Problem with ibm_emac driver

Problem with ibm_emac driver

[Ian Remmler]

Hi,

I'm having a problem with the ibm_emac driver for the built in
gigabit ethernet on the 440gx.  I was hoping someone could shed
some light or at least point me in the right direction.

I'm using a GMS P502 board runing 2.4.27-pre3 (from GMS).  The
problem we are having is this: when we push data over the emac
interface (eth0 and eth1 both show the problem), we sporadically
get a "MAL: Rx descriptor error..." from mal_rxde in
ibm_ocp_mal.c.

Occasionally, the interface will "freeze up" for a few seconds.
An ifconfig down/up will bring it back, but from then on it will
freeze up again right away.

It looks to me like this error indicates that we're out of RX
buffers, but I don't how we would be running out.  I'm no kernel
or networking expert, but I thought the TCP stack would take
care of throttling itself to prevent that sort of thing.  I
would appreciate any help.


Thanks,
    - Ian.

-- 
"A shark on whiskey is mighty risky.
 A shark on beer is a beer engineer."
        -- Dr. Worm

Re: Problem with ibm_emac driver

[Eugene Surovegin]

On Thu, Jul 20, 2006 at 01:32:42PM -0500, Ian Remmler wrote:
> Hi,
> 
> I'm having a problem with the ibm_emac driver for the built in
> gigabit ethernet on the 440gx.  I was hoping someone could shed
> some light or at least point me in the right direction.
> 
> I'm using a GMS P502 board runing 2.4.27-pre3 (from GMS).  The
> problem we are having is this: when we push data over the emac
> interface (eth0 and eth1 both show the problem), we sporadically
> get a "MAL: Rx descriptor error..." from mal_rxde in
> ibm_ocp_mal.c.
> 
> Occasionally, the interface will "freeze up" for a few seconds.
> An ifconfig down/up will bring it back, but from then on it will
> freeze up again right away.
> 
> It looks to me like this error indicates that we're out of RX
> buffers, but I don't how we would be running out.  I'm no kernel
> or networking expert, but I thought the TCP stack would take
> care of throttling itself to prevent that sort of thing.  I
> would appreciate any help.

No idea what GMS is, but they seem to use old buggy EMAC driver.

You can use kernel.org's 2.6 or 2.4.31 backport at 
http://kernel.ebshome.net/

As a side note, TCP cannot throttle _all_ Rx traffic, think for 
example of a fast box sending a lot of small UDP packets to the 440gx.

-- 
Eugene