PPC405GP Ethernet Driver

gregory.menke at gsfc.nasa.gov gregory.menke at gsfc.nasa.gov
Wed Aug 3 14:51:34 UTC 2005

Its not RTEMS.  This is the usual pathology a new lanboard driver
exhibits.  You still have a problem somewhere, unfortunately.  Maybe a
wild pointer or a subtle pointer problem in your dma descriptor chain.
Other things to check for include, are you sure your driver rx/tx
tasks are getting and releasing the network semaphore properly, and
not doing stuff outside the time they own it.  If you use signals
and/or message queues to move around descriptors or mbufs, check for

I went through this sort of thing when I worked on the dec21140 and
elnk drivers- its very tricky to get these last subtle bugs out.  I
had a very difficult time getting the transmit chaining working right
on the elnk driver- that bug allowed low packets/sec rx & tx just
fine, but once you ramped up to multiple packet tx's, then pointer
problems would start showing up.

I guess all I can add is since the lockup seems to happen randomly, it
suggests some kind of timing dependency, where two events have to be
"close enough" to trigger the problem.  Lacking an ICE or equiv, I
think the next thing is to thoroughly instrument the driver with
counters and monitor them while you run through test cases.  

One thing that may help is to write your own quick 'n dirty test
program that transmits and receives in a way that lets you usefully
produce the counter values.

Sounds like you're making headway though.



Doyle, Bryon Thomas (Bryon) writes:
 > Hello again, I have managed to correct the previous flaw of my
 > driver eating up all the available mbufs, thanks to everybody who
 > gave their input. Now however I have a seemingly more insidious
 > problem. I have been testing the driver using the netdemo
 > application and setting up my host PC to constantly ping away at
 > the board. I have noticed something rather strange, after a
 > completely random interval of time the board hangs. I have had the
 > board test for several hours, and then in other instances it hung
 > after only a couple of minutes, the only constant is that sometime
 > the board does eventually hang.  I am inclined to think that a
 > memory leak is the problem but I have no clue where it could be. My
 > mbuf usage is normal, and all the wrap bits and buffers for the
 > hardware DMA access buffers are properly configured. Has anyone
 > experienced a similar problem with RTEMS?
 > As always any help is appreciated, Thanks again.
 > Bryon Doyle
 > Bell Labs Summer Intern
 > Lucent Technologies

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