feat(cpu): implement skipBios method

GBA Bios requires a lot of implemented features, so we're ignoring it
for now

src/bus.zig

@@ -1,5 +1,6 @@
 const std = @import("std");
 
+const Io = @import("bus/io.zig").Io;
 const Bios = @import("bus/bios.zig").Bios;
 const GamePak = @import("bus/pak.zig").GamePak;
 const Allocator = std.mem.Allocator;
@@ -7,12 +8,14 @@ const Allocator = std.mem.Allocator;
 pub const Bus = struct {
     pak: GamePak,
     bios: Bios,
+    io: Io,
 
-    pub fn withPak(alloc: Allocator, path: []const u8) !@This() {
+    pub fn init(alloc: Allocator, path: []const u8) !@This() {
         return @This(){
-            .pak = try GamePak.fromPath(alloc, path),
+            .pak = try GamePak.init(alloc, path),
             // TODO: don't hardcode this + bundle open-sorce Boot ROM
-            .bios = try Bios.fromPath(alloc, "./bin/gba_bios.bin"),
+            .bios = try Bios.init(alloc, "./bin/gba_bios.bin"),
+            .io = Io.init(),
         };
     }
 
@@ -20,14 +23,14 @@ pub const Bus = struct {
         return switch (addr) {
             // General Internal Memory
             0x0000_0000...0x0000_3FFF => self.bios.get32(@as(usize, addr)),
-            0x0200_0000...0x0203FFFF => std.debug.panic("read32 from 0x{X:} in IWRAM", .{addr}),
-            0x0300_0000...0x0300_7FFF => std.debug.panic("read32 from 0x{X:} in EWRAM", .{addr}),
-            0x0400_0000...0x0400_03FE => std.debug.panic("read32 from 0x{X:} in I/O", .{addr}),
+            0x0200_0000...0x0203_FFFF => std.debug.panic("[Bus:32] read from 0x{X:} in IWRAM", .{addr}),
+            0x0300_0000...0x0300_7FFF => std.debug.panic("[Bus:32] read from 0x{X:} in EWRAM", .{addr}),
+            0x0400_0000...0x0400_03FE => self.read32(addr),
 
             // Internal Display Memory
-            0x0500_0000...0x0500_03FF => std.debug.panic("read32 from 0x{X:} in BG/OBJ Palette RAM", .{addr}),
-            0x0600_0000...0x0601_7FFF => std.debug.panic("read32 from 0x{X:} in VRAM", .{addr}),
-            0x0700_0000...0x0700_03FF => std.debug.panic("read32 from 0x{X:} in OAM", .{addr}),
+            0x0500_0000...0x0500_03FF => std.debug.panic("[Bus:32] read from 0x{X:} in BG/OBJ Palette RAM", .{addr}),
+            0x0600_0000...0x0601_7FFF => std.debug.panic("[Bus:32] read from 0x{X:} in VRAM", .{addr}),
+            0x0700_0000...0x0700_03FF => std.debug.panic("[Bus:32] read from 0x{X:} in OAM", .{addr}),
 
             // External Memory (Game Pak)
             0x0800_0000...0x09FF_FFFF => self.pak.get32(@as(usize, addr - 0x0800_0000)),
@@ -35,7 +38,7 @@ pub const Bus = struct {
             0x0C00_0000...0x0DFF_FFFF => self.pak.get32(@as(usize, addr - 0x0C00_0000)),
 
             else => {
-                std.log.warn("ZBA tried to read32 from 0x{X:}", .{addr});
+                std.log.warn("[Bus:32] ZBA tried to read from 0x{X:}", .{addr});
                 return 0x0000_0000;
             },
         };
@@ -46,16 +49,16 @@ pub const Bus = struct {
 
         switch (addr) {
             // General Internal Memory
-            0x0200_0000...0x0203FFFF => std.debug.panic("write32 0x{X:} to 0x{X:} in IWRAM", .{ word, addr }),
-            0x0300_0000...0x0300_7FFF => std.debug.panic("write32 0x{X:} to 0x{X:} in EWRAM", .{ word, addr }),
-            0x0400_0000...0x0400_03FE => std.debug.panic("write32 0x{X:} to 0x{X:} in I/O", .{ word, addr }),
+            0x0200_0000...0x0203_FFFF => std.debug.panic("[Bus:32] wrote 0x{X:} to 0x{X:} in IWRAM", .{ word, addr }),
+            0x0300_0000...0x0300_7FFF => std.debug.panic("[Bus:32] wrote 0x{X:} to 0x{X:} in EWRAM", .{ word, addr }),
+            0x0400_0000...0x0400_03FE => std.debug.panic("[Bus:32] wrote 0x{X:} to 0x{X:} in I/O", .{ word, addr }),
 
             // Internal Display Memory
-            0x0500_0000...0x0500_03FF => std.debug.panic("write32 0x{X:} to 0x{X:} in BG/OBJ Palette RAM", .{ word, addr }),
-            0x0600_0000...0x0601_7FFF => std.debug.panic("write32 0x{X:} to 0x{X:} in VRAM", .{ word, addr }),
-            0x0700_0000...0x0700_03FF => std.debug.panic("write32 0x{X:} to 0x{X:} in OAM", .{ word, addr }),
+            0x0500_0000...0x0500_03FF => std.debug.panic("[Bus:32] wrote 0x{X:} to 0x{X:} in BG/OBJ Palette RAM", .{ word, addr }),
+            0x0600_0000...0x0601_7FFF => std.debug.panic("[Bus:32] wrote 0x{X:} to 0x{X:} in VRAM", .{ word, addr }),
+            0x0700_0000...0x0700_03FF => std.debug.panic("[Bus:32] wrote 0x{X:} to 0x{X:} in OAM", .{ word, addr }),
 
-            else => std.log.warn("ZBA tried to write32 0x{X:} to 0x{X:}", .{ word, addr }),
+            else => std.log.warn("[Bus:32] ZBA tried to write 0x{X:} to 0x{X:}", .{ word, addr }),
         }
     }
 
@@ -63,14 +66,14 @@ pub const Bus = struct {
         return switch (addr) {
             // General Internal Memory
             0x0000_0000...0x0000_3FFF => self.bios.get16(@as(usize, addr)),
-            0x0200_0000...0x0203FFFF => std.debug.panic("read16 from 0x{X:} in IWRAM", .{addr}),
-            0x0300_0000...0x0300_7FFF => std.debug.panic("read16 from 0x{X:} in EWRAM", .{addr}),
-            0x0400_0000...0x0400_03FE => std.debug.panic("read16 from 0x{X:} in I/O", .{addr}),
+            0x0200_0000...0x0203_FFFF => std.debug.panic("[Bus:16] read from 0x{X:} in IWRAM", .{addr}),
+            0x0300_0000...0x0300_7FFF => std.debug.panic("[Bus:16] read from 0x{X:} in EWRAM", .{addr}),
+            0x0400_0000...0x0400_03FE => self.io.read16(addr),
 
             // Internal Display Memory
-            0x0500_0000...0x0500_03FF => std.debug.panic("read16 from 0x{X:} in BG/OBJ Palette RAM", .{addr}),
-            0x0600_0000...0x0601_7FFF => std.debug.panic("read16 from 0x{X:} in VRAM", .{addr}),
-            0x0700_0000...0x0700_03FF => std.debug.panic("read16 from 0x{X:} in OAM", .{addr}),
+            0x0500_0000...0x0500_03FF => std.debug.panic("[Bus:16] read from 0x{X:} in BG/OBJ Palette RAM", .{addr}),
+            0x0600_0000...0x0601_7FFF => std.debug.panic("[Bus:16] read from 0x{X:} in VRAM", .{addr}),
+            0x0700_0000...0x0700_03FF => std.debug.panic("[Bus:16] read from 0x{X:} in OAM", .{addr}),
 
             // External Memory (Game Pak)
             0x0800_0000...0x09FF_FFFF => self.pak.get16(@as(usize, addr - 0x0800_0000)),
@@ -78,27 +81,27 @@ pub const Bus = struct {
             0x0C00_0000...0x0DFF_FFFF => self.pak.get16(@as(usize, addr - 0x0C00_0000)),
 
             else => {
-                std.log.warn("ZBA tried to read16 from 0x{X:}", .{addr});
+                std.log.warn("[Bus:16] ZBA tried to read from 0x{X:}", .{addr});
                 return 0x0000;
             },
         };
     }
 
-    pub fn write16(_: *@This(), addr: u32, halfword: u16) void {
+    pub fn write16(self: *@This(), addr: u32, halfword: u16) void {
         // TODO: write16 can write to GamePak Flash
 
         switch (addr) {
             // General Internal Memory
-            0x0200_0000...0x0203FFFF => std.debug.panic("write16 0x{X:} to 0x{X:} in IWRAM", .{ halfword, addr }),
-            0x0300_0000...0x0300_7FFF => std.debug.panic("write16 0x{X:} to 0x{X:} in EWRAM", .{ halfword, addr }),
-            0x0400_0000...0x0400_03FE => std.debug.panic("write16 0x{X:} to 0x{X:} in I/O", .{ halfword, addr }),
+            0x0200_0000...0x0203_FFFF => std.debug.panic("[Bus:16] write 0x{X:} to 0x{X:} in IWRAM", .{ halfword, addr }),
+            0x0300_0000...0x0300_7FFF => std.debug.panic("[Bus:16] write 0x{X:} to 0x{X:} in EWRAM", .{ halfword, addr }),
+            0x0400_0000...0x0400_03FE => self.io.write16(addr, halfword),
 
             // Internal Display Memory
-            0x0500_0000...0x0500_03FF => std.debug.panic("write16 0x{X:} to 0x{X:} in BG/OBJ Palette RAM", .{ halfword, addr }),
-            0x0600_0000...0x0601_7FFF => std.debug.panic("write16 0x{X:} to 0x{X:} in VRAM", .{ halfword, addr }),
-            0x0700_0000...0x0700_03FF => std.debug.panic("write16 0x{X:} to 0x{X:} in OAM", .{ halfword, addr }),
+            0x0500_0000...0x0500_03FF => std.debug.panic("[Bus:16] write 0x{X:} to 0x{X:} in BG/OBJ Palette RAM", .{ halfword, addr }),
+            0x0600_0000...0x0601_7FFF => std.debug.panic("[Bus:16] write 0x{X:} to 0x{X:} in VRAM", .{ halfword, addr }),
+            0x0700_0000...0x0700_03FF => std.debug.panic("[Bus:16] write 0x{X:} to 0x{X:} in OAM", .{ halfword, addr }),
 
-            else => std.log.warn("ZBA tried to write16 0x{X:} to 0x{X:}", .{ halfword, addr }),
+            else => std.log.warn("[Bus:16] ZBA tried to write 0x{X:} to 0x{X:}", .{ halfword, addr }),
         }
     }
 
@@ -106,23 +109,23 @@ pub const Bus = struct {
         return switch (addr) {
             // General Internal Memory
             0x0000_0000...0x0000_3FFF => self.bios.get8(@as(usize, addr)),
-            0x0200_0000...0x0203FFFF => std.debug.panic("read8 from 0x{X:} in IWRAM", .{addr}),
-            0x0300_0000...0x0300_7FFF => std.debug.panic("read8 from 0x{X:} in EWRAM", .{addr}),
-            0x0400_0000...0x0400_03FE => std.debug.panic("read8 from 0x{X:} in I/O", .{addr}),
+            0x0200_0000...0x0203_FFFF => std.debug.panic("[Bus:8] read from 0x{X:} in IWRAM", .{addr}),
+            0x0300_0000...0x0300_7FFF => std.debug.panic("[Bus:8] read from 0x{X:} in EWRAM", .{addr}),
+            0x0400_0000...0x0400_03FE => self.io.read8(addr),
 
             // Internal Display Memory
-            0x0500_0000...0x0500_03FF => std.debug.panic("read8 from 0x{X:} in BG/OBJ Palette RAM", .{addr}),
-            0x0600_0000...0x0601_7FFF => std.debug.panic("read8 from 0x{X:} in VRAM", .{addr}),
-            0x0700_0000...0x0700_03FF => std.debug.panic("read8 from 0x{X:} in OAM", .{addr}),
+            0x0500_0000...0x0500_03FF => std.debug.panic("[Bus:8] read from 0x{X:} in BG/OBJ Palette RAM", .{addr}),
+            0x0600_0000...0x0601_7FFF => std.debug.panic("[Bus:8] read from 0x{X:} in VRAM", .{addr}),
+            0x0700_0000...0x0700_03FF => std.debug.panic("[Bus:8] read from 0x{X:} in OAM", .{addr}),
 
             // External Memory (Game Pak)
             0x0800_0000...0x09FF_FFFF => self.pak.get8(@as(usize, addr - 0x0800_0000)),
             0x0A00_0000...0x0BFF_FFFF => self.pak.get8(@as(usize, addr - 0x0A00_0000)),
             0x0C00_0000...0x0DFF_FFFF => self.pak.get8(@as(usize, addr - 0x0C00_0000)),
-            0x0E00_0000...0x0E00_FFFF => std.debug.panic("read8 from 0x{X:} in Game Pak SRAM", .{addr}),
+            0x0E00_0000...0x0E00_FFFF => std.debug.panic("[Bus:8] read from 0x{X:} in Game Pak SRAM", .{addr}),
 
             else => {
-                std.log.warn("ZBA tried to read8 from 0x{X:}", .{addr});
+                std.log.warn("[Bus:8] ZBA tried to read from 0x{X:}", .{addr});
                 return 0x00;
             },
         };
@@ -131,13 +134,13 @@ pub const Bus = struct {
     pub fn write8(_: *@This(), addr: u32, byte: u8) void {
         switch (addr) {
             // General Internal Memory
-            0x0200_0000...0x0203FFFF => std.debug.panic("write8 0x{X:} to 0x{X:} in IWRAM", .{ byte, addr }),
-            0x0300_0000...0x0300_7FFF => std.debug.panic("write8 0x{X:} to 0x{X:} in EWRAM", .{ byte, addr }),
-            0x0400_0000...0x0400_03FE => std.debug.panic("write8 0x{X:} to 0x{X:} in I/O", .{ byte, addr }),
+            0x0200_0000...0x0203_FFFF => std.debug.panic("[Bus:8] write 0x{X:} to 0x{X:} in IWRAM", .{ byte, addr }),
+            0x0300_0000...0x0300_7FFF => std.debug.panic("[Bus:8] write 0x{X:} to 0x{X:} in EWRAM", .{ byte, addr }),
+            0x0400_0000...0x0400_03FE => std.debug.panic("[Bus:8] write 0x{X:} to 0x{X:} in I/O", .{ byte, addr }),
 
             // External Memory (Game Pak)
-            0x0E00_0000...0x0E00_FFFF => std.debug.panic("write8 0x{X:} to 0x{X:} in Game Pak SRAM", .{ byte, addr }),
-            else => std.log.warn("ZBA tried to write8 0x{X:} to 0x{X:}", .{ byte, addr }),
+            0x0E00_0000...0x0E00_FFFF => std.debug.panic("[Bus:8] write 0x{X:} to 0x{X:} in Game Pak SRAM", .{ byte, addr }),
+            else => std.log.warn("[Bus:8] ZBA tried to write 0x{X:} to 0x{X:}", .{ byte, addr }),
         }
     }
 };

src/bus/bios.zig

@@ -5,7 +5,7 @@ const Allocator = std.mem.Allocator;
 pub const Bios = struct {
     buf: []u8,
 
-    pub fn fromPath(alloc: Allocator, path: []const u8) !@This() {
+    pub fn init(alloc: Allocator, path: []const u8) !@This() {
         const file = try std.fs.cwd().openFile(path, .{ .read = true });
         defer file.close();
 
@@ -17,14 +17,17 @@ pub const Bios = struct {
     }
 
     pub inline fn get32(self: *const @This(), idx: usize) u32 {
+        std.debug.panic("[BIOS] TODO: BIOS is not implemented", .{});
         return (@as(u32, self.buf[idx + 3]) << 24) | (@as(u32, self.buf[idx + 2]) << 16) | (@as(u32, self.buf[idx + 1]) << 8) | (@as(u32, self.buf[idx]));
     }
 
     pub inline fn get16(self: *const @This(), idx: usize) u16 {
+        std.debug.panic("[BIOS] TODO: BIOS is not implemented", .{});
         return (@as(u16, self.buf[idx + 1]) << 8) | @as(u16, self.buf[idx]);
     }
 
     pub inline fn get8(self: *const @This(), idx: usize) u8 {
+        std.debug.panic("[BIOS] TODO: BIOS is not implemented", .{});
         return self.buf[idx];
     }
 };

src/bus/io.zig

@@ -0,0 +1,56 @@
+const std = @import("std");
+const bitfield = @import("bitfield");
+
+const Bitfield = bitfield.Bitfield;
+const Bit = bitfield.Bit;
+
+pub const Io = struct {
+    dispcnt: Dispcnt,
+
+    pub fn init() @This() {
+        return .{
+            .dispcnt = .{ .val = 0x0000_0000 },
+        };
+    }
+
+    pub fn read32(self: *const @This(), addr: u32) u32 {
+        return switch (addr) {
+            0x0400_0000 => @as(u32, self.dispcnt.val),
+            else => std.debug.panic("[I/O:32] tried to read from {X:}", .{addr}),
+        };
+    }
+
+    pub fn read16(self: *const @This(), addr: u32) u16 {
+        return switch (addr) {
+            0x0400_0000 => self.dispcnt.val,
+            else => std.debug.panic("[I/O:16] tried to read from {X:}", .{addr}),
+        };
+    }
+
+    pub fn write16(self: *@This(), addr: u32, halfword: u16) void {
+        switch (addr) {
+            0x0400_000 => self.dispcnt.val = halfword,
+            else => std.debug.panic("[I/O:16] tried to write 0x{X:} to 0x{X:}", .{ halfword, addr }),
+        }
+    }
+
+    pub fn read8(self: *const @This(), addr: u32) u8 {
+        return switch (addr) {
+            0x0400_0000 => @truncate(u8, self.dispcnt.val),
+            else => std.debug.panic("[I/O:8] tried to read from {X:}", .{addr}),
+        };
+    }
+};
+
+const Dispcnt = extern union {
+    bg_mode: Bitfield(u16, 0, 3),
+    frame_select: Bit(u16, 4),
+    hblank_interval_free: Bit(u16, 5),
+    obj_mapping: Bit(u16, 6),
+    forced_blank: Bit(u16, 7),
+    bg_enable: Bitfield(u16, 8, 4),
+    obj_enable: Bit(u16, 12),
+    win_enable: Bitfield(u16, 13, 2),
+    obj_win_enable: Bit(u16, 15),
+    val: u16,
+};

src/bus/pak.zig

@@ -5,7 +5,7 @@ const Allocator = std.mem.Allocator;
 pub const GamePak = struct {
     buf: []u8,
 
-    pub fn fromPath(alloc: Allocator, path: []const u8) !@This() {
+    pub fn init(alloc: Allocator, path: []const u8) !@This() {
         const file = try std.fs.cwd().openFile(path, .{ .read = true });
         defer file.close();
 

src/cpu.zig

@@ -20,7 +20,7 @@ pub const Arm7tdmi = struct {
     bus: *Bus,
     cpsr: CPSR,
 
-    pub fn new(scheduler: *Scheduler, bus: *Bus) @This() {
+    pub fn init(scheduler: *Scheduler, bus: *Bus) @This() {
         return .{
             .r = [_]u32{0x00} ** 16,
             .sch = scheduler,
@@ -29,6 +29,19 @@ pub const Arm7tdmi = struct {
         };
     }
 
+    pub fn skipBios(self: *@This()) void {
+        self.r[0] = 0x08000000;
+        self.r[1] = 0x000000EA;
+        // GPRs 2 -> 12 *should* already be 0 initialized
+        self.r[13] = 0x0300_7F00;
+        self.r[14] = 0x0000_0000;
+        self.r[15] = 0x0800_0000;
+
+        // TODO: Set sp_irq = 0x0300_7FA0, sp_svc = 0x0300_7FE0
+
+        self.cpsr.val = 0x6000001F;
+    }
+
     pub inline fn step(self: *@This()) u64 {
         std.debug.print("PC: 0x{X:} ", .{self.r[15]});
         const opcode = self.fetch();
@@ -71,7 +84,7 @@ fn checkCond(cpsr: *const CPSR, opcode: u32) bool {
         0xC => !cpsr.z.read() and (cpsr.n.read() == cpsr.z.read()), // GT - Greater than
         0xD => cpsr.z.read() or (cpsr.n.read() != cpsr.v.read()), // LE - Less than or equal
         0xE => true, // AL - Always
-        0xF => std.debug.panic("0xF is a reserved condition field", .{}),
+        0xF => std.debug.panic("[CPU] 0xF is a reserved condition field", .{}),
     };
 }
 
@@ -145,7 +158,7 @@ const Mode = enum(u5) {
 
 fn undefinedInstruction(_: *Arm7tdmi, _: *Bus, opcode: u32) void {
     const id = armIdx(opcode);
-    std.debug.panic("[0x{X:}] 0x{X:} is an illegal opcode", .{ id, opcode });
+    std.debug.panic("[CPU] {{0x{X:}}} 0x{X:} is an illegal opcode", .{ id, opcode });
 }
 
 fn comptimeBranch(comptime L: bool) InstrFn {

src/cpu/data_processing.zig

@@ -23,13 +23,13 @@ pub fn comptimeDataProcessing(comptime I: bool, comptime S: bool, comptime instr
                     // ADD
                     cpu.r[rd] = cpu.r[op1] + op2;
 
-                    if (S) std.debug.panic("TODO: implement ADD condition codes", .{});
+                    if (S) std.debug.panic("[CPU] TODO: implement ADD condition codes", .{});
                 },
                 0xD => {
                     // MOV
                     cpu.r[rd] = op2;
 
-                    if (S) std.debug.panic("TODO: implement MOV condition codes", .{});
+                    if (S) std.debug.panic("[CPU] implement MOV condition codes", .{});
                 },
                 0xA => {
                     // CMP
@@ -45,7 +45,7 @@ pub fn comptimeDataProcessing(comptime I: bool, comptime S: bool, comptime instr
                     cpu.cpsr.z.write(result == 0x00);
                     cpu.cpsr.n.write(result >> 31 & 0x01 == 0x01);
                 },
-                else => std.debug.panic("TODO: implement data processing type {}", .{instrKind}),
+                else => std.debug.panic("[CPU] TODO: implement data processing type {}", .{instrKind}),
             }
         }
     }.dataProcessing;

src/cpu/half_signed_data_transfer.zig

@@ -30,7 +30,7 @@ pub fn comptimeHalfSignedDataTransfer(comptime P: bool, comptime U: bool, compti
                 switch (@truncate(u2, opcode >> 5)) {
                     0b00 => {
                         // SWP
-                        std.debug.panic("TODO: Implement SWP", .{});
+                        std.debug.panic("[CPU] TODO: Implement SWP", .{});
                     },
                     0b01 => {
                         // LDRH
@@ -56,7 +56,7 @@ pub fn comptimeHalfSignedDataTransfer(comptime P: bool, comptime U: bool, compti
                     bus.write16(address + 2, src);
                     bus.write16(address, src);
                 } else {
-                    std.debug.panic("TODO Figure out if this is also SWP", .{});
+                    std.debug.panic("[CPU] TODO: Figure out if this is also SWP", .{});
                 }
             }
 

src/main.zig

@@ -23,9 +23,11 @@ pub fn main() anyerror!void {
         return;
     }
 
-    var bus = try Bus.withPak(alloc, zba_args[0]);
-    var scheduler = Scheduler.new(alloc);
-    var cpu = Arm7tdmi.new(&scheduler, &bus);
+    var bus = try Bus.init(alloc, zba_args[0]);
+    var scheduler = Scheduler.init(alloc);
+    var cpu = Arm7tdmi.init(&scheduler, &bus);
+
+    cpu.skipBios();
 
     while (true) {
         emu.runFrame(&scheduler, &cpu, &bus);

src/scheduler.zig

@@ -10,7 +10,7 @@ pub const Scheduler = struct {
     tick: u64,
     queue: PriorityQueue(Event, void, lessThan),
 
-    pub fn new(alloc: Allocator) @This() {
+    pub fn init(alloc: Allocator) @This() {
         var scheduler = Scheduler{ .tick = 0, .queue = PriorityQueue(Event, void, lessThan).init(alloc, {}) };
 
         scheduler.queue.add(.{
@@ -29,7 +29,7 @@ pub const Scheduler = struct {
 
             switch (event.kind) {
                 .HeatDeath => {
-                    std.debug.panic("Somehow, a u64 overflowed", .{});
+                    std.debug.panic("[Scheduler] Somehow, a u64 overflowed", .{});
                 },
             }
         }