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Subject[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>

---
Jeff, I'll send two flavors of this patch. The other one will enable
AHCI_CMD_PREFETCH for both ATA and ATAPI devices. I've tested both
cases on ICH7R.

ahci.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/ahci.c b/drivers/scsi/ahci.c
index 00dfdef..e97ab3e 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_queu
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);
}
-
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