dmaengine: bcm2835-dma: Use vchan_terminate_vdesc() instead of desc_free

To avoid race with vchan_complete, use the race free way to terminate
running transfer.

Implement the device_synchronize callback to make sure that the terminated
descriptor is freed.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/bcm2835-dma.c

@@ -812,7 +812,7 @@ static int bcm2835_dma_terminate_all(struct dma_chan *chan)
 	 * c->desc is NULL and exit.)
 	 */
 	if (c->desc) {
-		bcm2835_dma_desc_free(&c->desc->vd);
+		vchan_terminate_vdesc(&c->desc->vd);
 		c->desc = NULL;
 		bcm2835_dma_abort(c->chan_base);
 
@@ -836,6 +836,13 @@ static int bcm2835_dma_terminate_all(struct dma_chan *chan)
 	return 0;
 }
 
+static void bcm2835_dma_synchronize(struct dma_chan *chan)
+{
+	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
+
+	vchan_synchronize(&c->vc);
+}
+
 static int bcm2835_dma_chan_init(struct bcm2835_dmadev *d, int chan_id,
 				 int irq, unsigned int irq_flags)
 {
@@ -942,6 +949,7 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
 	od->ddev.device_prep_dma_memcpy = bcm2835_dma_prep_dma_memcpy;
 	od->ddev.device_config = bcm2835_dma_slave_config;
 	od->ddev.device_terminate_all = bcm2835_dma_terminate_all;
+	od->ddev.device_synchronize = bcm2835_dma_synchronize;
 	od->ddev.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
 	od->ddev.dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
 	od->ddev.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV) |