ata: ATA Command Priority Disabled By Default

Add a sysfs entry to turn on priority information being passed
to a ATA device. By default this feature is turned off.

This patch depends on ata: Enabling ATA Command Priorities

tj: Renamed ncq_prio_on to ncq_prio_enable and removed trivial
    ata_ncq_prio_on() and open-coded the test.

Signed-off-by: Adam Manzanares <adam.manzanares@hgst.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

4 files changed, 73 insertions, 1 deletions

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index 0d028ead99e8..ee7db3119b18 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -140,6 +140,7 @@ EXPORT_SYMBOL_GPL(ahci_shost_attrs);
 struct device_attribute *ahci_sdev_attrs[] = {
         &dev_attr_sw_activity,
         &dev_attr_unload_heads,
+        &dev_attr_ncq_prio_enable,
         NULL
 };
 EXPORT_SYMBOL_GPL(ahci_sdev_attrs);
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 8346faf63337..b294339159a4 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -787,7 +787,8 @@ 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 ((dev->flags & ATA_DFLAG_NCQ_PRIO) &&
+                    (dev->flags & ATA_DFLAG_NCQ_PRIO_ENABLE)) {
                         if (class == IOPRIO_CLASS_RT)
                                 tf->hob_nsect |= ATA_PRIO_HIGH <<
                                                  ATA_SHIFT_PRIO;
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 2bccc3c7de48..87597a3f6149 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -271,6 +271,73 @@ DEVICE_ATTR(unload_heads, S_IRUGO | S_IWUSR,
             ata_scsi_park_show, ata_scsi_park_store);
 EXPORT_SYMBOL_GPL(dev_attr_unload_heads);
 
+static ssize_t ata_ncq_prio_enable_show(struct device *device,
+                                        struct device_attribute *attr, char *buf)
+{
+        struct scsi_device *sdev = to_scsi_device(device);
+        struct ata_port *ap;
+        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) {
+                rc = -ENODEV;
+                goto unlock;
+        }
+
+        ncq_prio_enable = dev->flags & ATA_DFLAG_NCQ_PRIO_ENABLE;
+
+unlock:
+        spin_unlock_irq(ap->lock);
+
+        return rc ? rc : snprintf(buf, 20, "%u\n", ncq_prio_enable);
+}
+
+static ssize_t ata_ncq_prio_enable_store(struct device *device,
+                                         struct device_attribute *attr,
+                                         const char *buf, size_t len)
+{
+        struct scsi_device *sdev = to_scsi_device(device);
+        struct ata_port *ap;
+        struct ata_device *dev;
+        long int input;
+        unsigned long flags;
+        int rc;
+
+        rc = kstrtol(buf, 10, &input);
+        if (rc)
+                return rc;
+        if ((input < 0) || (input > 1))
+                return -EINVAL;
+
+        ap = ata_shost_to_port(sdev->host);
+
+        spin_lock_irqsave(ap->lock, flags);
+        dev = ata_scsi_find_dev(ap, sdev);
+        if (unlikely(!dev)) {
+                rc = -ENODEV;
+                goto unlock;
+        }
+
+        if (input)
+                dev->flags |= ATA_DFLAG_NCQ_PRIO_ENABLE;
+        else
+                dev->flags &= ~ATA_DFLAG_NCQ_PRIO_ENABLE;
+
+unlock:
+        spin_unlock_irqrestore(ap->lock, flags);
+
+        return rc ? rc : len;
+}
+
+DEVICE_ATTR(ncq_prio_enable, S_IRUGO | S_IWUSR,
+            ata_ncq_prio_enable_show, ata_ncq_prio_enable_store);
+EXPORT_SYMBOL_GPL(dev_attr_ncq_prio_enable);
+
 void ata_scsi_set_sense(struct ata_device *dev, struct scsi_cmnd *cmd,
                         u8 sk, u8 asc, u8 ascq)
 {
@@ -402,6 +469,7 @@ EXPORT_SYMBOL_GPL(dev_attr_sw_activity);
 
 struct device_attribute *ata_common_sdev_attrs[] = {
         &dev_attr_unload_heads,
+        &dev_attr_ncq_prio_enable,
         NULL
 };
 EXPORT_SYMBOL_GPL(ata_common_sdev_attrs);
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 90b69a6293a3..c170be548b7f 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -167,6 +167,7 @@ enum {
         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_NCQ_PRIO_ENABLE = (1 << 21), /* Priority cmds sent to dev */
         ATA_DFLAG_INIT_MASK     = (1 << 24) - 1,
 
         ATA_DFLAG_DETACH        = (1 << 24),
@@ -545,6 +546,7 @@ typedef void (*ata_postreset_fn_t)(struct ata_link *link, unsigned int *classes)
 
 extern struct device_attribute dev_attr_link_power_management_policy;
 extern struct device_attribute dev_attr_unload_heads;
+extern struct device_attribute dev_attr_ncq_prio_enable;
 extern struct device_attribute dev_attr_em_message_type;
 extern struct device_attribute dev_attr_em_message;
 extern struct device_attribute dev_attr_sw_activity;