Rohit,
UART4 is not accessible from pin header in BPI-M1+, I think it is on BananaPro.
BPI-M1+ has the following UARTs reported on GPIO connector UART 2/3/5/6/7.
The procedure I've tested worked for me on bananian 15.08.
You have to modify script.bin file in the boot partition, so
- mount boot partition
- backup script.bin (in case the board doesn't reboot after editing use this backup to recover)
- convert script.bin in script.fex with bin2fex
- edit script.fex look at http://linux-sunxi.org/Fex_Guide for info
- convert back script.fex to script.bin with fex2bin
- reboot
Changes:
- use uart3 instead of uart4 (BPI-M1+)
- change usbc section for avoiding the usage of PH00 and PH01 pins assiged to uart3
Regards
Snafutzz