ASoC: MPC5200: Support for buffer wrap around

The code in psc_dma_bcom_enqueue_tx() didn't account for the fact that
s->runtime->control->appl_ptr can wrap around to the beginning of the
buffer. This change fixes this problem.
Signed-off-by: NJohn Bonesio <bones@secretlab.ca>
Acked-by: NGrant Likely <grant.likely@secretlab.ca>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/fsl/mpc5200_dma.c

@@ -69,6 +69,23 @@ static void psc_dma_bcom_enqueue_next_buffer(struct psc_dma_stream *s)
 
 static void psc_dma_bcom_enqueue_tx(struct psc_dma_stream *s)
 {
+	if (s->appl_ptr > s->runtime->control->appl_ptr) {
+		/*
+		 * In this case s->runtime->control->appl_ptr has wrapped around.
+		 * Play the data to the end of the boundary, then wrap our own
+		 * appl_ptr back around.
+		 */
+		while (s->appl_ptr < s->runtime->boundary) {
+			if (bcom_queue_full(s->bcom_task))
+				return;
+
+			s->appl_ptr += s->period_size;
+
+			psc_dma_bcom_enqueue_next_buffer(s);
+		}
+		s->appl_ptr -= s->runtime->boundary;
+	}
+
 	while (s->appl_ptr < s->runtime->control->appl_ptr) {
 
 		if (bcom_queue_full(s->bcom_task))