On 04/01/2014 08:06 AM, Peter Ujfalusi wrote: > To improve latency with cyclic DMA operation it is preferred to > use different eventq/tc than the default which is used by all > other drivers (mmc, spi, i2c, etc). > When preparing the cyclic dma ask for non default queue for the > channel which is going to be used with cyclic mode. > > Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx> > --- > drivers/dma/edma.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c > index 1dd9e8806975..10048b40fac8 100644 > --- a/drivers/dma/edma.c > +++ b/drivers/dma/edma.c > @@ -628,6 +628,9 @@ static struct dma_async_tx_descriptor *edma_prep_dma_cyclic( > edesc->pset[i].opt |= TCINTEN; > } > > + /* Use different eventq/tc for cyclic DMA to reduce latency */ > + edma_request_non_default_queue(echan->ch_num); > + > return vchan_tx_prep(&echan->vchan, &edesc->vdesc, tx_flags); > } > > Is there any way to guarantee that the non-default queue is of the highest priority, or in other words default queue is of lowest priority. I know you set queue 1 as default because by default 0 is higher priority. And then assigning non-default queue. When assigning default to Queue 1, it would be good to also call assign_priority_to_queue and set QUEPRI to 7 for Queue 1. Since 0, 2 and 4 are all non-defaults. Thanks, -Joel -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
