dmaengine: omap-dma: Start DMA without delay for cyclic channels
Peter Ujfalusi [Tue, 9 Apr 2013 14:33:06 +0000 (16:33 +0200)]
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

index c4b4fd2..08b43bf 100644 (file)
@@ -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);
 }