device,AXI4VGA: add FBHelper for emu

src/main/scala/device/AXI4VGA.scala

@@ -52,7 +52,36 @@ class VGACtrl extends AXI4SlaveModule(new AXI4Lite, new VGACtrlBundle) with HasV
   io.extra.get.sync := sync
 }
 
-class AXI4VGA extends Module with HasVGAConst {
+class FBHelper extends BlackBox with HasBlackBoxInline {
+  val io = IO(new Bundle {
+    val clk = Input(Clock())
+    val valid = Input(Bool())
+    val pixel = Input(UInt(32.W))
+    val sync = Input(Bool())
+  })
+
+  setInline("FBHelper.v",
+    s"""
+      |import "DPI-C" function void put_pixel(input int pixel);
+      |import "DPI-C" function void vmem_sync();
+      |
+      |module FBHelper (
+      |  input clk,
+      |  input valid,
+      |  input [31:0] pixel,
+      |  input sync
+      |);
+      |
+      |  always@(posedge clk) begin
+      |    if (valid) put_pixel(pixel);
+      |    if (sync) vmem_sync();
+      |  end
+      |
+      |endmodule
+     """.stripMargin)
+}
+
+class AXI4VGA(sim: Boolean = false) extends Module with HasVGAConst {
   val AXIidBits = 2
   // need a 50MHz clock
   val io = IO(new Bundle {
@@ -108,4 +137,12 @@ class AXI4VGA extends Module with HasVGAConst {
   io.vga.r := Mux(videoValid, color(23, 20), 0.U)
   io.vga.g := Mux(videoValid, color(15, 12), 0.U)
   io.vga.b := Mux(videoValid, color(7, 4), 0.U)
+
+  if (sim) {
+    val fbHelper = Module(new FBHelper)
+    fbHelper.io.clk := clock
+    fbHelper.io.valid := videoValid
+    fbHelper.io.pixel := color
+    fbHelper.io.sync := ctrl.io.extra.get.sync
+  }
 }

src/test/csrc/device.cpp

@@ -14,7 +14,7 @@ void uart_putc(char c);
 void init_uart(void);
 
 static struct timeval boot = {};
-static uint64_t vmem[0x400000 / sizeof(uint64_t)];
+static uint32_t vmem[800 * 600];
 
 void init_device(void) {
   init_sdl();
@@ -55,6 +55,16 @@ uint32_t uptime(void) {
   return s * 1000 + (us + 500) / 1000;
 }
 
+extern "C" void put_pixel(uint32_t pixel) {
+  static int i = 0;
+  vmem[i++] = pixel;
+  if (i >= 800 * 600) i = 0;
+}
+
+extern "C" void vmem_sync(void) {
+  update_screen(vmem);
+}
+
 extern "C" void device_helper(
     uint8_t req_wen, uint64_t req_addr, uint64_t req_wdata, uint8_t req_wmask, uint64_t *resp_rdata) {
   switch (req_addr) {

src/test/csrc/vga.cpp

@@ -4,8 +4,8 @@
 
 #define SCREEN_PORT 0x100 // Note that this is not the standard
 #define SCREEN_MMIO 0x4100
-#define SCREEN_H 320
-#define SCREEN_W 400
+#define SCREEN_H 600
+#define SCREEN_W 800
 
 
 static SDL_Window *window;
@@ -25,7 +25,7 @@ uint32_t screen_size(void) {
 
 void init_sdl() {
   SDL_Init(SDL_INIT_VIDEO);
-  SDL_CreateWindowAndRenderer(SCREEN_W * 2, SCREEN_H * 2, 0, &window, &renderer);
+  SDL_CreateWindowAndRenderer(SCREEN_W, SCREEN_H, 0, &window, &renderer);
   SDL_SetWindowTitle(window, "NOOP");
   texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_ARGB8888,
       SDL_TEXTUREACCESS_STATIC, SCREEN_W, SCREEN_H);

src/test/scala/top/SimMMIO.scala

@@ -36,7 +36,7 @@ class SimMMIO extends Module {
 
   val uart = Module(new AXI4UART)
   val timer = Module(new AXI4Timer)
-  val vga = Module(new AXI4VGA)
+  val vga = Module(new AXI4VGA(sim = true))
   uart.io.in <> xbar.io.out(0).toAXI4Lite()
   timer.io.in <> xbar.io.out(1).toAXI4Lite()
   vga.io.in.fb <> xbar.io.out(2).toAXI4Lite()