Add framebuffer device

CMakeLists.txt

@@ -8,12 +8,15 @@ message(STATUS "Build type: ${CMAKE_BUILD_TYPE}")
 
 set (CMAKE_CXX_FLAGS "-static-libgcc -static-libstdc++ -Werror -Wall -Wunused-result -Wno-unused-function -Wno-unused-variable -fno-omit-frame-pointer -fsanitize=address -Wno-c99-designator")
 
+find_package(SDL2 REQUIRED)
+
 add_library(vm_lib)
 target_sources(vm_lib
   PRIVATE
   src/vm.cpp
   src/debug.cpp
   src/elf.cpp
+  src/framebuffer.cpp
 
   PUBLIC
   FILE_SET HEADERS
@@ -26,5 +29,6 @@ target_sources(vm_lib
 
 add_executable(rve src/rve.cpp)
 target_link_libraries(rve vm_lib)
+target_link_libraries(rve ${SDL2_LIBRARIES})
 
 install(TARGETS rve)

example/Makefile

@@ -2,5 +2,5 @@ example: example.c Makefile boot.s linker.ld printf.h printf.c putchar.c
 	riscv32-none-elf-as -march=rv32i -mabi=ilp32 boot.s -o boot.o
 	riscv32-none-elf-gcc -fno-builtin -fvisibility=hidden -nostdlib -nostartfiles -march=rv32im -mabi=ilp32 -D PRINTF_DISABLE_SUPPORT_FLOAT=1 -D PRINTF_DISABLE_SUPPORT_LONG_LONG=1 -c printf.c -o printf.o -g
 	riscv32-none-elf-gcc -fno-builtin -fvisibility=hidden -nostdlib -nostartfiles -march=rv32im -mabi=ilp32 -c putchar.c -o putchar.o -g
-	riscv32-none-elf-gcc -fno-builtin -fvisibility=hidden -nostdlib -nostartfiles -march=rv32im -mabi=ilp32 -c example.c -o example.o -g
-	riscv32-none-elf-ld boot.o example.o printf.o putchar.o -T linker.ld -o example -g
+	riscv32-none-elf-gcc -fno-builtin -fvisibility=hidden -nostdlib -nostartfiles -march=rv32im -mabi=ilp32 -c example.c -o example.o -g -O2
+	riscv32-none-elf-ld boot.o example.o printf.o putchar.o -T linker.ld -o example -g -O2

example/example.c

@@ -4,13 +4,18 @@ typedef unsigned long long uint64_t;
 typedef unsigned long uint32_t;
 #define MTIME_BASE 0x0200BFF8
 
+volatile uint32_t* mtime_upper = (uint32_t*)(MTIME_BASE+4);
+volatile uint32_t* mtime_lower = (uint32_t*)MTIME_BASE;
+
+#define FRAMEBUFFER_BASE 0x1D385000
+
 uint64_t read_mtime_atomic() {
   uint32_t upper1, lower, upper2;
 
   do {
-    upper1 = *(uint32_t*)(MTIME_BASE + 4);
-    lower = *(uint32_t*)(MTIME_BASE);
-    upper2 = *(uint32_t*)(MTIME_BASE + 4);
+    upper1 = *mtime_upper;
+    lower = *mtime_lower;
+    upper2 = *mtime_upper;
   } while (upper1 != upper2); // Repeat if upper changed during the process
 
   return ((uint64_t)upper1 << 32) | lower;
@@ -29,11 +34,26 @@ int fib(int n) {
   return fib(n-1) + fib(n-2);
 }
 
+void draw() {
+  for (int i = 0; i< 640; i++) {
+    for (int j = 0; j < 480; j++) {
+      uint32_t color = i*j;
+      uint32_t* addr = (uint32_t*)(FRAMEBUFFER_BASE + ((j*640) + i) *4);
+      *addr = color;
+    }
+  }
+}
+
 int main() {
-  int n = 24;
   uint64_t start = read_mtime_atomic();
-  int res = fib(n);
+
+  draw();
+
   uint64_t end = read_mtime_atomic();
+
+  int n = 24;
+  int res = fib(n);
+
   uint32_t total_msec = timediff_ms(start, end);
 
   printf("fib(%d) = %d\n", n, res);

rve.nix

@@ -18,6 +18,7 @@ pkgs.gcc13Stdenv.mkDerivation rec {
     linuxPackages.perf
     jq
     lcov
+    (SDL2.overrideAttrs {waylandSupport= true;})
     #riscv-pkgs.buildPackages.gcc
     pkgsCross.riscv32-embedded.buildPackages.gcc
     pkgsCross.riscv32-embedded.buildPackages.binutils

src/framebuffer.cpp

@@ -0,0 +1,61 @@
+#include <SDL2/SDL.h>
+#include <SDL2/SDL_render.h>
+
+#include <iostream>
+
+#include "vm.hpp"
+
+SDL_Window* window = nullptr;
+SDL_Renderer* renderer = nullptr;
+SDL_Texture* texture = nullptr;
+
+Framebuffer::Framebuffer() : Device(FRAMEBUFFER_ADDR, 640 * 480 * 4) {
+  if (SDL_Init(SDL_INIT_VIDEO) < 0) {
+    throw std::runtime_error("Failed to initialize SDL");
+  }
+  window = SDL_CreateWindow("rve Framebuffer", SDL_WINDOWPOS_CENTERED,
+                            SDL_WINDOWPOS_CENTERED, 640, 480, 0);
+  if (!window) {
+    throw std::runtime_error("Failed to create SDL window");
+  }
+  /*
+  SDL_Surface* surface = SDL_GetWindowSurface(window);
+  if (!surface) {
+    throw std::runtime_error("Failed to create SDL surface");
+  }
+  */
+
+  // renderer = SDL_CreateSoftwareRenderer(surface);
+
+  // renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
+  renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_SOFTWARE);
+  if (!renderer) {
+    throw std::runtime_error("Failed to create SDL renderer");
+  }
+  texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_ARGB8888,
+                              SDL_TEXTUREACCESS_STREAMING, 640, 480);
+  if (!texture) {
+    throw std::runtime_error("Failed to create SDL texture");
+  }
+
+  SDL_ShowWindow(window);
+
+  draw();
+}
+
+void Framebuffer::draw() {
+  SDL_UpdateTexture(texture, nullptr, &mem[0],
+                    640 * 4);  // Update the SDL texture
+  SDL_RenderClear(renderer);
+  SDL_RenderCopy(renderer, texture, nullptr, nullptr);
+  SDL_RenderPresent(renderer);
+}
+
+void Framebuffer::write_mem(uint8_t* src, size_t addr, size_t size) {
+  Device::write_mem(src, addr, size);
+
+  if (addr + size == base() + (640 * 480) * 4) {
+    // draw to the screen when the last byte is written
+    draw();
+  }
+}

src/vm.cpp

@@ -15,10 +15,11 @@ inline int32_t sign_extend(int32_t value, int bits) {
 
 VM::VM(const std::vector<uint8_t>& memory, const std::string& file_path)
     : ram(memory), pc(PROGRAM_ADDR), file_path(file_path) {
-  devices = std::vector<Device*>(3, 0);
+  devices = std::vector<Device*>(4, 0);
   devices[0] = &ram;
   devices[1] = &uart;
   devices[2] = &timer;
+  devices[3] = &framebuffer;
 }
 
 void VM::setreg(size_t regnum, uint32_t value) {

src/vm.hpp

@@ -12,6 +12,7 @@ const int NUM_REGISTERS = 32;  // Standard RISC-V has 32 registers
 const uint32_t UART_ADDR = 0x10000000;
 const uint32_t PROGRAM_ADDR = 0x80000000;
 const uint32_t MTIME_ADDR = 0x0200BFF8;
+const uint32_t FRAMEBUFFER_ADDR = 0x1D385000;
 
 class Device {
  public:
@@ -28,7 +29,7 @@ class Device {
   uint32_t base() { return base_addr; }
   uint32_t size() { return mem_size; }
 
- private:
+ protected:
   uint32_t base_addr = 0;
   uint32_t mem_size = 0;
   std::vector<uint8_t> mem;
@@ -64,6 +65,15 @@ class Timer final : public Device {
   void set(uint64_t value) { write_mem((uint8_t *)&value, MTIME_ADDR, 8); }
 };
 
+class Framebuffer final : public Device {
+ public:
+  Framebuffer();
+  virtual void write_mem(uint8_t *src, size_t addr, size_t size);
+
+ protected:
+  void draw();
+};
+
 class VM {
  public:
   VM(const std::vector<uint8_t> &memory, const std::string &file_path);
@@ -90,5 +100,6 @@ class VM {
 
   UART uart;
   Timer timer;
+  Framebuffer framebuffer;
   std::vector<Device *> devices;
 };