[PATCH] ahci: enable prefetching

[Tejun Heo <htejun@gmail.com>]

Enable prefetching.  This hints AHCI controller that it can prefetch
PRT entries and CDB (for PACKET commands).  This is a hint.  AHCI
controller is free to ignore it or prefetch regardless of this bit.

Note that prefetching bit should be turned off for NCQ commands or
FIS-based switching PM support.

Signed-off-by: Tejun Heo <htejun@gmail.com>

---

And this is the second version.

 ahci.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/ahci.c b/drivers/scsi/ahci.c
index 00dfdef..454a393 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),
 
@@ -627,7 +628,7 @@ static void ahci_qc_prep(struct ata_queu
 	/*
 	 * Fill in command slot information.
 	 */
-	opts = cmd_fis_len | n_elem << 16;
+	opts = AHCI_CMD_PREFETCH | cmd_fis_len | n_elem << 16;
 	if (qc->tf.flags & ATA_TFLAG_WRITE)
 		opts |= AHCI_CMD_WRITE;
 	if (is_atapi)
-
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