GPU: Implement GPU Clock correctly.

src/video_core/gpu.cpp

@@ -6,6 +6,7 @@
 #include "common/microprofile.h"
 #include "core/core.h"
 #include "core/core_timing.h"
+#include "core/core_timing_util.h"
 #include "core/memory.h"
 #include "video_core/engines/fermi_2d.h"
 #include "video_core/engines/kepler_compute.h"
@@ -122,6 +123,17 @@ bool GPU::CancelSyncptInterrupt(const u32 syncpoint_id, const u32 value) {
     return true;
 }
 
+// This values were reversed engineered by fincs from NVN
+// The gpu clock is reported in units of 385/625 nanoseconds
+constexpr u64 gpu_ticks_num = 384;
+constexpr u64 gpu_ticks_den = 625;
+
+u64 GPU::GetTicks() const {
+    const u64 cpu_ticks = system.CoreTiming().GetTicks();
+    const u64 nanoseconds = Core::Timing::CyclesToNs(cpu_ticks).count();
+    return (nanoseconds * gpu_ticks_num) / gpu_ticks_den;
+}
+
 void GPU::FlushCommands() {
     renderer.Rasterizer().FlushCommands();
 }
@@ -340,7 +352,7 @@ void GPU::ProcessSemaphoreTriggerMethod() {
         block.sequence = regs.semaphore_sequence;
         // TODO(Kmather73): Generate a real GPU timestamp and write it here instead of
         // CoreTiming
-        block.timestamp = system.CoreTiming().GetTicks();
+        block.timestamp = GetTicks();
         memory_manager->WriteBlock(regs.semaphore_address.SemaphoreAddress(), &block,
                                    sizeof(block));
     } else {