From c1bd4c863ffc811c7a5881c45fae15e5d4eea086 Mon Sep 17 00:00:00 2001
From: Selim Mustafaev <selim@fastmail.fm>
Date: Sat, 23 Sep 2023 14:26:27 +0300
Subject: [PATCH] Adding DMA for OAM

---
 CMakeLists.txt |  2 +-
 main.cpp       |  2 +-
 src/Dma.cpp    | 44 ++++++++++++++++++++++++++++++++++++++++++++
 src/Dma.h      | 38 ++++++++++++++++++++++++++++++++++++++
 src/Nes.cpp    | 15 ++++++++++-----
 src/Nes.h      |  2 ++
 src/Ppu.cpp    |  5 +++++
 src/Ppu.h      |  3 ++-
 8 files changed, 103 insertions(+), 8 deletions(-)
 create mode 100644 src/Dma.cpp
 create mode 100644 src/Dma.h

diff --git a/CMakeLists.txt b/CMakeLists.txt
index ab8c120..f5c1d56 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -26,7 +26,7 @@ add_executable(nes
         src/Controller.cpp
         src/Controller.h
         src/SdlKeyboardController.cpp
-        src/SdlKeyboardController.h)
+        src/SdlKeyboardController.h src/Dma.cpp src/Dma.h)
 
 find_package(SDL2 CONFIG REQUIRED)
 find_package(fmt REQUIRED)
diff --git a/main.cpp b/main.cpp
index 0330a9d..9189efe 100644
--- a/main.cpp
+++ b/main.cpp
@@ -20,7 +20,7 @@ int main() {
         while(SDL_PollEvent(&e));
     });
     device.connect(std::make_shared<SdlKeyboardController>());
-    device.insertCartridge("/home/selim/Downloads/smb.nes");
+    device.insertCartridge("/home/selim/Downloads/dk.nes");
     //device.insertCartridge("/Users/selim/Documents/nestest.nes");
     //device.insertCartridge("C:\\Users\\selim\\Documents\\nestest.nes");
 
diff --git a/src/Dma.cpp b/src/Dma.cpp
new file mode 100644
index 0000000..cb07d40
--- /dev/null
+++ b/src/Dma.cpp
@@ -0,0 +1,44 @@
+//
+// Created by selim on 9/23/23.
+//
+
+#include "Dma.h"
+#include "Ppu.h"
+#include "Nes.h"
+
+namespace nes {
+
+    Dma::Dma(Nes *system, Ppu *ppu): _system{system}, _ppu{ppu} {
+
+    }
+
+    bool Dma::active() const {
+        return _active;
+    }
+
+    void Dma::tick(uint64_t cycles) {
+        if(_dummy) {
+            if(cycles % 2 == 1) {
+                _dummy = false;
+            }
+        } else {
+            if(cycles % 2 == 0) {
+                _data = _system->read((_page << 8) | _address);
+            } else {
+                _ppu->writeOam(_address, _data);
+                _address++;
+
+                if(_address == 0) {
+                    _active = false;
+                    _dummy = true;
+                }
+            }
+        }
+    }
+
+    void Dma::start(uint8_t page) {
+        _page = page;
+        _active = true;
+    }
+
+}
diff --git a/src/Dma.h b/src/Dma.h
new file mode 100644
index 0000000..0becb15
--- /dev/null
+++ b/src/Dma.h
@@ -0,0 +1,38 @@
+//
+// Created by selim on 9/23/23.
+//
+
+#ifndef NES_DMA_H
+#define NES_DMA_H
+
+#include <cstdint>
+
+namespace nes {
+
+    class Nes;
+    class Ppu;
+
+    class Dma {
+    public:
+        Dma(Nes* system, Ppu* ppu);
+        [[nodiscard]] bool active() const;
+        void tick(uint64_t cycles);
+        void start(uint8_t page);
+
+    private:
+        Nes* _system;
+        Ppu* _ppu;
+
+    private:
+        uint8_t _page = 0;
+        uint8_t _address = 0;
+        uint8_t _data = 0;
+
+    private:
+        bool _active = false;
+        bool _dummy = true;
+    };
+
+}
+
+#endif //NES_DMA_H
diff --git a/src/Nes.cpp b/src/Nes.cpp
index e5e8e6d..8a286d2 100644
--- a/src/Nes.cpp
+++ b/src/Nes.cpp
@@ -22,6 +22,7 @@ namespace nes {
         _ram = std::make_unique<uint8_t[]>(2*1024);
         _cpu = std::make_unique<Cpu>(this);
         _ppu = std::make_unique<Ppu>();
+        _dma = std::make_unique<Dma>(this, _ppu.get());
     }
 
     void Nes::insertCartridge(const fs::path &path, std::optional<uint16_t> address) {
@@ -54,12 +55,16 @@ namespace nes {
 #endif
 
         if(_cycles % 3 == 0) {
-            bool instructionExecuted = _cpu->tick();
+            if(_dma->active()) {
+                _dma->tick(_cycles);
+            } else {
+                bool instructionExecuted = _cpu->tick();
 #ifdef NES_LOGGING
-            if(instructionExecuted) {
-                _logger.addLine(_cycles, _cpu->state());
-            }
+                if(instructionExecuted) {
+                    _logger.addLine(_cycles, _cpu->state());
+                }
 #endif
+            }
         }
 
         if(needInterrupt) {
@@ -111,7 +116,7 @@ namespace nes {
             std::cout << "Cartridge write at address: " << address << std::endl;
         }
         else if(address == 0x4014) {
-            // DMA
+            _dma->start(value);
         }
         else if(address == 0x4016) {
             _controller1->poll();
diff --git a/src/Nes.h b/src/Nes.h
index f8a1f74..38759f6 100644
--- a/src/Nes.h
+++ b/src/Nes.h
@@ -9,6 +9,7 @@
 #include "Cpu.h"
 #include "Ppu.h"
 #include "Cartridge.h"
+#include "Dma.h"
 
 #include <filesystem>
 #include <optional>
@@ -40,6 +41,7 @@ namespace nes {
         std::unique_ptr<Ppu> _ppu;
         std::unique_ptr<Cartridge> _cartridge;
         std::shared_ptr<Controller> _controller1;
+        std::unique_ptr<Dma> _dma;
 
 #ifdef NES_LOGGING
         Logger _logger;
diff --git a/src/Ppu.cpp b/src/Ppu.cpp
index 4116cb4..1c9ee90 100644
--- a/src/Ppu.cpp
+++ b/src/Ppu.cpp
@@ -415,4 +415,9 @@ namespace nes {
                            _bgAttribShifter._lo,
                            _bgAttribShifter._hi);
     }
+
+    void Ppu::writeOam(uint8_t address, uint8_t data) {
+        auto oamPtr = reinterpret_cast<uint8_t*>(_oamData.get());
+        oamPtr[address] = data;
+    }
 }
\ No newline at end of file
diff --git a/src/Ppu.h b/src/Ppu.h
index d3bd7fd..7ae3c9f 100644
--- a/src/Ppu.h
+++ b/src/Ppu.h
@@ -112,7 +112,8 @@ namespace nes {
         void setPixel(uint16_t row, uint16_t column, Pixel pixel);
         void connect(Cartridge* cartridge);
         void reset();
-        std::string state() const;
+        [[nodiscard]] std::string state() const;
+        void writeOam(uint8_t address, uint8_t data);
 
     public:
         std::function<void(const Pixel*)> onNewFrame;