[PATCH] Revert "ata: libata-scsi: Improve CDL control"

[Igor Pylypiv <ipylypiv@google.com>]

This reverts commit 17e897a456752ec9c2d7afb3d9baf268b442451b.

The extra checks for the ATA_DFLAG_CDL_ENABLED flag prevent SET FEATURES
command from being issued to a drive when NCQ commands are active.

ata_mselect_control_ata_feature() sets / clears the ATA_DFLAG_CDL_ENABLED
flag during the translation of MODE SELECT to SET FEATURES. If SET FEATURES
gets deferred due to outstanding NCQ commands, the original MODE SELECT
command will be re-queued. When the re-queued MODE SELECT goes through
the ata_mselect_control_ata_feature() translation again, SET FEATURES
will not be issued because ATA_DFLAG_CDL_ENABLED has been already set or
cleared by the initial translation of MODE SELECT.

The ATA_DFLAG_CDL_ENABLED checks in ata_mselect_control_ata_feature()
are safe to remove because scsi_cdl_enable() implements a similar logic
that avoids enabling CDL if it has been already enabled.

Cc: stable@vger.kernel.org
Signed-off-by: Igor Pylypiv <ipylypiv@google.com>
---
 drivers/ata/libata-scsi.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 57f674f51b0c..856eabfd5a17 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -3904,27 +3904,17 @@ static int ata_mselect_control_ata_feature(struct ata_queued_cmd *qc,
 	/* Check cdl_ctrl */
 	switch (buf[0] & 0x03) {
 	case 0:
-		/* Disable CDL if it is enabled */
-		if (!(dev->flags & ATA_DFLAG_CDL_ENABLED))
-			return 0;
-		ata_dev_dbg(dev, "Disabling CDL\n");
+		/* Disable CDL */
 		cdl_action = 0;
 		dev->flags &= ~ATA_DFLAG_CDL_ENABLED;
 		break;
 	case 0x02:
-		/*
-		 * Enable CDL if not already enabled. Since this is mutually
-		 * exclusive with NCQ priority, allow this only if NCQ priority
-		 * is disabled.
-		 */
-		if (dev->flags & ATA_DFLAG_CDL_ENABLED)
-			return 0;
+		/* Enable CDL T2A/T2B: NCQ priority must be disabled */
 		if (dev->flags & ATA_DFLAG_NCQ_PRIO_ENABLED) {
 			ata_dev_err(dev,
 				"NCQ priority must be disabled to enable CDL\n");
 			return -EINVAL;
 		}
-		ata_dev_dbg(dev, "Enabling CDL\n");
 		cdl_action = 1;
 		dev->flags |= ATA_DFLAG_CDL_ENABLED;
 		break;
-- 
2.51.0.rc0.215.g125493bb4a-goog