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Subject: DEC driver DMA Underflow
From: Matt Rippa <mrippa@gemini.edu>
To: "tech-talk@aps.anl.gov" <tech-talk@aps.anl.gov>
Date: Wed, 25 Nov 2009 10:23:46 -1000
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;
}


Replies:
RE: DEC driver DMA Underflow Mark Rivers
RE: DEC driver DMA Underflow Jeff Hill

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