[tulip] Re: More DFE-570TX Tx Hung Problems

Tim Dixon dixon@webwork.co.uk
Thu, 25 May 2000 10:03:04 +0100

Just to update Donald and the several other people who've expressed interest
in this...

> [Just to summarise; we've been getting "Tx Hung" errors where we have
> several DFE-570TXs in one box so that some of the ports end up
> sharing IRQs. Simply ifconfig'ing the stuck port up and down makes
> no difference. Other ports on the same card continue to work.
>/proc/interrupts revealed that no  interrupts were being taken on the
>IRQ shared by the ports concerned. Although ifconfiging down the stuck
>port didn't make any difference, taking down ALL the ports sharing the
>IRQ and bringing them back up again seemed to do the trick.
>We've had the same problem on a couple of different IRQ lines in the
>same machine (in each case, 3 ports shared an IRQ)]

We've found the same problem running driver V0.92 and I'm seriously
starting to suspect the motherboard rather than the devices or the
drivers. It looks like the devices believe they have an interrupt request
pending on the shared IRQ but it isn't being delivered. My guess is that
a condition arises in which two simultaneous interrupts on the same IRQ
are mishandled by the arbitration hardware and it is essentially waiting
for the interrupt requests to be cleared before recognising another
interrupt - which will never happen because it's the ISR that clears the
requests (effectively that the hardware is behaving in an edge-triggered
rather than level-triggered manner). We've built a similar system with a
different brand of motherboard and have during initial testing experience
no similar problems. We'll replace the system in the field later in the week
and see if the problems go away.