From c13759454fa97248f2fd671d6a0de5144f317e7a Mon Sep 17 00:00:00 2001
From: xbzk <xbzk@eden-emu.dev>
Date: Wed, 10 Jun 2026 07:25:35 -0300
Subject: [PATCH] [patcher] CNTFRQ_EL0 impl based on CNTVCT_EL0

---
 src/core/arm/nce/patcher.cpp | 19 ++++++++++++++++++-
 src/core/arm/nce/patcher.h   |  2 ++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/core/arm/nce/patcher.cpp b/src/core/arm/nce/patcher.cpp
index 79ff3b1e31..7d2041d4d2 100644
--- a/src/core/arm/nce/patcher.cpp
+++ b/src/core/arm/nce/patcher.cpp
@@ -145,7 +145,14 @@ bool Patcher::PatchText(std::span<const u8> program_image, const Kernel::CodeSet
 
         // MRS Xn, CNTFRQ_EL0
         if (auto mrs = MRS{inst}; mrs.Verify() && mrs.GetSystemReg() == CntfrqEl0) {
-            UNREACHABLE();
+            bool pre_buffer = false;
+            auto ret = AddRelocations(pre_buffer);
+            if (pre_buffer) {
+                WriteCntfrqHandler(ret, oaknut::XReg{static_cast<int>(mrs.GetRt())}, c_pre);
+            } else {
+                WriteCntfrqHandler(ret, oaknut::XReg{static_cast<int>(mrs.GetRt())}, c);
+            }
+            continue;
         }
 
         // MSR TPIDR_EL0, Xn
@@ -577,6 +584,16 @@ void Patcher::WriteMsrHandler(ModuleDestLabel module_dest, oaknut::XReg src_reg,
         this->BranchToModule(module_dest);
 }
 
+void Patcher::WriteCntfrqHandler(ModuleDestLabel module_dest, oaknut::XReg dest_reg, oaknut::VectorCodeGenerator& cg) {
+    cg.MOV(dest_reg, Common::WallClock::CNTFRQ);
+
+    // Jump back to the instruction after the emulated MRS.
+    if (&cg == &c_pre)
+        this->BranchToModulePre(module_dest);
+    else
+        this->BranchToModule(module_dest);
+}
+
 void Patcher::WriteCntpctHandler(ModuleDestLabel module_dest, oaknut::XReg dest_reg, oaknut::VectorCodeGenerator& cg) {
 #if defined(HAS_NCE)
     static Common::WallClock clock(false, 1);
diff --git a/src/core/arm/nce/patcher.h b/src/core/arm/nce/patcher.h
index 980a0c81e0..04d8534351 100644
--- a/src/core/arm/nce/patcher.h
+++ b/src/core/arm/nce/patcher.h
@@ -80,6 +80,7 @@ private:
     void WriteSvcTrampoline(ModuleDestLabel module_dest, u32 svc_id, oaknut::VectorCodeGenerator& code, oaknut::Label& save_ctx, oaknut::Label& load_ctx);
     void WriteMrsHandler(ModuleDestLabel module_dest, oaknut::XReg dest_reg, oaknut::SystemReg src_reg, oaknut::VectorCodeGenerator& code);
     void WriteMsrHandler(ModuleDestLabel module_dest, oaknut::XReg src_reg, oaknut::VectorCodeGenerator& code);
+    void WriteCntfrqHandler(ModuleDestLabel module_dest, oaknut::XReg dest_reg, oaknut::VectorCodeGenerator& code);
     void WriteCntpctHandler(ModuleDestLabel module_dest, oaknut::XReg dest_reg, oaknut::VectorCodeGenerator& code);
 
     // Convenience wrappers using default code generator
@@ -90,6 +91,7 @@ private:
     void WriteSvcTrampoline(ModuleDestLabel module_dest, u32 svc_id) { WriteSvcTrampoline(module_dest, svc_id, c, m_save_context, m_load_context); }
     void WriteMrsHandler(ModuleDestLabel module_dest, oaknut::XReg dest_reg, oaknut::SystemReg src_reg) { WriteMrsHandler(module_dest, dest_reg, src_reg, c); }
     void WriteMsrHandler(ModuleDestLabel module_dest, oaknut::XReg src_reg) { WriteMsrHandler(module_dest, src_reg, c); }
+    void WriteCntfrqHandler(ModuleDestLabel module_dest, oaknut::XReg dest_reg) { WriteCntfrqHandler(module_dest, dest_reg, c); }
     void WriteCntpctHandler(ModuleDestLabel module_dest, oaknut::XReg dest_reg) { WriteCntpctHandler(module_dest, dest_reg, c); }
 
 private: