Does M4 run in same frequency during A9 core sleep and wakeup in imx6sx?

[rakesh_patel]

We are using imx6sx board.

We put A9 core in sleep mode using below command.

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echo mem > /sys/power/state

Output with suspend and resume.

====================

PM: Syncing filesystems ... done.
Freezing user space processes ... (elapsed 0.001 seconds) done.
Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
Suspending console(s) (use no_console_suspend to debug)
PM: suspend of devices complete after 137.546 msecs
PM: suspend devices took 0.140 seconds
PM: late suspend of devices complete after 0.948 msecs
PM: noirq suspend of devices complete after 0.854 msecs
Disabling non-boot CPUs ...
M4 is busy, enter WAIT mode instead of STOP!
PM: noirq resume of devices complete after 0.438 msecs
PM: early resume of devices complete after 0.529 msecs
PM: resume of devices complete after 166.078 msecs
PM: resume devices took 0.170 seconds
Restarting tasks ... done.

Query:

================

1) Does M4 run at same frequency during A9 suspend and wakeup ?

[igorpadykov]

Hi rakesh_patel

I believe yes, M4 runs at the same frequency. Example for changing

M4 frequency can be found in  sect.5.1 Deep-Sleep mode

i.MX 6SoloX Power Consumption Measurement - AN5050 

Best regards
igor

[rakesh_patel]

@igorpadykov :

Is there any M4 application for "Enter "S" on M4 console to change M4 to low frequency mode (12 MHz)." (Seciont#5.1 )?

I checked FreeRTOS_BSP_1.0.1_iMX6SX BSP. But could not find any application for the same.

Can you please help me here?

[igorpadykov · Accepted solution]

one can look at folder ../demo_apps/low_power_imx6sx

FreeRTOS_MX6SX_1.0.1_WIN

Best regards
igor

[rakesh_patel]

@igorpadykov :

We have custom application in M4 core running in TCM. 

In our application, we are doing GPIO reading and writing to RAM address operation from EPIT handler.

We found that, while A9 core coming back from Suspend to wakeup(from mem > sys/power/state), M4 core application speed degraded for couple of ms(2-3 ms) only. What can be the reason here? Any idea?

M4 core has an EPIT timer using "epitClockSourcePeriph" Clock. and EPIT handler doing GPIO reading and writing to RAM.

Any idea here? 

[rakesh_patel]

@igorpadykov : Do you have any idea for this?