spi_bfin5xx: use PIO for full duplex, not DMA

Use PIO for full-duplex transfers, instead of DMA.

Signed-off-by: Vitja Makarov <[e-mail]>
Signed-off-by: Bryan Wu <[e-mail]>
Signed-off-by: David Brownell <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/spi/spi_bfin5xx.c

···
 	u8 width;
 	u16 cr, dma_width, dma_config;
 	u32 tranf_success = 1;
+	u8 full_duplex = 0;
 
 	/* Get current state information */
 	message = drv_data->cur_msg;
···
 	}
 
 	if (transfer->rx_buf != NULL) {
+		full_duplex = transfer->tx_buf != NULL;
 		drv_data->rx = transfer->rx_buf;
 		drv_data->rx_end = drv_data->rx + transfer->len;
 		dev_dbg(&drv_data->pdev->dev, "rx_buf is %p, rx_end is %p\n",
···
 	 * successful use different way to r/w according to
 	 * drv_data->cur_chip->enable_dma
 	 */
-	if (drv_data->cur_chip->enable_dma && drv_data->len > 6) {
+	if (!full_duplex && drv_data->cur_chip->enable_dma
+				&& drv_data->len > 6) {
 
 		disable_dma(drv_data->dma_channel);
 		clear_dma_irqstat(drv_data->dma_channel);
···
 		/* IO mode write then read */
 		dev_dbg(&drv_data->pdev->dev, "doing IO transfer\n");
 
-		if (drv_data->tx != NULL && drv_data->rx != NULL) {
+		if (full_duplex) {
 			/* full duplex mode */
 			BUG_ON((drv_data->tx_end - drv_data->tx) !=
 			       (drv_data->rx_end - drv_data->rx));