------------------------------------------------------------------------------
	bx	lr

	.align
	.pool
	.end

The IRQ dispatcher is in libgba where it belongs, allowing the freedom to supply a custom dispatcher without messing with system files. It was designed to allow multiple interrupts but to default to standard single interrupts. Essentially any IRQ handler which should be interruptible simply re-enables interrupts on entry. Here's the dispatcher code :-

Code: Select all

/*

	libgba interrupt dispatcher routines

	Copyright 2003-2007 by Dave Murphy.

	This library is free software; you can redistribute it and/or
	modify it under the terms of the GNU Library General Public
	License as published by the Free Software Foundation; either
	version 2 of the License, or (at your option) any later version.

	This library is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
	Library General Public License for more details.

	You should have received a copy of the GNU Library General Public
	License along with this library; if not, write to the Free Software
	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
	USA.

	Please report all bugs and problems through the bug tracker at
	"http://sourceforge.net/tracker/?group_id=114505&atid=668551".


*/

@---------------------------------------------------------------------------------
	.section	.iwram,"ax",%progbits
	.extern	IntrTable
	.code 32

	.global	IntrMain
@---------------------------------------------------------------------------------
IntrMain:
@---------------------------------------------------------------------------------
	mov	r3, #0x4000000		@ REG_BASE
	ldr	r2, [r3,#0x200]		@ Read	REG_IE

	ldr	r1, [r3, #0x208]	@ r1 = IME
	str	r3, [r3, #0x208]	@ disable IME
	mrs	r0, spsr
	stmfd	sp!, {r0-r1,r3,lr}	@ {spsr, IME, REG_BASE, lr_irq}

	and	r1, r2,	r2, lsr #16	@ r1 =	IE & IF

	ldrh	r2, [r3, #-8]		@\mix up with BIOS irq flags at 3007FF8h,
	orr	r2, r2, r1		@ aka mirrored at 3FFFFF8h, this is required
	strh	r2, [r3, #-8]		@/when using the (VBlank)IntrWait functions

	ldr	r2,=IntrTable
	add	r3,r3,#0x200

@---------------------------------------------------------------------------------
findIRQ:
@---------------------------------------------------------------------------------
	ldr	r0, [r2, #4]		@ Interrupt mask
	cmp	r0,#0
	beq	no_handler
	ands	r0, r0, r1
	bne	jump_intr
	add	r2, r2, #8
	b	findIRQ

@---------------------------------------------------------------------------------
no_handler:
@---------------------------------------------------------------------------------
	strh	r1, [r3, #0x02]		@ IF Clear
	ldmfd	sp!, {r0-r1,r3,lr}	@ {spsr, IME, REG_BASE, lr_irq}
	str	r1, [r3, #0x208]	@ restore REG_IME
	mov	pc,lr

@---------------------------------------------------------------------------------
jump_intr:
@---------------------------------------------------------------------------------
	ldr	r2, [r2]		@ user IRQ handler address
	cmp	r2, #0
	beq	no_handler

@---------------------------------------------------------------------------------
got_handler:
@---------------------------------------------------------------------------------

	mrs	r1, cpsr
	bic	r1, r1, #0xdf		@ \__
	orr	r1, r1, #0x1f		@ /  --> Enable IRQ & FIQ. Set CPU mode to System.
	msr	cpsr,r1

	strh	r0, [r3, #0x02]		@ IF Clear
	
	push	{lr}
	adr	lr, IntrRet
	bx	r2

@---------------------------------------------------------------------------------
IntrRet:
@---------------------------------------------------------------------------------
	pop	{lr}
	mov	r3, #0x4000000		@ REG_BASE
	str	r3, [r3, #0x208]	@ disable IME

	mrs	r3, cpsr
	bic	r3, r3, #0xdf		@ \__
	orr	r3, r3, #0x92		@ /  --> Disable IRQ. Enable FIQ. Set CPU mode to IRQ.
	msr	cpsr, r3

	ldmfd   sp!, {r0-r1,r3,lr}	@ {spsr, IME, REG_BASE, lr_irq}
	str	r1, [r3, #0x208]	@ restore REG_IME
	msr	spsr, r0		@ restore spsr
	mov	pc,lr

	.pool
	.end

This was designed so that an interruptible dispatcher could simply start with REG_IME = 1 although it should probably mask REG_IE as well if there's a risk that it could interrupt itself. There were some issues doing that automatically although I've forgotten what now - the last time I even looked at that code was sometime in 2007 when I fixed the interrupt nesting!

It uses a table of masks and function pointers to allow a sort of priority if multiple interrupts occurred simultaneously. Interrupts would be serviced in the order they were set using irqSet(mask, function) although in testing I could never get this to happen. Either I just failed in attempting to provoke simultaneous interrupts or the GBA hardware just doesn't allow it - never really figured that one out.

Advising people to use cygwin to compile the windows binaries isn't a great idea - a cygwin install will interfere with an msys install and vice versa. I chose msys to provide unix like tools for the devkitPro toolchains mainly because the mingw/msys combination was designed to produce native windows code rather than the peculiar hybrid you get with cygwin and the corresponding issues you end up with when you have multiple cygwin dlls in various places.

In theory it should be possible to get cmake working with msys/mingw so I might have a look at doing that when I get a bit of time

[sebk]

Hi WinterMute!

Thanks for your elaborate feedback.

What you wrote about interrupts and how they're handled in devkitPro makes sense. I didn't look at how interrupts are handled with devkitPro,
hence my remark on the TODO was written with having "the old way" in mind. I'll rephrase it and (if I may) link to your post so someone giving it a go doesn't start hacking at the wrong place.

I wasn't aware of the Cygwin-issue. Cygwin may not be required for building at all, because CMake is pretty much self-contained.

Cheers,
seb