Experimental Physics and
Industrial Control System

"Mark Rivers" <[email protected]> · Wed, 25 Nov 2009 15:23:15 -0600

I don't know upgrading to 3.14.x will fix that, I have had problems that
sound similar on MVME2700 on 3.14.8.2 and 3.14.10.  But I don't recall
seeing the DMA underflow message. The network goes belly up and cannot
recover, though everything else looks OK.  Andrew Johnson made a change
to the BSP recently that he though might address the issue, but I have
not tested it.  On the other hand this has not happened for many months
now.  Sometimes it happened every week.

Mark

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Matt Rippa
Sent: Wednesday, November 25, 2009 2:24 PM
To: [email protected]
Subject: DEC driver DMA Underflow

Hello -

We're running an IOC on a MVME2700 board with VxWorks5.5 and 
EPICS 3.13.9. Yesterday we logged a DMA underflow event from the 
network which resulted in a restart of the driver. CA couldn't 
survive and we quickly had S_errno_ENOBUFS. We had to reboot to 
recover.

Does the DMA underflow indicate a bus error? Is CA designed to 
survive such an event? Short of upgrading to EPICS 3.14.x is 
there anything that can be done to prevent this?

Thanks,
-Matt

Here's some relevant code from the end driver:

/* restart if DMA underflow is detected */

if (pTxD->tDesc0 & PCISWAP(TDESC0_UF))
{
  LOG_MSG ("%s%d - fatal DMA underflow\n",
  (int) DRV_NAME, pDrvCtrl->unit, 0, 0, 0, 0);

   dec21x4xStop (pDrvCtrl);
   pDrvCtrl->txCleaning = FALSE;
   netJobAdd ((FUNCPTR)dec21x4xRestart, (int)pDrvCtrl, 0, 0, 0, 0);
   return;
}

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System