# HG changeset patch
# User John Tsiombikas <nuclear@member.fsf.org>
# Date 1489463973 -7200
# Node ID ce1b05082ac4a979f27f0240c58369dfbdaf758a

initial commit

diff -r 000000000000 -r ce1b05082ac4 .hgignore
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/.hgignore	Tue Mar 14 05:59:33 2017 +0200
@@ -0,0 +1,6 @@
+\.o$
+\.swp$
+\.d$
+\.map$
+\.elf$
+\.bin$
diff -r 000000000000 -r ce1b05082ac4 Makefile
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Makefile	Tue Mar 14 05:59:33 2017 +0200
@@ -0,0 +1,51 @@
+csrc = $(wildcard src/*.c) $(wildcard src/libc/*.c)
+asrc = $(wildcard src/*.s)
+aSsrc = $(wildcard src/*.S)
+obj = $(asrc:.s=.o) $(aSsrc:.S=.o) $(csrc:.c=.o)
+
+name = test2
+elf = $(name).elf
+bin = $(name).bin
+
+warn = -pedantic -Wall
+dbg = -g
+def = -DGAMENAME=\"testgame\" -DVERSTR=\"01\" -D__NO_CTYPE
+inc = -Isrc/libc
+
+tool_prefix = m68k-linux-gnu-
+
+CC = $(tool_prefix)gcc
+AS = $(tool_prefix)as
+LD = $(tool_prefix)ld
+OBJCOPY = $(tool_prefix)objcopy
+
+CFLAGS = -m68000 -ffreestanding -fno-builtin $(warn) $(dbg) $(opt) $(def) $(inc)
+CPPFLAGS = $(def)
+ASFLAGS = -m68000
+LDFLAGS = -T megadrive.ldscript -print-gc-sections \
+		  -L/usr/lib/gcc-cross/m68k-linux-gnu/6 -lgcc
+
+$(bin): $(elf)
+	$(OBJCOPY) -O binary $< $@
+
+$(elf): $(obj)
+	$(LD) -o $@ $(obj) -Map link.map $(LDFLAGS)
+
+.PHONY: clean
+clean:
+	rm -f $(obj) $(elf) $(bin)
+
+.PHONY: run
+run: $(bin)
+	gens-sdl $<
+
+.PHONY: copy
+copy: $(bin)
+	mount /media/usbmass && cp $(bin) /media/usbmass/$(bin)
+	umount /media/usbmass
+
+.PHONY: install
+install: $(bin)
+	mount /media/usbmass
+	[ -f /media/usbmass/MEGA/MEGA.RBF ] || cp $(bin) /media/usbmass/MEGA/MEGA.BIN
+	umount /media/usbmass
diff -r 000000000000 -r ce1b05082ac4 megadrive.ldscript
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/megadrive.ldscript	Tue Mar 14 05:59:33 2017 +0200
@@ -0,0 +1,47 @@
+OUTPUT_ARCH(m68k)
+
+MEMORY
+{
+	rom : ORIGIN = 0x00000000, LENGTH = 0x00a00000
+	ram : ORIGIN = 0x00ff0000, LENGTH = 0x00010000
+}
+
+PROVIDE (_stacktop = 0x01000000);
+
+SECTIONS {
+	/* ---- start of ROM ---- */
+	/* .vect section is used to place the m68k exception vectors at the
+	 * beginning of the address space
+	 */
+	.vect : { * (.vect); } >rom
+	/* .romhdr section is used to place the SEGA ROM header at 0x100 */
+	. = 0x100;
+	.romhdr : { * (.romhdr); } >rom
+	.text : { * (.text); } >rom
+	.rodata : { * (.rodata); } >rom
+
+	/* place the load address of the .data section after .rodata */
+	. = ALIGN(4);
+	_data_lma = .;
+	_rom_end = _data_lma + _data_size;
+
+	/* ---- start of RAM ---- */
+	. = 0xff0000;
+	/* place the .data section at the start of RAM */
+	.data ALIGN(4): AT (_data_lma) {
+		_data_start = .;
+		* (.data);
+		. = ALIGN(4);
+		_data_end = .;
+	} >ram
+	_data_size = SIZEOF(.data);
+
+	/* place the .bss section at the end */
+	.bss ALIGN(4): {
+		_bss_start = .;
+		* (.bss);
+		. = ALIGN(4);
+		_bss_end = .;
+	} >ram
+	_bss_size = SIZEOF(.bss);
+}
diff -r 000000000000 -r ce1b05082ac4 src/intr.s
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/intr.s	Tue Mar 14 05:59:33 2017 +0200
@@ -0,0 +1,82 @@
+| the following will go into the .vect section which will be placed at the very
+| begining of the binary at address 0 by the linker (see lnkscript).
+	.section .vect,"a"
+	.extern start
+| exception vectors
+	.long _stacktop		| 00 reset - initial SSP
+	.long start		| 01 reset - initial PC
+	.long intr_fatal	| 02 bus error
+	.long intr_fatal	| 03 address error
+	.long intr_fatal	| 04 illegal instruction
+	.long intr_fatal	| 05 zero divide
+	.long intr_fatal	| 06 chk instruction
+	.long intr_fatal	| 07 trapv instruction
+	.long intr_fatal	| 08 privilege violation
+	.long intr_fatal	| 09 trace
+	.long intr_fatal	| 0a line 1010 emulator
+	.long intr_fatal	| 0b line 1111 emulator
+	.long intr_fatal	| 0c reserved
+	.long intr_fatal	| 0d reserved
+	.long intr_fatal	| 0e format error (mc68010 only)
+	.long intr_fatal	| 0f uninitialized interrupt vector
+	.long intr_fatal	| 10 \
+	.long intr_fatal	| 11 |
+	.long intr_fatal	| 12 |
+	.long intr_fatal	| 13  > reserved
+	.long intr_fatal	| 14 |
+	.long intr_fatal	| 15 |
+	.long intr_fatal	| 16 |
+	.long intr_fatal	| 17 /
+	.long intr_fatal	| 18 spurious interrupt 
+	.long intr_fatal	| 19 level 1 interrupt
+	.long intr_fatal	| 1a level 2 interrupt
+	.long intr_fatal	| 1b level 3 interrupt
+	.long intr_hblank	| 1c level 4 interrupt (hblank in the mega drive)
+	.long intr_fatal	| 1d level 5 interrupt
+	.long intr_vblank	| 1e level 6 interrupt (vblank in the mega drive)
+	.long intr_fatal	| 1f level 7 interrupt
+	.long intr_fatal	| 20 trap 0
+	.long intr_fatal	| 21 trap 1
+	.long intr_fatal	| 22 trap 2
+	.long intr_fatal	| 23 trap 3
+	.long intr_fatal	| 24 trap 4
+	.long intr_fatal	| 25 trap 5
+	.long intr_fatal	| 26 trap 6
+	.long intr_fatal	| 27 trap 7
+	.long intr_fatal	| 28 trap 8
+	.long intr_fatal	| 29 trap 9
+	.long intr_fatal	| 2a trap a
+	.long intr_fatal	| 2b trap b
+	.long intr_fatal	| 2c trap c
+	.long intr_fatal	| 2d trap d
+	.long intr_fatal	| 2e trap e
+	.long intr_fatal	| 2f trap f
+	.long intr_fatal	| 30 \
+	.long intr_fatal	| 31 |
+	.long intr_fatal	| 32 |
+	.long intr_fatal	| 33 |
+	.long intr_fatal	| 34 |
+	.long intr_fatal	| 35 |
+	.long intr_fatal	| 36 |
+	.long intr_fatal	| 37 |
+	.long intr_fatal	| 38  > reserved
+	.long intr_fatal	| 39 |
+	.long intr_fatal	| 3a |
+	.long intr_fatal	| 3b |
+	.long intr_fatal	| 3c |
+	.long intr_fatal	| 3d |
+	.long intr_fatal	| 3e |
+	.long intr_fatal	| 3f /
+
+| from here on we continue in the regular .text section since we don't care
+| where this code ends up.
+	.text
+| interrupt handlers
+intr_fatal:
+	stop #0x2700
+
+| TODO hblank/vblank code
+intr_hblank:
+	rte
+intr_vblank:
+	rte
diff -r 000000000000 -r ce1b05082ac4 src/main.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/main.c	Tue Mar 14 05:59:33 2017 +0200
@@ -0,0 +1,13 @@
+#include "vdp.h"
+
+int main(void)
+{
+	vdp_init();
+
+	vdp_set_pal_entry(0, 1, 7, 0, 3);
+	vdp_set_bgcolor(0, 1);
+
+	for(;;);
+
+	return 0;
+}
diff -r 000000000000 -r ce1b05082ac4 src/romhdr.S
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/romhdr.S	Tue Mar 14 05:59:33 2017 +0200
@@ -0,0 +1,37 @@
+| the following will go into the custom .romhdr section which will be placed at
+| address 100h of the binary by the linker (see lnkscript).
+	.section .romhdr,"a"
+
+#ifndef GAMENAME
+#define GAMENAME "unnamed"
+#endif
+#ifndef VERSTR
+#define VERSTR "00"
+#endif
+
+	.ascii "SEGA MEGA DRIVE (C)MINDLAPSE2017"
+hdr_game_dom:
+	.ascii GAMENAME
+hdr_game_dom_end:
+	.fill 48 - (hdr_game_dom_end - hdr_game_dom),1,32 | pad to 48 bytes with spaces
+hdr_game_int:
+	.ascii GAMENAME
+hdr_game_int_end:
+	.fill 48 - (hdr_game_int_end - hdr_game_int),1,32 | pad to 48 bytes with spaces
+	.ascii "GM"		| it's a game (who cares what it is?)
+	.ascii "0000000-"	| product code
+	.ascii VERSTR		| version string
+	.short 0		| checksum
+	.ascii "J               " | I/O support (joypad)
+	.long 0			| start address of ROM
+	.long _rom_end		| last address of ROM
+	.long 0xff0000		| start address of RAM
+	.long 0xffffff		| last address of RAM
+	.long 0			| SRAM enabled(?)
+	.long 0			| ???
+	.long 0			| start address of SRAM
+	.long 0			| last address of SRAM
+	.long 0			| ???
+	.long 0			| ???
+	.fill 40,1,32		| notes (fill with spaces for now TODO)
+	.ascii "JUE             " | country codes
diff -r 000000000000 -r ce1b05082ac4 src/startup.s
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/startup.s	Tue Mar 14 05:59:33 2017 +0200
@@ -0,0 +1,47 @@
+	.text
+	.extern main
+
+	.global start
+	.global halt_cpu
+start:
+	bsr.s disable_intr
+
+	| copy .data section from ROM to RAM
+	move.l #_data_lma, %a0
+	move.l #_data_start, %a1
+	move.l #_data_end, %a2
+	cmp.l %a1, %a2
+	beq.s 1f	| skip data copy if the section is empty
+0:	move.l (%a0)+, (%a1)+
+	cmp.l %a1, %a2
+	bne.s 0b
+1:
+
+	| zero the .bss section
+	move.l #_bss_start, %a0
+	move.l #_bss_end, %a1
+	cmp.l %a0, %a1
+	beq.s 1f	| skip bss zeroing if the section is empty
+0:	clr.l (%a0)+
+	cmp.l %a0, %a1
+	bne.s 0b
+1:
+
+	| setup the stack pointer stack
+	move.l #_stacktop, %sp
+	| now that we have a stack, we can enable interrupts
+	bsr.s enable_intr
+
+	jsr main
+halt_cpu:
+	stop #0x2700
+
+.global enable_intr
+enable_intr:
+	andi.w #0xf8ff, %sr
+	rts
+
+.global disable_intr
+disable_intr:
+	ori.w #0x0300, %sr
+	rts
diff -r 000000000000 -r ce1b05082ac4 src/vdp.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/vdp.c	Tue Mar 14 05:59:33 2017 +0200
@@ -0,0 +1,9 @@
+#include "vdp.h"
+
+void vdp_init(void)
+{
+	vdp_setreg(VDP_REG_MODE1, VDP_MODE1_BASE);
+	vdp_setreg(VDP_REG_MODE2, VDP_MODE2_BASE | VDP_MODE2_DISP);
+
+	vdp_set_autoinc(2);
+}
diff -r 000000000000 -r ce1b05082ac4 src/vdp.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/vdp.h	Tue Mar 14 05:59:33 2017 +0200
@@ -0,0 +1,157 @@
+#ifndef VDP_H_
+#define VDP_H_
+
+#include <stdint.h>
+
+#define VDP_PORT_DATA		*((volatile uint16_t*)0xc00000)
+#define VDP_PORT_DATA32		*((volatile uint32_t*)0xc00000)
+#define VDP_PORT_CTL		*((volatile uint16_t*)0xc00004)
+#define VDP_PORT_CTL32		*((volatile uint32_t*)0xc00004)
+#define VDP_PORT_HVCNT		*((volatile uint16_t*)0xc00008)
+#define VDP_PORT_PSG		*((volatile uint16_t*)0xc00010)
+
+#define VDP_PORT_STATUS		*((volatile uint16_t*)0xc00004)
+
+enum {
+	VDP_REG_MODE1			= 0,
+	VDP_REG_MODE2			= 1,
+	VDP_REG_NAMETAB_A		= 2,
+	VDP_REG_NAMETAB_WIN		= 3,
+	VDP_REG_NAMETAB_B		= 4,
+	VDP_REG_SPRITE_TAB		= 5,
+	VDP_REG_BGCOL			= 7,
+	VDP_REG_INTR			= 10,
+	VDP_REG_MODE3			= 11,
+	VDP_REG_MODE4			= 12,
+	VDP_REG_SCROLL_TAB		= 13,
+	VDP_REG_AUTOINC			= 15,
+	VDP_REG_SCROLL_SIZE		= 16,
+	VDP_REG_WIN_XPOS		= 17,
+	VDP_REG_WIN_YPOS		= 18,
+	VDP_REG_DMA_LEN_LOW		= 19,
+	VDP_REG_DMA_LEN_HIGH	= 20,
+	VDP_REG_DMA_SRC_LOW		= 21,
+	VDP_REG_DMA_SRC_MID		= 22,
+	VDP_REG_DMA_SRC_HIGH	= 23,
+
+	VDP_NUM_REGS
+};
+
+uint16_t vdp_reg_shadow[VDP_NUM_REGS];
+
+/* access VDP memory */
+enum { VDP_MEM_READ, VDP_MEM_WRITE };
+enum {
+	VDP_MEM_VRAM	= 0,
+	VDP_MEM_CRAM	= 0xa,	/* CD5->CD0: 0 0 r 0 w 0 */
+	VDP_MEM_VSRAM	= 4		/* CD5->CD0: 0 0 0 1 0 0 */
+};
+
+static inline void vdp_setup_access(uint16_t addr, int rw, int memid)
+{
+	uint32_t type;
+	if(rw == VDP_MEM_WRITE) {
+		type = (memid & 7) | 1;
+	} else {
+		type = memid & 0xc;
+	}
+
+	VDP_PORT_CTL32 = (((uint32_t)addr & 0x3fff) << 16) | ((addr >> 14) & 3) |
+		((type << 2) & 0xf0) | (type << 30);
+}
+
+
+/* mode register 1 */
+enum {
+	VDP_MODE1_BASE	= 0x4,
+	VDP_MODE1_HVCNT = 0x2,
+	VDP_MODE1_HINTR = 0x10
+};
+
+/* mode register 2 */
+enum {
+	VDP_MODE2_BASE		= 0x4,
+	VDP_MODE2_V30CELL	= 0x8,
+	VDP_MODE2_DMA		= 0x10,
+	VDP_MODE2_VINTR		= 0x20,
+	VDP_MODE2_DISP		= 0x40
+};
+
+/* mode register 3 */
+enum {
+	VDP_MODE3_BASE			= 0,
+	VDP_MODE3_HSCROLL_CELL	= 2,
+	VDP_MODE3_HSCROLL_LINE	= 3,
+	VDP_MODE3_VSCROLL_2CELL	= 4,
+	VDP_MODE3_EXTINTR		= 8
+};
+
+/* mode register 4 */
+enum {
+	VDP_MODE4_BASE			= 0,
+	VDP_MODE4_H40CELL		= 0x81,
+	VDP_MODE4_ILACE			= 2,
+	VDP_MODE4_ILACE_2XRES	= 6,
+	VDP_MODE4_SH			= 8	/* shadow/highlight enable */
+};
+
+/* scroll size register */
+enum {
+	VDP_SCROLL_H32		= 0,
+	VDP_SCROLL_H64		= 1,
+	VDP_SCROLL_H128		= 3,
+	VDP_SCROLL_V32		= 0,
+	VDP_SCROLL_V64		= 0x10,
+	VDP_SCROLL_V128		= 0x30
+};
+
+/* window X/Y position register */
+enum {
+	VDP_WIN_LEFT	= 0,
+	VDP_WIN_UP		= 0,
+	VDP_WIN_RIGHT	= 0x80,
+	VDP_WIN_DOWN	= 0x80,
+	VDP_WIN_POSMASK	= 0x1f
+};
+
+#define VDP_PACK_RGB(r, g, b)	\
+	((((uint16_t)(r) & 7) << 1) | (((uint16_t)(g) & 7) << 5) | (((uint16_t)(b) & 7) << 9))
+
+
+static inline void vdp_setreg(int reg, uint8_t value)
+{
+	/*vdp_reg_shadow[reg] = value;*/
+	VDP_PORT_CTL = (uint16_t)value | (reg << 8) | (uint16_t)0x8000;
+}
+
+static inline uint16_t vdp_getreg(int reg)
+{
+	return vdp_reg_shadow[reg];
+}
+
+static inline uint16_t vdp_status(void)
+{
+	return VDP_PORT_CTL;
+}
+
+static inline void vdp_set_bgcolor(int palidx, int colidx)
+{
+	vdp_setreg(VDP_REG_BGCOL, (colidx & 0xf) | (palidx << 4));
+}
+
+static inline void vdp_set_autoinc(int stride)
+{
+	vdp_setreg(VDP_REG_AUTOINC, stride);
+}
+
+static inline void vdp_set_pal_entry(int pidx, int cidx, int r, int g, int b)
+{
+	uint16_t paddr = (pidx << 5) | (cidx << 1);
+
+	vdp_setup_access(paddr, VDP_MEM_WRITE, VDP_MEM_CRAM);
+	VDP_PORT_DATA = VDP_PACK_RGB(r, g, b);
+}
+
+void vdp_init(void);
+
+#endif	/* VDP_H_ */