On Mon, Nov 19, 2012 at 11:01:44AM +0100, Peter Ujfalusi wrote:
> Hi,
>
> On 10/19/2012 12:20 AM, Mark A. Greer wrote:
> > Enable DMA prefetching by setting the 'OMAP_DMA_DST_SYNC_PREFETCH'
> > flag whenever there is a destination synchronized DMA transfer.
> > Prefetching is not allowed on source synchronized DMA transfers.
> >
> > Enabling prefetch significantly improves DMA performance.
> > For example, running 'modprobe tcrypt sec=2 mode=403' which
> > exercises the omap-sham driver on an am37x EVM yeilds the
> > following results:
>
> > drivers/dma/omap-dma.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/dma/omap-dma.c b/drivers/dma/omap-dma.c
> > index bb2d8e7..aadddb2 100644
> > --- a/drivers/dma/omap-dma.c
> > +++ b/drivers/dma/omap-dma.c
> > @@ -310,7 +310,7 @@ static struct dma_async_tx_descriptor
> > *omap_dma_prep_slave_sg(
> > dev_addr = c->cfg.dst_addr;
> > dev_width = c->cfg.dst_addr_width;
> > burst = c->cfg.dst_maxburst;
> > - sync_type = OMAP_DMA_DST_SYNC;
> > + sync_type = OMAP_DMA_DST_SYNC | OMAP_DMA_DST_SYNC_PREFETCH;
>
> This should be:
> - sync_type = OMAP_DMA_DST_SYNC;
> + sync_type = OMAP_DMA_DST_SYNC_PREFETCH;
Ah, right. I will fix.
> > } else {
> > dev_err(chan->device->dev, "%s: bad direction?\n", __func__);
> > return NULL;
> > @@ -387,7 +387,7 @@ static struct dma_async_tx_descriptor
> > *omap_dma_prep_dma_cyclic(
> > dev_addr = c->cfg.dst_addr;
> > dev_width = c->cfg.dst_addr_width;
> > burst = c->cfg.dst_maxburst;
> > - sync_type = OMAP_DMA_DST_SYNC;
> > + sync_type = OMAP_DMA_DST_SYNC | OMAP_DMA_DST_SYNC_PREFETCH;
>
> We should not enable the prefetch for cyclic right now. We will investigate it
> more.
OK. I'll send a patch in a few minutes.
Mark
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