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

Signed-off-by: Adam Manzanares <adam.manzana...@wdc.com>
---
 drivers/ata/libahci.c     |  1 +
 drivers/ata/libata-core.c |  2 +-
 drivers/ata/libata-scsi.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/libata.h    |  8 ++++++
 4 files changed, 78 insertions(+), 1 deletion(-)

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index dcf2c72..383adf7 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_enable_prio,
        NULL
 };
 EXPORT_SYMBOL_GPL(ahci_sdev_attrs);
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 181b530..d0cf987 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -787,7 +787,7 @@ int ata_build_rw_tf(struct ata_taskfile *tf, struct 
ata_device *dev,
                if (tf->flags & ATA_TFLAG_FUA)
                        tf->device |= 1 << 7;
 
-               if (ata_ncq_prio_enabled(dev)) {
+               if (ata_ncq_prio_enabled(dev) && ata_prio_enabled(dev)) {
                        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 18629e8..10ba118 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_enable_prio_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;
+       int rc = 0;
+       int enable_prio;
+
+       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;
+       }
+
+       enable_prio = ata_prio_enabled(dev);
+
+unlock:
+       spin_unlock_irq(ap->lock);
+
+       return rc ? rc : snprintf(buf, 20, "%u\n", enable_prio);
+}
+
+static ssize_t ata_enable_prio_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_ENABLE_PRIO;
+       else
+               dev->flags &= ~ATA_DFLAG_ENABLE_PRIO;
+
+unlock:
+       spin_unlock_irqrestore(ap->lock, flags);
+
+       return rc ? rc : len;
+}
+
+DEVICE_ATTR(enable_prio, S_IRUGO | S_IWUSR,
+           ata_enable_prio_show, ata_enable_prio_store);
+EXPORT_SYMBOL_GPL(dev_attr_enable_prio);
+
 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_enable_prio,
        NULL
 };
 EXPORT_SYMBOL_GPL(ata_common_sdev_attrs);
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 244f261..c8acb16 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -166,6 +166,7 @@ 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_ENABLE_PRIO   = (1 << 21), /* User enable device priority */
        ATA_DFLAG_INIT_MASK     = (1 << 24) - 1,
 
        ATA_DFLAG_DETACH        = (1 << 24),
@@ -544,6 +545,7 @@ 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_enable_prio;
 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;
@@ -1627,6 +1629,12 @@ static inline int ata_ncq_prio_enabled(struct ata_device 
*dev)
        return (dev->flags & ATA_DFLAG_NCQ_PRIO) == ATA_DFLAG_NCQ_PRIO;
 }
 
+static inline int ata_prio_enabled(struct ata_device *dev)
+{
+       return ((dev->flags & ATA_DFLAG_ENABLE_PRIO) ==
+                ATA_DFLAG_ENABLE_PRIO);
+}
+
 static inline bool ata_fpdma_dsm_supported(struct ata_device *dev)
 {
        return (dev->flags & ATA_DFLAG_NCQ_SEND_RECV) &&
-- 
2.1.4

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