[PATCH] ahci: enable prefetching for PACKET commands

Turn on AHCI_CMD_PREFETCH for PACKET commands.  This hints the
controller that it can prefetch the CDB and the PRD entries.  This
patch is originally from Jeff Garzik.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/scsi/ahci.c b/drivers/scsi/ahci.c
index 00dfdefe2967..e97ab3e6de4d 100644
--- a/drivers/scsi/ahci.c
+++ b/drivers/scsi/ahci.c
@@ -66,6 +66,7 @@ enum {
         AHCI_IRQ_ON_SG          = (1 << 31),
         AHCI_CMD_ATAPI          = (1 << 5),
         AHCI_CMD_WRITE          = (1 << 6),
+        AHCI_CMD_PREFETCH       = (1 << 7),
         AHCI_CMD_RESET          = (1 << 8),
         AHCI_CMD_CLR_BUSY       = (1 << 10),
 
@@ -631,7 +632,7 @@ static void ahci_qc_prep(struct ata_queued_cmd *qc)
         if (qc->tf.flags & ATA_TFLAG_WRITE)
                 opts |= AHCI_CMD_WRITE;
         if (is_atapi)
-                opts |= AHCI_CMD_ATAPI;
+                opts |= AHCI_CMD_ATAPI | AHCI_CMD_PREFETCH;
 
         ahci_fill_cmd_slot(pp, opts);
 }