PPU: setup OBJ VRAM and OAM access stalling

nba-emu · Aug 30, 2022 · eab9098 · eab9098
1 parent 2868db5
commit eab9098
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Showing 4 changed files with 36 additions and 6 deletions.
diff --git a/src/nba/src/bus/bus.cpp b/src/nba/src/bus/bus.cpp
@@ -112,8 +112,7 @@ auto Bus::Read(u32 address, int access) -> T {
     }
     // OAM (object attribute map)
     case 0x07: {
-      Step(1);
-      return hw.ppu.ReadOAM<T>(Align<T>(address));
+      return ReadOAM<T>(Align<T>(address));
     }
     // ROM (WS0, WS1, WS2)
     case 0x08 ... 0x0D: {
@@ -208,8 +207,7 @@ void Bus::Write(u32 address, int access, T value) {
     }
     // OAM (object attribute map)
     case 0x07: {
-      Step(1);
-      hw.ppu.WriteOAM<T>(Align<T>(address), value);
+      WriteOAM<T>(Align<T>(address), value);
       break;
     }
     // ROM (WS0, WS1, WS2)

diff --git a/src/nba/src/bus/bus.hpp b/src/nba/src/bus/bus.hpp
@@ -213,6 +213,26 @@ struct Bus {
     }
   }
 
+  template<typename T>
+  auto ALWAYS_INLINE ReadOAM(u32 address) noexcept -> T {
+    do {
+      Step(1);
+      hw.ppu.Sync();
+    } while(hw.ppu.DidAccessOAM());
+
+    return hw.ppu.ReadOAM<T>(address);
+  }
+
+  template<typename T>
+  void ALWAYS_INLINE WriteOAM(u32 address, T value) noexcept {
+    do {
+      Step(1);
+      hw.ppu.Sync();
+    } while(hw.ppu.DidAccessOAM());
+
+    hw.ppu.WriteOAM<T>(address, value);
+  }
+
   auto ReadBIOS(u32 address) -> u32;
   auto ReadOpenBus(u32 address) -> u32;
 

diff --git a/src/nba/src/hw/ppu/ppu.cpp b/src/nba/src/hw/ppu/ppu.cpp
@@ -78,6 +78,8 @@ void PPU::Reset() {
 
   pram_access = false;
   vram_bg_access = false;
+  vram_obj_access = false;
+  oam_access = false;
 }
 
 void PPU::LatchEnabledBGs() {
@@ -353,8 +355,10 @@ void PPU::InitLineRender() {
     InitCompose();
   }
 
-  vram_bg_access = false;
   pram_access = false;
+  vram_bg_access = false;
+  vram_obj_access = false;
+  oam_access = false;
 }
 
 void PPU::SyncLineRender() {
@@ -376,6 +380,8 @@ void PPU::SyncLineRender() {
 
   pram_access = false;
   vram_bg_access = false;
+  vram_obj_access = false;
+  oam_access = false;
 
   for (int id = 0; id < 4; id++) {
     if (bg[id].engaged) {

diff --git a/src/nba/src/hw/ppu/ppu.hpp b/src/nba/src/hw/ppu/ppu.hpp
@@ -125,7 +125,11 @@ struct PPU {
   }
 
   bool ALWAYS_INLINE DidAccessVRAM_OBJ() const {
-    return false;
+    return vram_obj_access;
+  }
+
+  bool ALWAYS_INLINE DidAccessOAM() const {
+    return oam_access;
   }
 
   struct MMIO {
@@ -300,6 +304,8 @@ struct PPU {
 
   bool pram_access;
   bool vram_bg_access;
+  bool vram_obj_access;
+  bool oam_access;
 
   Scheduler& scheduler;
   IRQ& irq;