From 1c173eb4b8d59a7e3196f67acd66967ed1478aec Mon Sep 17 00:00:00 2001
From: Rekai Musuka <rekai@musuka.dev>
Date: Wed, 12 Jan 2022 02:19:26 -0400
Subject: [PATCH] chore(io): implement IE and IME

---
 src/Bus.zig    |  4 ++--
 src/bus/io.zig | 52 +++++++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 49 insertions(+), 7 deletions(-)

diff --git a/src/Bus.zig b/src/Bus.zig
index 0b0d7c6..0c30d49 100644
--- a/src/Bus.zig
+++ b/src/Bus.zig
@@ -69,7 +69,7 @@ pub fn write32(self: *Self, addr: u32, word: u32) void {
         // General Internal Memory
         0x0200_0000...0x0203_FFFF => self.iwram.set32(addr - 0x0200_0000, word),
         0x0300_0000...0x0300_7FFF => self.ewram.set32(addr - 0x0300_0000, word),
-        0x0400_0000...0x0400_03FE => std.debug.panic("[Bus:32] wrote 0x{X:} to 0x{X:} in I/O", .{ word, addr }),
+        0x0400_0000...0x0400_03FE => self.io.write32(addr, word),
 
         // Internal Display Memory
         0x0500_0000...0x0500_03FF => self.ppu.palette.set32(@as(usize, addr - 0x0500_0000), word),
@@ -153,7 +153,7 @@ pub fn write8(self: *Self, addr: u32, byte: u8) void {
         // General Internal Memory
         0x0200_0000...0x0203_FFFF => self.iwram.set8(addr - 0x0200_0000, byte),
         0x0300_0000...0x0300_7FFF => self.ewram.set8(addr - 0x0300_0000, byte),
-        0x0400_0000...0x0400_03FE => self.io.set8(addr - 0x0400_0000, byte),
+        0x0400_0000...0x0400_03FE => self.io.write8(addr, byte),
 
         // External Memory (Game Pak)
         0x0E00_0000...0x0E00_FFFF => std.debug.panic("[Bus:8] write 0x{X:} to 0x{X:} in Game Pak SRAM", .{ byte, addr }),
diff --git a/src/bus/io.zig b/src/bus/io.zig
index a934b7a..4fc915e 100644
--- a/src/bus/io.zig
+++ b/src/bus/io.zig
@@ -6,15 +6,20 @@ const Bitfield = @import("bitfield").Bitfield;
 pub const Io = struct {
     const Self = @This();
 
-    dispcnt: DispCnt,
-    dispstat: DispStat,
+    dispcnt: DisplayControl,
+    dispstat: DisplayStatus,
     vcount: VCount,
+    /// Read / Write
+    ime: bool,
+    ie: InterruptEnable,
 
     pub fn init() Self {
         return .{
             .dispcnt = .{ .raw = 0x0000_0000 },
             .dispstat = .{ .raw = 0x0000_0000 },
             .vcount = .{ .raw = 0x0000_0000 },
+            .ime = false,
+            .ie = .{ .raw = 0x0000_0000 },
         };
     }
 
@@ -23,15 +28,27 @@ pub const Io = struct {
             0x0400_0000 => @as(u32, self.dispcnt.raw),
             0x0400_0004 => @as(u32, self.dispstat.raw),
             0x0400_0006 => @as(u32, self.vcount.raw),
+            0x0400_0200 => @as(u32, self.ie.raw),
+            0x0400_0208 => @boolToInt(self.ime),
             else => std.debug.panic("[I/O:32] tried to read from {X:}", .{addr}),
         };
     }
 
+    pub fn write32(self: *Self, addr: u32, word: u32) void {
+        switch (addr) {
+            0x0400_0200 => self.ie.raw = @truncate(u16, word),
+            0x0400_0208 => self.ime = word & 1 == 1,
+            else => std.debug.panic("[I/O:32] tried to write 0x{X:} to 0x{X:}", .{ word, addr }),
+        }
+    }
+
     pub fn read16(self: *const Self, addr: u32) u16 {
         return switch (addr) {
             0x0400_0000 => self.dispcnt.raw,
             0x0400_0004 => self.dispstat.raw,
             0x0400_0006 => self.vcount.raw,
+            0x0400_0200 => self.ie.raw,
+            0x0400_0208 => @boolToInt(self.ime),
             else => std.debug.panic("[I/O:16] tried to read from {X:}", .{addr}),
         };
     }
@@ -40,6 +57,8 @@ pub const Io = struct {
         switch (addr) {
             0x0400_0000 => self.dispcnt.raw = halfword,
             0x0400_0004 => self.dispstat.raw = halfword,
+            0x0400_0200 => self.ie.raw = halfword,
+            0x0400_0208 => self.ime = halfword & 1 == 1,
             else => std.debug.panic("[I/O:16] tried to write 0x{X:} to 0x{X:}", .{ halfword, addr }),
         }
     }
@@ -48,17 +67,19 @@ pub const Io = struct {
         return switch (addr) {
             0x0400_0000 => @truncate(u8, self.dispcnt.raw),
             0x0400_0004 => @truncate(u8, self.dispstat.raw),
+            0x0400_0200 => @truncate(u8, self.ie.raw),
             0x0400_0006 => @truncate(u8, self.vcount.raw),
             else => std.debug.panic("[I/O:8] tried to read from {X:}", .{addr}),
         };
     }
 
-    pub fn set8(_: *Self, addr: u32, byte: u8) void {
+    pub fn write8(_: *Self, addr: u32, byte: u8) void {
         std.debug.panic("[I/0:8] tried to write 0x{X:} to 0x{X:}", .{ byte, addr });
     }
 };
 
-const DispCnt = extern union {
+/// Read / Write
+const DisplayControl = extern union {
     bg_mode: Bitfield(u16, 0, 3),
     frame_select: Bit(u16, 4),
     hblank_interval_free: Bit(u16, 5),
@@ -71,7 +92,8 @@ const DispCnt = extern union {
     raw: u16,
 };
 
-const DispStat = extern union {
+/// Read / Write
+const DisplayStatus = extern union {
     vblank: Bit(u16, 0),
     hblank: Bit(u16, 1),
     coincidence: Bit(u16, 2),
@@ -82,7 +104,27 @@ const DispStat = extern union {
     raw: u16,
 };
 
+/// Read Only
 const VCount = extern union {
     scanline: Bitfield(u16, 0, 8),
     raw: u16,
 };
+
+/// Read / Write
+const InterruptEnable = extern union {
+    vblank: Bit(u16, 0),
+    hblank: Bit(u16, 1),
+    coincidence: Bit(u16, 2),
+    tm0_overflow: Bit(u16, 3),
+    tm1_overflow: Bit(u16, 4),
+    tm2_overflow: Bit(u16, 5),
+    tm3_overflow: Bit(u16, 6),
+    serial: Bit(u16, 7),
+    dma0: Bit(u16, 8),
+    dma1: Bit(u16, 9),
+    dma2: Bit(u16, 10),
+    dma3: Bit(u16, 11),
+    keypad: Bit(u16, 12),
+    game_pak: Bit(u16, 13),
+    raw: u16,
+};