emu: implement thread sleep in granular steps

src/core/Bus.zig

@@ -1,6 +1,5 @@
 const std = @import("std");
 
-const AudioDeviceId = @import("sdl2").SDL_AudioDeviceID;
 const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
 const Bios = @import("bus/Bios.zig");
 const Ewram = @import("bus/Ewram.zig");

src/core/apu.zig

@@ -3,8 +3,6 @@ const SDL = @import("sdl2");
 const io = @import("bus/io.zig");
 const util = @import("../util.zig");
 
-const AudioDeviceId = SDL.SDL_AudioDeviceID;
-
 const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
 const Scheduler = @import("scheduler.zig").Scheduler;
 const ToneSweep = @import("apu/ToneSweep.zig");
@@ -20,7 +18,8 @@ const setLo = @import("../util.zig").setLo;
 
 const log = std.log.scoped(.APU);
 
-pub const host_sample_rate = 1 << 15;
+pub const host_rate = @import("../platform.zig").sample_rate;
+pub const host_format = @import("../platform.zig").sample_format;
 
 pub fn read(comptime T: type, apu: *const Apu, addr: u32) ?T {
     const byte = @truncate(u8, addr);
@@ -189,7 +188,7 @@ pub const Apu = struct {
             .bias = .{ .raw = 0x0200 },
 
             .sampling_cycle = 0b00,
-            .stream = SDL.SDL_NewAudioStream(SDL.AUDIO_U16, 2, 1 << 15, SDL.AUDIO_U16, 2, host_sample_rate).?,
+            .stream = SDL.SDL_NewAudioStream(SDL.AUDIO_U16, 2, 1 << 15, host_format, 2, host_rate).?,
             .sched = sched,
 
             .capacitor = 0,
@@ -356,7 +355,7 @@ pub const Apu = struct {
         defer SDL.SDL_FreeAudioStream(old_stream);
 
         self.sampling_cycle = self.bias.sampling_cycle.read();
-        self.stream = SDL.SDL_NewAudioStream(SDL.AUDIO_U16, 2, @intCast(c_int, sample_rate), SDL.AUDIO_U16, 2, host_sample_rate).?;
+        self.stream = SDL.SDL_NewAudioStream(SDL.AUDIO_U16, 2, @intCast(c_int, sample_rate), host_format, 2, host_rate).?;
     }
 
     fn interval(self: *const Self) u64 {
@@ -456,8 +455,8 @@ const DmaSoundKind = enum {
 };
 
 pub const FrameSequencer = struct {
-    const interval = (1 << 24) / 512;
     const Self = @This();
+    pub const interval = (1 << 24) / 512;
 
     step: u3,
 

src/core/apu/signal/Lfsr.zig

@@ -1,9 +1,7 @@
+//! Linear Feedback Shift Register
 const io = @import("../../bus/io.zig");
 
-/// Linear Feedback Shift Register
 const Scheduler = @import("../../scheduler.zig").Scheduler;
-const FrameSequencer = @import("../../apu.zig").FrameSequencer;
-const Noise = @import("../Noise.zig");
 
 const Self = @This();
 pub const interval: u64 = (1 << 24) / (1 << 22);

src/core/apu/signal/Square.zig

@@ -2,7 +2,6 @@ const std = @import("std");
 const io = @import("../../bus/io.zig");
 
 const Scheduler = @import("../../scheduler.zig").Scheduler;
-const FrameSequencer = @import("../../apu.zig").FrameSequencer;
 const ToneSweep = @import("../ToneSweep.zig");
 const Tone = @import("../Tone.zig");
 

src/core/apu/signal/Wave.zig

@@ -2,8 +2,6 @@ const std = @import("std");
 const io = @import("../../bus/io.zig");
 
 const Scheduler = @import("../../scheduler.zig").Scheduler;
-const FrameSequencer = @import("../../apu.zig").FrameSequencer;
-const Wave = @import("../Wave.zig");
 
 const buf_len = 0x20;
 pub const interval: u64 = (1 << 24) / (1 << 22);

src/core/bus/GamePak.zig

@@ -1,10 +1,6 @@
 const std = @import("std");
 const config = @import("../../config.zig");
 
-const Bit = @import("bitfield").Bit;
-const Bitfield = @import("bitfield").Bitfield;
-const DateTime = @import("datetime").datetime.Datetime;
-
 const Arm7tdmi = @import("../cpu.zig").Arm7tdmi;
 const Backup = @import("backup.zig").Backup;
 const Gpio = @import("gpio.zig").Gpio;

src/core/bus/gpio.zig

@@ -1,6 +1,5 @@
 const std = @import("std");
 const Bit = @import("bitfield").Bit;
-const Bitfield = @import("bitfield").Bitfield;
 const DateTime = @import("datetime").datetime.Datetime;
 
 const Arm7tdmi = @import("../cpu.zig").Arm7tdmi;

src/core/bus/io.zig

@@ -1,5 +1,4 @@
 const std = @import("std");
-const builtin = @import("builtin");
 const timer = @import("timer.zig");
 const dma = @import("dma.zig");
 const apu = @import("../apu.zig");
@@ -8,8 +7,6 @@ const util = @import("../../util.zig");
 const Bit = @import("bitfield").Bit;
 const Bitfield = @import("bitfield").Bitfield;
 const Bus = @import("../Bus.zig");
-const DmaController = @import("dma.zig").DmaController;
-const Scheduler = @import("../scheduler.zig").Scheduler;
 
 const setHi = util.setHi;
 const setLo = util.setLo;

src/core/bus/timer.zig

@@ -2,9 +2,7 @@ const std = @import("std");
 const util = @import("../../util.zig");
 
 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;
 
 pub const TimerTuple = std.meta.Tuple(&[_]type{ Timer(0), Timer(1), Timer(2), Timer(3) });

src/core/cpu.zig

@@ -1,11 +1,9 @@
 const std = @import("std");
-const util = @import("../util.zig");
 
 const Bus = @import("Bus.zig");
 const Bit = @import("bitfield").Bit;
 const Bitfield = @import("bitfield").Bitfield;
 const Scheduler = @import("scheduler.zig").Scheduler;
-const FilePaths = @import("../util.zig").FilePaths;
 const Logger = @import("../util.zig").Logger;
 
 const File = std.fs.File;

src/core/cpu/arm/branch.zig

@@ -1,5 +1,3 @@
-const std = @import("std");
-
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
 const InstrFn = @import("../../cpu.zig").arm.InstrFn;

src/core/cpu/arm/half_signed_data_transfer.zig

@@ -1,5 +1,3 @@
-const std = @import("std");
-
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
 const InstrFn = @import("../../cpu.zig").arm.InstrFn;

src/core/cpu/arm/single_data_swap.zig

@@ -1,5 +1,3 @@
-const std = @import("std");
-
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
 const InstrFn = @import("../../cpu.zig").arm.InstrFn;

src/core/cpu/arm/single_data_transfer.zig

@@ -1,6 +1,3 @@
-const std = @import("std");
-const util = @import("../../../util.zig");
-
 const shifter = @import("../barrel_shifter.zig");
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;

src/core/cpu/barrel_shifter.zig

@@ -1,5 +1,3 @@
-const std = @import("std");
-
 const Arm7tdmi = @import("../cpu.zig").Arm7tdmi;
 const CPSR = @import("../cpu.zig").PSR;
 

src/core/cpu/thumb/data_processing.zig

@@ -1,5 +1,3 @@
-const std = @import("std");
-
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
 const InstrFn = @import("../../cpu.zig").thumb.InstrFn;

src/core/cpu/thumb/data_transfer.zig

@@ -1,5 +1,3 @@
-const std = @import("std");
-
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
 const InstrFn = @import("../../cpu.zig").thumb.InstrFn;

src/core/emu.zig

@@ -2,29 +2,29 @@ const std = @import("std");
 const SDL = @import("sdl2");
 const config = @import("../config.zig");
 
-const Bus = @import("Bus.zig");
 const Scheduler = @import("scheduler.zig").Scheduler;
 const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
 const FpsTracker = @import("../util.zig").FpsTracker;
-const FilePaths = @import("../util.zig").FilePaths;
 
 const Timer = std.time.Timer;
-const Thread = std.Thread;
 const Atomic = std.atomic.Atomic;
-const Allocator = std.mem.Allocator;
 
-// 228 Lines which consist of 308 dots (which are 4 cycles long)
-const cycles_per_frame: u64 = 228 * (308 * 4); //280896
-const clock_rate: u64 = 1 << 24; // 16.78MHz
+/// 4 Cycles in 1 dot
+const cycles_per_dot = 4;
 
-// TODO: Don't truncate this, be more accurate w/ timing
-// 59.6046447754ns (truncated to just 59ns)
-const clock_period: u64 = std.time.ns_per_s / clock_rate;
-const frame_period = (clock_period * cycles_per_frame);
+/// The GBA draws 228 Horizontal which each consist 308 dots
+/// (note: not all lines are visible)
+const cycles_per_frame = 228 * (308 * cycles_per_dot); //280896
 
-// 59.7275005696Hz
-pub const frame_rate = @intToFloat(f64, std.time.ns_per_s) /
-    ((@intToFloat(f64, std.time.ns_per_s) / @intToFloat(f64, clock_rate)) * @intToFloat(f64, cycles_per_frame));
+/// The GBA ARM7TDMI runs at 2^24 Hz
+const clock_rate = 1 << 24; // 16.78MHz
+
+/// The # of nanoseconds a frame should take
+const frame_period = (std.time.ns_per_s * cycles_per_frame) / clock_rate;
+
+/// Exact Value:  59.7275005696Hz
+/// The inverse of the frame period
+pub const frame_rate: f64 = @intToFloat(f64, clock_rate) / cycles_per_frame;
 
 const log = std.log.scoped(.Emulation);
 
@@ -36,7 +36,7 @@ const RunKind = enum {
 };
 
 pub fn run(quit: *Atomic(bool), scheduler: *Scheduler, cpu: *Arm7tdmi, tracker: *FpsTracker) void {
-    const audio_sync = config.config().guest.audio_sync;
+    const audio_sync = config.config().guest.audio_sync and !config.config().host.mute;
     if (audio_sync) log.info("Audio sync enabled", .{});
 
     if (config.config().guest.video_sync) {
@@ -132,11 +132,10 @@ fn videoSync(timer: *Timer, wake_time: u64) u64 {
 
 // TODO: Better sleep impl?
 fn sleep(timer: *Timer, wake_time: u64) ?u64 {
-    // const step = std.time.ns_per_ms * 10; // 10ms
     const timestamp = timer.read();
 
     // ns_late is non zero if we are late.
-    const ns_late = timestamp -| wake_time;
+    var ns_late = timestamp -| wake_time;
 
     // If we're more than a frame late, skip the rest of this loop
     // Recalculate what our new wake time should be so that we can
@@ -144,15 +143,18 @@ fn sleep(timer: *Timer, wake_time: u64) ?u64 {
     if (ns_late > frame_period) return timestamp + frame_period;
     const sleep_for = frame_period - ns_late;
 
-    // // Employ several sleep calls in periods of 10ms
-    // // By doing this the behaviour should average out to be
-    // // more consistent
-    // const loop_count = sleep_for / step; // How many groups of 10ms
+    const step = 2 * std.time.ns_per_ms; // Granularity of 2ms
+    const times = sleep_for / step;
+    var i: usize = 0;
 
-    // var i: usize = 0;
-    // while (i < loop_count) : (i += 1) std.time.sleep(step);
+    while (i < times) : (i += 1) {
+        std.time.sleep(step);
 
-    std.time.sleep(sleep_for);
+        // Upon wakeup, check to see if this particular sleep was longer than expected
+        // if so we should exit early, but probably not skip a whole frame period
+        ns_late = timer.read() -| wake_time;
+        if (ns_late > frame_period) return null;
+    }
 
     return null;
 }

src/core/ppu.zig

@@ -1,7 +1,6 @@
 const std = @import("std");
 const io = @import("bus/io.zig");
 
-const EventKind = @import("scheduler.zig").EventKind;
 const Scheduler = @import("scheduler.zig").Scheduler;
 const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
 

src/core/scheduler.zig

@@ -1,6 +1,5 @@
 const std = @import("std");
 
-const Bus = @import("Bus.zig");
 const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
 const Clock = @import("bus/gpio.zig").Clock;
 

src/platform.zig

@@ -11,10 +11,12 @@ const FpsTracker = @import("util.zig").FpsTracker;
 
 const span = @import("util.zig").span;
 
-const pitch = @import("core/ppu.zig").framebuf_pitch;
 const gba_width = @import("core/ppu.zig").width;
 const gba_height = @import("core/ppu.zig").height;
 
+pub const sample_rate = 44100;
+pub const sample_format = SDL.AUDIO_F32;
+
 const default_title: []const u8 = "ZBA";
 
 pub const Gui = struct {
@@ -253,7 +255,6 @@ pub const Gui = struct {
 const Audio = struct {
     const Self = @This();
     const log = std.log.scoped(.PlatformAudio);
-    const sample_rate = @import("core/apu.zig").host_sample_rate;
 
     device: SDL.SDL_AudioDeviceID,
 
@@ -261,16 +262,22 @@ const Audio = struct {
         var have: SDL.SDL_AudioSpec = undefined;
         var want: SDL.SDL_AudioSpec = std.mem.zeroes(SDL.SDL_AudioSpec);
         want.freq = sample_rate;
-        want.format = SDL.AUDIO_U16;
+        want.format = sample_format;
         want.channels = 2;
         want.samples = 0x100;
         want.callback = Self.callback;
         want.userdata = apu;
 
+        std.debug.assert(sample_format == SDL.AUDIO_F32);
+        log.info("Host Sample Rate: {}Hz, Host Format: SDL.AUDIO_F32", .{sample_rate});
+
         const device = SDL.SDL_OpenAudioDevice(null, 0, &want, &have, 0);
         if (device == 0) panic();
 
-        SDL.SDL_PauseAudioDevice(device, 0); // Unpause Audio
+        if (!config.config().host.mute) {
+            SDL.SDL_PauseAudioDevice(device, 0); // Unpause Audio
+            log.info("Unpaused Device", .{});
+        }
 
         return .{ .device = device };
     }
@@ -281,18 +288,10 @@ const Audio = struct {
     }
 
     export fn callback(userdata: ?*anyopaque, stream: [*c]u8, len: c_int) void {
-        const apu = @ptrCast(*Apu, @alignCast(@alignOf(*Apu), userdata));
+        const T = *Apu;
+        const apu = @ptrCast(T, @alignCast(@alignOf(T), userdata));
 
-        // TODO: Find a better way to mute this
-        if (!config.config().host.mute) {
-            _ = SDL.SDL_AudioStreamGet(apu.stream, stream, len);
-        } else {
-            // FIXME: I don't think this hack to remove DC Offset is acceptable :thinking:
-            std.mem.set(u8, stream[0..@intCast(usize, len)], 0x40);
-        }
-
-        // If we don't write anything, play silence otherwise garbage will be played
-        // if (written == 0) std.mem.set(u8, stream[0..@intCast(usize, len)], 0x40);
+        _ = SDL.SDL_AudioStreamGet(apu.stream, stream, len);
     }
 };