cpufreq —
CPU frekans ölçekleme.

┌─────────────────────────────────────────────┐
│           userspace / sysfs                 │
│  /sys/devices/system/cpu/cpu0/cpufreq/      │
├─────────────────────────────────────────────┤
│           cpufreq core (kernel)             │
│   governor → policy → driver               │
├──────────────┬──────────────────────────────┤
│  cpufreq     │  cpufreq driver              │
│  governor    │  (platform-specific)         │
│  (schedutil) │  intel_pstate / acpi-cpufreq │
│              │  cpufreq-dt / arm_big_little  │
├──────────────┴──────────────────────────────┤
│    clock subsystem (clk_set_rate)           │
│    regulator subsystem (regulator_set_v)    │
└─────────────────────────────────────────────┘

# CPU0 cpufreq dizini
ls /sys/devices/system/cpu/cpu0/cpufreq/
# affected_cpus  cpuinfo_cur_freq  cpuinfo_max_freq  cpuinfo_min_freq
# cpuinfo_transition_latency  related_cpus  scaling_available_governors
# scaling_available_frequencies  scaling_cur_freq  scaling_driver
# scaling_governor  scaling_max_freq  scaling_min_freq  scaling_setspeed

# mevcut frekans (kHz)
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
# 1500000

# aktif governor
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
# schedutil

# donanımın desteklediği frekanslar
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
# 600000 900000 1200000 1500000 1800000

# tüm CPU'larda schedutil'e geç
for cpu in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor; do
    echo schedutil > "$cpu"
done

# ya da cpupower ile
cpupower frequency-set -g schedutil

# ondemand parametrelerini ayarla
ls /sys/devices/system/cpu/cpufreq/ondemand/
# ignore_nice_load  powersave_bias  sampling_down_factor
# sampling_rate  sampling_rate_min  up_threshold

# örnekleme hızını artır (ms cinsinden, mikrosaniye değil)
echo 50000 > /sys/devices/system/cpu/cpufreq/ondemand/sampling_rate

# schedutil için rate_limit_us ayarı
cat /sys/devices/system/cpu/cpufreq/schedutil/rate_limit_us
# 1000  (1ms — frekans değişim hızı sınırı)

Gerçek zamanlı / düşük gecikme   → performance
Pil ömrü öncelikli (IoT, sensor) → powersave veya schedutil
Genel amaçlı masaüstü/sunucu    → schedutil (Linux 4.7+)
big.LITTLE / EAS etkin sistem    → schedutil (zorunlu)
Eski çekirdek (< 4.7)            → ondemand
Enerji profili / test            → userspace

/ {
    cpu0_opp_table: opp-table-0 {
        compatible = "operating-points-v2";
        opp-shared;   /* tüm CPU'lar aynı tabloyu paylaşır */

        opp-600000000 {
            opp-hz = /bits/ 64 <600000000>;    /* 600 MHz */
            opp-microvolt = <950000>;            /* 0.95 V */
            clock-latency-ns = <300000>;
        };
        opp-900000000 {
            opp-hz = /bits/ 64 <900000000>;    /* 900 MHz */
            opp-microvolt = <1025000>;           /* 1.025 V */
        };
        opp-1200000000 {
            opp-hz = /bits/ 64 <1200000000>;   /* 1.2 GHz */
            opp-microvolt = <1100000>;           /* 1.1 V */
        };
        opp-1500000000 {
            opp-hz = /bits/ 64 <1500000000>;   /* 1.5 GHz */
            opp-microvolt = <1200000>;           /* 1.2 V */
            turbo-mode;                          /* turbo OPP */
        };
    };

    cpus {
        cpu@0 {
            compatible = "arm,cortex-a53";
            operating-points-v2 = <&cpu0_opp_table>;
            clocks = <&ccu CLK_CPU>;
            clock-names = "cpu";
            cpu-supply = <&reg_vdd_cpu>;  /* regulator bağlantısı */
        };
    };
};

# OPP tablosunu debugfs'ten oku
cat /sys/kernel/debug/opp/cpu0/opp_summary
# OPP: 600000000 Hz, 950000 uV
# OPP: 900000000 Hz, 1025000 uV
# OPP: 1200000000 Hz, 1100000 uV
# OPP: 1500000000 Hz, 1200000 uV  [turbo]

# scaling_available_frequencies ile kontrol et
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
# 600000 900000 1200000 1500000

# devfreq cihazlarını listele (GPU, DDR vb.)
ls /sys/class/devfreq/
# ff400000.gpu  ff610000.dmc

cat /sys/class/devfreq/ff400000.gpu/cur_freq
# 400000000

# CPU0'ı manuel moda al
echo userspace > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

# frekansı 900 MHz'e sabitle (kHz cinsinden)
echo 900000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed

# doğrula
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
# 900000

# frekans aralığını kısıtla (governor hâlâ aktifken)
echo 600000  > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
echo 1200000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq

# tüm CPU'larda aynı anda uygula
for i in $(seq 0 3); do
    echo 1200000 > /sys/devices/system/cpu/cpu$i/cpufreq/scaling_max_freq
done

# cpufreq-set ile governor değiştir
cpufreq-set -c 0 -g schedutil         # CPU0
cpufreq-set -g ondemand               # tüm CPU'lar

# frekans aralığını ayarla
cpufreq-set -c 0 -d 600MHz -u 1.2GHz

# sabit frekans (userspace governor otomatik seçilir)
cpufreq-set -c 0 -f 900MHz

# mevcut ayarları göster
cpufreq-info -c 0

/* Cortex-A55 (LITTLE cluster) */
cpu@0 {
    compatible = "arm,cortex-a55";
    capacity-dmips-mhz = <406>;    /* normalize kapasite */
    dynamic-power-coefficient = <100>;
};

/* Cortex-A76 (big cluster) */
cpu@4 {
    compatible = "arm,cortex-a76";
    capacity-dmips-mhz = <1024>;
    dynamic-power-coefficient = <530>;
};

# EAS durumunu göster
cat /proc/sys/kernel/sched_energy_aware
# 1 = aktif

# Energy Model var mı?
ls /sys/kernel/debug/energy_model/
# cpu0  cpu4

cat /sys/kernel/debug/energy_model/cpu0/table
# cap    freq     power
#  73   500000     50
# 146  1000000     90
# 219  1500000    145

# EAS'ı geçici olarak kapat
echo 0 > /proc/sys/kernel/sched_energy_aware

# boost durumunu göster
cat /sys/devices/system/cpu/cpufreq/boost
# 1 = etkin

# boost'u devre dışı bırak
echo 0 > /sys/devices/system/cpu/cpufreq/boost

# tekrar etkinleştir
echo 1 > /sys/devices/system/cpu/cpufreq/boost

# Intel P-state sürücüsü ile turbo kontrolü
cat /sys/devices/system/cpu/intel_pstate/no_turbo
# 0 = turbo etkin, 1 = kapalı

echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo

# enerji/performans tercihi (EPP)
cat /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_preference
# balance_performance

# mevcut seçenekler
cat /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_available_preferences
# default performance balance_performance balance_power power

echo power > /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_preference

# AMD P-state modu (Linux 5.17+)
cat /sys/devices/system/cpu/amd_pstate/status
# active  (passive veya guided olabilir)

# AMD P-state EPP (Linux 6.3+)
cat /sys/devices/system/cpu/cpu0/cpufreq/amd_pstate_epp
# balance_performance

# Ubuntu/Debian
apt install linux-tools-$(uname -r) cpufrequtils

# Fedora/RHEL
dnf install kernel-tools

# tüm CPU'ların frekans bilgisi
cpupower frequency-info
# analyzing CPU 0:
#   driver: cpufreq-dt
#   CPUs which run at the same hardware frequency: 0
#   hardware limits: 600 MHz - 1.50 GHz
#   available frequency steps:  600 MHz, 900 MHz, 1.20 GHz, 1.50 GHz
#   available cpufreq governors: conservative ondemand userspace
#                                powersave performance schedutil
#   current policy: frequency should be within 600 MHz and 1.50 GHz.
#                   The governor "schedutil" may decide which speed to use
#   current CPU frequency: 900 MHz (asserted by call to hardware)

# governor değiştir (tüm CPU'lar)
cpupower frequency-set -g performance

# maksimum frekansı sınırla
cpupower frequency-set -u 1.2GHz

# minimum frekansı ayarla
cpupower frequency-set -d 900MHz

# belirli CPU için
cpupower -c 2 frequency-set -g powersave

# mevcut monitor'leri listele
cpupower monitor -l
# Monitor "Mperf" (3 states) - Might overflow after 922000000 s
# Monitor "Idle_Stats" (4 states)

# 5 saniye boyunca C-state ve frekans istatistiklerini göster
cpupower monitor -m Mperf,Idle_Stats sleep 5
#               || Mperf                   || Idle_Stats
# PKG |CORE|CPU || C0   | Cx   | Freq  ||POLL | C1   | C2
#   0 |  0 |  0 ||  2.3 | 97.7 |  1024 ||   0 |  1.2 | 96.5

# powertop entegrasyonu
powertop --auto-tune   # mevcut tüm güç tasarruf özelliklerini etkinleştir
powertop --csv=report.csv --time=60  # 60s raporla

CONFIG_CPU_FREQ=y
CONFIG_CPU_FREQ_STAT=y             # sysfs istatistik dosyaları
CONFIG_CPU_FREQ_GOV_PERFORMANCE=y
CONFIG_CPU_FREQ_GOV_POWERSAVE=y
CONFIG_CPU_FREQ_GOV_ONDEMAND=y
CONFIG_CPU_FREQ_GOV_CONSERVATIVE=y
CONFIG_CPU_FREQ_GOV_USERSPACE=y
CONFIG_CPU_FREQ_GOV_SCHEDUTIL=y    # önerilir
CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL=y

# Platform driver (ARM/DT tabanlı)
CONFIG_CPUFREQ_DT=y                # generic DT-based driver
CONFIG_CPUFREQ_DT_PLATDEV=y

# ARM big.LITTLE
CONFIG_ARM_BIG_LITTLE_CPUFREQ=y

# Energy Model
CONFIG_ENERGY_MODEL=y

cpus {
    #address-cells = <1>;
    #size-cells = <0>;

    cpu0: cpu@0 {
        device_type = "cpu";
        compatible = "arm,cortex-a53";
        reg = <0>;
        enable-method = "psci";
        operating-points-v2 = <&cpu_opp_table>;
        clocks = <&ccu CLK_CPU>;       /* clock provider */
        clock-names = "cpu";
        cpu-supply = <&reg_vdd_cpu>;   /* regulator consumer */
        #cooling-cells = <2>;           /* thermal cooling */
    };
};

/* PMIC regulator tanımı */
&axp209 {
    regulators {
        reg_vdd_cpu: dcdc2 {
            regulator-name = "vdd-cpu";
            regulator-min-microvolt = <700000>;
            regulator-max-microvolt = <1300000>;
            regulator-always-on;
        };
    };
};

# throttling durumunu oku (vcgencmd)
vcgencmd get_throttled
# throttled=0x0        → normal
# throttled=0x50000   → throttling oluştu (geçmişte)
# throttled=0x50005   → şu an throttling aktif!

# bit maskeleri:
# bit 0: under-voltage
# bit 1: arm freq capped
# bit 2: currently throttled
# bit 16-18: yukarıdakilerin geçmişte oluşup oluşmadığı

# sıcaklık ve frekansı aynı anda izle
while true; do
    temp=$(vcgencmd measure_temp | cut -d= -f2)
    freq=$(cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq)
    throttle=$(vcgencmd get_throttled)
    echo "$(date +%T) | $temp | ${freq}kHz | $throttle"
    sleep 1
done

# CPU'yu yükle ve throttling'i tetikle
stress-ng --cpu 4 --timeout 60s &

# throttling eşiği: RPi4 85°C üzerinde frekansı 1500→600 MHz'e düşürür
# soğutucu takarak veya frekansı sınırlayarak önle
echo 1200000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq

# mevcut governor ve OPP'leri gör
cpufreq-info
# available frequency steps: 300 MHz, 600 MHz, 720 MHz, 800 MHz, 1000 MHz

# schedutil'e geç (TPS65217 regulator otomatik voltaj ayarı yapar)
cpupower frequency-set -g schedutil

# schedutil rate_limit_us ayarı (gömülü için 4ms önerilir)
echo 4000 > /sys/devices/system/cpu/cpufreq/schedutil/rate_limit_us

# boşta ve yük altındaki frekansı karşılaştır
watch -n0.5 'cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq'

# systemd service ile kalıcı hale getir
cat /etc/systemd/system/cpufreq.service

[Unit]
Description=Set cpufreq governor
After=multi-user.target

[Service]
Type=oneshot
ExecStart=/usr/bin/cpupower frequency-set -g schedutil
ExecStart=/bin/sh -c 'echo 4000 > /sys/devices/system/cpu/cpufreq/schedutil/rate_limit_us'
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

#!/usr/bin/env python3
"""
INA219 I2C güç sensörü ile CPU governor karşılaştırması.
Devre: INA219 0.1Ω shunt, 0x40 adresi, I2C bus 1
Pip: pip3 install pi-ina219
"""
import time, subprocess
from ina219 import INA219, DeviceRangeError

SHUNT_OHMS = 0.1
ina = INA219(SHUNT_OHMS, address=0x40)
ina.configure()

def set_governor(gov):
    subprocess.run(["cpupower", "frequency-set", "-g", gov],
                   capture_output=True)
    time.sleep(0.5)

def measure(duration=10, label=""):
    samples = []
    t_end = time.time() + duration
    while time.time() < t_end:
        try:
            power_mw = ina.power()
            voltage  = ina.voltage()
            samples.append(power_mw)
        except DeviceRangeError:
            pass
        time.sleep(0.1)
    avg = sum(samples) / len(samples) if samples else 0
    print(f"[{label:15s}] Ortalama güç: {avg:6.1f} mW  "
          f"(n={len(samples)})")
    return avg

print("=== Governor Güç Karşılaştırması ===")
for gov in ["powersave", "schedutil", "ondemand", "performance"]:
    set_governor(gov)
    # boşta ölç
    idle  = measure(10, f"{gov}/idle")
    # yük altında ölç
    load  = subprocess.Popen(["stress-ng", "--cpu", "1"])
    time.sleep(1)
    under = measure(10, f"{gov}/load")
    load.terminate()
    print(f"  Tasarruf vs performance: {(1 - idle/under)*100:.1f}%")
    print()