Thanks for your response. Do you have an update on this ? If you could help me confirm the max baud rate on UART3, will be highly appreciated.
Meantime got a chance to debug this little further and found that baud rate of 115200, 9600 etc. are all producing garbage on UART3. The problem is that the baud rate is halved on the actual h/w line. So if you set 115200, the actual UART output is 57600.
To reproduce this, sort the UART3 and UART6 pins as below and check the output:
UART3_TXD <-> DEBUG_UART6_RXD
UART3_RXD <-> DEBUG_UART6_TXD
// Set UART3 to 230400 (so actual line is set to 115200). UART6 is already running at 115200 by default.
// Now read output of UART6_TXD on UART3_RXD, kmsg logs appears fine.
busybox stty -F /dev/ttyAMA3 raw ispeed 230400 ospeed 230400 cs8 -ignpar -cstopb -echo -crtscts
cat < /dev/ttyAMA3
This issue appears to be known bug here - https://bugs.96boards.org/show_bug.cgi?id=520
Is it possible to raise the priority of this bug and provide a fix ASAP ?