I have... the problem isn't that I am overflowing the UART FIFOs.
I have 16650 UARTs and I have enabled automatic flow contol on
them. It can automatically throttle the flow when the FIFOs get
too full.
The problem is that the flip buffer (a temporary buffer that we
use to dump the UART data into) is not being processed fast
enough in the timer bottom-half routine. This causes the
flip buffer to overflow before it can be swapped (or flipped).
If the problem were with the FIFO overflowing, it is possible
that irqtune would help. In this case however, it won't do
much good.
-Rob