mseries-power

#!/bin/bash
# Battery and CPU policy for Apple Silicon (macsmc-battery + apple-cpufreq).
#   mseries-power status          show charge limit, power source, CPU caps
#   mseries-power limit 80|100    set (and persist) the battery charge limit
#   mseries-power apply           apply policy for the current power source (run by systemd/udev)
#   mseries-power cap             set only the CPU ceiling from the power source AND the active power profile
#   mseries-power follow          run forever: re-apply the cap whenever the power profile changes (systemd service)
# The CPU ceiling only applies on battery in the power-saver profile. Switching to balanced (e.g. a burst for local AI
# or a build) lifts it; switching back or unplugging/replugging restores the policy.
# Policy comes from /etc/mseries/power.conf. Needs root to change anything.
set -euo pipefail
shopt -s nullglob
SYS=${MSERIES_SYS:-/sys}   # overridable so the policy can be tested against a fake tree
conf=${MSERIES_CONF:-/etc/mseries/power.conf}
bat=$SYS/class/power_supply/macsmc-battery
ac=$SYS/class/power_supply/macsmc-ac/online
CHARGE_LIMIT=80
CHARGE_START=75
BATTERY_PROFILE=power-saver
AC_PROFILE=balanced
BATTERY_CAP_KHZ=2400000   # performance-cluster ceiling on battery (hardware max 3036000); 0 = no cap
# shellcheck disable=SC1090
[[ -f $conf ]] && . "$conf"

write() {
  if ! { printf '%s' "$2" > "$1"; } 2>/dev/null; then
    echo "could not write $2 to $1" >&2
    return 1
  fi
}

apply_limit() {
  # The start threshold must stay below the end threshold, so lower/raise them in the right order.
  if (( CHARGE_LIMIT >= 100 )); then
    write "$bat/charge_control_end_threshold" 100; write "$bat/charge_control_start_threshold" 95
  else
    write "$bat/charge_control_start_threshold" "$CHARGE_START"; write "$bat/charge_control_end_threshold" "$CHARGE_LIMIT"
  fi
}

# CPU ceiling in kHz for the current state: 0 means no cap. Only on battery AND in the power-saver profile.
wanted_cap() {
  local on_ac profile
  on_ac=$(cat "$ac" 2>/dev/null || echo 1)
  profile=$(powerprofilesctl get 2>/dev/null || echo unknown)
  if [[ $on_ac == 1 || $profile != power-saver ]]; then echo 0; else echo "$BATTERY_CAP_KHZ"; fi
}

apply_cap() {
  local cap p max min target
  cap=$(wanted_cap)
  for p in "$SYS"/devices/system/cpu/cpufreq/policy*; do
    max=$(cat "$p/cpuinfo_max_freq")
    min=$(cat "$p/cpuinfo_min_freq")
    [[ $max =~ ^[0-9]+$ && $min =~ ^[0-9]+$ && $cap =~ ^[0-9]+$ ]] || {
      echo "invalid CPU frequency policy: $p" >&2; return 1;
    }
    # Only the performance clusters are capped; the efficiency cores are already slow.
    if (( max > 2500000 && cap > 0 )); then
      target=$cap
      (( target > max )) && target=$max
      (( target < min )) && target=$min
    else target=$max; fi
    write "$p/scaling_max_freq" "$target"
  done
}

apply_source() {
  local on_ac profile
  on_ac=$(cat "$ac" 2>/dev/null || echo 1)
  if [[ $on_ac == 1 ]]; then profile=$AC_PROFILE; else profile=$BATTERY_PROFILE; fi
  powerprofilesctl set "$profile"
  apply_cap
}

follow() {
  apply_cap
  # Re-apply whenever power-profiles-daemon reports a profile change.
  gdbus monitor --system --dest net.hadess.PowerProfiles --object-path /net/hadess/PowerProfiles 2>/dev/null |
    while read -r line; do
      if [[ $line == *ActiveProfile* || $line == *'is owned by'* ]]; then apply_cap; fi
    done
  # A disconnected monitor is not a successful completion of this long-running service.
  return 1
}

case ${1:-status} in
  apply) apply_limit; apply_source ;;
  cap) apply_cap ;;
  follow) follow; exit 0 ;;
  limit)
    [[ ${2:-} =~ ^(80|100)$ ]] || { echo 'usage: mseries-power limit 80|100' >&2; exit 1; }
    CHARGE_LIMIT=$2; apply_limit
    mkdir -p "$(dirname "$conf")"; touch "$conf"
    if grep -q '^CHARGE_LIMIT=' "$conf"; then sed -i "s/^CHARGE_LIMIT=.*/CHARGE_LIMIT=$2/" "$conf"; else echo "CHARGE_LIMIT=$2" >> "$conf"; fi
    ;;
  status) ;;
  *) echo 'usage: mseries-power status|limit 80|100|apply|cap|follow' >&2; exit 1 ;;
esac

# Mutating commands report failures directly; status is best effort on machines missing a sensor.
[[ ${1:-status} == status ]] || exit 0
read_value() { cat "$1" 2>/dev/null || printf 'unknown'; }
full=$(read_value "$bat/energy_full"); design=$(read_value "$bat/energy_full_design")
health=unknown
if [[ $full =~ ^[0-9]+$ && $design =~ ^[0-9]+$ ]] && (( design > 0 )); then
  health=$(( full * 100 / design ))
fi
echo "battery: $(read_value "$bat/capacity")% ($(read_value "$bat/status")), health $health%, $(read_value "$bat/cycle_count") cycles"
echo "charge limit: stop at $(read_value "$bat/charge_control_end_threshold")%, resume at $(read_value "$bat/charge_control_start_threshold")%"
echo "power source online: $(read_value "$ac"); profile: $(powerprofilesctl get 2>/dev/null || echo unknown)"
for p in "$SYS"/devices/system/cpu/cpufreq/policy*; do
  echo "cpus $(read_value "$p/related_cpus"): max $(read_value "$p/scaling_max_freq") kHz (hardware $(read_value "$p/cpuinfo_max_freq"))"
done