ieee1394: sbp2: optimize DMA direction of s/g tables

Unlike the name suggests, "cmd->scatter_gather_element" holds only the
s/g table, not the actual s/g elements.  Since the table is only read
but never written by the device, DMA_BIDIRECTIONAL can be replaced by
DMA_TO_DEVICE which may be cheaper on some architectures.
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/ieee1394/sbp2.c

@@ -489,7 +489,7 @@ static int sbp2util_create_command_orb_pool(struct sbp2_lu *lu)
 		cmd->sge_dma = dma_map_single(hi->host->device.parent,
 					&cmd->scatter_gather_element,
 					sizeof(cmd->scatter_gather_element),
-					DMA_BIDIRECTIONAL);
+					DMA_TO_DEVICE);
 		INIT_LIST_HEAD(&cmd->list);
 		list_add_tail(&cmd->list, &lu->cmd_orb_completed);
 	}
@@ -514,7 +514,7 @@ static void sbp2util_remove_command_orb_pool(struct sbp2_lu *lu)
 					 DMA_TO_DEVICE);
 			dma_unmap_single(host->device.parent, cmd->sge_dma,
 					 sizeof(cmd->scatter_gather_element),
-					 DMA_BIDIRECTIONAL);
+					 DMA_TO_DEVICE);
 			kfree(cmd);
 		}
 	spin_unlock_irqrestore(&lu->cmd_orb_lock, flags);
@@ -1633,7 +1633,7 @@ static void sbp2_link_orb_command(struct sbp2_lu *lu,
 				   DMA_TO_DEVICE);
 	dma_sync_single_for_device(hi->host->device.parent, cmd->sge_dma,
 				   sizeof(cmd->scatter_gather_element),
-				   DMA_BIDIRECTIONAL);
+				   DMA_TO_DEVICE);
 
 	/* check to see if there are any previous orbs to use */
 	spin_lock_irqsave(&lu->cmd_orb_lock, flags);
@@ -1799,7 +1799,7 @@ static int sbp2_handle_status_write(struct hpsb_host *host, int nodeid,
 					DMA_TO_DEVICE);
 		dma_sync_single_for_cpu(hi->host->device.parent, cmd->sge_dma,
 					sizeof(cmd->scatter_gather_element),
-					DMA_BIDIRECTIONAL);
+					DMA_TO_DEVICE);
 		/* Grab SCSI command pointers and check status. */
 		/*
 		 * FIXME: If the src field in the status is 1, the ORB DMA must
@@ -1931,7 +1931,7 @@ static void sbp2scsi_complete_all_commands(struct sbp2_lu *lu, u32 status)
 					DMA_TO_DEVICE);
 		dma_sync_single_for_cpu(hi->host->device.parent, cmd->sge_dma,
 					sizeof(cmd->scatter_gather_element),
-					DMA_BIDIRECTIONAL);
+					DMA_TO_DEVICE);
 		sbp2util_mark_command_completed(lu, cmd);
 		if (cmd->Current_SCpnt) {
 			cmd->Current_SCpnt->result = status << 16;
@@ -2062,7 +2062,7 @@ static int sbp2scsi_abort(struct scsi_cmnd *SCpnt)
 			dma_sync_single_for_cpu(hi->host->device.parent,
 					cmd->sge_dma,
 					sizeof(cmd->scatter_gather_element),
-					DMA_BIDIRECTIONAL);
+					DMA_TO_DEVICE);
 			sbp2util_mark_command_completed(lu, cmd);
 			if (cmd->Current_SCpnt) {
 				cmd->Current_SCpnt->result = DID_ABORT << 16;