arm - Random Timeout TFTP using KSZ8863 and AT91RM9200

Question

Newbie in the community, here. First of all, thanks for all the help in all these years i've been working on embedded development :D

I have a problem with an Atmel AT91RM9200 ARM microprocessor, connected via RMII to a Mikrel KSZ8863 ethernet physical interface. The ARM is loaded with U-Boot 1.1.2, which loads the Linux Kernel v2.4.27.

I manually added the code to interface U-Boot with the KSZ.

The problem is: Using U-Boot, if I try to download something from my TFTP server (located in the same network), the connection sometimes has so many timeouts that the download fails, and sometimes has just 2 or 3 timeouts.

I checked the U-Boot FAQ page, and the most probable reason for the timeouts is a wrong speed configuration, which I double checked.

What could be the reason for the unreliability of my connection?

Thanks, Loranzp.

Answer 1

Setup a minimalist network consistent of TFTP server, client and Sniffer (Wireshark in promiscuous mode) (if you use a switch it must have a repeater port where to connect the sniffer PC)

Next run traffic captures and analyze when and how the timeouts occur.

Consider:

1. TFTP BlockSize too big leading to mishandled IP fragmentation.
2. Server provides the packets too fast after REQ or ACK
3. Not correctly handling block number roll-over (only when handling big files)
4. etc