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Bus: Better managing of memory access from Bus
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@AlessioC31
AlessioC31 committed Aug 3, 2023
1 parent e7865ad commit 41924ef
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259 changes: 249 additions & 10 deletions emu/src/bus.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,6 @@ use crate::bitwise::Bits;
use crate::cpu::hardware::lcd::Lcd;
use crate::cpu::hardware::HardwareComponent;
use crate::memory::{internal_memory::InternalMemory, io_device::IoDevice};
use crate::cpu::hardware::lcd::Lcd;

#[derive(Default)]
pub struct Bus {
Expand All @@ -18,20 +17,173 @@ pub struct Bus {
}

impl Bus {
pub fn read_at(&mut self, address: usize) -> u8 {
fn read_lcd_raw(&self, address: usize) -> u8 {
match address {
0x04000000 => self.lcd.dispcnt.get_byte(0),
0x04000001 => self.lcd.dispcnt.get_byte(1),
0x04000002 => self.lcd.green_swap.get_byte(0),
0x04000003 => self.lcd.green_swap.get_byte(1),
0x04000004 => self.lcd.dispstat.get_byte(0),
0x04000005 => self.lcd.dispstat.get_byte(1),
0x04000006 => self.lcd.vcount.get_byte(0),
0x04000007 => self.lcd.vcount.get_byte(1),
0x04000008 => self.lcd.bg0cnt.get_byte(0),
0x04000009 => self.lcd.bg0cnt.get_byte(1),
0x0400000A => self.lcd.bg1cnt.get_byte(0),
0x0400000B => self.lcd.bg1cnt.get_byte(1),
0x0400000C => self.lcd.bg2cnt.get_byte(0),
0x0400000D => self.lcd.bg2cnt.get_byte(1),
0x0400000E => self.lcd.bg3cnt.get_byte(0),
0x0400000F => self.lcd.bg3cnt.get_byte(1),
0x04000010..=0x04000047 => panic!("Reading a write-only LCD I/O register"),
0x04000048 => self.lcd.winin.get_byte(0),
0x04000049 => self.lcd.winin.get_byte(1),
0x0400004A => self.lcd.winout.get_byte(0),
0x0400004B => self.lcd.winout.get_byte(1),
0x0400004C => self.lcd.mosaic.get_byte(0),
0x0400004D => self.lcd.mosaic.get_byte(1),
0x04000050 => self.lcd.bldcnt.get_byte(0),
0x04000051 => self.lcd.bldcnt.get_byte(1),
0x04000052 => self.lcd.bldalpha.get_byte(0),
0x04000053 => self.lcd.bldalpha.get_byte(1),
0x04000054..=0x04000055 => panic!("Reading a write-only LCD I/O register"),
0x0400004E..=0x0400004F | 0x04000056..=0x0400005F => {
log("read on unused memory");
self.unused_region.get(&address).map_or(0, |v| *v)
}
_ => panic!("LCD read address is out of bound"),
}
}

fn write_lcd_raw(&mut self, address: usize, value: u8) {
match address {
0x04000000 => self.lcd.dispcnt.set_byte(0, value),
0x04000001 => self.lcd.dispcnt.set_byte(1, value),
0x04000002 => self.lcd.green_swap.set_byte(0, value),
0x04000003 => self.lcd.green_swap.set_byte(1, value),
0x04000004 => self.lcd.dispstat.set_byte(0, value),
0x04000005 => self.lcd.dispstat.set_byte(1, value),
0x04000008 => self.lcd.bg0cnt.set_byte(0, value),
0x04000006 => self.lcd.vcount.set_byte(0, value),
0x04000007 => self.lcd.vcount.set_byte(1, value),
0x04000009 => self.lcd.bg0cnt.set_byte(1, value),
0x0400000A => self.lcd.bg1cnt.set_byte(0, value),
0x0400000B => self.lcd.bg1cnt.set_byte(1, value),
0x0400000C => self.lcd.bg2cnt.set_byte(0, value),
0x0400000D => self.lcd.bg2cnt.set_byte(1, value),
0x0400000E => self.lcd.bg3cnt.set_byte(0, value),
0x0400000F => self.lcd.bg3cnt.set_byte(1, value),
0x04000010 => self.lcd.bg0hofs.set_byte(0, value),
0x04000011 => self.lcd.bg0hofs.set_byte(1, value),
0x04000012 => self.lcd.bg0vofs.set_byte(0, value),
0x04000013 => self.lcd.bg0vofs.set_byte(1, value),
0x04000014 => self.lcd.bg1hofs.set_byte(0, value),
0x04000015 => self.lcd.bg1hofs.set_byte(1, value),
0x04000016 => self.lcd.bg1vofs.set_byte(0, value),
0x04000017 => self.lcd.bg1vofs.set_byte(1, value),
0x04000018 => self.lcd.bg2hofs.set_byte(0, value),
0x04000019 => self.lcd.bg2hofs.set_byte(1, value),
0x0400001A => self.lcd.bg2vofs.set_byte(0, value),
0x0400001B => self.lcd.bg2vofs.set_byte(1, value),
0x0400001C => self.lcd.bg3hofs.set_byte(0, value),
0x0400001D => self.lcd.bg3hofs.set_byte(1, value),
0x0400001E => self.lcd.bg3vofs.set_byte(0, value),
0x0400001F => self.lcd.bg3vofs.set_byte(1, value),
0x04000020 => self.lcd.bg2pa.set_byte(0, value),
0x04000021 => self.lcd.bg2pa.set_byte(1, value),
0x04000022 => self.lcd.bg2pb.set_byte(0, value),
0x04000023 => self.lcd.bg2pb.set_byte(1, value),
0x04000024 => self.lcd.bg2pc.set_byte(0, value),
0x04000025 => self.lcd.bg2pc.set_byte(1, value),
0x04000026 => self.lcd.bg2pd.set_byte(0, value),
0x04000027 => self.lcd.bg2pd.set_byte(1, value),
0x04000028 => self.lcd.bg2x.set_byte(0, value),
0x04000029 => self.lcd.bg2x.set_byte(1, value),
0x0400002A => self.lcd.bg2x.set_byte(2, value),
0x0400002B => self.lcd.bg2x.set_byte(3, value),
0x0400002C => self.lcd.bg2y.set_byte(0, value),
0x0400002D => self.lcd.bg2y.set_byte(1, value),
0x0400002E => self.lcd.bg2y.set_byte(2, value),
0x0400002F => self.lcd.bg2y.set_byte(3, value),
0x04000030 => self.lcd.bg3pa.set_byte(0, value),
0x04000031 => self.lcd.bg3pa.set_byte(1, value),
0x04000032 => self.lcd.bg3pb.set_byte(0, value),
0x04000033 => self.lcd.bg3pb.set_byte(1, value),
0x04000034 => self.lcd.bg3pc.set_byte(0, value),
0x04000035 => self.lcd.bg3pc.set_byte(1, value),
0x04000036 => self.lcd.bg3pd.set_byte(0, value),
0x04000037 => self.lcd.bg3pd.set_byte(1, value),
0x04000038 => self.lcd.bg3x.set_byte(0, value),
0x04000039 => self.lcd.bg3x.set_byte(1, value),
0x0400003A => self.lcd.bg3x.set_byte(2, value),
0x0400003B => self.lcd.bg3x.set_byte(3, value),
0x0400003C => self.lcd.bg3y.set_byte(0, value),
0x0400003D => self.lcd.bg3y.set_byte(1, value),
0x0400003E => self.lcd.bg3y.set_byte(2, value),
0x0400003F => self.lcd.bg3y.set_byte(3, value),
0x04000040 => self.lcd.win0h.set_byte(0, value),
0x04000041 => self.lcd.win0h.set_byte(1, value),
0x04000042 => self.lcd.win1h.set_byte(0, value),
0x04000043 => self.lcd.win1h.set_byte(1, value),
0x04000044 => self.lcd.win0v.set_byte(0, value),
0x04000045 => self.lcd.win0v.set_byte(1, value),
0x04000046 => self.lcd.win1v.set_byte(0, value),
0x04000047 => self.lcd.win1v.set_byte(1, value),
0x04000048 => self.lcd.winin.set_byte(0, value),
0x04000049 => self.lcd.winin.set_byte(1, value),
0x0400004A => self.lcd.winout.set_byte(0, value),
0x0400004B => self.lcd.winout.set_byte(1, value),
0x0400004C => self.lcd.mosaic.set_byte(0, value),
0x0400004D => self.lcd.mosaic.set_byte(1, value),
// 0x0400004E, 0x0400004F are not used
0x04000050 => self.lcd.bldcnt.set_byte(0, value),
0x04000051 => self.lcd.bldcnt.set_byte(1, value),
0x04000052 => self.lcd.bldalpha.set_byte(0, value),
0x04000053 => self.lcd.bldalpha.set_byte(1, value),
0x04000054 => self.lcd.bldy.set_byte(0, value),
0x04000055 => self.lcd.bldy.set_byte(1, value),
0x0400004E..=0x0400004F | 0x04000056..=0x0400005F => {
log("write on unused memory");
self.unused_region.insert(address, value);
}
_ => panic!("LCD write address is out of bound"),
}
}

fn read_raw(&self, address: usize) -> u8 {
match address {
0x4000000..=0x4000057 => self.read_lcd_raw(address),
// TODO: change also other devices similar to how LCD is handled
_ => self.internal_memory.read_at(address),
}
}

fn write_raw(&mut self, address: usize, value: u8) {
match address {
0x4000000..=0x4000057 => self.write_lcd_raw(address, value),
// TODO: read read_raw
_ => self.internal_memory.write_at(address, value),
}
}

pub fn read_byte(&mut self, address: usize) -> u8 {
for _ in 0..self.get_wait_cycles(address) {
self.step();
}

self.internal_memory.read_at(address)
self.last_used_address = address;

self.read_raw(address)
}

pub fn write_at(&mut self, address: usize, value: u8) {
pub fn write_byte(&mut self, address: usize, value: u8) {
for _ in 0..self.get_wait_cycles(address) {
self.step();
}

self.internal_memory.write_at(address, value);
self.last_used_address = address;

self.write_raw(address, value);
}

fn step(&mut self) {
Expand Down Expand Up @@ -59,7 +211,10 @@ impl Bus {
.unwrap();
self.internal_memory.interrupts.interrupt_request.push(val);

self.internal_memory.step(); // FIXME: We can do better than this.
// A pixel takes 4 cycles to get drawn
if self.cycles_count % 4 == 0 {
self.lcd.step();
}
}

pub fn with_memory(memory: InternalMemory) -> Self {
Expand All @@ -81,38 +236,122 @@ impl Bus {
}

pub fn read_word(&mut self, address: usize) -> u32 {
// TODO: here we have to see how many times to wait for the waitcycles
// It depends on the bus width of the memory region
// Right now we're assuming that every region has a bus width of 32 bits
// So we wait only once to read a word.
// In reality for example WRAM has a bus width of 16 bits so we would
// have to repeat this cycle 2 times (to emulate the fact that we will access the memory
// two times)
for _ in 0..self.get_wait_cycles(address) {
self.step();
}

self.last_used_address = address;

self.internal_memory.read_word(address)
if address & 3 != 0 {
log("warning, read_word has address not word aligned");
}

let part_0: u32 = self.read_raw(address).try_into().unwrap();
let part_1: u32 = self.read_raw(address + 1).try_into().unwrap();
let part_2: u32 = self.read_raw(address + 2).try_into().unwrap();
let part_3: u32 = self.read_raw(address + 3).try_into().unwrap();

part_3 << 24_u32 | part_2 << 16_u32 | part_1 << 8_u32 | part_0
}

pub fn write_word(&mut self, address: usize, value: u32) {
// TODO: Look at read_word
for _ in 0..self.get_wait_cycles(address) {
self.step();
}

self.last_used_address = address;

self.internal_memory.write_word(address, value);
if address & 3 != 0 {
log("warning, write_word has address not word aligned");
}

let part_0: u8 = value.get_bits(0..=7).try_into().unwrap();
let part_1: u8 = value.get_bits(8..=15).try_into().unwrap();
let part_2: u8 = value.get_bits(16..=23).try_into().unwrap();
let part_3: u8 = value.get_bits(24..=31).try_into().unwrap();

self.write_raw(address, part_0);
self.write_raw(address + 1, part_1);
self.write_raw(address + 2, part_2);
self.write_raw(address + 3, part_3);
}

pub fn read_half_word(&mut self, address: usize) -> u16 {
// TODO: Look at read_word
for _ in 0..self.get_wait_cycles(address) {
self.step();
}

self.internal_memory.read_half_word(address)
self.last_used_address = address;

if address & 1 != 0 {
log("warning, read_half_word has address not half-word aligned");
}

let part_0: u16 = self.read_raw(address).try_into().unwrap();
let part_1: u16 = self.read_raw(address + 1).try_into().unwrap();

part_1 << 8 | part_0
}

pub fn write_half_word(&mut self, address: usize, value: u16) {
// TODO: Look at read_word
for _ in 0..self.get_wait_cycles(address) {
self.step();
}

self.internal_memory.write_half_word(address, value);
self.last_used_address = address;

if address & 1 != 0 {
log("warning, write_half_word has address not half-word aligned");
}

let part_0: u8 = value.get_bits(0..=7).try_into().unwrap();
let part_1: u8 = value.get_bits(8..=15).try_into().unwrap();

self.write_raw(address, part_0);
self.write_raw(address + 1, part_1);
}
}

#[cfg(test)]
mod tests {
use crate::bus::Bus;

#[test]
fn test_write_lcd_reg() {
let mut bus = Bus::default();
let address = 0x04000048; // WININ lower byte

bus.write_raw(address, 10);

assert_eq!(bus.lcd.winin, 10);

let address = 0x04000049; // WININ higher byte

bus.write_raw(address, 5);
assert_eq!(bus.lcd.winin, (5 << 8) | 10);
}

#[test]
fn test_read_lcd_reg() {
let mut bus = Bus::default();
let address = 0x04000048; // WININ lower byte

bus.lcd.winin = (5 << 8) | 10;

assert_eq!(bus.read_raw(address), 10);

let address = 0x04000049; // WININ higher byte

assert_eq!(bus.read_raw(address), 5);
}
}
18 changes: 6 additions & 12 deletions emu/src/cpu/arm/operations.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -579,7 +579,7 @@ impl Arm7tdmi {
.set_register_at(source_destination_register as usize, v.into());
}
HalfwordTransferKind::SignedByte => {
let v = self.bus.read_at(address) as u32;
let v = self.bus.read_byte(address) as u32;
self.registers
.set_register_at(source_destination_register as usize, v.sign_extended(8));
}
Expand Down Expand Up @@ -656,7 +656,7 @@ impl Arm7tdmi {
match kind {
SingleDataTransferKind::Ldr => match quantity {
ReadWriteKind::Byte => {
let value = self.bus.read_at(address) as u32;
let value = self.bus.read_byte(address) as u32;
self.registers
.set_register_at(rd.try_into().unwrap(), value)
}
Expand All @@ -674,7 +674,7 @@ impl Arm7tdmi {
v += 4;
}

self.bus.write_at(address, v as u8)
self.bus.write_byte(address, v as u8)
}
ReadWriteKind::Word => {
let mut v = self.registers.register_at(rd.try_into().unwrap());
Expand All @@ -684,10 +684,7 @@ impl Arm7tdmi {
v += 4;
}

self.bus.write_at(address, v.get_bits(0..=7) as u8);
self.bus.write_at(address + 1, v.get_bits(8..=15) as u8);
self.bus.write_at(address + 2, v.get_bits(16..=23) as u8);
self.bus.write_at(address + 3, v.get_bits(24..=31) as u8);
self.bus.write_word(address, v);
}
},
_ => todo!("implement single data transfer operation"),
Expand Down Expand Up @@ -2416,7 +2413,7 @@ mod tests {
cpu.registers.set_program_counter(0x03000050);

// simulate mem already contains something.
cpu.bus.write_at(0x03000068, 99);
cpu.bus.write_byte(0x03000068, 99);

cpu.execute_arm(op_code);
assert_eq!(cpu.registers.register_at(13), 99);
Expand Down Expand Up @@ -2540,10 +2537,7 @@ mod tests {

// simulate mem already contains something.
// in u32 this is 16843009 00000001_00000001_00000001_00000001.
cpu.bus.write_at(0x28, 1);
cpu.bus.write_at(0x28 + 1, 1);
cpu.bus.write_at(0x28 + 2, 1);
cpu.bus.write_at(0x28 + 3, 1);
cpu.bus.write_word(0x28, 0x01010101);
cpu.execute_arm(op_code);
assert_eq!(cpu.registers.register_at(13), 16843009);
assert_eq!(cpu.registers.program_counter(), 0);
Expand Down
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