i.MX8M mini TMU DC offset issue

[Tori-san]

Hello, According to the IMX8MMRM.pdf clause 5.4.6, hardware will do 1 point calibration. And when I tried the following command, response was shown below. "cat /sys/devices/virtual/thermal/thermal_zone0/slope" returns "1" and "cat /sys/devices/virtual/thermal/thermal_zone0/offset" returns "0". Does that mean hardware calibration use not slope-intercept form but linear function? Doesn't it mean that each IMX8M mini has no DC offset?

[Yuri · Accepted solution]

@Tori-san 
Hello,

   In out BSP, we have the fsl,imx8mm-tmu driver implemented in /drivers/thermal/imx8mm_thermal.c, which is enabled by default. One thing to note is that (in tmu_get_temp) the driver will report the value stored in TRITSR as current temperature, which means that the 1-point hardware calibration value is returned. If the customer wants to do the 2-points software calibration, they will have to update the driver by applying the formula described in the RM on the values returned in the registers. To get the result, there is an interface for the driver in /sys/class/thermal.

Regards,
Yuri.

[Tori-san]

Hi Yuri, Thank you for your reply. I understood that the 1-point calibrated value will be stored in TRITSR (Addr: 3026_0020h) and it enabled by default. I also understood the 2-points calibration is not currently supported by im8mm_thermal.c. I interpret that the slope and offset under /sys/devices/virtual/thermal/thermal_zone0 are not used. Best regards, Tori-san.

[Tori-san]

Hi Tech Support. Is this community not supported by IE? It seems that line breaks are not worked.