From: "Suresh Vishnu-B05022" Subject: RE: [PATCH v0 1/2] DMA: fsldma: Disable DMA_INTERRUPT when Async_tx enabled Date: Tue, 20 Oct 2009 18:39:53 +0530 Message-ID: <76952DF81420A349876E087D089DF03438B8C1@zin33exm21.fsl.freescale.net> References: <1255588866-4133-1-git-send-email-Vishnu@freescale.com> <20091016153334.GA27401@ovro.caltech.edu> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Cc: herbert@gondor.apana.org.au, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, linuxppc-dev@ozlabs.org, linux-crypto@vger.kernel.org, Tabi Timur-B04825 To: "Ira W. Snyder" , "Dan Williams" Return-path: Content-class: urn:content-classes:message In-Reply-To: <20091016153334.GA27401@ovro.caltech.edu> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linuxppc-dev-bounces+glppd-linuxppc64-dev=m.gmane.org@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+glppd-linuxppc64-dev=m.gmane.org@lists.ozlabs.org List-Id: linux-crypto.vger.kernel.org > -----Original Message----- > From: Ira W. Snyder [mailto:iws@ovro.caltech.edu] = > Sent: Friday, October 16, 2009 9:04 PM > To: Dan Williams > Cc: Suresh Vishnu-B05022; herbert@gondor.apana.org.au; = > linux-kernel@vger.kernel.org; linux-raid@vger.kernel.org; = > linuxppc-dev@ozlabs.org; linux-crypto@vger.kernel.org; Tabi = > Timur-B04825 > Subject: Re: [PATCH v0 1/2] DMA: fsldma: Disable = > DMA_INTERRUPT when Async_tx enabled > = > 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 =A0results in a hang. > > > > > > Signed-off-by: Vishnu Suresh > > > --- > > > =A0drivers/dma/fsldma.c | =A0 =A06 ++++++ > > > =A01 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, > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 = =A0 =A0 =A0 =A0 =A0 =A0 =A0- = > fdev->reg.start + = > > > 1); > > > > > > =A0 =A0 =A0 =A0dma_cap_set(DMA_MEMCPY, fdev->common.cap_mask); > > > +#ifndef CONFIG_ASYNC_CORE > > > + =A0 =A0 =A0 /* > > > + =A0 =A0 =A0 =A0* The DMA_INTERRUPT async_tx is a NULL transfer, = > which will > > > + =A0 =A0 =A0 =A0* triger a PE interrupt. > > > + =A0 =A0 =A0 =A0*/ > > > =A0 =A0 =A0 =A0dma_cap_set(DMA_INTERRUPT, fdev->common.cap_mask); > > > +#endif > > > =A0 =A0 =A0 =A0dma_cap_set(DMA_SLAVE, fdev->common.cap_mask); > > > =A0 =A0 =A0 =A0fdev->common.device_alloc_chan_resources =3D = > > > fsl_dma_alloc_chan_resources; > > > =A0 =A0 =A0 =A0fdev->common.device_free_chan_resources =3D = > > > 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. We are working to fix this issue. > > = > = > 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. This works fine as long as only DMA_MEMCPY is being used. The async_tx_channel_switch does not occur and the = device_prep_dma_interrupt is not called. = However, when a DMA_XOR capable device is exposed, = which is differnet from the DMA_MEMCPY/INTERRUPT device, this path is hit. Is it proper to schedule a dma_interrupt from the channel switch call, = even when the depend_tx and tx channels correspond to different devices? > = > 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 =3D chan->device; > struct dma_async_tx_descriptor *tx; = > = > /* Set up the DMA */ > tx =3D dev->device_prep_dma_interrupt(chan, DMA_PREP_INTERRUPT); > if (!tx) > return -ENOMEM; > = > tx->callback =3D callback; > tx->callback_param =3D data; > = > return tx->tx_submit(tx); > } > = > Ira > = > =