input overrun on serial port

Hi,

I am using the Nios II dev board with 4 NIOS UARTs. I am communicating with another UART device at 115200 bps 8-n-1 without flow control. Occasionally, I get the error:

<div class='quotetop'>QUOTE </div>

--- Quote Start ---

ttyS0: 1 input overrun(s)[/b]

--- Quote End ---

on the system console. After this, serial communication does not work, and the serial port must be close()&#39;d and re-open()&#39;ed. I have been trying to find out the source of this error, and have suspected interrupts that are firing too quickly, but I have no way to really diagnose that. I have tried setting the IRQ of ttyS0-3 to 0 to have the kernel use polling, but without success. I&#39;ve looked over NIOSserial.c and have undefined DEBUG as an attempt to reduce overruns.

Could the problem be that the FIFO buffers are too small?

I&#39;m at a loss here.... I have tried both the stable 2.6.17 and 2.6.19 kernels/source trees, but both have the same problem.

I would appreciate any suggestions!

Thanks!

- Amir