MPC5200B FEC Fullduplex Performance problem

Thomas Schnürer TSchnuerer at
Fri Aug 11 01:52:39 EST 2006

Hello everybody,

I experience a Problem with obtaining the maximum FEC Performance.

I use Linux 2.6.15 with bestcomm 2.2 already and use the FEC in fullduplex mode. When I use
a test tool, the maximum transfer rates I get are 90 Mbit vs. 40 Mbit.
(the tool is called iperf, can be downloaded).

Also when checking /proc/interrupts after some time of fullduplex data transfer I see that there
are much more rx IRQs than tx IRQs.
In the driver linux/drivers/net/fec_mpc52xx.c I made some debug outputs which show me that
also TX FIFO underruns occur.

It seems to me that somehow the RX SDMA task is priorized before TX task, and this doesnt change
when I alter the priority values used in the driver.

The board is a MEN Mikro EM01, used clocks are XLB 128 MHz, CPU 384 MHz, SDRAM 132 MHz.

Does anyone have Performance measurements for FEC made on the 5200B ?

I would be happy already with reaching some 60/60 Mbits/s.



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