Re: [PATCH 4/8] platform: arm64: qcom-hamoa-ec: Add fan RPM query and LUT calibration

[Konrad Dybcio]

On 7/30/26 8:35 AM, Anvesh Jain P wrote:
> 
> 
> On 7/29/2026 4:37 PM, Konrad Dybcio wrote:
>> On 7/28/26 7:44 PM, Anvesh Jain P wrote:
>>> Add the EC command definitions and handler functions for querying fan
>>> RPM and programming per-fan LUTs (lookup tables mapping SoC
>>> temperature to target RPM), and introduce a raw i2c_transfer()-based
>>> transport for the two commands, since their variable-length,
>>> sub-command-addressed payloads don't fit the smbus block-data model
>>> used by the existing commands.
>>>
>>> Fan LUT geometry and temperature breakpoints vary by board, so encode
>>> them in per-compatible qcom_ec_lut_config data selected via
>>> device_get_match_data(). Add configs for the Hamoa CRD, Hamoa/Purwa
>>> IOT EVK, and Glymur CRD ECs; IOT EVK boards share the Hamoa LUT
>>> geometry but are bring-up platforms without a calibrated fan curve,
>>> so skip_lut_set suppresses the LUT-set command on those boards.

[...]

>>> Since the LUT values depend on each fan's maximum RPM, which varies
>>> per board assembly, calibrate it at runtime: drive the fan to full
>>> PWM, wait for it to spin up, and read back the achieved RPM via the
>>> new query command. Run calibration in a work item at probe time and
>>> after EC reset recovery, and make it abortable via a completion so
>>> suspend can cut it short. Track calibration completion state so the
>>> LUT is programmed once calibration finishes and again on every
>>> subsequent power-supply-driven profile switch.
>>
>> I don't want my laptop to become a jetplane on every bootup. I
>> doubt anyone does.
>>
>> Konrad
> 
> There's no EC command that reports a fan's max/rated RPM directly — the
> only way to learn it is to drive the fan to full PWM and read back what
> it actually spins up to, which is what calibration does. It's bounded to
> a 10s timeout per fan and only runs once at probe (and again after EC
> reset recovery).

1. please fix the firmware so new designs will have that
2a. if we're storing a LUT already, can't we store the max RPM too?
2b. if we don't know fan RPM, we can still expose a PWM hwmon

Konrad