From af77f9298a527e4cd03ade14f6397dfd2011e7a4 Mon Sep 17 00:00:00 2001
From: Thomas <thomas@thomasw.dev>
Date: Sun, 19 Nov 2023 06:27:14 +0100
Subject: [PATCH] Increase interrupt/HDMA cycle accuracy

---
 src/snes/bus/mainbus.rs | 60 +++++++++++++++++++++--------------------
 1 file changed, 31 insertions(+), 29 deletions(-)

diff --git a/src/snes/bus/mainbus.rs b/src/snes/bus/mainbus.rs
index 00486a3..23c80b9 100644
--- a/src/snes/bus/mainbus.rs
+++ b/src/snes/bus/mainbus.rs
@@ -745,41 +745,43 @@ where
 {
     fn tick(&mut self, ticks: Ticks) -> Result<()> {
         // This ratio is not based on anything that makes sense yet
-        self.ppu.tick(ticks * 8)?;
+        for _ in 0..(ticks * 8) {
+            self.ppu.tick(1)?;
 
-        let entered_vblank = self.ppu.get_clr_intreq_vblank();
-        let entered_hblank = self.ppu.get_clr_intreq_hblank();
+            let entered_vblank = self.ppu.get_clr_intreq_vblank();
+            let entered_hblank = self.ppu.get_clr_intreq_hblank();
 
-        if entered_hblank && !self.ppu.in_vblank() {
-            if self.ppu.get_current_scanline() == 0 {
-                self.hdma_reset();
-            }
+            if entered_hblank && !self.ppu.in_vblank() {
+                if self.ppu.get_current_scanline() == 0 {
+                    self.hdma_reset();
+                }
 
-            self.hdma_run();
-        }
+                self.hdma_run();
+            }
 
-        if entered_vblank && self.nmitimen & (1 << 7) != 0 {
-            self.intreq_nmi = true;
-        }
+            if entered_vblank && self.nmitimen & (1 << 7) != 0 {
+                self.intreq_nmi = true;
+            }
 
-        // H/V interrupt
-        // TODO stop at EXACT H rather than at 0
-        let hvint = match (self.nmitimen >> 4) & 0x03 {
-            // Disabled
-            0 => false,
-            // H=H + V=*
-            1 => self.ppu.get_current_scanline() != self.last_scanline,
-            // H=0, V=V (2) + H=H, V=V (3)
-            2 | 3 => {
-                self.ppu.get_current_scanline() != self.last_scanline
-                    && self.ppu.get_current_scanline() == usize::from(self.vtime)
+            // H/V interrupt
+            // TODO stop at EXACT H rather than at 0
+            let hvint = match (self.nmitimen >> 4) & 0x03 {
+                // Disabled
+                0 => false,
+                // H=H + V=*
+                1 => self.ppu.get_current_scanline() != self.last_scanline,
+                // H=0, V=V (2) + H=H, V=V (3)
+                2 | 3 => {
+                    self.ppu.get_current_scanline() != self.last_scanline
+                        && self.ppu.get_current_scanline() == usize::from(self.vtime)
+                }
+                _ => unreachable!(),
+            };
+            self.last_scanline = self.ppu.get_current_scanline();
+            if hvint {
+                self.intreq_int = true;
+                self.timeup.set(true);
             }
-            _ => unreachable!(),
-        };
-        self.last_scanline = self.ppu.get_current_scanline();
-        if hvint {
-            self.intreq_int = true;
-            self.timeup.set(true);
         }
 
         Ok(())