saphid--frame-control/docs/power-and-heat.md

Power, heat and what you can control

What the Frame spends power on while it's on, where the heat comes from, and which controls exist. Everything here was read on the Frame on 2026-09-29 (BUILD_ID 20260925.6191901). Nothing was changed. Numbers under load haven't been measured yet.

Sensors you can read without sudo

What	Where
Power per rail (W ×10⁶)	hwmon max34417_10: vph (whole system), s1c, s3c, s6c. max34417_12: apc0/apc1/apc2 (CPU clusters), nsp1. max34417_1a: gfx (GPU), nsp2, bob. Each powerN_input has a powerN_label
Board temperatures (m°C)	/sys/bus/iio/devices/iio:device0/in_temp_*_input: battery, left and right display, heatsink fins, fan exhaust, Wi-Fi, flash, 40-pin connector, nRF radio, PMIC and charger die
CPU, GPU and modem zones	/sys/class/thermal/thermal_zone*/{type,temp} (per-core top and bottom, gpuss-*, nsp*, video)
Charger input and charge current	iio:device0/in_current_pm8550b_{iin,ichg}_fb_input (µA)
Battery	/sys/class/power_supply/max1720x_bat_7-36/uevent (cycle count, health, current)
Fan	hwmon slg4ax46073v: fan1_input (RPM), pwm1 (%)
Proximity (worn or not)	/sys/bus/iio/devices/iio:device2/in_proximity_raw
Why the fan ramped	journalctl -u deckard-fan-control (C3 temperature of 95.36 greater than max 95! Setting fan to max speed.)

The right display thermistor reads −16 °C, so it's absent or broken. Ignore it.

Idle baseline (2026-09-29 08:05)

Conditions:

• On the 12 V USB-C charger, battery 100%, 5 cycles.
• Headset off-head, SteamVR in standby, backlight 0.
• Steam, SteamVR, the tracking service and one Chromium (Mac view) running.
• pauseCompositorOnStandby = false, set by another session this morning for testing.

30 s average:

Rail	W	Notes
vph (everything)	4.71
CPU apc0+1+2	0.61	91% idle overall
GPU gfx	0.25	GPU at 366 of 903 MHz
NSP nsp1+2	0.08	Neural and DSP processors
s1c + s3c + s6c + bob	1.01	SoC, memory and peripheral supplies (which rail is which isn't documented)
Unmetered remainder	~2.8	Cameras, display link, Wi-Fi, fan, sensors, conversion losses (inferred)

Temperatures:

Sensor	°C
CPU cores	40–45
Board (heatsink, Wi-Fi, flash)	34–37
Left display thermistor	46 (the warmest)
Charger IC	37
Battery	23

The fan ran at about 8,350 RPM at pwm1 41.

What was running while idle (top):

• The compositor was at about 14% of one core.
• Steam was at about 7%.
• The tracking service (XRService) was at about 4%, and still had 4 camera nodes open (/dev/video0,3,9,13).
• vrserver and gamescope were at about 3% each.

Why it's warm while "doing nothing"

• The compositor keeps rendering in standby when power.pauseCompositorOnStandby is false. The default is true. Check ~/.config/openvr/config/steamvr.vrsettings.
• The tracking cameras stay open in standby. XRService holds them so tracking resumes instantly.
• The fan never goes below 40% on the charger. That's by design in /usr/share/deckard-fan-control/deckard-config.yaml: fan_charging_min_speed: 40, against fan_min_speed: 30 on battery. Charging, including topping up at 100%, heats the charger IC and battery area.
• The display link stays up at backlight 0. The DSI connector reports dpms=On while the backlight is 0, so the panels are dark but still driven.
• Heavy load reaches the throttle limit. On 2026-09-28 at 22:09–22:12, cores C3, C5 and C7 hit 95 °C and the fan went to max. The cause wasn't investigated. It came around a Steam restart after the reboot.

Controls

No sudo needed:

Control	How	Effect	Caveat
Steam idle sleep	scripts/keep-awake.sh, system_idle_suspend_{ac,battery}_sec	When it sleeps	Sleep has no remote wake
Compositor pause in standby	vrcmd --set-settings-bool power.pauseCompositorOnStandby 1	Stops rendering while off-head	Other sessions toggle it for testing, so coordinate
Screens-off delay	vrcmd --set-settings-float power.turnOffScreensTimeout <s>	Backlight off sooner or later	Default 5 s
Stop the whole VR stack	systemctl --user stop steamvr.service	Cameras, tracking and compositor off	Also stops the gamescope VR session and Steam (seen 2026-09-28), so panels and Mac view go too. The restart cost hasn't been measured
Background apps	Close Mac-view Chromium, stop Lepton containers (podman)	Less CPU and memory	Mac view needs relaunching
Brightness	Steam settings	Panel power while worn	—

Needs root (reset at reboot unless made persistent):

Control	Where	Effect
CPU governor and max frequency per cluster	/sys/devices/system/cpu/cpufreq/policy{0,2,5,7}/scaling_{governor,max_freq} (powersave, conservative, schedutil, …)	Caps CPU power and heat
Take cores offline	/sys/devices/system/cpu/cpuN/online	Fewer active cores
GPU max frequency	/sys/class/devfreq/3d00000.gpu/max_freq	Caps GPU power (it hurts VR smoothness when worn)
Fan curve	The service reads /usr/share/…/deckard-config.yaml, which is on the read-only rootfs. It could be overridden with a systemd drop-in pointing at a copy in /etc	Quieter fan while charging, but hotter parts
Charge current	pm8550b-charger constant_charge_current (1.0 A, max 1.2 A)	Writability unverified. There's no charge-limit or end-threshold file, so the battery sits at 100% on the charger

None of these have been tried yet.

Plan: leave it on, but cheaply

Goal: the Frame stays on the charger, reachable over SSH, drawing as little power and making as little heat, fan wear and battery wear as possible while nobody wears it. When someone puts it on, everything comes back quickly. Sleeping isn't an option until remote wake works (see open-questions.md).

Rules for every step:

• Change one thing at a time. Snapshot the setting first, measure 5 minutes (vph plus temperatures and fan), then restore it unless it's being kept.
• Freeze the Steam and SteamVR health-check trackers first (frame-doctor.md §4).
• Anything that could leave the Frame unreachable, and every root change, waits until someone is home to recover it.
• power.pauseCompositorOnStandby belongs to another session's testing. Ask before touching it.

1. Measure (read-only, safe remotely)

• Idle baseline off-head on the charger (above).
• A sampler script (scripts/frame-power-sample.sh) that logs vph, the CPU/GPU rails, key temperatures, fan RPM, the proximity sensor and the charger current every few seconds to a CSV. Every later step uses it.
• The same baseline worn, idle in the home space.
• Under load: Mac view streaming, and one VR game.
• On battery (unplugged) to separate charging heat from everything else.
• Find what caused the 95 °C spike on 2026-09-28 22:09–22:12 (journal and process history around the Steam restart).

2. Settings without sudo (one at a time, measured)

• Compositor pause in standby (after asking the owning session).
• Shorter screens-off delay.
• Stop steamvr.service while off-head. Measure the saving and how long it takes to come back, since it also stops the gamescope session and Steam.
• Close Mac-view Chromium and stop idle Lepton containers.
• Steam's "never sleep on AC" (system_idle_suspend_ac_sec = 0), keeping the battery timer. Confirm the displays go dark.

3. Root settings (at home, with approval)

• CPU: powersave or a lower max frequency while off-head.
• Fan: a copy of the fan config with a lower charging minimum, through a systemd drop-in. Only if temperatures in steps 1–2 leave headroom.
• Battery: check whether charge current is writable. There's no charge limit, so the fallback is a Home Assistant smart plug that lets the battery cycle between roughly 80% and 100%.
• Decide which root changes to make persistent (drop-ins in /etc, which survive SteamOS updates, unlike /usr).

4. A quiet mode

• Put the kept settings behind one switch: off-head for N minutes → quiet mode; on-head (proximity sensor) or a Frame Control request → normal.
• Run it from Frame Control / keep-awake, not a hand-edited setting, so it can always be undone.
• Add a doctor check that reports whether quiet mode is on and that it restores cleanly.

5. Remote wake (at home)

• Charger wake: during confirmed sleep, plug in, unplug, and switch the charger's AC off and on, one at a time.
• Controller-button wake.
• RTC dark wake (root timer that wakes, checks for queued work, sleeps).
• Re-test WoWLAN after each SteamOS or kernel update.

6. Doctor script

• Turn frame-doctor.md into scripts/frame-doctor.sh: read-only checks by default, fixes only with a flag, and ask fixes never automatic. Add the sensor reads from this page.