MPC8xx, FEC and DP83847 !?

Jean-Denis Boyer jdboyer at
Fri Mar 22 05:55:44 EST 2002

> In most cases you can just switch off the whole MDIO stuff  and  rely
> on  autonegotiation; the only thing you lose is a kernel message when
> the link status changes. Of course this requires sane hardware, which
> is not always the case :-(

On full duplex connections, we have experienced problems with
the kernel-level BOOTP/DHCP. The offer returned by the server was not
caught. After investigating, it appeared that even though the PHY
auto-negociated correctly, the FEC was not aware of the full duplex
condition. I had to fix it by correctly reading the duplex mode
from the PHY, since this information should be given to the FEC.

It may also cause a 'working but deficient' communication,
especially under heavy traffic, since the collision detection should
be disabled in full duplex.

 Jean-Denis Boyer, B.Eng., System Architect
 Mediatrix Telecom Inc.
 4229 Garlock Street
 Sherbrooke (Québec)
 (819)829-8749 x241

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