iMX8QM temperature sensors

[vzeric]

Hello community,
I am working with temperature sensors on IMX8QM processor. I need information which temperature sensors are available. I checked the device tree and on my IMX8QM MEK board and on our custom board that uses IMX8QM processor and we have 6 thermal zones, thermal_zone0 - thermal_zone5. In device tree, these thermal zones are named as cpu-thermal0 (A53 cores), cpu-thermal1 (A72 cores), gpu-thermal0 (GPU1), gpu-thermal1 (GPU2), drc-thermal0 (internal DDR controller) and pmic-thermal0 (PMIC), respectively. But I found out that thermal-zone5 defaults to 70000 [m°C] which is case with both of my boards. I am not sure now if drc-thermal0 zone exists actually and if it exists, how can I get real readings for pmic-thermal0 zone.
In device tree pmic-thermal0 zone is defined as here:
https://github.com/nxp-imx/linux-imx/blob/lf-6.1.y/arch/arm64/boot/dts/freescale/imx8qm-mek.dts#L183...
Other zones are defined as here:
https://github.com/nxp-imx/linux-imx/blob/lf-6.1.y/arch/arm64/boot/dts/freescale/imx8qm.dtsi#L404-L5...

Best regards,
Vanja

[AldoG · Accepted solution]

Hello,

As indicated in the SCFW porting guide:

The PMIC temp sensors are controlled via the board_set_control() and board_get_control() functions. The SC_C_TEMP control allows reading of the temp and SC_C_TEMP_HI allows for R/W of the alarm value (by default set to max).

The NXP PMICs cannot return the actual temperature. They only indicate if the temperature is above various fixed temp points with pretty large gaps between them.

Best regards/Saludos,
Aldo.

[vzeric]

Thank you for answering, this makes sense. We have some app that communicate with SCFW and there I can read all PMIC temperatures correctly.
Also I checked on IMX8QM MEK with official image (and same kernel version as on our custom board) and I have always same readings for thermal zone 5.