PowerPC: partially implement thermal related SPRs

Doesn't support triggering interrupts when the thermal threshold is
exceeded, but allows polling for temperature information.

The THRM[123] registers are documented in most PPC datasheets, see e.g.
this PPC750CX one: http://datasheets.chipdb.org/IBM/PowerPC/750/750cx_um3-17-05.pdf

3 files changed, 70 insertions, 0 deletions

diff --git a/Source/Core/Core/PowerPC/Gekko.h b/Source/Core/Core/PowerPC/Gekko.h
index b11a7565f0..590bd5c3ea 100644
--- a/Source/Core/Core/PowerPC/Gekko.h
+++ b/Source/Core/Core/PowerPC/Gekko.h
@@ -744,6 +744,38 @@ union UReg_BAT_Lo
   explicit UReg_BAT_Lo(u32 hex_) : Hex{hex_} {}
 };
 
+union UReg_THRM12
+{
+  struct
+  {
+    u32 V : 1;    // Valid
+    u32 TIE : 1;  // Thermal Interrupt Enable
+    u32 TID : 1;  // Thermal Interrupt Direction
+    u32 : 20;
+    u32 THRESHOLD : 7;  // Temperature Threshold, 0-127°C
+    u32 TIV : 1;        // Thermal Interrupt Valid
+    u32 TIN : 1;        // Thermal Interrupt
+  };
+  u32 Hex = 0;
+
+  UReg_THRM12() = default;
+  explicit UReg_THRM12(u32 hex_) : Hex{hex_} {}
+};
+
+union UReg_THRM3
+{
+  struct
+  {
+    u32 E : 1;      // Enable
+    u32 SITV : 13;  // Sample Interval Timer Value
+    u32 : 18;
+  };
+  u32 Hex = 0;
+
+  UReg_THRM3() = default;
+  explicit UReg_THRM3(u32 hex_) : Hex{hex_} {}
+};
+
 union UReg_PTE
 {
   struct
@@ -854,6 +886,10 @@ enum
   SPR_MMCR1 = 956,
   SPR_PMC3 = 957,
   SPR_PMC4 = 958,
+
+  SPR_THRM1 = 1020,
+  SPR_THRM2 = 1021,
+  SPR_THRM3 = 1022,
 };
 
 // Exceptions
diff --git a/Source/Core/Core/PowerPC/Interpreter/Interpreter_SystemRegisters.cpp b/Source/Core/Core/PowerPC/Interpreter/Interpreter_SystemRegisters.cpp
index d40462c7b5..7a5c0455b5 100644
--- a/Source/Core/Core/PowerPC/Interpreter/Interpreter_SystemRegisters.cpp
+++ b/Source/Core/Core/PowerPC/Interpreter/Interpreter_SystemRegisters.cpp
@@ -459,6 +459,37 @@ void Interpreter::mtspr(UGeckoInstruction inst)
       PowerPC::IBATUpdated();
     }
     break;
+
+  case SPR_THRM1:
+  case SPR_THRM2:
+  case SPR_THRM3:
+  {
+    // We update both THRM1 and THRM2 when either of the 3 thermal control
+    // registers are updated. THRM1 and THRM2 are independent, but THRM3 has
+    // settings that impact both.
+    //
+    // TODO: Support thermal interrupts when enabled.
+    constexpr u32 SIMULATED_TEMP = 42;  // °C
+
+    auto UpdateThermalReg = [](UReg_THRM12* reg) {
+      if (!THRM3.E || !reg->V)
+      {
+        reg->TIV = 0;
+      }
+      else
+      {
+        reg->TIV = 1;
+        if (reg->TID)
+          reg->TIN = SIMULATED_TEMP < reg->THRESHOLD;
+        else
+          reg->TIN = SIMULATED_TEMP > reg->THRESHOLD;
+      }
+    };
+
+    UpdateThermalReg(&THRM1);
+    UpdateThermalReg(&THRM2);
+    break;
+  }
   }
 }
 
diff --git a/Source/Core/Core/PowerPC/PowerPC.h b/Source/Core/Core/PowerPC/PowerPC.h
index fe1e11ef03..9d551de056 100644
--- a/Source/Core/Core/PowerPC/PowerPC.h
+++ b/Source/Core/Core/PowerPC/PowerPC.h
@@ -220,6 +220,9 @@ void UpdatePerformanceMonitor(u32 cycles, u32 num_load_stores, u32 num_fp_inst);
 #define DMAL (*(UReg_DMAL*)&PowerPC::ppcState.spr[SPR_DMAL])
 #define MMCR0 ((UReg_MMCR0&)PowerPC::ppcState.spr[SPR_MMCR0])
 #define MMCR1 ((UReg_MMCR1&)PowerPC::ppcState.spr[SPR_MMCR1])
+#define THRM1 ((UReg_THRM12&)PowerPC::ppcState.spr[SPR_THRM1])
+#define THRM2 ((UReg_THRM12&)PowerPC::ppcState.spr[SPR_THRM2])
+#define THRM3 ((UReg_THRM3&)PowerPC::ppcState.spr[SPR_THRM3])
 #define PC PowerPC::ppcState.pc
 #define NPC PowerPC::ppcState.npc
 #define FPSCR PowerPC::ppcState.fpscr