libata: cleanup NCQ priority handling

The ata device flag ATA_DFLAG_NCQ_PRIO indicates if a device supports
the NCQ Priority feature while the ATA_DFLAG_NCQ_PRIO_ENABLE device
flag indicates if the feature is enabled. Enabling NCQ priority use is
controlled by the user through the device sysfs attribute
ncq_prio_enable. As a result, the ATA_DFLAG_NCQ_PRIO flag should not be
cleared when ATA_DFLAG_NCQ_PRIO_ENABLE is not set as the device still
supports the feature even after the user disables it. This leads to the
following cleanups:
- In ata_build_rw_tf(), set a command high priority bit based on the
  ATA_DFLAG_NCQ_PRIO_ENABLE flag, not on the ATA_DFLAG_NCQ flag. That
  is, set a command high priority only if the user enabled NCQ priority
  use.
- In ata_dev_config_ncq_prio(), ATA_DFLAG_NCQ_PRIO should not be cleared
  if ATA_DFLAG_NCQ_PRIO_ENABLE is not set. If the device does not
  support NCQ priority, both ATA_DFLAG_NCQ_PRIO and
  ATA_DFLAG_NCQ_PRIO_ENABLE must be cleared.

With the above ata_dev_config_ncq_prio() change, ATA_DFLAG_NCQ_PRIO flag
is set on device scan and revalidation. There is no need to trigger a
device revalidation in ata_ncq_prio_enable_store() when the user enables
the use of NCQ priority. Remove the revalidation code from that funciton
to simplify it. Also change the return value from -EIO to -EINVAL when a
user tries to enable NCQ priority for a device that does not support
this feature.  While at it, also simplify ata_ncq_prio_enable_show().

Overall, there is no functional change introduced by this patch.
Signed-off-by: NDamien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210816014456.2191776-7-damien.lemoal@wdc.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

drivers/ata/libata-core.c

@@ -712,11 +712,9 @@ int ata_build_rw_tf(struct ata_taskfile *tf, struct ata_device *dev,
 		if (tf->flags & ATA_TFLAG_FUA)
 			tf->device |= 1 << 7;
 
-		if (dev->flags & ATA_DFLAG_NCQ_PRIO) {
-			if (class == IOPRIO_CLASS_RT)
-				tf->hob_nsect |= ATA_PRIO_HIGH <<
-						 ATA_SHIFT_PRIO;
-		}
+		if (dev->flags & ATA_DFLAG_NCQ_PRIO_ENABLE &&
+		    class == IOPRIO_CLASS_RT)
+			tf->hob_nsect |= ATA_PRIO_HIGH << ATA_SHIFT_PRIO;
 	} else if (dev->flags & ATA_DFLAG_LBA) {
 		tf->flags |= ATA_TFLAG_LBA;
 
@@ -2178,11 +2176,6 @@ static void ata_dev_config_ncq_prio(struct ata_device *dev)
 	struct ata_port *ap = dev->link->ap;
 	unsigned int err_mask;
 
-	if (!(dev->flags & ATA_DFLAG_NCQ_PRIO_ENABLE)) {
-		dev->flags &= ~ATA_DFLAG_NCQ_PRIO;
-		return;
-	}
-
 	err_mask = ata_read_log_page(dev,
 				     ATA_LOG_IDENTIFY_DEVICE,
 				     ATA_LOG_SATA_SETTINGS,
@@ -2190,18 +2183,21 @@ static void ata_dev_config_ncq_prio(struct ata_device *dev)
 				     1);
 	if (err_mask) {
 		ata_dev_dbg(dev,
-			    "failed to get Identify Device data, Emask 0x%x\n",
+			    "failed to get SATA settings log, Emask 0x%x\n",
 			    err_mask);
-		return;
+		goto not_supported;
 	}
 
-	if (ap->sector_buf[ATA_LOG_NCQ_PRIO_OFFSET] & BIT(3)) {
-		dev->flags |= ATA_DFLAG_NCQ_PRIO;
-	} else {
-		dev->flags &= ~ATA_DFLAG_NCQ_PRIO;
-		ata_dev_dbg(dev, "SATA page does not support priority\n");
-	}
+	if (!(ap->sector_buf[ATA_LOG_NCQ_PRIO_OFFSET] & BIT(3)))
+		goto not_supported;
+
+	dev->flags |= ATA_DFLAG_NCQ_PRIO;
+
+	return;
 
+not_supported:
+	dev->flags &= ~ATA_DFLAG_NCQ_PRIO_ENABLE;
+	dev->flags &= ~ATA_DFLAG_NCQ_PRIO;
 }
 
 static int ata_dev_config_ncq(struct ata_device *dev,

drivers/ata/libata-sata.c

@@ -839,23 +839,17 @@ static ssize_t ata_ncq_prio_enable_show(struct device *device,
 					char *buf)
 {
 	struct scsi_device *sdev = to_scsi_device(device);
-	struct ata_port *ap;
+	struct ata_port *ap = ata_shost_to_port(sdev->host);
 	struct ata_device *dev;
 	bool ncq_prio_enable;
 	int rc = 0;
 
-	ap = ata_shost_to_port(sdev->host);
-
 	spin_lock_irq(ap->lock);
 	dev = ata_scsi_find_dev(ap, sdev);
-	if (!dev) {
+	if (!dev)
 		rc = -ENODEV;
-		goto unlock;
-	}
-
-	ncq_prio_enable = dev->flags & ATA_DFLAG_NCQ_PRIO_ENABLE;
-
-unlock:
+	else
+		ncq_prio_enable = dev->flags & ATA_DFLAG_NCQ_PRIO_ENABLE;
 	spin_unlock_irq(ap->lock);
 
 	return rc ? rc : snprintf(buf, 20, "%u\n", ncq_prio_enable);
@@ -869,7 +863,7 @@ static ssize_t ata_ncq_prio_enable_store(struct device *device,
 	struct ata_port *ap;
 	struct ata_device *dev;
 	long int input;
-	int rc;
+	int rc = 0;
 
 	rc = kstrtol(buf, 10, &input);
 	if (rc)
@@ -883,27 +877,20 @@ static ssize_t ata_ncq_prio_enable_store(struct device *device,
 		return  -ENODEV;
 
 	spin_lock_irq(ap->lock);
+
+	if (!(dev->flags & ATA_DFLAG_NCQ_PRIO)) {
+		rc = -EINVAL;
+		goto unlock;
+	}
+
 	if (input)
 		dev->flags |= ATA_DFLAG_NCQ_PRIO_ENABLE;
 	else
 		dev->flags &= ~ATA_DFLAG_NCQ_PRIO_ENABLE;
 
-	dev->link->eh_info.action |= ATA_EH_REVALIDATE;
-	dev->link->eh_info.flags |= ATA_EHI_QUIET;
-	ata_port_schedule_eh(ap);
+unlock:
 	spin_unlock_irq(ap->lock);
 
-	ata_port_wait_eh(ap);
-
-	if (input) {
-		spin_lock_irq(ap->lock);
-		if (!(dev->flags & ATA_DFLAG_NCQ_PRIO)) {
-			dev->flags &= ~ATA_DFLAG_NCQ_PRIO_ENABLE;
-			rc = -EIO;
-		}
-		spin_unlock_irq(ap->lock);
-	}
-
 	return rc ? rc : len;
 }