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;
> } 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.
> } else {
> dev_err(chan->device->dev, "%s: bad direction?\n", __func__);
> return NULL;
>
--
Péter
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