7.10. Thermal management (tsens, zones, mitigation)¶

The SoC’s thermal subsystem spans hardware (on-die temperature sensors and PMIC ADC thermistor channels), the kernel (95 device-tree thermal zones and two governors), and firmware throttle actors that were documented per-subsystem elsewhere — LMh on the CPU clusters (Base kernel device tree (the SoC boot contract)), the AOP DDR manager (AOP — the Always-On Processor (RPMh / power back-end)), and the CDSP HVX/sysmon throttle (ADSP and CDSP firmware). This page ties those together into the thermal control loop. All addresses, zone names, sensor bindings and trip temperatures are read directly from artifacts/boot_a/board.dts; the userspace thermal-engine daemon that consumes the monitor zones is out of scope (it is HLOS userspace) and is noted only as the reader of those zones.

7.10.1. Temperature sensors¶

Two kinds of sensor feed the zones:

On-die TSENS — two qcom,tsens24xx controllers, each a SROT + TM register pair, up to 16 sensors, with upper/lower, critical and 0 °C interrupts:

Controller	Registers (SROT / TM)	phandle	Notes
tsens0	`0xc222000` / `0xc263000`	`0x3a`	`0C-sensor-num = 16`, `tsens-reinit-wa`
tsens1	`0xc223000` / `0xc265000`	`0x3b`	`0C-sensor-num = 16`, `tsens-reinit-wa`

Zones reference these as thermal-sensors = <0x3a N> (tsens0, sensor N) or <0x3b N> (tsens1). TSENS measures the silicon (CPU/GPU/DSP/DDR/AOSS dies).

PMIC ADC thermal-monitor — qcom,adc-tm5 (phandle 0x58, PMIC register 0x3500) exposes board thermistor channels through the PMIC’s VADC (io-channels e.g. 0x4d, 0x4f). The board/skin zones (chg-skin-therm, conn-therm, sdm-skin-therm, …) read these — physical NTCs on the PCB, not die sensors. See PMIC reset timers, charging and reachability.

7.10.2. Thermal-zone taxonomy¶

The thermal-zones node defines 95 zones. Almost every heat-producing IP has a pair — a *-usr monitor zone and a *-step mitigation zone — plus the board thermistor zones. Categories:

Group	Zones (examples)	Sensed thing
CPU cores	`cpu-0-0`…`cpu-0-5` (little), `cpu-1-0`…`cpu-1-3` (big), `cpuss-0/1`	per-core die temp of the 6+2 Kryo 660 cores (Base kernel device tree (the SoC boot contract))
GPU	`gpuss-0`, `gpuss-1`, `gpuss-max-step`	Adreno GPU die
DSP / compute	`q6-hvx`, `npu`, `video`, `camera`, `audio`	CDSP HVX, NPU, Venus, camera, ADSP audio
Memory / always-on	`ddr`, `aoss-0`, `aoss-1`	DRAM die (AOP-managed) and the always-on subsystem
Connectivity	`cwlan`	WCN3990 combo (Bluetooth / FM controller firmware (WCN3990 “Cherokee”))
Board thermistors	`chg-skin-therm`, `conn-therm`, `sdm-skin-therm`, `rfc-cam-pa3`	PCB skin/connector NTCs via PMIC ADC-TM5
Modem (dormant)	`modem-mmw0`…`mmw3`, `modem-pa`, `mdm-core-0/1`, `mdm-vec`, `mdm-scl`, `modem-wifi`, `modem-ambient` …	stock SM6350 modem/mmWave RF thermal zones — unpopulated (no cellular RF), the same reference-base leftovers as the RF assets in ADSP and CDSP firmware

The dormant modem-* set is the single largest category of thermal zones.

7.10.3. Monitoring vs. mitigation — the two governors¶

Each actor typically has two zones on the same sensor, differing only in governor:

*-usr — thermal-governor = "user_space": High trips (115 °C reset-mon-cfg / 125 °C active-config0, type = "passive"), reported to the HLOS thermal-engine for policy. These are notification/monitor points, no in-kernel action. Example — cpu-0-0-usr on tsens0 sensor 1; ddr-usr on tsens1 sensor 3.
*-step — thermal-governor = "step_wise": Lower trips (95–110 °C) that the in-kernel step-wise governor acts on directly by driving a bound cooling device. This is the automatic below-userspace mitigation. The cooling device each -step zone drives:

`-step` zone	Trip	Cooling device (throttle actor)
`cpu-0-0-step` … per-core	110 °C	the per-core CPU cooling device (cpufreq DCVS / core-isolation, e.g. `cpu0-isolate` phandle `0x3f`) — backstopped in hardware by LMh (Base kernel device tree (the SoC boot contract))
`gpuss-max-step`	95 °C	Adreno GPU DCVS (GPU node phandle `0x3d`)
`q6-hvx-step`	95–100 °C	a cascade from one compute sensor (tsens1 #4): CDSP DCVS (`0x53`), NPU (`0x57`), GPU (`0x3d`), CXIP limiter (`0x51`) and the (dormant) modem-PA/Tj devices — the CDSP side is the `libsysmonhvxthrottle` HVX clock throttle (ADSP and CDSP firmware)

(DDR has no -step cooling-map: DRAM thermal mitigation is done by the AOP DDR manager’s own frequency/self-refresh control, ddr_temp in AOP — the Always-On Processor (RPMh / power back-end), not by the kernel governor.)

7.10.4. The below-userspace thermal loop¶

The closed loop that runs without any userspace involvement:

Sense — TSENS (die) / PMIC ADC-TM5 (board) sample temperature and raise threshold interrupts.
Decide — the kernel step_wise governor evaluates the -step zones’ passive trips.
Throttle — it drives the bound cooling device, whose real effect is in firmware/hardware: LMh clamps CPU-cluster frequency (Base kernel device tree (the SoC boot contract)), the AOP scales DDR (AOP — the Always-On Processor (RPMh / power back-end)), the CDSP throttles HVX clocks (ADSP and CDSP firmware), and GPU/NPU DCVS drop their operating points.

The -usr zones run in parallel at higher trips purely to hand telemetry to the userspace policy daemon; the protective floor is the in-kernel/firmware path above.

7.10.5. Provenance¶

Source:: artifacts/boot_a/board.dts — the tsens@c222000 / tsens@c223000 controllers, qcom,adc-tm5 (phandle 0x58), and the thermal-zones node (95 zones: sensor bindings, trips temperatures, cooling-maps).
Method:: Node/zone enumeration and phandle resolution (sensors 0x3a/0x3b, cooling devices 0x3d GPU, 0x53 CDSP, 0x3f cpu-isolate, 0x58 ADC-TM5); millidegree trip values converted to °C. No code executed.
Cross-refs:: Base kernel device tree (the SoC boot contract) (LMh CPU limiter, CPU topology), AOP — the Always-On Processor (RPMh / power back-end) (AOP DDR thermal manager), ADSP and CDSP firmware (CDSP HVX/sysmon throttle, ADSP /therm/sensor, modem/RF leftovers), PMIC reset timers, charging and reachability (PMIC ADC thermistor channels), Bluetooth / FM controller firmware (WCN3990 “Cherokee”) (WCN3990 cwlan zone).