MX8MN: Thermal driver doesn`t report temperatures below 10 degree celcius

[MikeEngel]

Hi all,

using the Linux  kernel 5.4 and the MX8MN we have seen that when temperature drops below 10 degree celius the thermal driver report resource temporarily unavailable. 

In the source code of the driver (drivers/thermal/imx8mm_thermal.c) the following code will cause this behavior. 

if (tmu->socdata->flags == FLAGS_TMU_VER1) {
       val = readl_relaxed(tmu->base + TRITSR) & TRITSR_VAL_MASK;
       if (val < TEMP_LOW_LIMIT) {
               return -EAGAIN;
       }
}

Any explanation why the MX8MN has this low temperature limitation? 

Can this limitation be removed for industrial versions of the CPU?

Best regards,

--

Mike

[nxf63675 · Accepted solution]

Hi @MikeEngel ,

Based on IMX8MN Datasheet we have Temperature Sensor Accuracy set to 10-105 (Table 10. Operating ranges).

This is the reason of the limitation and it is applied in industrial products.

Regards,

Israel H.

[MikeEngel]

Thanks for this information. I found the data in the document you mentioned.