From 84273cbdada6ed2cc205323717b4cce8d2c3ee76 Mon Sep 17 00:00:00 2001
From: Rekai Musuka <rekai@musuka.dev>
Date: Fri, 21 Oct 2022 05:12:30 -0300
Subject: [PATCH] chore: tick on memory access instead of 1cpi

---
 src/Bus.zig | 16 ++++++++++++++--
 src/emu.zig |  6 +++---
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/Bus.zig b/src/Bus.zig
index a1eec70..a805fec 100644
--- a/src/Bus.zig
+++ b/src/Bus.zig
@@ -27,6 +27,8 @@ tim: Timers,
 iwram: Iwram,
 ewram: Ewram,
 
+sched: *Scheduler,
+
 io: Io,
 
 pub fn init(alloc: Allocator, sched: *Scheduler, rom_path: []const u8, bios_path: ?[]const u8, save_path: ?[]const u8) !Self {
@@ -40,6 +42,7 @@ pub fn init(alloc: Allocator, sched: *Scheduler, rom_path: []const u8, bios_path
         .dma = DmaControllers.init(),
         .tim = Timers.init(sched),
         .io = Io.init(),
+        .sched = sched,
     };
 }
 
@@ -52,6 +55,8 @@ pub fn deinit(self: Self) void {
 }
 
 pub fn read32(self: *const Self, addr: u32) u32 {
+    self.sched.tick += 1;
+
     return switch (addr) {
         // General Internal Memory
         0x0000_0000...0x0000_3FFF => self.bios.get32(addr),
@@ -74,7 +79,7 @@ pub fn read32(self: *const Self, addr: u32) u32 {
 }
 
 pub fn write32(self: *Self, addr: u32, word: u32) void {
-    // TODO: write32 can write to GamePak Flash
+    self.sched.tick += 1;
 
     switch (addr) {
         // General Internal Memory
@@ -92,6 +97,8 @@ pub fn write32(self: *Self, addr: u32, word: u32) void {
 }
 
 pub fn read16(self: *const Self, addr: u32) u16 {
+    self.sched.tick += 1;
+
     return switch (addr) {
         // General Internal Memory
         0x0000_0000...0x0000_3FFF => self.bios.get16(addr),
@@ -114,7 +121,8 @@ pub fn read16(self: *const Self, addr: u32) u16 {
 }
 
 pub fn write16(self: *Self, addr: u32, halfword: u16) void {
-    // TODO: write16 can write to GamePak Flash
+    self.sched.tick += 1;
+
     switch (addr) {
         // General Internal Memory
         0x0200_0000...0x02FF_FFFF => self.ewram.set16(addr & 0x3FFFF, halfword),
@@ -132,6 +140,8 @@ pub fn write16(self: *Self, addr: u32, halfword: u16) void {
 }
 
 pub fn read8(self: *const Self, addr: u32) u8 {
+    self.sched.tick += 1;
+
     return switch (addr) {
         // General Internal Memory
         0x0000_0000...0x0000_3FFF => self.bios.get8(addr),
@@ -155,6 +165,8 @@ pub fn read8(self: *const Self, addr: u32) u8 {
 }
 
 pub fn write8(self: *Self, addr: u32, byte: u8) void {
+    self.sched.tick += 1;
+
     switch (addr) {
         // General Internal Memory
         0x0200_0000...0x02FF_FFFF => self.ewram.set8(addr & 0x3FFFF, byte),
diff --git a/src/emu.zig b/src/emu.zig
index 2ff3990..fd34689 100644
--- a/src/emu.zig
+++ b/src/emu.zig
@@ -43,9 +43,9 @@ pub fn run(kind: RunKind, quit: *Atomic(bool), fps: *FpsAverage, sched: *Schedul
 }
 
 pub fn runFrame(sched: *Scheduler, cpu: *Arm7tdmi, bus: *Bus) void {
-    var cycles: u64 = 0;
-    while (cycles < cycles_per_frame) : (cycles += 1) {
-        sched.tick += 1;
+    const frame_end = sched.tick + cycles_per_frame;
+
+    while (sched.tick < frame_end) {
         _ = cpu.step();
 
         while (sched.tick >= sched.nextTimestamp()) {