Banana Pi BPI-M2S gpio serial port not working

I’m trying to make a serial communication thru the GPIO port, but when using the armbian-config overlay for the uart, it register the serial device, but doesn’t show at the /dev folder. The debug uart seems to be there. Also found the pins are not properly assigned a function. Is there any device tree patch or method to have this uart working?

Check with Armbian if you are using Armbian. It is based on different kernel stack than stock FW.

are you saying the other distributions work? can you point me to an example of other distributions dtb’s to check for it?

I am saying - if you use Armbian, their forums are better target to search for clues.

Other distributions take Armbian work too, yes. Armbian is not just distribution. It controls hw from when you power it on. It make those devices run Linux. Not just distribute. If you can’t do it with Armbian, its often no-go.

This is not x86 world, a few of them are worse or equal at best. I am forum user and I have provided you some ideas and clues. I won’t be dealing with your problem.

not asking for solutions, just guidance, we tested the custom build from bananapi and the uart works, so seems to be an armbian problem.

Then it is not a problem you fix this on Armbian? Download SDK, sent a patch. Armbian have no benefits whatsoever if you do that, but you will help someone else.

You can also try to report it right - “Reporting bugs”.

https://docs.armbian.com/User-Guide_FAQ/#why-does-hardware-feature-xy-work-in-old-kernel-but-not-in-more-recent-one

actualoly we just found the problem is the bluetooth/wifi uart module that is pre-installed and block that uart port from being used. doesn’t seems to be a hardware problem as the port outputs character but under that hci_uart control.

I am glad you find the problem.