VideoCommon: reset some CP registers during PI_FIFO_RESET

This fixes the shutdown error in SpongeBob Globs of Doom.

Source/Core/Core/HW/MMIO.cpp

@@ -175,7 +175,7 @@ ReadHandlingMethod<T>* InvalidRead()
   return ComplexRead<T>([](Core::System&, u32 addr) {
     ERROR_LOG_FMT(MEMMAP, "Trying to read {} bits from an invalid MMIO (addr={:08x})",
                   8 * sizeof(T), addr);
-    return -1;
+    return 0;
   });
 }
 template <typename T>

Source/Core/Core/HW/ProcessorInterface.cpp

@@ -20,6 +20,7 @@
 #include "Core/PowerPC/PowerPC.h"
 #include "Core/System.h"
 #include "VideoCommon/AsyncRequests.h"
+#include "VideoCommon/CommandProcessor.h"
 #include "VideoCommon/Fifo.h"
 
 namespace ProcessorInterface
@@ -96,11 +97,11 @@ void ProcessorInterfaceManager::RegisterMMIO(MMIO::Mapping* mmio, u32 base)
                    INFO_LOG_FMT(PROCESSORINTERFACE, "Wrote PI_FIFO_RESET: {:08x}", val);
                    if ((val & 1) != 0)
                    {
+                     // TODO: Is this still necessary now that we reset the CP registers?
                      system.GetGPFifo().ResetGatherPipe();
 
-                     // Assume that all bytes that made it into the GPU fifo did in fact execute
-                     // before this MMIO write takes effect.
-                     system.GetFifo().SyncGPUForRegisterAccess();
+                     // Reset some CP registers. This may trigger an ad-hoc GPU time slice.
+                     system.GetCommandProcessor().ResetFifo();
 
                      // Call Fifo::ResetVideoBuffer() from the video thread. Since that function
                      // resets various pointers used by the video thread, we can't call it directly

Source/Core/Core/State.cpp

@@ -99,7 +99,7 @@ static size_t s_state_writes_in_queue;
 static std::condition_variable s_state_write_queue_is_empty;
 
 // Don't forget to increase this after doing changes on the savestate system
-constexpr u32 STATE_VERSION = 172;  // Last changed in PR 13385
+constexpr u32 STATE_VERSION = 173;  // Last changed in PR 13342
 
 // Increase this if the StateExtendedHeader definition changes
 constexpr u32 EXTENDED_HEADER_VERSION = 1;  // Last changed in PR 12217

Source/Core/VideoCommon/CommandProcessor.cpp

@@ -87,6 +87,8 @@ void CommandProcessorManager::DoState(PointerWrap& p)
   p.Do(m_cp_status_reg);
   p.Do(m_cp_ctrl_reg);
   p.Do(m_cp_clear_reg);
+  p.Do(m_perf_select);
+  p.Do(m_unk_0a_reg);
   m_fifo.DoState(p);
 
   p.Do(m_interrupt_set);
@@ -200,13 +202,13 @@ void CommandProcessorManager::RegisterMMIO(MMIO::Mapping* mmio, u32 base)
   mmio->Register(base | CTRL_REGISTER, MMIO::DirectRead<u16>(&m_cp_ctrl_reg.Hex),
                  MMIO::ComplexWrite<u16>([](Core::System& system_, u32, u16 val) {
                    auto& cp = system_.GetCommandProcessor();
-                   UCPCtrlReg tmp(val);
+                   UCPCtrlReg tmp(val & 0x3F);
                    cp.m_cp_ctrl_reg.Hex = tmp.Hex;
                    cp.SetCpControlRegister();
                    system_.GetFifo().RunGpu();
                  }));
 
-  mmio->Register(base | CLEAR_REGISTER, MMIO::DirectRead<u16>(&m_cp_clear_reg.Hex),
+  mmio->Register(base | CLEAR_REGISTER, MMIO::Constant<u16>(0),
                  MMIO::ComplexWrite<u16>([](Core::System& system_, u32, u16 val) {
                    auto& cp = system_.GetCommandProcessor();
                    UCPClearReg tmp(val);
@@ -215,7 +217,14 @@ void CommandProcessorManager::RegisterMMIO(MMIO::Mapping* mmio, u32 base)
                    system_.GetFifo().RunGpu();
                  }));
 
-  mmio->Register(base | PERF_SELECT, MMIO::InvalidRead<u16>(), MMIO::Nop<u16>());
+  // TODO: Figure out how this works. Written by GXSetGPMetric. Nicktoons MLB has DWARF v2 with enum
+  // names.
+  mmio->Register(base | PERF_SELECT, MMIO::DirectRead<u16>(&m_perf_select),
+                 MMIO::DirectWrite<u16>(&m_perf_select, 0x0007));
+
+  // TODO: Figure out what this is.
+  mmio->Register(base | UNK_0A_REGISTER, MMIO::DirectRead<u16>(&m_unk_0a_reg),
+                 MMIO::DirectWrite<u16>(&m_unk_0a_reg, 0x00FF));
 
   // Some MMIOs have different handlers for single core vs. dual core mode.
   const bool is_on_thread = IsOnThread(m_system);
@@ -565,6 +574,7 @@ void CommandProcessorManager::SetCpStatusRegister()
 
 void CommandProcessorManager::SetCpControlRegister()
 {
+  // Just before disabling reads, give the GPU a chance to catch up.
   if (m_fifo.bFF_GPReadEnable.load(std::memory_order_relaxed) && !m_cp_ctrl_reg.GPReadEnable)
   {
     m_system.GetFifo().SyncGPUForRegisterAccess();
@@ -591,6 +601,18 @@ void CommandProcessorManager::SetCpClearRegister()
 {
 }
 
+void CommandProcessorManager::ResetFifo()
+{
+  // Link fifos, disable interrupts, disable reads.
+  m_cp_ctrl_reg.Hex = 0x0010;
+  SetCpControlRegister();
+  m_perf_select = 0;
+  m_unk_0a_reg = 0;
+  m_fifo.CPLoWatermark = 0;
+  m_fifo.CPHiWatermark = GetPhysicalAddressMask(m_system.IsWii()) & ~31u;
+  SetCpStatusRegister();
+}
+
 void CommandProcessorManager::HandleUnknownOpcode(u8 cmd_byte, const u8* buffer, bool preprocess)
 {
   // Datel software uses 0x01 during startup, and Mario Party 5's Wiggler capsule accidentally uses

Source/Core/VideoCommon/CommandProcessor.h

@@ -60,6 +60,7 @@ enum
   CTRL_REGISTER = 0x02,
   CLEAR_REGISTER = 0x04,
   PERF_SELECT = 0x06,
+  UNK_0A_REGISTER = 0x0A,
   FIFO_BASE_LO = 0x20,
   FIFO_BASE_HI = 0x22,
   FIFO_END_LO = 0x24,
@@ -142,7 +143,8 @@ union UCPClearReg
   {
     u16 ClearFifoOverflow : 1;
     u16 ClearFifoUnderflow : 1;
-    u16 ClearMetrices : 1;
+    // set by GXClearGPMetric
+    u16 ClearMetrics : 1;
     u16 : 13;
   };
   u16 Hex;
@@ -178,6 +180,7 @@ public:
   void SetCpClearRegister();
   void SetCpControlRegister();
   void SetCpStatusRegister();
+  void ResetFifo();
 
   void HandleUnknownOpcode(u8 cmd_byte, const u8* buffer, bool preprocess);
 
@@ -194,6 +197,8 @@ private:
   UCPStatusReg m_cp_status_reg;
   UCPCtrlReg m_cp_ctrl_reg;
   UCPClearReg m_cp_clear_reg;
+  u16 m_perf_select = 0;
+  u16 m_unk_0a_reg = 0;
 
   u16 m_bbox_left = 0;
   u16 m_bbox_top = 0;