Detect or signal Linux (A7) shutdown on M4 core (i.MX 7ULP)

[bram]

Hello everyone,

Is there a way to check for a Linux shutdown (A7) from wihtin the M4 core? or in other words, is there already a signal, or a way to signal to the M4 core that Linux has succesfully shut down?

We are using the i.MX 7ULP.

With kind regards,
Bram

[igorpadykov]

Hi Bram

one can look at function MU_GetOtherCorePowerMode() defined in fsl_mu.h,
example can be found in ../demo_apps/power_mode_switch SDK_MX7ULP EVK

available on  https://mcuxpresso.nxp.com/en/welcome

Best regards
igor

[bram]

Thanks for the quick reply!

I tried your solution, but when I poll the MU_GetOtherCorePowerMode(MUA) during shutdown, I see it oscillating between RUN (0) and STOP (2) (see logging below). I can't determine when it Linux has finished shutting down from this data. From my understanding a Kernel driver handles setting the power mode during this time. Which driver is responsible for this power mode switching during shutdown? Or do I need to set it myself? I am using Kernel linux-imx version 5.4.70 (Hardknott).

Start of shutdown procedure:

0000044631 POWER MODE OTHER CORE A: 0
0000045631 POWER MODE OTHER CORE A: 0
0000046631 POWER MODE OTHER CORE A: 2
0000047631 POWER MODE OTHER CORE A: 0
0000048631 POWER MODE OTHER CORE A: 0
0000049631 POWER MODE OTHER CORE A: 0
0000050631 POWER MODE OTHER CORE A: 0
0000051631 POWER MODE OTHER CORE A: 2
0000052631 POWER MODE OTHER CORE A: 2
0000053631 POWER MODE OTHER CORE A: 2
0000054631 POWER MODE OTHER CORE A: 2
0000055631 POWER MODE OTHER CORE A: 2
0000056631 POWER MODE OTHER CORE A: 0
0000057631 POWER MODE OTHER CORE A: 0
0000058631 POWER MODE OTHER CORE A: 0
0000059631 POWER MODE OTHER CORE A: 0
0000060631 POWER MODE OTHER CORE A: 0
0000061631 POWER MODE OTHER CORE A: 0
0000062631 POWER MODE OTHER CORE A: 0

Shutdown completed was completed around timestamp: 0000057631 

With kind regards:
Bram