Re: DEC driver DMA Underflow

[Matt Rippa <mrippa@gemini.edu>]

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: tech-talk-bounces@aps.anl.gov
> [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Matt Rippa
> Sent: Wednesday, November 25, 2009 2:24 PM
> To: tech-talk@aps.anl.gov
> 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;
> }