IMX6Q: how critical and passive temperature handling is done in driver

[shreeharsha_ind]

SoC: IMX6Q

Kernel: 4.1.15

Hi All,

For one of our programme I want to know what actions are performed by imx thermal driver on encountering passive and critical temperature. Also does SoC restarts when critical temperature is reached.  

Thanks in advance.

Regards,

Shree

[justin_jiang]

SoC will shutdown and won't restart when reach critical point.

[shreeharsha_ind]

In one of our programm we see following behaviour in case of reaching critical temperature:

On reaching critical temperature during the normal run-time, SOC doesnt shutdown, only prints "SOC will shutdown, critical temperature reached" and it continues,  we still have access to console.

can we know what could be the reason for such behaviour.

Regards,

Shree

[Yuri]

@shreeharsha_ind 
Hello,

   i.MX6 reference design uses WDOG output for total system power reset
for shutdown. Is such circuit implemented on Your board?

Regards,
Yuri.

[shreeharsha_ind]

Hi,

Thanks for the quick reply.

Q.  i.MX6 reference design uses WDOG output for total system power reset for shutdown. Is such circuit implemented on Your board?

[A] Such HW circuit not implemented in the board used by program

We have couple of queries against same issue.

1. can we avoid soc shutsown form imx thermal code during bootup time just in case it reaches critical temp during boot time, as we have a master initiaing soc shutdown on reaching critical temp which requires few application to comeup. Now Soc shutdown happens even before application are up. 

2. In system running scenerio when passive temperature is reached and frequency scaling is done they see IPC communication over uart breaks. why is the uart communication disrupted upon frequency scaling.

Regards,

Shree

[Yuri]

@shreeharsha_ind 
Hello,

1. You can try to build the thermal driver as module.
2. Do You use NXP Linux ?

Regards,
Yuri.

[Yuri]

@shreeharsha_ind 
Hello,

  according to i.MX_Linux_Reference_Manual.pdf:

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 to run at a lower frequency.
• When the temperature drops to 10 °C below passive point, cooling device will
release all the cooling actions.

Regards,
Yuri.