junk character issue on minicom and screen

[Shyam Saini]

Hello everyone,

I'm working on Rockchip rk3399 Nanopc t4 board and I'm trying get serial output
from board using minicom and my board has baudrate 1500000.

I'm using a usb to serial converter. So, when i power on my board minicom starts
to give junk characters.
Minicom version:  2.7.1
USB driver probed : cp210x

But when I use the same setup with my colleagues laptop it gives correct output
(kernel version 4.15.0-52-generic ).

Note that my colleague and i used same setup
Same usb driver probed
Same power adapter
same usb to serial converter wire
same minicom version.
same baudrate

Other thing which i tried is switching kernel version and it turns out
that one of the older
distro kernel on my system (debian 4.9.0-5-amd64 ) is working fine and
it seems like
there is something changed in newer kernel vesions.
Here is the quick summary
4.19.0-4-amd64    -> not working
4.15.0-52-generic -> working
4.9.0-5-amd64      -> working
5.2.0-rc4+             -> not working

Did anyone else faced the similar problem.
Is there any patch available if it is bug ?
Please let me know.

Thanks a lot,
Shyam