mmc: bcm2835: Properly handle dmaengine_prep_slave_sg

In case dmaengine_prep_slave_sg fails we need to call dma_unmap_sg.
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/bcm2835.c

@@ -507,13 +507,16 @@ void bcm2835_prepare_dma(struct bcm2835_host *host, struct mmc_data *data)
 	desc = dmaengine_prep_slave_sg(dma_chan, data->sg, sg_len, dir_slave,
 				       DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
 
-	if (desc) {
-		desc->callback = bcm2835_dma_complete;
-		desc->callback_param = host;
-		host->dma_desc = desc;
-		host->dma_chan = dma_chan;
-		host->dma_dir = dir_data;
+	if (!desc) {
+		dma_unmap_sg(dma_chan->device->dev, data->sg, sg_len, dir_data);
+		return;
 	}
+
+	desc->callback = bcm2835_dma_complete;
+	desc->callback_param = host;
+	host->dma_desc = desc;
+	host->dma_chan = dma_chan;
+	host->dma_dir = dir_data;
 }
 
 static void bcm2835_start_dma(struct bcm2835_host *host)