MPC5200 FEC Ethernet only halfduplex ?

MPC5200 FEC Ethernet only halfduplex ?

[Thomas Schnürer]

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Im working with Linux on our MPC5200 Board, with the latest Rev. B3 Processor.
I was updating our Linux BSP from BestComm 2.1 to 2.2 some time ago and used your patches which increased usability of the FEC very much.
 
There is a line in the driver code which I dont understand, it says:
+ fec_restart(dev, 0); /* always use half duplex mode only */
 
Why can only half duplex be used ? I made a test with the iperf tool and saw that with the driver in its current state I get 90 Mbit/s in one direction and only 10 kBit/ other way. When changing the fec_restart call to (dev, 1) it turns to 90 Mbit and 250 kBit/s.
Then I changed for couriosity the BestComm task prioritisation and suddenly I get 90 Mbit in both directions.
So whats the reason for this setting above ?
 
Thanks in advance!

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Re: MPC5200 FEC Ethernet only halfduplex ?

[Dale Farnsworth]

TSchnuerer@men.de wrote:
> Im working with Linux on our MPC5200 Board, with the latest Rev. B3 
> Processor.
> I was updating our Linux BSP from BestComm 2.1 to 2.2 some time ago and
> used your patches which increased usability of the FEC very much.
> 
> There is a line in the driver code which I dont understand, it says:
> + fec_restart(dev, 0); /* always use half duplex mode only */
> 
> Why can only half duplex be used ?

The reason is simple, but not satisfying.  The driver has no
mechanism to detect PHY status changes and thus no way to determine
when a connection changes from full to half duplex.  It needs a
poll function for PHY status change.  Doing only half-duplex
avoids this issue--at a big performance cost.

I think a poll function was added in the Denx version.

The MPC5200 FEC driver desperately needs a rewrite.

-Dale