Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760453AbZJPPeN (ORCPT ); Fri, 16 Oct 2009 11:34:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760296AbZJPPeM (ORCPT ); Fri, 16 Oct 2009 11:34:12 -0400 Received: from ovro.ovro.caltech.edu ([192.100.16.2]:55685 "EHLO ovro.ovro.caltech.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759471AbZJPPeM (ORCPT ); Fri, 16 Oct 2009 11:34:12 -0400 Date: Fri, 16 Oct 2009 08:33:34 -0700 From: "Ira W. Snyder" To: Dan Williams Cc: Vishnu Suresh , herbert@gondor.apana.org.au, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, linuxppc-dev@ozlabs.org, linux-crypto@vger.kernel.org, Timur Tabi Subject: Re: [PATCH v0 1/2] DMA: fsldma: Disable DMA_INTERRUPT when Async_tx enabled Message-ID: <20091016153334.GA27401@ovro.caltech.edu> References: <1255588866-4133-1-git-send-email-Vishnu@freescale.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.0 (ovro.ovro.caltech.edu); Fri, 16 Oct 2009 08:33:35 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2863 Lines: 72 On Thu, Oct 15, 2009 at 06:25:14PM -0700, Dan Williams wrote: > [ added Leo and Timur to the Cc ] > > On Wed, Oct 14, 2009 at 11:41 PM, Vishnu Suresh wrote: > > This patch disables the use of DMA_INTERRUPT capability with Async_tx > > > > The fsldma produces a null transfer with DMA_INTERRUPT > > capability when used with Async_tx. When RAID devices queue > > a transaction via Async_tx, this ?results in a hang. > > > > Signed-off-by: Vishnu Suresh > > --- > > ?drivers/dma/fsldma.c | ? ?6 ++++++ > > ?1 files changed, 6 insertions(+), 0 deletions(-) > > > > diff --git a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c > > index 296f9e7..66d9b39 100644 > > --- a/drivers/dma/fsldma.c > > +++ b/drivers/dma/fsldma.c > > @@ -1200,7 +1200,13 @@ static int __devinit of_fsl_dma_probe(struct of_device *dev, > > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?- fdev->reg.start + 1); > > > > ? ? ? ?dma_cap_set(DMA_MEMCPY, fdev->common.cap_mask); > > +#ifndef CONFIG_ASYNC_CORE > > + ? ? ? /* > > + ? ? ? ?* The DMA_INTERRUPT async_tx is a NULL transfer, which will > > + ? ? ? ?* triger a PE interrupt. > > + ? ? ? ?*/ > > ? ? ? ?dma_cap_set(DMA_INTERRUPT, fdev->common.cap_mask); > > +#endif > > ? ? ? ?dma_cap_set(DMA_SLAVE, fdev->common.cap_mask); > > ? ? ? ?fdev->common.device_alloc_chan_resources = fsl_dma_alloc_chan_resources; > > ? ? ? ?fdev->common.device_free_chan_resources = fsl_dma_free_chan_resources; > > You are basically saying that fsl_dma_prep_interrupt() is buggy. Can > that routine be fixed rather than this piecemeal solution? If it > cannot be fixed (i.e. hardware issue) then fsl_dma_prep_interrupt() > should just be disabled/deleted altogether. > For what it's worth, I've used the following code in the recent past, without any issues. This was on an 83xx, within the last few kernel releases. I haven't tried it on the latest -rc. Using device_prep_dma_memcpy() can trigger a callback as well, so the interrupt feature isn't strictly needed. Just attach the callback to the last memcpy operation. static dma_cookie_t dma_async_interrupt(struct dma_chan *chan, dma_async_tx_callback callback, void *data) { struct dma_device *dev = chan->device; struct dma_async_tx_descriptor *tx; /* Set up the DMA */ tx = dev->device_prep_dma_interrupt(chan, DMA_PREP_INTERRUPT); if (!tx) return -ENOMEM; tx->callback = callback; tx->callback_param = data; return tx->tx_submit(tx); } Ira -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/