i.MX8M mini thermal-zone issue (passive/critical trip point about consumer and industrial products)

[Tori-san]

Hello, Isn't it necessary to change the passive/critical trip point between IMX8MMCEC (0 to 95 Celsius) and IMX8MMIEC (-40 to 105 Celsius) in the imx8mm.dtsi? Also, what temperature should be quoted as the passive/critical trip point? What is the relationship between the temperature to be quated as passive/critical and the calibration temperature?

[emma_y]

Hi, I also have a similar question. I don't understand why the trip points would be the same for both IMX8MMCEC (0 to 95 Celsius) and IMX8MMIEC (-40 to 105 Celsius). If the temp sensor has a 10C accuracy, why does a 95C critical trip point work for IMX8MMCEC (0 to 95 Celsius)? 

Thanks, Emma

[Yuri]

@emma_y 
Hello,

  customers can try own settings. But note:  NXP BSP has been tested.

Regards,
Yuri.

[Tori-san]

Hi Yuri,

I appreciate your help.

Best regards,

Tori-san.

[Yuri]

@Tori-san 
Hello,

  The thermal parameters are application dependent. NXP settings in NXP Linux BSP
may be considered as base recommendations. 

  From NXP Linux description:

Thermal driver is a necessary driver for monitoring and protecting the SoC. The thermal driver monitors the SoC temperature in a certain frequency from an internal thermal sensor.
It defines two trip points: critical and passive. Cooling device will take actions to protect the SoC according to the different trip points that SoC has reached:
• When reaching critical point, cooling device will shut down the system.
• When reaching passive point, cooling device will lower CPU frequency and notify GPU/VPU to run at a lower frequency.
• When the temperature drops to 10 °C below passive point, cooling device will release all the cooling actions.

Thermal driver has two parts:
• Thermal zone defines trip points and monitors the SoC's temperature.
• Cooling device takes the actions according to the different trip points.

Regards,
Yuri.

[Tori-san]

Hi Yuri,

Thank you for your reply.

Base recommendations are as follows in imx8mm.dtsi.

-------------------------------

trips {

    cpu_alert0: trip0 {

        temperature = <85000>;

        hysteresis = <2000>;

        type = "passive";

    };

    cpu_crit0: trip1 {

        temperature = <95000>;

        hysteresis = <2000>;

        type = "critical";

    };

};

-------------------------------

Would you recommend the following changes to the IMX8MMIEC (-40C to 105C)?

Is this changes at my own risk?

-------------------------------

trips {

    cpu_alert0: trip0 {

        temperature = <95000>;

        hysteresis = <2000>;

        type = "passive";

    };

    cpu_crit0: trip1 {

        temperature = <105000>;

        hysteresis = <2000>;

        type = "critical";

    };

};

-------------------------------

Best regards,

Tori-san.

[Yuri]

@Tori-san 
Hello,

   I do not think Your settings are reasonable, since temperature sensor
accuracy of 10 C is not taken into account there.

Regards,
Yuri.

[Tori-san]

Hi Yuri, What are the recommended passive and critical trip temperatures when using IMX8MMIEC? Could you give us a recommendation?

[Yuri · Accepted solution]

@Tori-san 
Hello,

   I think using default settings in our BSP may be left as is.
The temperature settings  in themselves are not the problem for thermal considerations:
the main problem is how to implement optimal power dissipation in system.

Regards,
Yuri.

[Tori-san]

Hi Yuri,

I appreciate your help.

Best regards,

Tori-san.