ARM: S3C64XX: DMA: Callback with correct buffer pointer

buffdone callback should be called per buffer request with pointer
to the latest serviced request.
'next' should point to the one next to currently active.
Signed-off-by: NJassi Brar <jassi.brar@samsung.com>
Signed-off-by: NBen Dooks <ben-linux@fluff.org>

arch/arm/plat-s3c64xx/dma.c

@@ -576,6 +576,7 @@ static irqreturn_t s3c64xx_dma_irq(int irq, void *pw)
 	errstat = readl(dmac->regs + PL080_ERR_STATUS);
 
 	for (offs = 0, bit = 1; offs < 8; offs++, bit <<= 1) {
+		struct s3c64xx_dma_buff *buff;
 
 		if (!(errstat & bit) && !(tcstat & bit))
 			continue;
@@ -591,7 +592,33 @@ static irqreturn_t s3c64xx_dma_irq(int irq, void *pw)
 		if (errstat & bit)
 			writel(bit, dmac->regs + PL080_ERR_CLEAR);
 
-		s3c64xx_dma_bufffdone(chan, chan->curr, res);
+		/* 'next' points to the buffer that is next to the
+		 * currently active buffer.
+		 * For CIRCULAR queues, 'next' will be same as 'curr'
+		 * when 'end' is the active buffer.
+		 */
+		buff = chan->curr;
+		while (buff && buff != chan->next
+				&& buff->next != chan->next)
+			buff = buff->next;
+
+		if (!buff)
+			BUG();
+
+		if (buff == chan->next)
+			buff = chan->end;
+
+		s3c64xx_dma_bufffdone(chan, buff, res);
+
+		/* Update 'next' */
+		buff = chan->next;
+		if (chan->next == chan->end) {
+			chan->next = chan->curr;
+			if (!(chan->flags & S3C2410_DMAF_CIRCULAR))
+				chan->end = NULL;
+		} else {
+			chan->next = buff->next;
+		}
 	}
 
 	return IRQ_HANDLED;