AM62A7: main*_thermal critical temperature threshold is too high?

Hello Jonathan Cormier

Thank you for the query.

Please add some additional details.

Help me understand where are you seeing these setting.

We have the below temperature grades for the device.

Table 10-1. Nomenclature Description

t Temperature(3) A –40°C to 105°C - Extended Industrial (see Recommended Operation
Conditions)
I –40°C to 125°C - Automotive (see Recommended Operation Conditions

Regards,

Sreenivasa

In the kernel, there is a critical temperature threshold that is set to shutdown the SOM when the temperature is hit.

For the AM62P there is only automotives parts right now, so 125C makes sense. But for the AM62A, most part variants are extended industrial, so it seems like 105C (like the AM62x) would make sense.

arch/arm64/boot/dts/ti/k3-am62-thermal.dtsi:

			main0_crit: main0-crit {
				temperature = <105000>;	/* milliCelsius */
..
			main1_crit: main1-crit {
				temperature = <105000>;	/* milliCelsius */

arch/arm64/boot/dts/ti/k3-am62a-thermal.dtsi:
arch/arm64/boot/dts/ti/k3-am62p-thermal.dtsi:

			main0_crit: main0-crit {
				temperature = <125000>;	/* milliCelsius */
...
			main1_crit: main1-crit {
				temperature = <125000>;	/* milliCelsius */
...
			main2_crit: main2-crit {
				temperature = <125000>;	/* milliCelsius */

Hello Jonathan Cormier

Thank you.

Jonathan Cormier said:

In the kernel, there is a critical temperature threshold that is set to shutdown the SOM when the temperature is hit.

For the AM62P there is only automotives parts right now, so 125C makes sense. But for the AM62A, most part variants are extended industrial, so it seems like 105C (like the AM62x) would make sense.

Noted. Let me check with the team and update you.

I may have to reassign to a software expert since i mostly support Hardware queries.

Regards,

Sreenivasa

Hi, any updates?

Hello Jonathan Cormier

Thank you for following.

I did not receive any inputs, let me follow-up and update.

Regards,

Sreenivasa

Hello Jonathan Cormier,

Please refer below inputs i received from the experts.

We set the SDK to primary market for each SoC.. Am62x is industrial. AM62a and am62p were launched for auto only and then industrial parts added.. We havent done any formal kick off or support for industrial package.
Expecting customers to modify the values offline

The critical temperature threshold is set to shutdown the SOM when the temperature is hit only after the boot is complete.

Regards,

Sreenivasa

Kallikuppa Sreenivasa said:

Expecting customers to modify the values offline

Okay thanks for the guidance.

Note in another e2e post, it was stated the temp sensors are only accurate to +/- 7C.  Does having the shutdown at 105C for extended temp present any risks in that case?  Ex: The processor is reading at 104C but is actually running at 111C? Or is there enough margin built in?

Okay thanks for the reference

Hello Jonathan Cormier,

Thank you.

Regards,

Sreenivasa

Kallikuppa Sreenivasa said:

There are no additional margins included in the max operating temp to account for the sensor error.  The shutdown point needs to be set 5C degrees lower than the max operating temp to ensure the limit is not exceeded.

When trip point is set to 120C there is a likely chance that the SOC trips at 115C which is 10C less that the specified.

Customer should be considering this variation in their design. 

Thanks Kallikuppa, I expected this but was confused by the thresholds chosen by the TI software team in the dts.  It seems like TI should reduce those thresholds by 5C.

I can create some patches for TI and the linux mailing list.

I will also add some dynamic temp grade device tree fixups in u-boot based on the processors temp grade.  Which I can submit either to TI or the u-boot mailing list.

Is there anyone you would like to get cc'd on those patches?

Hello Jonathan Cormier,

Thank you for the inputs.

Jonathan Cormier said:

I can create some patches for TI and the linux mailing list.

I will also add some dynamic temp grade device tree fixups in u-boot based on the processors temp grade.  Which I can submit either to TI or the u-boot mailing list.

Thank you for your initiative to support TI.

Let me know when you make progress.

Regards,

Sreenivasa

Hello Jonathan Cormier,

Jonathan Cormier said:

Is there anyone you would like to get cc'd on those patches?

I need to check with the software team.

Please allow some time.

Regards,

Sreenivasa