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>

diff --git a/drivers/ieee1394/sbp2.c b/drivers/ieee1394/sbp2.c
index e15b5d7..cae3816 100644 (file)
--- a/drivers/ieee1394/sbp2.c
+++ b/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;