[GPU] Small ring buffer setup function cleanup

src/xenia/gpu/command_processor.cc

@@ -257,22 +257,21 @@ bool CommandProcessor::SetupContext() { return true; }
 
 void CommandProcessor::ShutdownContext() { context_.reset(); }
 
-void CommandProcessor::InitializeRingBuffer(uint32_t ptr, uint32_t log2_size) {
+void CommandProcessor::InitializeRingBuffer(uint32_t ptr, uint32_t size_log2) {
   read_ptr_index_ = 0;
   primary_buffer_ptr_ = ptr;
-  primary_buffer_size_ = 1 << log2_size;
+  primary_buffer_size_ = uint32_t(1) << (size_log2 + 3);
 }
 
 void CommandProcessor::EnableReadPointerWriteBack(uint32_t ptr,
-                                                  uint32_t block_size) {
+                                                  uint32_t block_size_log2) {
   // CP_RB_RPTR_ADDR Ring Buffer Read Pointer Address 0x70C
   // ptr = RB_RPTR_ADDR, pointer to write back the address to.
   read_ptr_writeback_ptr_ = ptr;
   // CP_RB_CNTL Ring Buffer Control 0x704
-  // block_size = RB_BLKSZ, number of quadwords read between updates of the
-  //              read pointer.
-  read_ptr_update_freq_ =
-      static_cast<uint32_t>(pow(2.0, static_cast<double>(block_size)) / 4);
+  // block_size = RB_BLKSZ, log2 of number of quadwords read between updates of
+  //              the read pointer.
+  read_ptr_update_freq_ = uint32_t(1) << block_size_log2 >> 2;
 }
 
 void CommandProcessor::UpdateWritePointer(uint32_t value) {

src/xenia/gpu/command_processor.h

@@ -144,8 +144,8 @@ class CommandProcessor {
 
   virtual void RestoreEdramSnapshot(const void* snapshot) = 0;
 
-  void InitializeRingBuffer(uint32_t ptr, uint32_t page_count);
-  void EnableReadPointerWriteBack(uint32_t ptr, uint32_t block_size);
+  void InitializeRingBuffer(uint32_t ptr, uint32_t size_log2);
+  void EnableReadPointerWriteBack(uint32_t ptr, uint32_t block_size_log2);
 
   void UpdateWritePointer(uint32_t value);
 

src/xenia/gpu/graphics_system.cc

@@ -220,13 +220,13 @@ void GraphicsSystem::WriteRegister(uint32_t addr, uint32_t value) {
   register_file_.values[r].u32 = value;
 }
 
-void GraphicsSystem::InitializeRingBuffer(uint32_t ptr, uint32_t log2_size) {
-  command_processor_->InitializeRingBuffer(ptr, log2_size + 0x3);
+void GraphicsSystem::InitializeRingBuffer(uint32_t ptr, uint32_t size_log2) {
+  command_processor_->InitializeRingBuffer(ptr, size_log2);
 }
 
 void GraphicsSystem::EnableReadPointerWriteBack(uint32_t ptr,
-                                                uint32_t block_size) {
-  command_processor_->EnableReadPointerWriteBack(ptr, block_size);
+                                                uint32_t block_size_log2) {
+  command_processor_->EnableReadPointerWriteBack(ptr, block_size_log2);
 }
 
 void GraphicsSystem::SetInterruptCallback(uint32_t callback,

src/xenia/gpu/graphics_system.h

@@ -55,8 +55,9 @@ class GraphicsSystem {
     return command_processor_.get();
   }
 
-  virtual void InitializeRingBuffer(uint32_t ptr, uint32_t log2_size);
-  virtual void EnableReadPointerWriteBack(uint32_t ptr, uint32_t block_size);
+  virtual void InitializeRingBuffer(uint32_t ptr, uint32_t size_log2);
+  virtual void EnableReadPointerWriteBack(uint32_t ptr,
+                                          uint32_t block_size_log2);
 
   virtual void SetInterruptCallback(uint32_t callback, uint32_t user_data);
   void DispatchInterruptCallback(uint32_t source, uint32_t cpu);

src/xenia/kernel/xboxkrnl/xboxkrnl_video.cc

@@ -228,19 +228,19 @@ void VdSetGraphicsInterruptCallback(function_t callback, lpvoid_t user_data) {
 }
 DECLARE_XBOXKRNL_EXPORT1(VdSetGraphicsInterruptCallback, kVideo, kImplemented);
 
-void VdInitializeRingBuffer(lpvoid_t ptr, int_t log2_size) {
+void VdInitializeRingBuffer(lpvoid_t ptr, int_t size_log2) {
   // r3 = result of MmGetPhysicalAddress
   // r4 = log2(size)
   // Buffer pointers are from MmAllocatePhysicalMemory with WRITE_COMBINE.
   auto graphics_system = kernel_state()->emulator()->graphics_system();
-  graphics_system->InitializeRingBuffer(ptr, log2_size);
+  graphics_system->InitializeRingBuffer(ptr, size_log2);
 }
 DECLARE_XBOXKRNL_EXPORT1(VdInitializeRingBuffer, kVideo, kImplemented);
 
-void VdEnableRingBufferRPtrWriteBack(lpvoid_t ptr, int_t block_size) {
-  // r4 = 6, usually --- <=19
+void VdEnableRingBufferRPtrWriteBack(lpvoid_t ptr, int_t block_size_log2) {
+  // r4 = log2(block size), 6, usually --- <=19
   auto graphics_system = kernel_state()->emulator()->graphics_system();
-  graphics_system->EnableReadPointerWriteBack(ptr, block_size);
+  graphics_system->EnableReadPointerWriteBack(ptr, block_size_log2);
 }
 DECLARE_XBOXKRNL_EXPORT1(VdEnableRingBufferRPtrWriteBack, kVideo, kImplemented);