GPU: Partial render polygon command processing

src/pse/gpu.cpp

@@ -4,6 +4,14 @@
 #include "dma.h"
 Log_SetChannel(GPU);
 
+static constexpr s32 S11ToS32(u32 value)
+{
+  if (value & (UINT16_C(1) << 10))
+    return static_cast<s32>(UINT32_C(0xFFFFF800) | value);
+  else
+    return value;
+}
+
 GPU::GPU() = default;
 
 GPU::~GPU() = default;
@@ -80,7 +88,17 @@ u32 GPU::DMARead()
 
 void GPU::DMAWrite(u32 value)
 {
-  Log_ErrorPrintf("GPU DMA Write %08X", value);
+  switch (m_GPUSTAT.dma_direction)
+  {
+    case DMADirection::CPUtoGP0:
+      WriteGP0(value);
+      break;
+
+    default:
+      Log_ErrorPrintf("Unhandled GPU DMA write mode %u for value %08X",
+                      static_cast<u32>(m_GPUSTAT.dma_direction.GetValue()), value);
+      break;
+  }
 }
 
 u32 GPU::ReadGPUREAD()
@@ -91,9 +109,97 @@ u32 GPU::ReadGPUREAD()
 
 void GPU::WriteGP0(u32 value)
 {
-  const u8 command = Truncate8(value >> 24);
+  Assert(m_GP0_command_length < MAX_GP0_COMMAND_LENGTH);
+
+  m_GP0_command[m_GP0_command_length++] = value;
+
+  const u8 command = Truncate8(m_GP0_command[0] >> 24);
+  const u32 param = m_GP0_command[0] & UINT32_C(0x00FFFFFF);
+  switch (command)
+  {
+    case 0x00: // NOP
+      break;
+
+    case 0xE1: // Set draw mode
+    {
+      // 0..10 bits match GPUSTAT
+      const u32 MASK = ((UINT32_C(1) << 11) - 1);
+      m_GPUSTAT.bits = (m_GPUSTAT.bits & ~MASK) | param & MASK;
+      m_GPUSTAT.texture_disable = (param & (UINT32_C(1) << 11)) != 0;
+      m_texture_config.x_flip = (param & (UINT32_C(1) << 12)) != 0;
+      m_texture_config.y_flip = (param & (UINT32_C(1) << 13)) != 0;
+      Log_DebugPrintf("Set draw mode %08X", param);
+    }
+    break;
+
+    case 0xE2: // set texture window
+    {
+      m_texture_config.window_mask_x = param & UINT32_C(0x1F);
+      m_texture_config.window_mask_y = (param >> 5) & UINT32_C(0x1F);
+      m_texture_config.window_offset_x = (param >> 10) & UINT32_C(0x1F);
+      m_texture_config.window_offset_y = (param >> 15) & UINT32_C(0x1F);
+      Log_DebugPrintf("Set texture window %02X %02X %02X %02X", m_texture_config.window_mask_x,
+                      m_texture_config.window_mask_y, m_texture_config.window_offset_x,
+                      m_texture_config.window_offset_y);
+    }
+    break;
+
+    case 0xE3: // Set drawing area top left
+    {
+      m_drawing_area.top_left_x = param & UINT32_C(0x3FF);
+      m_drawing_area.top_left_y = (param >> 10) & UINT32_C(0x1FF);
+      Log_DebugPrintf("Set drawing area top-left: (%u, %u)", m_drawing_area.top_left_x, m_drawing_area.top_left_y);
+    }
+    break;
+
+    case 0xE4: // Set drawing area bottom right
+    {
+      m_drawing_area.bottom_right_x = param & UINT32_C(0x3FF);
+      m_drawing_area.bottom_right_y = (param >> 10) & UINT32_C(0x1FF);
+      Log_DebugPrintf("Set drawing area bottom-right: (%u, %u)", m_drawing_area.bottom_right_x,
+                      m_drawing_area.bottom_right_y);
+    }
+    break;
+
+    case 0xE5: // Set drawing offset
+    {
+      m_drawing_offset.x = S11ToS32(param & UINT32_C(0x7FF));
+      m_drawing_offset.y = S11ToS32((param >> 11) & UINT32_C(0x7FF));
+      Log_DebugPrintf("Set drawing offset (%d, %d)", m_drawing_offset.x, m_drawing_offset.y);
+    }
+    break;
+
+    case 0xE6: // Mask bit setting
+    {
+      m_GPUSTAT.draw_set_mask_bit = (param & UINT32_C(0x01)) != 0;
+      m_GPUSTAT.draw_to_masked_pixels = (param & UINT32_C(0x01)) != 0;
+      Log_DebugPrintf("Set mask bit %u %u", BoolToUInt32(m_GPUSTAT.draw_set_mask_bit),
+                      BoolToUInt32(m_GPUSTAT.draw_to_masked_pixels));
+    }
+    break;
+
+    default:
+    {
+      if (command < 0x20)
+      {
+      }
+      else if (command < 0x40)
+      {
+        // Draw polygon
+        if (!HandleRenderPolygonCommand())
+          return;
+
+        break;
+      }
+
       Log_ErrorPrintf("Unimplemented GP0 command 0x%02X", command);
     }
+    break;
+  }
+
+  m_GP0_command.fill(UINT32_C(0));
+  m_GP0_command_length = 0;
+}
 
 void GPU::WriteGP1(u32 value)
 {
@@ -114,3 +220,26 @@ void GPU::WriteGP1(u32 value)
       break;
   }
 }
+
+bool GPU::HandleRenderPolygonCommand()
+{
+  const u8 command = Truncate8(m_GP0_command[0] >> 24);
+  const bool semi_transparent = !!(command & 0x02);
+  const bool textured = !!(command & 0x04);
+  const bool four_points = !!(command & 0x08);
+  const bool shaded = !!(command & 0x10);
+
+  // shaded vertices use the colour from the first word for the first vertex
+  const u8 words_per_vertex = 1 + BoolToUInt8(textured) + BoolToUInt8(shaded);
+  const u8 num_vertices = four_points ? 4 : 3;
+  const u8 total_words = words_per_vertex * num_vertices + BoolToUInt8(!shaded);
+  if (m_GP0_command_length < total_words)
+    return false;
+
+  Log_DebugPrintf("Render %s %s %s %s polygon (%u verts, %u words per vert)",
+                  four_points ? "four-point" : "three-point", semi_transparent ? "semi-transparent" : "opaque",
+                  textured ? "textured" : "non-textured", shaded ? "shaded" : "monochrome", ZeroExtend32(num_vertices),
+                  ZeroExtend32(words_per_vertex));
+
+  return true;
+}

src/pse/gpu.h

@@ -23,6 +23,8 @@ public:
   void DMAWrite(u32 value);
 
 private:
+  static constexpr u32 MAX_GP0_COMMAND_LENGTH = 12;
+
   enum class DMADirection : u32
   {
     Off = 0,
@@ -37,6 +39,9 @@ private:
   void WriteGP0(u32 value);
   void WriteGP1(u32 value);
 
+  // Rendering commands, returns false if not enough data is provided
+  bool HandleRenderPolygonCommand();
+
   Bus* m_bus = nullptr;
   DMA* m_dma = nullptr;
 
@@ -69,4 +74,29 @@ private:
     BitField<u32, DMADirection, 29, 2> dma_direction;
     BitField<u32, bool, 31, 1> drawing_even_line;
   } m_GPUSTAT = {};
+
+  struct TextureConfig
+  {
+    u8 window_mask_x;   // in 8 pixel steps
+    u8 window_mask_y;   // in 8 pixel steps
+    u8 window_offset_x; // in 8 pixel steps
+    u8 window_offset_y; // in 8 pixel steps
+    bool x_flip;
+    bool y_flip;
+  } m_texture_config = {};
+
+  struct DrawingArea
+  {
+    u32 top_left_x, top_left_y;
+    u32 bottom_right_x, bottom_right_y;
+  } m_drawing_area = {};
+
+  struct DrawingOffset
+  {
+    s32 x;
+    s32 y;
+  } m_drawing_offset = {};
+
+  std::array<u32, MAX_GP0_COMMAND_LENGTH> m_GP0_command = {};
+  u32 m_GP0_command_length = 0;
 };