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 <Vishnu@xxxxxxxxxxxxx> 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 <Vishnu@xxxxxxxxxxxxx>
> > ---
> > 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
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