libata: don't check whether to use DMA or not for no data commands

There's no reason to check whether to use DMA or not for no data
commands.  Don't do it.  While at it, make local variable using_pio in
atapi_xlat() set iff ATAPI_PROT_PIO is going to be used and rename
ata_check_atapi_dma() to atapi_check_dma() for consistency.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 7 insertions, 9 deletions

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 2e6e1622dc6d..57a43649a461 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -2343,8 +2343,8 @@ static unsigned int atapi_xlat(struct ata_queued_cmd *qc)
 {
         struct scsi_cmnd *scmd = qc->scsicmd;
         struct ata_device *dev = qc->dev;
-        int using_pio = (dev->flags & ATA_DFLAG_PIO);
         int nodata = (scmd->sc_data_direction == DMA_NONE);
+        int using_pio = !nodata && (dev->flags & ATA_DFLAG_PIO);
         unsigned int nbytes;
 
         memset(qc->cdb, 0, dev->cdb_len);
@@ -2362,7 +2362,7 @@ static unsigned int atapi_xlat(struct ata_queued_cmd *qc)
         ata_qc_set_pc_nbytes(qc);
 
         /* check whether ATAPI DMA is safe */
-        if (!using_pio && ata_check_atapi_dma(qc))
+        if (!nodata && !using_pio && atapi_check_dma(qc))
                 using_pio = 1;
 
         /* Some controller variants snoop this value for Packet
@@ -2402,13 +2402,11 @@ static unsigned int atapi_xlat(struct ata_queued_cmd *qc)
         qc->tf.lbam = (nbytes & 0xFF);
         qc->tf.lbah = (nbytes >> 8);
 
-        if (using_pio || nodata) {
-                /* no data, or PIO data xfer */
-                if (nodata)
-                        qc->tf.protocol = ATAPI_PROT_NODATA;
-                else
-                        qc->tf.protocol = ATAPI_PROT_PIO;
-        } else {
+        if (nodata)
+                qc->tf.protocol = ATAPI_PROT_NODATA;
+        else if (using_pio)
+                qc->tf.protocol = ATAPI_PROT_PIO;
+        else {
                 /* DMA data xfer */
                 qc->tf.protocol = ATAPI_PROT_DMA;
                 qc->tf.feature |= ATAPI_PKT_DMA;