Experimental Physics and
Industrial Control System

Matt Rippa <[email protected]> · Wed, 25 Nov 2009 12:40:10 -1000

Thanks Mark. This is the first time I've seen it so it's not

chronic. We also suffer occasionally from the network going

belly up and unable to recover. This event had similar symptoms

but the DMA underflow was certainly new.

FWIW, I've also received some BSP patches from Andrew related to

L2 cache. This was 2 years ago but was for Vxworks 5.5.2 rather

than 5.5. Not sure if this is the same BSP change you're

referring to.

Matt

On 11/25/2009 11:23 AM, Mark Rivers wrote:

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