dmaengine: omap-dma: Start DMA without delay for cyclic channels

cyclic DMA is only used by audio which needs DMA to be started without a
delay.
If the DMA for audio is started using the tasklet we experience random
channel switch (to be more precise: channel shift).
Reported-by: Peter Meerwald <pmeerw@pmeerw.net>
CC: stable@vger.kernel.org  # v3.7+
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/omap-dma.c

@@ -276,12 +276,20 @@ static void omap_dma_issue_pending(struct dma_chan *chan)
 
 	spin_lock_irqsave(&c->vc.lock, flags);
 	if (vchan_issue_pending(&c->vc) && !c->desc) {
-		struct omap_dmadev *d = to_omap_dma_dev(chan->device);
-		spin_lock(&d->lock);
-		if (list_empty(&c->node))
-			list_add_tail(&c->node, &d->pending);
-		spin_unlock(&d->lock);
-		tasklet_schedule(&d->task);
+		/*
+		 * c->cyclic is used only by audio and in this case the DMA need
+		 * to be started without delay.
+		 */
+		if (!c->cyclic) {
+			struct omap_dmadev *d = to_omap_dma_dev(chan->device);
+			spin_lock(&d->lock);
+			if (list_empty(&c->node))
+				list_add_tail(&c->node, &d->pending);
+			spin_unlock(&d->lock);
+			tasklet_schedule(&d->task);
+		} else {
+			omap_dma_start_desc(c);
+		}
 	}
 	spin_unlock_irqrestore(&c->vc.lock, flags);
 }