diff --git a/src/Bus.zig b/src/Bus.zig index 63b9f11..9a48680 100644 --- a/src/Bus.zig +++ b/src/Bus.zig @@ -27,7 +27,7 @@ pub fn init(alloc: Allocator, sched: *Scheduler, rom_path: []const u8, maybe_bio .ppu = try Ppu.init(alloc, sched), .iwram = try Iwram.init(alloc), .ewram = try Ewram.init(alloc), - .io = Io.init(), + .io = Io.init(sched), }; } diff --git a/src/bus/io.zig b/src/bus/io.zig index 96d2a8d..8ccdaef 100644 --- a/src/bus/io.zig +++ b/src/bus/io.zig @@ -4,6 +4,8 @@ const Bit = @import("bitfield").Bit; const Bitfield = @import("bitfield").Bitfield; const Bus = @import("../Bus.zig"); const DmaController = @import("dma.zig").DmaController; +const Timer = @import("timer.zig").Timer; +const Scheduler = @import("../scheduler.zig").Scheduler; const log = std.log.scoped(.@"I/O"); @@ -24,9 +26,16 @@ pub const Io = struct { dma2: DmaController(2), dma3: DmaController(3), + // Timers + // TODO: Figure out how to turn this into an array + tim0: Timer(0), + tim1: Timer(1), + tim2: Timer(2), + tim3: Timer(3), + keyinput: KeyInput, - pub fn init() Self { + pub fn init(sched: *Scheduler) Self { return .{ .ime = false, .ie = .{ .raw = 0x0000 }, @@ -35,11 +44,17 @@ pub const Io = struct { .postflg = .FirstBoot, .haltcnt = .Execute, - // Dma Transfers + // Dma Controllers .dma0 = DmaController(0).init(), .dma1 = DmaController(1).init(), .dma2 = DmaController(2).init(), .dma3 = DmaController(3).init(), + + // Timers + .tim0 = Timer(0).init(sched), + .tim1 = Timer(1).init(sched), + .tim2 = Timer(2).init(sched), + .tim3 = Timer(3).init(sched), }; } @@ -60,6 +75,10 @@ pub fn read32(bus: *const Bus, addr: u32) u32 { 0x0400_00C4 => @as(u32, bus.io.dma1.cnt.raw) << 16, 0x0400_00D0 => @as(u32, bus.io.dma1.cnt.raw) << 16, 0x0400_00DC => @as(u32, bus.io.dma3.cnt.raw) << 16, + 0x0400_0100 => @as(u32, bus.io.tim0.cnt.raw) << 16 | bus.io.tim0.counter(), + 0x0400_0104 => @as(u32, bus.io.tim1.cnt.raw) << 16 | bus.io.tim1.counter(), + 0x0400_0108 => @as(u32, bus.io.tim2.cnt.raw) << 16 | bus.io.tim2.counter(), + 0x0400_010C => @as(u32, bus.io.tim3.cnt.raw) << 16 | bus.io.tim3.counter(), else => std.debug.panic("Tried to read word from 0x{X:0>8}", .{addr}), }; } @@ -91,6 +110,10 @@ pub fn write32(bus: *Bus, addr: u32, word: u32) void { 0x0400_00D4 => bus.io.dma3.writeSad(word), 0x0400_00D8 => bus.io.dma3.writeDad(word), 0x0400_00DC => bus.io.dma3.writeCnt(word), + 0x0400_0100 => bus.io.tim0.writeCnt(word), + 0x0400_0104 => bus.io.tim1.writeCnt(word), + 0x0400_0108 => bus.io.tim2.writeCnt(word), + 0x0400_010C => bus.io.tim3.writeCnt(word), 0x0400_0200 => bus.io.setIrqs(word), 0x0400_0204 => log.warn("Wrote 0x{X:0>8} to WAITCNT", .{word}), 0x0400_0208 => bus.io.ime = word & 1 == 1, @@ -107,10 +130,14 @@ pub fn read16(bus: *const Bus, addr: u32) u16 { 0x0400_0200 => bus.io.ie.raw, 0x0400_0202 => bus.io.irq.raw, 0x0400_0208 => @boolToInt(bus.io.ime), - 0x0400_0102 => failedRead("Tried to read halfword from TM0CNT_H", .{}), - 0x0400_0106 => failedRead("Tried to read halfword from TM1CNT_H", .{}), - 0x0400_010A => failedRead("Tried to read halfword from TM2CNT_H", .{}), - 0x0400_010E => failedRead("Tried to read halfword from TM3CNT_H", .{}), + 0x0400_0100 => bus.io.tim0.counter(), + 0x0400_0102 => bus.io.tim0.cnt.raw, + 0x0400_0104 => bus.io.tim1.counter(), + 0x0400_0106 => bus.io.tim1.cnt.raw, + 0x0400_0108 => bus.io.tim2.counter(), + 0x0400_010A => bus.io.tim2.cnt.raw, + 0x0400_010C => bus.io.tim3.counter(), + 0x0400_010E => bus.io.tim3.cnt.raw, 0x0400_0204 => failedRead("Tried to read halfword from WAITCNT", .{}), else => std.debug.panic("Tried to read halfword from 0x{X:0>8}", .{addr}), }; @@ -153,14 +180,14 @@ pub fn write16(bus: *Bus, addr: u32, halfword: u16) void { 0x0400_00D2 => bus.io.dma2.writeCntHigh(halfword), 0x0400_00DC => bus.io.dma3.writeWordCount(halfword), 0x0400_00DE => bus.io.dma3.writeCntHigh(halfword), - 0x0400_0100 => log.warn("Wrote 0x{X:0>4} to TM0CNT_L", .{halfword}), - 0x0400_0102 => log.warn("Wrote 0x{X:0>4} to TM0CNT_H", .{halfword}), - 0x0400_0104 => log.warn("Wrote 0x{X:0>4} to TM1CNT_L", .{halfword}), - 0x0400_0106 => log.warn("Wrote 0x{X:0>4} to TM1CNT_H", .{halfword}), - 0x0400_0108 => log.warn("Wrote 0x{X:0>4} to TM2CNT_L", .{halfword}), - 0x0400_010A => log.warn("Wrote 0x{X:0>4} to TM2CNT_H", .{halfword}), - 0x0400_010C => log.warn("Wrote 0x{X:0>4} to TM3CNT_L", .{halfword}), - 0x0400_010E => log.warn("Wrote 0x{X:0>4} to TM3CNT_H", .{halfword}), + 0x0400_0100 => bus.io.tim0.writeCntLow(halfword), + 0x0400_0102 => bus.io.tim0.writeCntHigh(halfword), + 0x0400_0104 => bus.io.tim1.writeCntLow(halfword), + 0x0400_0106 => bus.io.tim1.writeCntHigh(halfword), + 0x0400_0108 => bus.io.tim2.writeCntLow(halfword), + 0x0400_010A => bus.io.tim2.writeCntHigh(halfword), + 0x0400_010C => bus.io.tim3.writeCntLow(halfword), + 0x0400_010E => bus.io.tim3.writeCntHigh(halfword), 0x0400_0120 => log.warn("Wrote 0x{X:0>4} to SIOMULTI0", .{halfword}), 0x0400_0122 => log.warn("Wrote 0x{X:0>4} to SIOMULTI1", .{halfword}), 0x0400_0124 => log.warn("Wrote 0x{X:0>4} to SIOMULTI2", .{halfword}), @@ -343,3 +370,12 @@ pub const DmaControl = extern union { enabled: Bit(u16, 15), raw: u16, }; + +/// Read / Write +pub const TimerControl = extern union { + frequency: Bitfield(u16, 0, 2), + cascade: Bit(u16, 2), + irq: Bit(u16, 6), + enabled: Bit(u16, 7), + raw: u16, +}; diff --git a/src/bus/timer.zig b/src/bus/timer.zig new file mode 100644 index 0000000..14fd851 --- /dev/null +++ b/src/bus/timer.zig @@ -0,0 +1,131 @@ +const std = @import("std"); + +const TimerControl = @import("io.zig").TimerControl; +const Io = @import("io.zig").Io; +const Scheduler = @import("../scheduler.zig").Scheduler; +const Event = @import("../scheduler.zig").Event; +const Arm7tdmi = @import("../cpu.zig").Arm7tdmi; + +const log = std.log.scoped(.Timer); + +pub fn Timer(comptime id: u2) type { + return struct { + const Self = @This(); + + /// Read Only, Internal. Please use self.counter() + _counter: u16, + + /// Write Only, Internal. Please use self.writeCntLow() + _reload: u16, + + /// Write Only, Internal. Please use self.WriteCntHigh() + cnt: TimerControl, + + /// Internal. + sched: *Scheduler, + + /// Internal + _start_timestamp: u64, + + pub fn init(sched: *Scheduler) Self { + return .{ + ._reload = 0, + ._counter = 0, + .cnt = .{ .raw = 0x0000 }, + .sched = sched, + ._start_timestamp = 0, + }; + } + + pub fn counter(self: *const Self) u16 { + if (self.cnt.cascade.read()) + return self._counter + else + return self._counter +% @truncate(u16, (self.sched.now() - self._start_timestamp) / self.frequency()); + } + + pub fn writeCnt(self: *Self, word: u32) void { + self.writeCntLow(@truncate(u16, word)); + self.writeCntHigh(@truncate(u16, word >> 16)); + } + + pub fn writeCntLow(self: *Self, halfword: u16) void { + self._reload = halfword; + } + + pub fn writeCntHigh(self: *Self, halfword: u16) void { + const new = TimerControl{ .raw = halfword }; + + // If Timer happens to be enabled, It will either be resheduled or disabled + self.sched.removeScheduledEvent(.{ .TimerOverflow = id }); + + if (!self.cnt.enabled.read() and new.enabled.read()) { + // Reload on Rising edge + self._counter = self._reload; + + if (!new.cascade.read()) self.scheduleOverflow(); + } + + self.cnt.raw = halfword; + } + + pub fn handleOverflow(self: *Self, cpu: *Arm7tdmi, io: *Io) void { + // Fire IRQ if enabled + if (self.cnt.irq.read()) { + switch (id) { + 0 => io.irq.tim0_overflow.set(), + 1 => io.irq.tim1_overflow.set(), + 2 => io.irq.tim2_overflow.set(), + 3 => io.irq.tim3_overflow.set(), + } + + cpu.handleInterrupt(); + } + + // Perform Cascade Behaviour + switch (id) { + 0 => if (io.tim1.cnt.cascade.read()) { + io.tim1._counter +%= 1; + + if (io.tim1._counter == 0) + io.tim1.handleOverflow(cpu, io); + }, + 1 => if (io.tim2.cnt.cascade.read()) { + io.tim2._counter +%= 1; + + if (io.tim2._counter == 0) + io.tim2.handleOverflow(cpu, io); + }, + 2 => if (io.tim3.cnt.cascade.read()) { + io.tim3._counter +%= 1; + + if (io.tim3._counter == 0) + io.tim3.handleOverflow(cpu, io); + }, + 3 => {}, // There is no Timer for TIM3 to "cascade" to, + } + + // Reschedule Timer if we're not cascading + if (!self.cnt.cascade.read()) { + self._counter = self._reload; + self.scheduleOverflow(); + } + } + + fn scheduleOverflow(self: *Self) void { + const when = (@as(u64, 0x10000) - self._counter) * self.frequency(); + + self._start_timestamp = self.sched.now(); + self.sched.push(.{ .TimerOverflow = id }, self.sched.now() + when); + } + + fn frequency(self: *const Self) u16 { + return switch (self.cnt.frequency.read()) { + 0 => 1, + 1 => 64, + 2 => 256, + 3 => 1024, + }; + } + }; +} diff --git a/src/scheduler.zig b/src/scheduler.zig index 0e9db84..4a17e08 100644 --- a/src/scheduler.zig +++ b/src/scheduler.zig @@ -27,6 +27,10 @@ pub const Scheduler = struct { self.queue.deinit(); } + pub inline fn now(self: *const Self) u64 { + return self.tick; + } + pub fn handleEvent(self: *Self, cpu: *Arm7tdmi, bus: *Bus) void { const should_handle = if (self.queue.peek()) |e| self.tick >= e.tick else false; const stat = &bus.ppu.dispstat; @@ -39,7 +43,8 @@ pub const Scheduler = struct { switch (event.kind) { .HeatDeath => { - std.debug.panic("[Scheduler] Somehow, a u64 overflowed", .{}); + log.err("A u64 overflowered. This *actually* should never happen.", .{}); + unreachable; }, .HBlank => { // The End of a Hblank (During Draw or Vblank) @@ -110,6 +115,35 @@ pub const Scheduler = struct { bus.ppu.dispstat.hblank.set(); self.push(.HBlank, self.tick + (68 * 4)); }, + .TimerOverflow => |id| { + // log.warn("TIM{} Overflowed", .{id}); + + switch (id) { + 0 => bus.io.tim0.handleOverflow(cpu, &bus.io), + 1 => bus.io.tim1.handleOverflow(cpu, &bus.io), + 2 => bus.io.tim2.handleOverflow(cpu, &bus.io), + 3 => bus.io.tim3.handleOverflow(cpu, &bus.io), + } + }, + } + } + } + + /// Removes the **first** scheduled event of type `needle` + pub fn removeScheduledEvent(self: *Self, needle: EventKind) void { + var it = self.queue.iterator(); + + var i: usize = 0; + while (it.next()) |event| : (i += 1) { + if (std.meta.eql(event.kind, needle)) { + + // This invalidates the iterator + _ = self.queue.removeIndex(i); + + // Since removing something from the PQ invalidates the iterator, + // this implementation can safely only remove the first instance of + // a Scheduled Event. Exit Early + break; } } } @@ -134,9 +168,10 @@ fn lessThan(_: void, a: Event, b: Event) Order { return std.math.order(a.tick, b.tick); } -pub const EventKind = enum { +pub const EventKind = union(enum) { HeatDeath, HBlank, VBlank, Draw, + TimerOverflow: u2, };