feat: add CPU clock rate slider to settings

Implement a slider in the CPU settings tab to adjust the BASE_CLOCK_RATE
up to 1,785 MHz (Switch's official maximum clock rate). Default remains
at 1,020 MHz.

This change:
- Adds UI slider and spinbox to configure_cpu.ui with range 500-1785 MHz
- Makes BASE_CLOCK_RATE dynamic by reading from settings
- Modifies WallClock to handle dynamic clock rate changes
- Updates APM controller to properly set the clock rate
- Changes clock rate settings category from Core to CPU

The user can now easily adjust the CPU clock rate to improve performance
or manage thermals and power consumption.

Signed-off-by: Zephyron <zephyron@citron-emu.org>

6 files changed, 116 insertions, 10 deletions

diff --git a/src/common/settings.h b/src/common/settings.h
index ae90eda83..2df3325e8 100644
--- a/src/common/settings.h
+++ b/src/common/settings.h
@@ -199,6 +199,7 @@ struct Values {
                                                              MemoryLayout::Memory_12Gb,
                                                              "memory_layout_mode",
                                                              Category::Core};
+    SwitchableSetting<u32> cpu_clock_rate{linkage, 1'020'000'000, "cpu_clock_rate", Category::Cpu};
     SwitchableSetting<bool> use_speed_limit{
         linkage, true, "use_speed_limit", Category::Core, Specialization::Paired, false, true};
     SwitchableSetting<u16, true> speed_limit{linkage,
diff --git a/src/common/wall_clock.h b/src/common/wall_clock.h
index 3a0c43909..8b971c3be 100644
--- a/src/common/wall_clock.h
+++ b/src/common/wall_clock.h
@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: Copyright 2020 yuzu Emulator Project
+// SPDX-FileCopyrightText: Copyright 2025 citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #pragma once
@@ -8,6 +9,7 @@
 #include <ratio>
 
 #include "common/common_types.h"
+#include "core/hardware_properties.h"
 
 namespace Common {
 
@@ -15,7 +17,10 @@ class WallClock {
 public:
     static constexpr u64 CNTFRQ = 19'200'000;         // CNTPCT_EL0 Frequency = 19.2 MHz
     static constexpr u64 GPUTickFreq = 614'400'000;   // GM20B GPU Tick Frequency = 614.4 MHz
-    static constexpr u64 CPUTickFreq = 1'020'000'000; // T210/4 A57 CPU Tick Frequency = 1020.0 MHz
+    // Changed from constexpr to function to get dynamic value from settings
+    static inline u64 CPUTickFreq() {
+        return Core::Hardware::BASE_CLOCK_RATE();
+    } // T210/4 A57 CPU Tick Frequency from settings
 
     virtual ~WallClock() = default;
 
@@ -76,12 +81,28 @@ protected:
     using NsToCNTPCTRatio = std::ratio<CNTFRQ, std::nano::den>;
     using NsToGPUTickRatio = std::ratio<GPUTickFreq, std::nano::den>;
 
-    // Cycle Timing
+    // Cycle Timing - using functions for dynamic values
+
+    // Update these to use functions instead of constexpr
+    struct CPUTickToNsRatio {
+        static inline std::intmax_t num = std::nano::den;
+        static inline std::intmax_t den = CPUTickFreq();
+    };
+
+    struct CPUTickToUsRatio {
+        static inline std::intmax_t num = std::micro::den;
+        static inline std::intmax_t den = CPUTickFreq();
+    };
+
+    struct CPUTickToCNTPCTRatio {
+        static inline std::intmax_t num = CNTFRQ;
+        static inline std::intmax_t den = CPUTickFreq();
+    };
 
-    using CPUTickToNsRatio = std::ratio<std::nano::den, CPUTickFreq>;
-    using CPUTickToUsRatio = std::ratio<std::micro::den, CPUTickFreq>;
-    using CPUTickToCNTPCTRatio = std::ratio<CNTFRQ, CPUTickFreq>;
-    using CPUTickToGPUTickRatio = std::ratio<GPUTickFreq, CPUTickFreq>;
+    struct CPUTickToGPUTickRatio {
+        static inline std::intmax_t num = GPUTickFreq;
+        static inline std::intmax_t den = CPUTickFreq();
+    };
 };
 
 std::unique_ptr<WallClock> CreateOptimalClock();
diff --git a/src/core/hardware_properties.h b/src/core/hardware_properties.h
index 5b4630ec5..1b389be29 100644
--- a/src/core/hardware_properties.h
+++ b/src/core/hardware_properties.h
@@ -9,12 +9,13 @@
 
 #include "common/bit_util.h"
 #include "common/common_types.h"
+#include "common/settings.h"
 
 namespace Core {
 
 namespace Hardware {
 
-constexpr u64 BASE_CLOCK_RATE = 1'020'000'000; // Default CPU Frequency = 1020 MHz
+inline u64 BASE_CLOCK_RATE() { return Settings::values.cpu_clock_rate.GetValue(); } // Default CPU Frequency set in settings, defaults to 1020 MHz
 constexpr u64 CNTFREQ = 19'200'000;            // CNTPCT_EL0 Frequency = 19.2 MHz
 constexpr u32 NUM_CPU_CORES = 4;               // Number of CPU Cores
 
diff --git a/src/core/hle/service/apm/apm_controller.cpp b/src/core/hle/service/apm/apm_controller.cpp
index 4f1aa5cc2..abbee804b 100644
--- a/src/core/hle/service/apm/apm_controller.cpp
+++ b/src/core/hle/service/apm/apm_controller.cpp
@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: Copyright 2019 yuzu Emulator Project
+// SPDX-FileCopyrightText: Copyright 2025 citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include <algorithm>
@@ -81,8 +82,8 @@ PerformanceConfiguration Controller::GetCurrentPerformanceConfiguration(Performa
 
 void Controller::SetClockSpeed(u32 mhz) {
     LOG_DEBUG(Service_APM, "called, mhz={:08X}", mhz);
-    // TODO(DarkLordZach): Actually signal core_timing to change clock speed.
-    // TODO(Rodrigo): Remove [[maybe_unused]] when core_timing is used.
+    // Update the clock rate setting with the provided MHz value (convert to Hz)
+    Settings::values.cpu_clock_rate = mhz * 1'000'000;
 }
 
 } // namespace Service::APM
diff --git a/src/yuzu/configuration/configure_cpu.cpp b/src/yuzu/configuration/configure_cpu.cpp
index 36232a1e4..35780fc24 100644
--- a/src/yuzu/configuration/configure_cpu.cpp
+++ b/src/yuzu/configuration/configure_cpu.cpp
@@ -1,10 +1,13 @@
 // SPDX-FileCopyrightText: Copyright 2020 yuzu Emulator Project
+// SPDX-FileCopyrightText: Copyright 2025 citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include <memory>
 #include <typeinfo>
 #include <vector>
 #include <QComboBox>
+#include <QSpinBox>
+#include <QSlider>
 #include "common/common_types.h"
 #include "common/settings.h"
 #include "common/settings_enums.h"
@@ -38,7 +41,22 @@ ConfigureCpu::ConfigureCpu(const Core::System& system_,
 
 ConfigureCpu::~ConfigureCpu() = default;
 
-void ConfigureCpu::SetConfiguration() {}
+void ConfigureCpu::SetConfiguration() {
+    // Set clock rate values from settings
+    const u32 clock_rate_mhz = Settings::values.cpu_clock_rate.GetValue() / 1'000'000;
+    ui->clock_rate_slider->setValue(static_cast<int>(clock_rate_mhz));
+    ui->clock_rate_spinbox->setValue(static_cast<int>(clock_rate_mhz));
+
+    // Connect slider and spinbox signals to keep them in sync
+    connect(ui->clock_rate_slider, &QSlider::valueChanged, this, [this](int value) {
+        ui->clock_rate_spinbox->setValue(value);
+    });
+
+    connect(ui->clock_rate_spinbox, QOverload<int>::of(&QSpinBox::valueChanged), this, [this](int value) {
+        ui->clock_rate_slider->setValue(value);
+    });
+}
+
 void ConfigureCpu::Setup(const ConfigurationShared::Builder& builder) {
     auto* accuracy_layout = ui->widget_accuracy->layout();
     auto* backend_layout = ui->widget_backend->layout();
@@ -99,6 +117,9 @@ void ConfigureCpu::ApplyConfiguration() {
     for (const auto& apply_func : apply_funcs) {
         apply_func(is_powered_on);
     }
+
+    // Save the clock rate setting (convert from MHz to Hz)
+    Settings::values.cpu_clock_rate = static_cast<u32>(ui->clock_rate_spinbox->value()) * 1'000'000;
 }
 
 void ConfigureCpu::changeEvent(QEvent* event) {
diff --git a/src/yuzu/configuration/configure_cpu.ui b/src/yuzu/configuration/configure_cpu.ui
index 13fd43605..3521f3ab1 100644
--- a/src/yuzu/configuration/configure_cpu.ui
+++ b/src/yuzu/configuration/configure_cpu.ui
@@ -127,6 +127,67 @@
       </widget>
      </item>
      <item>
+      <widget class="QGroupBox" name="clock_rate_group">
+       <property name="title">
+        <string>CPU Clock Rate</string>
+       </property>
+       <layout class="QVBoxLayout">
+        <item>
+         <widget class="QLabel" name="label_clock_description">
+          <property name="text">
+           <string>CPU clock rate in MHz. Setting a higher clock rate will improve performance but may cause system instability. Default is 1020 MHz.</string>
+          </property>
+          <property name="wordWrap">
+           <bool>true</bool>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <layout class="QHBoxLayout">
+          <item>
+           <widget class="QSlider" name="clock_rate_slider">
+            <property name="minimum">
+             <number>500</number>
+            </property>
+            <property name="maximum">
+             <number>1785</number>
+            </property>
+            <property name="value">
+             <number>1020</number>
+            </property>
+            <property name="orientation">
+             <enum>Qt::Horizontal</enum>
+            </property>
+            <property name="tickPosition">
+             <enum>QSlider::TicksBelow</enum>
+            </property>
+            <property name="tickInterval">
+             <number>100</number>
+            </property>
+           </widget>
+          </item>
+          <item>
+           <widget class="QSpinBox" name="clock_rate_spinbox">
+            <property name="suffix">
+             <string> MHz</string>
+            </property>
+            <property name="minimum">
+             <number>500</number>
+            </property>
+            <property name="maximum">
+             <number>1785</number>
+            </property>
+            <property name="value">
+             <number>1020</number>
+            </property>
+           </widget>
+          </item>
+         </layout>
+        </item>
+       </layout>
+      </widget>
+     </item>
+     <item>
       <spacer name="verticalSpacer">
        <property name="orientation">
         <enum>Qt::Vertical</enum>