GPIO control during shutdown

[jordang]

Hi all,

I’ve been working on battery powered Jetson projects for a while and have come across something I havent been able to find an answer to regarding the Orin nano. I have a latching microcontroller based module for powering on the jetson from battery on a button press. This works great however to unlatch the circuit during shutdown I need to pulse a pin high. what are the GPIO control options at the end of shutdown? Is it possible to set a GPIO pin to be pulsed as the last event during shutdown and if so what is the best method.

I’m familiar with setting the initial pinmux states and controlling GPIO from sysfs and other libraries in userspace however i’m struggling to find a method that sets a pin state on shutdown.

Kind Regards,
Jordan

[WayneWWW]

Try to write a script to toggle power key GPIO that will be executed during shutdown process?

[jordang]

Are you able to tell me at what point during the shutdown process the GPIO can longer be interacted with?

I’ve had a read through some of the the linux Kernel docs and by my current understanding calling device_shutdown is likely what the gpio driver hooks into. Is there any specific documentation for the Orin shutdown procedure in particular how machine_power_off is handled?

[WayneWWW]

Hi,

We didn’t have any document for this because we don’ t really expect a use case that still control GPIO during shutdown.

The gpio driver is kernel/kernel-5.10/drivers/gpio/gpio-tegra186.c. You can try to check driver and see when it got removed.

[jordang]

Thank you, I will give that a look. One thing i’ve just noticed looking through through the pinmux is the SYS_RST_N. Does this go high on shutdown? or are there any accessible pins which change state when the Orin has sucessfully shutdown, that way using GPIO can be avoided

[WayneWWW]

Basically we have product design guide and power down sequence info will be listed there. You can find the info you need.