We are working on the system low power mode. When we disable all I/O in the kernel, we can see M4 will enter the lower power mode The VDD_SOC will have small power consumption. But in real case, we will not have all interface to be off to let the M4 enter the idle mode. Such as that we will still need WiFi module to be active under DTIM mode (no traffic, just link to the server to be connection alive checking). We found we need to remove the SDIO to unload the wifi driver then to enter the M4 low power mode.
So, to let M4 be idle, disable all interface is a mandatory action? How does it implement on Saber board since saber also has muRATA WLAN module?
We see the AN5383, there is the test cases that A7 working but M4 idle (4.3 and 4.4.1).