ata: Enabling ATA Command Priorities
This patch checks to see if an ATA device supports NCQ command priorities.
If so and the user has specified an iocontext that indicates
IO_PRIO_CLASS_RT then we build a tf with a high priority command.
This is done to improve the tail latency of commands that are high
priority by passing priority to the device.
tj: Removed trivial ata_ncq_prio_enabled() and open-coded the test.
Signed-off-by: Adam Manzanares <adam.manzanares@hgst.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 616eef4..90b69a6 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -166,6 +166,7 @@ enum {
ATA_DFLAG_NO_UNLOAD = (1 << 17), /* device doesn't support unload */
ATA_DFLAG_UNLOCK_HPA = (1 << 18), /* unlock HPA */
ATA_DFLAG_NCQ_SEND_RECV = (1 << 19), /* device supports NCQ SEND and RECV */
+ ATA_DFLAG_NCQ_PRIO = (1 << 20), /* device supports NCQ priority */
ATA_DFLAG_INIT_MASK = (1 << 24) - 1,
ATA_DFLAG_DETACH = (1 << 24),
@@ -342,7 +343,9 @@ enum {
ATA_SHIFT_PIO = 0,
ATA_SHIFT_MWDMA = ATA_SHIFT_PIO + ATA_NR_PIO_MODES,
ATA_SHIFT_UDMA = ATA_SHIFT_MWDMA + ATA_NR_MWDMA_MODES,
+ ATA_SHIFT_PRIO = 6,
+ ATA_PRIO_HIGH = 2,
/* size of buffer to pad xfers ending on unaligned boundaries */
ATA_DMA_PAD_SZ = 4,