To disable i.MX6DQ thermal control with L3.10.17_1.0.0-ga.

[satoshishimoda]

Hi community,

I have some questions about i.MX6DQ thermal control.

Actually, our partner want to disable the thermal control to prevent lower cpu frequency.

Then, please see our questions as following.

[Q1]

Please see chapter 26 of i.MX6 linux reference manual in L3.10.17_1.0.0-ga (IMX6LXRM Rev L3.10.17_1.0.0-ga).

I understand i.MX6DQ CPU and GPU run at a lower frequency when reaching passive point.

So decreasing of processing capacity of CPU and GPU is not avoidable when cooling is active.

Is this correct?

[Q2]

To disable the thermal control, I think there are two method.

A. Remove thermal driver with bitbake menuconfig.

B. Execute the following command.

   cat disable > /sys/class/thermal/thermal_zone0/mode

Is this correct?

Best Regards,

Satoshi Shimoda

[Yuri · Accepted solution]

  You are right, that thermal control can decrease system performance, assuming

  using low frequency configuration to avoid device overheating. In the same time,
hardly it makes sense to disable the thermal control, since it does not affect the
system performance, when die temperature is not (critically) high. Such control is
intended to avoid i.MX6 destroying. 
Another way, that customers can try to allow operation under more high temperature,
than default one, using sysfs interface. But, please be careful, and take into account
that accuracy of temperature, measured by internal sensor is not high (~10 C).

Have a great day,
Yuri

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[satoshishimoda]

Hi Yuri,

> But, please be careful, and take into account

> that accuracy of temperature, measured by internal sensor is not high (~10 C).

I feel the sensor accuracy (~10 C) is too low.

BSP (L3.10.17_1.0.0-ga) set the critical point to 100 C.

So in worst case, there is possibility the die temperature have reached 110 C when the sensor detect 100 C and thermal driver shutdown the system, it is out of operating range (Tj <= 105  C).

Best Regards,

Satoshi Shimoda

[Yuri]

Yes, I do not think, that the critical point of 100 C is good practice.

~Yuri.

[satoshishimoda]

Hi Yuri,

Please feedback to your BSP team and request to modify this risk caused by the low sensor accuracy.

Best Regards,

Satoshi Shimoda

[Yuri]

  Generally our BSP should be considered as base for designers, who will
provide final releases for customers. In this sense it makes sense to leave
many options "free" for designers. 

~Yuri.