Port of the new em(4) to RELENG_6 and some problems with 82540EM

[Sten Daniel Soersdal]

Eygene Ryabinkin wrote:
> Jack, good day.
> 
> I happened to make a quick and dirty patch for your latest (for the
> 16.05.2007) em(4) driver from 7-CURRENT. I had seen that you mentioned
> TSO and 6.3, so I assume that you're going to merge the driver to
> the RELENG_6 someday, so maybe my effort may be helpful.
> 
> To my problems.
> 
> I have the '82540EM Gigabit Ethernet Controller' branded card
> (PWLA8390MT) and I am currently expiriencing troubles with the
> Gigabit switch (D-Link DGS-1008, the cheap one). Plugged into that
> switch I have
> 
>  - broken packets and SSH messages 'Disconnecting: Corrupted MAC
>  on input.' when checksumming is turned on and gigabit speed,
> 
>  - abyssmal rates for the HTTP downloads (about 10Mbit/sec) when
>  checksums are turned off and the speed is gigabit again,
> 
>  - having switched the media on the adapter to the 100BaseTX
>  full-duplex, but still using the same switch the speed drops to
>  200Kbit/sec,
> 
>  - using another D-Link switch (sorry, have no other brand in
>  hand) the above situation is completely reproducible.
> 
>  - working in the half-duplex mode (for 10BaseT/UTP and 100BaseTX)
>  I have no problems to reach the 90% of the theoretical bandwidth
>  of the link via HTTP either with checksums enabled or disabled.
> 
> So, the full-duplex mode is not usable to me now. If someone can
> help in this situation, I am all ears.

That's what we call a self inflicted network problem.
When one end is configured full-duplex and the other end is in auto 
speed/duplex and you want to set fixed speed/duplex, then you need to do 
it on both ends. Otherwise the auto-negotiating side will default to 
half-duplex. This is to be backwards compatible with hubs.

-- 
Sten Daniel Soersdal