From b26a9556f77fcb99cdee3df19d0171db01fff4e1 Mon Sep 17 00:00:00 2001
From: Stenzek <stenzek@gmail.com>
Date: Mon, 22 Apr 2024 00:19:44 +1000
Subject: [PATCH] System: Improve reset determinism

---
 src/core/cpu_core.cpp |  7 ++++---
 src/core/gpu.cpp      |  6 ++++--
 src/core/spu.cpp      |  3 ++-
 src/core/system.cpp   |  2 +-
 src/core/timers.cpp   | 15 ++++++++-------
 5 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/src/core/cpu_core.cpp b/src/core/cpu_core.cpp
index 7d8ff20cf..681ba1bb5 100644
--- a/src/core/cpu_core.cpp
+++ b/src/core/cpu_core.cpp
@@ -183,8 +183,6 @@ void CPU::Shutdown()
 
 void CPU::Reset()
 {
-  g_state.pending_ticks = 0;
-  g_state.downcount = 0;
   g_state.exception_raised = false;
   g_state.bus_error = false;
 
@@ -208,8 +206,11 @@ void CPU::Reset()
   if (g_settings.gpu_pgxp_enable)
     PGXP::Reset();
 
-  // TODO: This consumes cycles...
+  // This consumes cycles, so do it first.
   SetPC(RESET_VECTOR);
+
+  g_state.pending_ticks = 0;
+  g_state.downcount = 0;
 }
 
 bool CPU::DoState(StateWrapper& sw)
diff --git a/src/core/gpu.cpp b/src/core/gpu.cpp
index 9fc0cc810..62998ab8d 100644
--- a/src/core/gpu.cpp
+++ b/src/core/gpu.cpp
@@ -164,6 +164,10 @@ void GPU::Reset(bool clear_vram)
   if (clear_vram)
     std::memset(g_vram, 0, sizeof(g_vram));
 
+  // Force event to reschedule itself.
+  m_crtc_tick_event->Deactivate();
+  m_command_tick_event->Deactivate();
+
   SoftReset();
   UpdateDisplay();
 }
@@ -211,7 +215,6 @@ void GPU::SoftReset()
   SetTextureWindow(0);
   UpdateDMARequest();
   UpdateCRTCConfig();
-  UpdateCRTCTickEvent();
   UpdateCommandTickEvent();
   UpdateGPUIdle();
 }
@@ -342,7 +345,6 @@ bool GPU::DoState(StateWrapper& sw, GPUTexture** host_texture, bool update_displ
     if (update_display)
       UpdateDisplay();
 
-    UpdateCRTCTickEvent();
     UpdateCommandTickEvent();
   }
 
diff --git a/src/core/spu.cpp b/src/core/spu.cpp
index 8d260dcc9..b0d9e0726 100644
--- a/src/core/spu.cpp
+++ b/src/core/spu.cpp
@@ -529,8 +529,9 @@ void SPU::Reset()
     v.ignore_loop_address = false;
   }
 
-  s_transfer_fifo.Clear();
+  s_tick_event->Deactivate();
   s_transfer_event->Deactivate();
+  s_transfer_fifo.Clear();
   s_ram.fill(0);
   UpdateEventInterval();
 }
diff --git a/src/core/system.cpp b/src/core/system.cpp
index 222d9820b..1f586fd28 100644
--- a/src/core/system.cpp
+++ b/src/core/system.cpp
@@ -2266,6 +2266,7 @@ void System::InternalReset()
   if (IsShutdown())
     return;
 
+  TimingEvents::Reset();
   CPU::Reset();
   CPU::CodeCache::Reset();
   if (g_settings.gpu_pgxp_enable)
@@ -2284,7 +2285,6 @@ void System::InternalReset()
   PCDrv::Reset();
   s_frame_number = 1;
   s_internal_frame_number = 0;
-  TimingEvents::Reset();
   InterruptExecution();
   ResetPerformanceCounters();
 
diff --git a/src/core/timers.cpp b/src/core/timers.cpp
index 00470a739..eb5cb49d9 100644
--- a/src/core/timers.cpp
+++ b/src/core/timers.cpp
@@ -75,9 +75,9 @@ static void UpdateSysClkEvent();
 static std::unique_ptr<TimingEvent> s_sysclk_event;
 
 static std::array<CounterState, NUM_TIMERS> s_states{};
-static TickCount s_syclk_ticks_carry = 0; // 0 unless overclocking is enabled
-static u32 s_sysclk_div_8_carry = 0;      // partial ticks for timer 3 with sysclk/8
-};                                        // namespace Timers
+static TickCount s_sysclk_ticks_carry = 0; // 0 unless overclocking is enabled
+static u32 s_sysclk_div_8_carry = 0;       // partial ticks for timer 3 with sysclk/8
+};                                         // namespace Timers
 
 void Timers::Initialize()
 {
@@ -105,7 +105,8 @@ void Timers::Reset()
     cs.irq_done = false;
   }
 
-  s_syclk_ticks_carry = 0;
+  s_sysclk_event->Deactivate();
+  s_sysclk_ticks_carry = 0;
   s_sysclk_div_8_carry = 0;
   UpdateSysClkEvent();
 }
@@ -124,7 +125,7 @@ bool Timers::DoState(StateWrapper& sw)
     sw.Do(&cs.irq_done);
   }
 
-  sw.Do(&s_syclk_ticks_carry);
+  sw.Do(&s_sysclk_ticks_carry);
   sw.Do(&s_sysclk_div_8_carry);
 
   if (sw.IsReading())
@@ -135,7 +136,7 @@ bool Timers::DoState(StateWrapper& sw)
 
 void Timers::CPUClocksChanged()
 {
-  s_syclk_ticks_carry = 0;
+  s_sysclk_ticks_carry = 0;
 }
 
 bool Timers::IsUsingExternalClock(u32 timer)
@@ -264,7 +265,7 @@ void Timers::CheckForIRQ(u32 timer, u32 old_counter)
 
 void Timers::AddSysClkTicks(void*, TickCount sysclk_ticks, TickCount ticks_late)
 {
-  sysclk_ticks = System::UnscaleTicksToOverclock(sysclk_ticks, &s_syclk_ticks_carry);
+  sysclk_ticks = System::UnscaleTicksToOverclock(sysclk_ticks, &s_sysclk_ticks_carry);
 
   if (!s_states[0].external_counting_enabled && s_states[0].counting_enabled)
     AddTicks(0, sysclk_ticks);