Re: [PATCH 2/3] arm64: dts: qcom: hamoa-crd: Add thermal control
From: Stephan Gerhold
Date: Mon Aug 31 2026 - 15:12:30 EST
On Mon, Aug 31, 2026 at 09:20:14AM -0500, Bjorn Andersson wrote:
> On Mon, Aug 31, 2026 at 10:58:56AM +0200, Stephan Gerhold wrote:
> > On Sun, Aug 30, 2026 at 09:02:03PM +0000, Bjorn Andersson wrote:
> > > The "limits" hardware performs rapid thermal management of the CPU
> > > cores, but during prolonged CPU usage the system's overall temperature
> > > need to be further managed by software.
> > >
> > > The reference design provides seven "system thermistors", connected to
> > > the PMK8550 VADC. Particularly interesting is the "keyboard hotspot
> > > thermistor", which is wired up to sys_therm1.
> > >
> > > Use this to throttle the CPUs, in the same way that we're throttling
> > > previous generation laptops based on "skin-temp". The trips are chosen
> > > from those existing examples, but are comparable with the ACPI thermal
> > > policy.
> > >
> >
> > In general, following the ACPI thermal policy as close as possible is
> > better than following existing examples. Most X1E-based devices use
> > hybrid active/passive cooling, with the fan controlled independently by
> > the EC. If you start throttling even just 1-2°C before the EC reaches
> > its highest fan trip point, it will result in bad performance. Linux
> > will try to keep the temperature below the specified temperature, and
> > the EC will never fully ramp up the fan.
> >
>
> That's certainly true. On X13s it was a bit easier as it's passively
> cooled, but these things needs to be taken into consideration.
>
> > This is what I determined from the CRD ACPI tables last year:
> > https://github.com/stephan-gh/linux/commit/24f053436ec2eaf70968803adfa8c17905e53cae.patch
> >
>
> Why don't you post your patches!? Have I missed it?
>
No, you haven't missed it. I wanted to send them back when I wrote them
(early 2025), but unfortunately the PMIC5 Gen3 ADC patches then blocked
sending it for almost 1.5 years... :/
I lost track of the long ongoing series at some point and nowadays
I don't even have a CRD to test on anymore, that's why my patch is sadly
stuck in the archive.
> > The fact that GPU is only throttled based on back-thermal is a little
> > odd, but this is what the ACPI tables specified back then as far as
> > I could tell (maybe it was fixed since then).
> >
> > Your changes seem close enough to not cause the performance problem
> > I mentioned above, although I think it would be worth setting a good
> > examples for others to follow.
> >
>
> Sure, I'll compare with ACPI tables and adjust the numbers accordingly.
>
Thanks!
As far as I remember, ACPI has separate thresholds for each of the EC
fan profiles (see [1]). I don't think we can model dynamic temperature
thresholds in the DT, so we'll have to pick some default. IIRC the
default is "best performance without charger", which - back then - was
the 326 kelvin (~53°C) I used in my patch.
[1]: https://lore.kernel.org/linux-arm-msm/20260728-ec_add_more_commands-v1-3-771abd65ee1a@xxxxxxxxxxxxxxxx/
> > > While not used for cooling/throttling, also add the other thermal zones
> > > for temperature reporting purposes.
> > >
> > > Enable thermal-monitor mode for all 7 channels in the ADC.
> > >
> > > Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxxxxxxxx>
> > > ---
> > > arch/arm64/boot/dts/qcom/x1e80100-crd.dts | 116 ++++++++++++++++++++++++++++++
> > > 1 file changed, 116 insertions(+)
> > >
> > > diff --git a/arch/arm64/boot/dts/qcom/x1e80100-crd.dts b/arch/arm64/boot/dts/qcom/x1e80100-crd.dts
> > > index 429deffcf3e9..065af18357d7 100644
> > > --- a/arch/arm64/boot/dts/qcom/x1e80100-crd.dts
> > > +++ b/arch/arm64/boot/dts/qcom/x1e80100-crd.dts
> > > @@ -11,6 +11,92 @@
> > > / {
> > > model = "Qualcomm Technologies, Inc. X1E80100 CRD";
> > > compatible = "qcom,x1e80100-crd", "qcom,x1e80100";
> > > +
> > > + thermal-zones {
> > > + soc-thermal {
> > > + thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX1_GPIO_100K_PU(1)>;
> > > + };
> > > +
> > > + keyboard-thermal {
> > > + polling-delay-passive = <250>;
> > > +
> > > + thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX2_GPIO_100K_PU(1)>;
> > > +
> > > + trips {
> > > + skin_alert0: trip-point0 {
> > > + temperature = <55000>;
> > > + hysteresis = <1000>;
> > > + type = "passive";
> > > + };
> > > +
> > > + skin_alert1: trip-point1 {
> > > + temperature = <58000>;
> > > + hysteresis = <1000>;
> > > + type = "passive";
> > > + };
> >
> > What does this second trip point do differently than the first? It has
> > the same cooling devices. Will it try throttling "harder" than before?
> >
> > I know sc8280xp-lenovo-thinkpad-x13s.dts has the same, but I'm not
> > entirely sure what it does there either.
> >
> > My experience was if you specify 55°C as one passive trip point, then
> > Linux will try its best to keep it with the specified cooling devices.
> >
>
> I didn't dive into this rabbit hole... I'll review and update
> accordingly.
>
Thanks!
> > > +
> > > + skin-crit {
> > > + temperature = <73000>;
>
> Your patch has 115C here. That may be what the ACPI tables are saying,
> but it seems a bit excessive.
>
I agree, feel free to change that.
> > > + hysteresis = <1000>;
> > > + type = "critical";
> > > + };
> > > + };
> > > +
> > > + cooling-maps {
> > > + map0 {
> > > + trip = <&skin_alert0>;
> > > + cooling-device = <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu2 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu3 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu4 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu5 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu6 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu7 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu8 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu9 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu10 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu11 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
> > > + };
> > > +
> > > + map1 {
> > > + trip = <&skin_alert1>;
> > > + cooling-device = <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu2 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu3 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu4 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu5 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu6 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu7 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu8 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu9 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu10 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > > + <&cpu11 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
> > > + };
> > > + };
> > > + };
> > > +
> > > + backcover-thermal {
> > > + thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX1_THM_100K_PU(1)>;
> > > + };
> >
> > Should we add throttling here as well to match Windows?
> >
>
> Then there are the reports that indicate that we should throttle things
> when the SMB temperatures reaches something like 80C, which doesn't seem
> to be something represented in the ACPI tables.
>
Windows has quite some extra logic in the PEP driver that does
additional fine-grained throttling based on PMIC die temperatures,
battery current, power source / battery percentage and other factors.
Unfortunately, I never fully understood how that works, but it may be
handled in there.
> I'll do a respin of this and then we can tweak it from there. The
> important thing for me is to get some reference in, so we can propagate
> this to the consumer devices (NB: which doesn't have the same sys_therm
> mapping).
>
Thanks!
I have been working on finishing up my corresponding patch for the T14s
(which is something I can still test unlike the CRD). That one is
unfortunately currently stuck because the SYS_THERMx mapping really is
different from the CRD and even the schematics are not sufficient to
understand where each sensor is located. The mapping seems to be
different from the CRD, unfortunately.
The ACPI side is also extra tricky because it takes the thermal
thresholds for the thermal zones through some lookup table in a random
firmware memory region, which is also applied depending on the selected
fan profile (for the T14s: "low power", "balanced", "performance").
I had some luck with using PowerShell on Windows to obtain the computed
ACPI values using
Get-CimInstance -Namespace "root/wmi" -ClassName MSAcpi_ThermalZoneTemperature
With that I could see the thresholds (PassiveTripPoint) changing when I
change the power profile in Windows.
For fun I had LLM create this PowerShell script that directly outputs DT
snippets, although unfortunately the missing part is actually mapping
the thermal zones to their purpose (right now it outputs zones like
qcom0658-1-0-thermal or even just tz73-0-thermal).
Just sharing it for reference below.
Thanks,
Stephan
---
<#
.SYNOPSIS
Exports Windows WMI MSAcpi_ThermalZoneTemperature instances to Linux Devicetree (DTS) format.
.DESCRIPTION
Queries the 'root\wmi' namespace for ACPI thermal zone instances and translates
temperatures, passive/active/critical trip points, and sampling rates into Linux
kernel thermal zone DTS nodes.
.PARAMETER OutputFile
Optional file path to save the generated DTS nodes. If omitted, prints directly to stdout.
.EXAMPLE
.\Convert-AcpiToDts.ps1
.EXAMPLE
.\Convert-AcpiToDts.ps1 -OutputFile "thermal_zones.dtsi"
#>
[CmdletBinding()]
param (
[Parameter(Mandatory = $false, Position = 0)]
[string]$OutputFile
)
function ConvertTo-Millicelsius ([uint32]$tenthsKelvin) {
# ACPI trip points of 0, >= 65535 (0xFFFF), or <= 2732 (<= 0°C) are uninitialized/disabled
if ($tenthsKelvin -le 2732 -or $tenthsKelvin -ge 65535) {
return $null
}
return [long]($tenthsKelvin * 100) - 273150
}
function Get-DTNames ([string]$instanceName) {
# Sanitize instance name (e.g. "ACPI\QCOM0658\0_0" -> "qcom0658-0-0")
$parts = $instanceName -split '\\'
if ($parts.Count -ge 3) {
if ($parts[1] -ieq "ThermalZone") {
$raw = $parts[2]
} else {
$raw = "$($parts[1])-$($parts[2])"
}
} else {
$raw = $parts[-1]
}
$cleanNode = ($raw.ToLower() -replace '_', '-' -replace '[^a-z0-9-]', '') -replace '-thermal$', ''
$cleanLabel = $cleanNode -replace '-', '_'
return @{
NodeName = "${cleanNode}-thermal"
BaseName = $cleanNode
LabelName = $cleanLabel
}
}
# Fetch CIM instances safely into an array
$zones = @(Get-CimInstance -Namespace "root/wmi" -ClassName MSAcpi_ThermalZoneTemperature -ErrorAction SilentlyContinue)
if ($zones.Count -eq 0) {
Write-Error "No MSAcpi_ThermalZoneTemperature instances found in root\wmi."
return
}
$dtsNodes = [System.Collections.Generic.List[string]]::new()
foreach ($zone in $zones) {
$names = Get-DTNames $zone.InstanceName
$nodeName = $names.NodeName
$baseName = $names.BaseName
$labelName = $names.LabelName
# Check for passive trip point
$psvMC = ConvertTo-Millicelsius $zone.PassiveTripPoint
$hasPassive = ($null -ne $psvMC)
# Collect valid trip points
$tripsList = [System.Collections.Generic.List[string]]::new()
$tripIndex = 0
# 1. Passive Trip Point (_PSV)
if ($hasPassive) {
$tripsList.Add(" ${labelName}_alert${tripIndex}: trip-point${tripIndex} {")
$tripsList.Add(" temperature = <${psvMC}>;")
$tripsList.Add(" hysteresis = <1000>;")
$tripsList.Add(" type = `"passive`";")
$tripsList.Add(" };")
$tripIndex++
}
# 2. Active Trip Points (_AC0.._ACx)
if ($zone.ActiveTripPointCount -gt 0 -and $zone.ActiveTripPoint) {
for ($i = 0; $i -lt $zone.ActiveTripPointCount; $i++) {
$acMC = ConvertTo-Millicelsius $zone.ActiveTripPoint[$i]
if ($null -ne $acMC) {
$tripsList.Add(" ${labelName}_active${i}: trip-point${tripIndex} {")
$tripsList.Add(" temperature = <${acMC}>;")
$tripsList.Add(" hysteresis = <1000>;")
$tripsList.Add(" type = `"active`";")
$tripsList.Add(" };")
$tripIndex++
}
}
}
# 3. Critical Trip Point (_CRT)
$crtMC = ConvertTo-Millicelsius $zone.CriticalTripPoint
if ($null -ne $crtMC) {
$tripsList.Add(" ${baseName}-critical {")
$tripsList.Add(" temperature = <${crtMC}>;")
$tripsList.Add(" hysteresis = <1000>;")
$tripsList.Add(" type = `"critical`";")
$tripsList.Add(" };")
}
# Assemble thermal zone node
$nodeLines = [System.Collections.Generic.List[string]]::new()
$nodeLines.Add("${nodeName} {")
$nodeLines.Add(" thermal-sensors = <&placeholder_sensor>; /* Replace with target sensor phandle */")
# Include polling-delay-passive ONLY if a passive trip point exists
if ($hasPassive) {
$pollingPassiveMs = if ($zone.SamplingPeriod -gt 0) { $zone.SamplingPeriod * 100 } else { 1000 }
$nodeLines.Add(" polling-delay-passive = <${pollingPassiveMs}>;")
}
# Include trips {} block ONLY if trip points exist
if ($tripsList.Count -gt 0) {
$nodeLines.Add("")
$nodeLines.Add(" trips {")
foreach ($line in $tripsList) {
$nodeLines.Add($line)
}
$nodeLines.Add(" };")
}
$nodeLines.Add("};")
$dtsNodes.Add(($nodeLines -join "`n"))
}
$finalOutput = $dtsNodes -join "`n`n"
if (-not [string]::IsNullOrWhiteSpace($OutputFile)) {
$finalOutput | Out-File -FilePath $OutputFile -Encoding utf8
Write-Host "Successfully exported Devicetree thermal zones to: $OutputFile" -ForegroundColor Green
} else {
$finalOutput
}