isci: unify can_queue tracking on the tci_pool, uplevel tag assignment

The tci_pool tracks our outstanding command slots which are also the 'index'
portion of our tags.  Grabbing the tag early in ->lldd_execute_task let's us
drop the isci_host_can_queue() and ->was_tag_assigned_by_user infrastructure.
->was_tag_assigned_by_user required the task context to be duplicated in
request-local buffer.  With the tci established early we can build the
task_context directly into its final location and skip a memcpy.

With the task context buffer at a known address at request construction we
have the opportunity/obligation to also fix sgl handling.  This rework feels
like it belongs in another patch but the sgl handling and task_context are too
intertwined.
1/ fix the 'ab' pair embedded in the task context to point to the 'cd' pair in
   the task context (previously we were prematurely linking to the staging
   buffer).
2/ fix the broken iteration of pio sgls that assumes all sgls are relative to
   the request, and does a dangerous looking reverse lookup of physical
   address to virtual address.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

7 files changed, 303 insertions, 687 deletions

diff --git a/drivers/scsi/isci/host.c b/drivers/scsi/isci/host.c
index b08455f0d350..c99fab53dd0c 100644
--- a/drivers/scsi/isci/host.c
+++ b/drivers/scsi/isci/host.c
@@ -1018,33 +1018,11 @@ done:
 	spin_unlock_irqrestore(&ihost->scic_lock, flags);
 }
 
-static void isci_tci_free(struct isci_host *ihost, u16 tci)
-{
-	u16 tail = ihost->tci_tail & (SCI_MAX_IO_REQUESTS-1);
-
-	ihost->tci_pool[tail] = tci;
-	ihost->tci_tail = tail + 1;
-}
-
-static u16 isci_tci_alloc(struct isci_host *ihost)
-{
-	u16 head = ihost->tci_head & (SCI_MAX_IO_REQUESTS-1);
-	u16 tci = ihost->tci_pool[head];
-
-	ihost->tci_head = head + 1;
-	return tci;
-}
-
 static u16 isci_tci_active(struct isci_host *ihost)
 {
 	return CIRC_CNT(ihost->tci_head, ihost->tci_tail, SCI_MAX_IO_REQUESTS);
 }
 
-static u16 isci_tci_space(struct isci_host *ihost)
-{
-	return CIRC_SPACE(ihost->tci_head, ihost->tci_tail, SCI_MAX_IO_REQUESTS);
-}
-
 static enum sci_status scic_controller_start(struct scic_sds_controller *scic,
 					     u32 timeout)
 {
@@ -1205,6 +1183,11 @@ static void isci_host_completion_routine(unsigned long data)
 				task->task_done(task);
 			}
 		}
+
+		spin_lock_irq(&isci_host->scic_lock);
+		isci_free_tag(isci_host, request->sci.io_tag);
+		spin_unlock_irq(&isci_host->scic_lock);
+
 		/* Free the request object. */
 		isci_request_free(isci_host, request);
 	}
@@ -1242,6 +1225,7 @@ static void isci_host_completion_routine(unsigned long data)
 			* of pending requests.
 			*/
 			list_del_init(&request->dev_node);
+			isci_free_tag(isci_host, request->sci.io_tag);
 			spin_unlock_irq(&isci_host->scic_lock);
 
 			/* Free the request object. */
@@ -2375,6 +2359,7 @@ static int scic_controller_mem_init(struct scic_sds_controller *scic)
 	if (!scic->task_context_table)
 		return -ENOMEM;
 
+	scic->task_context_dma = dma;
 	writel(lower_32_bits(dma), &scic->smu_registers->host_task_table_lower);
 	writel(upper_32_bits(dma), &scic->smu_registers->host_task_table_upper);
 
@@ -2409,11 +2394,9 @@ int isci_host_init(struct isci_host *isci_host)
 
 	spin_lock_init(&isci_host->state_lock);
 	spin_lock_init(&isci_host->scic_lock);
-	spin_lock_init(&isci_host->queue_lock);
 	init_waitqueue_head(&isci_host->eventq);
 
 	isci_host_change_state(isci_host, isci_starting);
-	isci_host->can_queue = ISCI_CAN_QUEUE_VAL;
 
 	status = scic_controller_construct(&isci_host->sci, scu_base(isci_host),
 					   smu_base(isci_host));
@@ -2611,51 +2594,6 @@ void scic_sds_controller_post_request(
 	writel(request, &scic->smu_registers->post_context_port);
 }
 
-/**
- * This method will copy the soft copy of the task context into the physical
- *    memory accessible by the controller.
- * @scic: This parameter specifies the controller for which to copy
- *    the task context.
- * @sci_req: This parameter specifies the request for which the task
- *    context is being copied.
- *
- * After this call is made the SCIC_SDS_IO_REQUEST object will always point to
- * the physical memory version of the task context. Thus, all subsequent
- * updates to the task context are performed in the TC table (i.e. DMAable
- * memory). none
- */
-void scic_sds_controller_copy_task_context(
-	struct scic_sds_controller *scic,
-	struct scic_sds_request *sci_req)
-{
-	struct scu_task_context *task_context_buffer;
-
-	task_context_buffer = scic_sds_controller_get_task_context_buffer(
-		scic, sci_req->io_tag);
-
-	memcpy(task_context_buffer,
-	       sci_req->task_context_buffer,
-	       offsetof(struct scu_task_context, sgl_snapshot_ac));
-
-	/*
-	 * Now that the soft copy of the TC has been copied into the TC
-	 * table accessible by the silicon.  Thus, any further changes to
-	 * the TC (e.g. TC termination) occur in the appropriate location. */
-	sci_req->task_context_buffer = task_context_buffer;
-}
-
-struct scu_task_context *scic_sds_controller_get_task_context_buffer(struct scic_sds_controller *scic,
-								     u16 io_tag)
-{
-	u16 tci = ISCI_TAG_TCI(io_tag);
-
-	if (tci < scic->task_context_entries) {
-		return &scic->task_context_table[tci];
-	}
-
-	return NULL;
-}
-
 struct scic_sds_request *scic_request_by_tag(struct scic_sds_controller *scic, u16 io_tag)
 {
 	u16 task_index;
@@ -2801,6 +2739,60 @@ void scic_sds_controller_release_frame(
 			&scic->scu_registers->sdma.unsolicited_frame_get_pointer);
 }
 
+void isci_tci_free(struct isci_host *ihost, u16 tci)
+{
+	u16 tail = ihost->tci_tail & (SCI_MAX_IO_REQUESTS-1);
+
+	ihost->tci_pool[tail] = tci;
+	ihost->tci_tail = tail + 1;
+}
+
+static u16 isci_tci_alloc(struct isci_host *ihost)
+{
+	u16 head = ihost->tci_head & (SCI_MAX_IO_REQUESTS-1);
+	u16 tci = ihost->tci_pool[head];
+
+	ihost->tci_head = head + 1;
+	return tci;
+}
+
+static u16 isci_tci_space(struct isci_host *ihost)
+{
+	return CIRC_SPACE(ihost->tci_head, ihost->tci_tail, SCI_MAX_IO_REQUESTS);
+}
+
+u16 isci_alloc_tag(struct isci_host *ihost)
+{
+	if (isci_tci_space(ihost)) {
+		u16 tci = isci_tci_alloc(ihost);
+		u8 seq = ihost->sci.io_request_sequence[tci];
+
+		return ISCI_TAG(seq, tci);
+	}
+
+	return SCI_CONTROLLER_INVALID_IO_TAG;
+}
+
+enum sci_status isci_free_tag(struct isci_host *ihost, u16 io_tag)
+{
+	struct scic_sds_controller *scic = &ihost->sci;
+	u16 tci = ISCI_TAG_TCI(io_tag);
+	u16 seq = ISCI_TAG_SEQ(io_tag);
+
+	/* prevent tail from passing head */
+	if (isci_tci_active(ihost) == 0)
+		return SCI_FAILURE_INVALID_IO_TAG;
+
+	if (seq == scic->io_request_sequence[tci]) {
+		scic->io_request_sequence[tci] = (seq+1) & (SCI_MAX_SEQ-1);
+
+		isci_tci_free(ihost, tci);
+
+		return SCI_SUCCESS;
+	}
+	return SCI_FAILURE_INVALID_IO_TAG;
+}
+
 /**
  * scic_controller_start_io() - This method is called by the SCI user to
  *    send/start an IO request. If the method invocation is successful, then
@@ -2811,27 +2803,11 @@ void scic_sds_controller_release_frame(
  *    IO request.
  * @io_request: the handle to the io request object to start.
  * @io_tag: This parameter specifies a previously allocated IO tag that the
- *    user desires to be utilized for this request. This parameter is optional.
- *     The user is allowed to supply SCI_CONTROLLER_INVALID_IO_TAG as the value
- *    for this parameter.
- *
- * - IO tags are a protected resource.  It is incumbent upon the SCI Core user
- * to ensure that each of the methods that may allocate or free available IO
- * tags are handled in a mutually exclusive manner.  This method is one of said
- * methods requiring proper critical code section protection (e.g. semaphore,
- * spin-lock, etc.). - For SATA, the user is required to manage NCQ tags.  As a
- * result, it is expected the user will have set the NCQ tag field in the host
- * to device register FIS prior to calling this method.  There is also a
- * requirement for the user to call scic_stp_io_set_ncq_tag() prior to invoking
- * the scic_controller_start_io() method. scic_controller_allocate_tag() for
- * more information on allocating a tag. Indicate if the controller
- * successfully started the IO request. SCI_SUCCESS if the IO request was
- * successfully started. Determine the failure situations and return values.
+ *    user desires to be utilized for this request.
  */
 enum sci_status scic_controller_start_io(struct scic_sds_controller *scic,
 					 struct scic_sds_remote_device *rdev,
-					 struct scic_sds_request *req,
-					 u16 io_tag)
+					 struct scic_sds_request *req)
 {
 	enum sci_status status;
 
@@ -2902,17 +2878,6 @@ enum sci_status scic_controller_terminate_request(
  * @remote_device: The handle to the remote device object for which to complete
  *    the IO request.
  * @io_request: the handle to the io request object to complete.
- *
- * - IO tags are a protected resource.  It is incumbent upon the SCI Core user
- * to ensure that each of the methods that may allocate or free available IO
- * tags are handled in a mutually exclusive manner.  This method is one of said
- * methods requiring proper critical code section protection (e.g. semaphore,
- * spin-lock, etc.). - If the IO tag for a request was allocated, by the SCI
- * Core user, using the scic_controller_allocate_io_tag() method, then it is
- * the responsibility of the caller to invoke the scic_controller_free_io_tag()
- * method to free the tag (i.e. this method will not free the IO tag). Indicate
- * if the controller successfully completed the IO request. SCI_SUCCESS if the
- * completion process was successful.
  */
 enum sci_status scic_controller_complete_io(
 	struct scic_sds_controller *scic,
@@ -2963,31 +2928,11 @@ enum sci_status scic_controller_continue_io(struct scic_sds_request *sci_req)
  * @remote_device: the handle to the remote device object for which to start
  *    the task management request.
  * @task_request: the handle to the task request object to start.
- * @io_tag: This parameter specifies a previously allocated IO tag that the
- *    user desires to be utilized for this request.  Note this not the io_tag
- *    of the request being managed.  It is to be utilized for the task request
- *    itself. This parameter is optional.  The user is allowed to supply
- *    SCI_CONTROLLER_INVALID_IO_TAG as the value for this parameter.
- *
- * - IO tags are a protected resource.  It is incumbent upon the SCI Core user
- * to ensure that each of the methods that may allocate or free available IO
- * tags are handled in a mutually exclusive manner.  This method is one of said
- * methods requiring proper critical code section protection (e.g. semaphore,
- * spin-lock, etc.). - The user must synchronize this task with completion
- * queue processing.  If they are not synchronized then it is possible for the
- * io requests that are being managed by the task request can complete before
- * starting the task request. scic_controller_allocate_tag() for more
- * information on allocating a tag. Indicate if the controller successfully
- * started the IO request. SCI_TASK_SUCCESS if the task request was
- * successfully started. SCI_TASK_FAILURE_REQUIRES_SCSI_ABORT This value is
- * returned if there is/are task(s) outstanding that require termination or
- * completion before this request can succeed.
  */
 enum sci_task_status scic_controller_start_task(
 	struct scic_sds_controller *scic,
 	struct scic_sds_remote_device *rdev,
-	struct scic_sds_request *req,
-	u16 task_tag)
+	struct scic_sds_request *req)
 {
 	enum sci_status status;
 
@@ -3022,85 +2967,3 @@ enum sci_task_status scic_controller_start_task(
 
 	return status;
 }
-
-/**
- * scic_controller_allocate_io_tag() - This method will allocate a tag from the
- *    pool of free IO tags. Direct allocation of IO tags by the SCI Core user
- *    is optional. The scic_controller_start_io() method will allocate an IO
- *    tag if this method is not utilized and the tag is not supplied to the IO
- *    construct routine.  Direct allocation of IO tags may provide additional
- *    performance improvements in environments capable of supporting this usage
- *    model.  Additionally, direct allocation of IO tags also provides
- *    additional flexibility to the SCI Core user.  Specifically, the user may
- *    retain IO tags across the lives of multiple IO requests.
- * @controller: the handle to the controller object for which to allocate the
- *    tag.
- *
- * IO tags are a protected resource.  It is incumbent upon the SCI Core user to
- * ensure that each of the methods that may allocate or free available IO tags
- * are handled in a mutually exclusive manner.  This method is one of said
- * methods requiring proper critical code section protection (e.g. semaphore,
- * spin-lock, etc.). An unsigned integer representing an available IO tag.
- * SCI_CONTROLLER_INVALID_IO_TAG This value is returned if there are no
- * currently available tags to be allocated. All return other values indicate a
- * legitimate tag.
- */
-u16 scic_controller_allocate_io_tag(struct scic_sds_controller *scic)
-{
-	struct isci_host *ihost = scic_to_ihost(scic);
-
-	if (isci_tci_space(ihost)) {
-		u16 tci = isci_tci_alloc(ihost);
-		u8 seq = scic->io_request_sequence[tci];
-
-		return ISCI_TAG(seq, tci);
-	}
-
-	return SCI_CONTROLLER_INVALID_IO_TAG;
-}
-
-/**
- * scic_controller_free_io_tag() - This method will free an IO tag to the pool
- *    of free IO tags. This method provides the SCI Core user more flexibility
- *    with regards to IO tags.  The user may desire to keep an IO tag after an
- *    IO request has completed, because they plan on re-using the tag for a
- *    subsequent IO request.  This method is only legal if the tag was
- *    allocated via scic_controller_allocate_io_tag().
- * @controller: This parameter specifies the handle to the controller object
- *    for which to free/return the tag.
- * @io_tag: This parameter represents the tag to be freed to the pool of
- *    available tags.
- *
- * - IO tags are a protected resource.  It is incumbent upon the SCI Core user
- * to ensure that each of the methods that may allocate or free available IO
- * tags are handled in a mutually exclusive manner.  This method is one of said
- * methods requiring proper critical code section protection (e.g. semaphore,
- * spin-lock, etc.). - If the IO tag for a request was allocated, by the SCI
- * Core user, using the scic_controller_allocate_io_tag() method, then it is
- * the responsibility of the caller to invoke this method to free the tag. This
- * method returns an indication of whether the tag was successfully put back
- * (freed) to the pool of available tags. SCI_SUCCESS This return value
- * indicates the tag was successfully placed into the pool of available IO
- * tags. SCI_FAILURE_INVALID_IO_TAG This value is returned if the supplied tag
- * is not a valid IO tag value.
- */
-enum sci_status scic_controller_free_io_tag(struct scic_sds_controller *scic,
-					    u16 io_tag)
-{
-	struct isci_host *ihost = scic_to_ihost(scic);
-	u16 tci = ISCI_TAG_TCI(io_tag);
-	u16 seq = ISCI_TAG_SEQ(io_tag);
-
-	/* prevent tail from passing head */
-	if (isci_tci_active(ihost) == 0)
-		return SCI_FAILURE_INVALID_IO_TAG;
-
-	if (seq == scic->io_request_sequence[tci]) {
-		scic->io_request_sequence[tci] = (seq+1) & (SCI_MAX_SEQ-1);
-
-		isci_tci_free(ihost, ISCI_TAG_TCI(io_tag));
-
-		return SCI_SUCCESS;
-	}
-	return SCI_FAILURE_INVALID_IO_TAG;
-}
diff --git a/drivers/scsi/isci/host.h b/drivers/scsi/isci/host.h
index a54397e1bf16..d8164f5d7988 100644
--- a/drivers/scsi/isci/host.h
+++ b/drivers/scsi/isci/host.h
@@ -192,6 +192,7 @@ struct scic_sds_controller {
 	 * context table.  This data is shared between the hardware and software.
 	 */
 	struct scu_task_context *task_context_table;
+	dma_addr_t task_context_dma;
 
 	/**
 	 * This field is a pointer to the memory allocated by the driver for the
@@ -302,12 +303,8 @@ struct isci_host {
 	struct isci_port ports[SCI_MAX_PORTS + 1]; /* includes dummy port */
 	struct sas_ha_struct sas_ha;
 
-	int can_queue;
-	spinlock_t queue_lock;
 	spinlock_t state_lock;
-
 	struct pci_dev *pdev;
-
 	enum isci_status status;
 	#define IHOST_START_PENDING 0
 	#define IHOST_STOP_PENDING 1
@@ -451,36 +448,6 @@ static inline void isci_host_change_state(struct isci_host *isci_host,
 
 }
 
-static inline int isci_host_can_queue(struct isci_host *isci_host, int num)
-{
-	int ret = 0;
-	unsigned long flags;
-
-	spin_lock_irqsave(&isci_host->queue_lock, flags);
-	if ((isci_host->can_queue - num) < 0) {
-		dev_dbg(&isci_host->pdev->dev,
-			"%s: isci_host->can_queue = %d\n",
-			__func__,
-			isci_host->can_queue);
-		ret = -SAS_QUEUE_FULL;
-
-	} else
-		isci_host->can_queue -= num;
-
-	spin_unlock_irqrestore(&isci_host->queue_lock, flags);
-
-	return ret;
-}
-
-static inline void isci_host_can_dequeue(struct isci_host *isci_host, int num)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&isci_host->queue_lock, flags);
-	isci_host->can_queue += num;
-	spin_unlock_irqrestore(&isci_host->queue_lock, flags);
-}
-
 static inline void wait_for_start(struct isci_host *ihost)
 {
 	wait_event(ihost->eventq, !test_bit(IHOST_START_PENDING, &ihost->flags));
@@ -646,10 +613,6 @@ union scu_remote_node_context *scic_sds_controller_get_remote_node_context_buffe
 struct scic_sds_request *scic_request_by_tag(struct scic_sds_controller *scic,
 					     u16 io_tag);
 
-struct scu_task_context *scic_sds_controller_get_task_context_buffer(
-	struct scic_sds_controller *scic,
-	u16 io_tag);
-
 void scic_sds_controller_power_control_queue_insert(
 	struct scic_sds_controller *scic,
 	struct scic_sds_phy *sci_phy);
@@ -681,6 +644,9 @@ void scic_sds_controller_register_setup(struct scic_sds_controller *scic);
 enum sci_status scic_controller_continue_io(struct scic_sds_request *sci_req);
 int isci_host_scan_finished(struct Scsi_Host *, unsigned long);
 void isci_host_scan_start(struct Scsi_Host *);
+u16 isci_alloc_tag(struct isci_host *ihost);
+enum sci_status isci_free_tag(struct isci_host *ihost, u16 io_tag);
+void isci_tci_free(struct isci_host *ihost, u16 tci);
 
 int isci_host_init(struct isci_host *);
 
@@ -708,14 +674,12 @@ void scic_controller_disable_interrupts(
 enum sci_status scic_controller_start_io(
 	struct scic_sds_controller *scic,
 	struct scic_sds_remote_device *remote_device,
-	struct scic_sds_request *io_request,
-	u16 io_tag);
+	struct scic_sds_request *io_request);
 
 enum sci_task_status scic_controller_start_task(
 	struct scic_sds_controller *scic,
 	struct scic_sds_remote_device *remote_device,
-	struct scic_sds_request *task_request,
-	u16 io_tag);
+	struct scic_sds_request *task_request);
 
 enum sci_status scic_controller_terminate_request(
 	struct scic_sds_controller *scic,
@@ -727,13 +691,6 @@ enum sci_status scic_controller_complete_io(
 	struct scic_sds_remote_device *remote_device,
 	struct scic_sds_request *io_request);
 
-u16 scic_controller_allocate_io_tag(
-	struct scic_sds_controller *scic);
-
-enum sci_status scic_controller_free_io_tag(
-	struct scic_sds_controller *scic,
-	u16 io_tag);
-
 void scic_sds_port_configuration_agent_construct(
 	struct scic_sds_port_configuration_agent *port_agent);
 
diff --git a/drivers/scsi/isci/port.c b/drivers/scsi/isci/port.c
index 5f4a4e3954db..0e84e29335dd 100644
--- a/drivers/scsi/isci/port.c
+++ b/drivers/scsi/isci/port.c
@@ -695,35 +695,21 @@ static void scic_sds_port_construct_dummy_rnc(struct scic_sds_port *sci_port, u1
  */
 static void scic_sds_port_construct_dummy_task(struct scic_sds_port *sci_port, u16 tag)
 {
+	struct scic_sds_controller *scic = sci_port->owning_controller;
 	struct scu_task_context *task_context;
 
-	task_context = scic_sds_controller_get_task_context_buffer(sci_port->owning_controller, tag);
-
+	task_context = &scic->task_context_table[ISCI_TAG_TCI(tag)];
 	memset(task_context, 0, sizeof(struct scu_task_context));
 
-	task_context->abort = 0;
-	task_context->priority = 0;
 	task_context->initiator_request = 1;
 	task_context->connection_rate = 1;
-	task_context->protocol_engine_index = 0;
 	task_context->logical_port_index = sci_port->physical_port_index;
 	task_context->protocol_type = SCU_TASK_CONTEXT_PROTOCOL_SSP;
 	task_context->task_index = ISCI_TAG_TCI(tag);
 	task_context->valid = SCU_TASK_CONTEXT_VALID;
 	task_context->context_type = SCU_TASK_CONTEXT_TYPE;
-
 	task_context->remote_node_index = sci_port->reserved_rni;
-	task_context->command_code = 0;
-
-	task_context->link_layer_control = 0;
 	task_context->do_not_dma_ssp_good_response = 1;
-	task_context->strict_ordering = 0;
-	task_context->control_frame = 0;
-	task_context->timeout_enable = 0;
-	task_context->block_guard_enable = 0;
-
-	task_context->address_modifier = 0;
-
 	task_context->task_phase = 0x01;
 }
 
@@ -731,15 +717,15 @@ static void scic_sds_port_destroy_dummy_resources(struct scic_sds_port *sci_port
 {
 	struct scic_sds_controller *scic = sci_port->owning_controller;
 
-	if (sci_port->reserved_tci != SCU_DUMMY_INDEX)
-		scic_controller_free_io_tag(scic, sci_port->reserved_tci);
+	if (sci_port->reserved_tag != SCI_CONTROLLER_INVALID_IO_TAG)
+		isci_free_tag(scic_to_ihost(scic), sci_port->reserved_tag);
 
 	if (sci_port->reserved_rni != SCU_DUMMY_INDEX)
 		scic_sds_remote_node_table_release_remote_node_index(&scic->available_remote_nodes,
 								     1, sci_port->reserved_rni);
 
 	sci_port->reserved_rni = SCU_DUMMY_INDEX;
-	sci_port->reserved_tci = SCU_DUMMY_INDEX;
+	sci_port->reserved_tag = SCI_CONTROLLER_INVALID_IO_TAG;
 }
 
 /**
@@ -1119,18 +1105,17 @@ scic_sds_port_suspend_port_task_scheduler(struct scic_sds_port *port)
  */
 static void scic_sds_port_post_dummy_request(struct scic_sds_port *sci_port)
 {
-	u32 command;
-	struct scu_task_context *task_context;
 	struct scic_sds_controller *scic = sci_port->owning_controller;
-	u16 tci = sci_port->reserved_tci;
-
-	task_context = scic_sds_controller_get_task_context_buffer(scic, tci);
+	u16 tag = sci_port->reserved_tag;
+	struct scu_task_context *tc;
+	u32 command;
 
-	task_context->abort = 0;
+	tc = &scic->task_context_table[ISCI_TAG_TCI(tag)];
+	tc->abort = 0;
 
 	command = SCU_CONTEXT_COMMAND_REQUEST_TYPE_POST_TC |
 		  sci_port->physical_port_index << SCU_CONTEXT_COMMAND_LOGICAL_PORT_SHIFT |
-		  tci;
+		  ISCI_TAG_TCI(tag);
 
 	scic_sds_controller_post_request(scic, command);
 }
@@ -1145,17 +1130,16 @@ static void scic_sds_port_post_dummy_request(struct scic_sds_port *sci_port)
 static void scic_sds_port_abort_dummy_request(struct scic_sds_port *sci_port)
 {
 	struct scic_sds_controller *scic = sci_port->owning_controller;
-	u16 tci = sci_port->reserved_tci;
+	u16 tag = sci_port->reserved_tag;
 	struct scu_task_context *tc;
 	u32 command;
 
-	tc = scic_sds_controller_get_task_context_buffer(scic, tci);
-
+	tc = &scic->task_context_table[ISCI_TAG_TCI(tag)];
 	tc->abort = 1;
 
 	command = SCU_CONTEXT_COMMAND_REQUEST_POST_TC_ABORT |
 		  sci_port->physical_port_index << SCU_CONTEXT_COMMAND_LOGICAL_PORT_SHIFT |
-		  tci;
+		  ISCI_TAG_TCI(tag);
 
 	scic_sds_controller_post_request(scic, command);
 }
@@ -1333,15 +1317,16 @@ enum sci_status scic_sds_port_start(struct scic_sds_port *sci_port)
 		sci_port->reserved_rni = rni;
 	}
 
-	if (sci_port->reserved_tci == SCU_DUMMY_INDEX) {
-		/* Allocate a TCI and remove the sequence nibble */
-		u16 tci = scic_controller_allocate_io_tag(scic);
+	if (sci_port->reserved_tag == SCI_CONTROLLER_INVALID_IO_TAG) {
+		struct isci_host *ihost = scic_to_ihost(scic);
+		u16 tag;
 
-		if (tci != SCU_DUMMY_INDEX)
-			scic_sds_port_construct_dummy_task(sci_port, tci);
-		else
+		tag = isci_alloc_tag(ihost);
+		if (tag == SCI_CONTROLLER_INVALID_IO_TAG)
 			status = SCI_FAILURE_INSUFFICIENT_RESOURCES;
-		sci_port->reserved_tci = tci;
+		else
+			scic_sds_port_construct_dummy_task(sci_port, tag);
+		sci_port->reserved_tag = tag;
 	}
 
 	if (status == SCI_SUCCESS) {
@@ -1859,7 +1844,7 @@ void scic_sds_port_construct(struct scic_sds_port *sci_port, u8 index,
 	sci_port->assigned_device_count = 0;
 
 	sci_port->reserved_rni = SCU_DUMMY_INDEX;
-	sci_port->reserved_tci = SCU_DUMMY_INDEX;
+	sci_port->reserved_tag = SCI_CONTROLLER_INVALID_IO_TAG;
 
 	sci_init_timer(&sci_port->timer, port_timeout);
 
diff --git a/drivers/scsi/isci/port.h b/drivers/scsi/isci/port.h
index 45c01f80bf83..a44e541914f5 100644
--- a/drivers/scsi/isci/port.h
+++ b/drivers/scsi/isci/port.h
@@ -108,7 +108,7 @@ struct scic_sds_port {
 	u8 active_phy_mask;
 
 	u16 reserved_rni;
-	u16 reserved_tci;
+	u16 reserved_tag;
 
 	/**
 	 * This field contains the count of the io requests started on this port
diff --git a/drivers/scsi/isci/request.c b/drivers/scsi/isci/request.c
index 08a7340b33bf..55859d5331b1 100644
--- a/drivers/scsi/isci/request.c
+++ b/drivers/scsi/isci/request.c
@@ -61,42 +61,50 @@
 #include "scu_event_codes.h"
 #include "sas.h"
 
-/**
- * This method returns the sgl element pair for the specificed sgl_pair index.
- * @sci_req: This parameter specifies the IO request for which to retrieve
- *    the Scatter-Gather List element pair.
- * @sgl_pair_index: This parameter specifies the index into the SGL element
- *    pair to be retrieved.
- *
- * This method returns a pointer to an struct scu_sgl_element_pair.
- */
-static struct scu_sgl_element_pair *scic_sds_request_get_sgl_element_pair(
-	struct scic_sds_request *sci_req,
-	u32 sgl_pair_index
-	) {
-	struct scu_task_context *task_context;
+static struct scu_sgl_element_pair *to_sgl_element_pair(struct scic_sds_request *sci_req,
+							int idx)
+{
+	if (idx == 0)
+		return &sci_req->tc->sgl_pair_ab;
+	else if (idx == 1)
+		return &sci_req->tc->sgl_pair_cd;
+	else if (idx < 0)
+		return NULL;
+	else
+		return &sci_req->sg_table[idx - 2];
+}
 
-	task_context = (struct scu_task_context *)sci_req->task_context_buffer;
+static dma_addr_t to_sgl_element_pair_dma(struct scic_sds_controller *scic,
+					  struct scic_sds_request *sci_req, u32 idx)
+{
+	u32 offset;
 
-	if (sgl_pair_index == 0) {
-		return &task_context->sgl_pair_ab;
-	} else if (sgl_pair_index == 1) {
-		return &task_context->sgl_pair_cd;
+	if (idx == 0) {
+		offset = (void *) &sci_req->tc->sgl_pair_ab -
+			 (void *) &scic->task_context_table[0];
+		return scic->task_context_dma + offset;
+	} else if (idx == 1) {
+		offset = (void *) &sci_req->tc->sgl_pair_cd -
+			 (void *) &scic->task_context_table[0];
+		return scic->task_context_dma + offset;
 	}
 
-	return &sci_req->sg_table[sgl_pair_index - 2];
+	return scic_io_request_get_dma_addr(sci_req, &sci_req->sg_table[idx - 2]);
+}
+
+static void init_sgl_element(struct scu_sgl_element *e, struct scatterlist *sg)
+{
+	e->length = sg_dma_len(sg);
+	e->address_upper = upper_32_bits(sg_dma_address(sg));
+	e->address_lower = lower_32_bits(sg_dma_address(sg));
+	e->address_modifier = 0;
 }
 
-/**
- * This function will build the SGL list for an IO request.
- * @sci_req: This parameter specifies the IO request for which to build
- *    the Scatter-Gather List.
- *
- */
 static void scic_sds_request_build_sgl(struct scic_sds_request *sds_request)
 {
 	struct isci_request *isci_request = sci_req_to_ireq(sds_request);
 	struct isci_host *isci_host = isci_request->isci_host;
+	struct scic_sds_controller *scic = &isci_host->sci;
 	struct sas_task *task = isci_request_access_task(isci_request);
 	struct scatterlist *sg = NULL;
 	dma_addr_t dma_addr;
@@ -108,25 +116,19 @@ static void scic_sds_request_build_sgl(struct scic_sds_request *sds_request)
 		sg = task->scatter;
 
 		while (sg) {
-			scu_sg = scic_sds_request_get_sgl_element_pair(
-					sds_request,
-					sg_idx);
-
-			SCU_SGL_COPY(scu_sg->A, sg);
-
+			scu_sg = to_sgl_element_pair(sds_request, sg_idx);
+			init_sgl_element(&scu_sg->A, sg);
 			sg = sg_next(sg);
-
 			if (sg) {
-				SCU_SGL_COPY(scu_sg->B, sg);
+				init_sgl_element(&scu_sg->B, sg);
 				sg = sg_next(sg);
 			} else
-				SCU_SGL_ZERO(scu_sg->B);
+				memset(&scu_sg->B, 0, sizeof(scu_sg->B));
 
 			if (prev_sg) {
-				dma_addr =
-					scic_io_request_get_dma_addr(
-							sds_request,
-							scu_sg);
+				dma_addr = to_sgl_element_pair_dma(scic,
+								   sds_request,
+								   sg_idx);
 
 				prev_sg->next_pair_upper =
 					upper_32_bits(dma_addr);
@@ -138,8 +140,7 @@ static void scic_sds_request_build_sgl(struct scic_sds_request *sds_request)
 			sg_idx++;
 		}
 	} else {	/* handle when no sg */
-		scu_sg = scic_sds_request_get_sgl_element_pair(sds_request,
-							       sg_idx);
+		scu_sg = to_sgl_element_pair(sds_request, sg_idx);
 
 		dma_addr = dma_map_single(&isci_host->pdev->dev,
 					  task->scatter,
@@ -246,35 +247,12 @@ static void scu_ssp_reqeust_construct_task_context(
 	/* task_context->type.ssp.tag = sci_req->io_tag; */
 	task_context->task_phase = 0x01;
 
-	if (sds_request->was_tag_assigned_by_user) {
-		/*
-		 * Build the task context now since we have already read
-		 * the data
-		 */
-		sds_request->post_context =
-			(SCU_CONTEXT_COMMAND_REQUEST_TYPE_POST_TC |
-			 (scic_sds_controller_get_protocol_engine_group(
-							controller) <<
-			  SCU_CONTEXT_COMMAND_PROTOCOL_ENGINE_GROUP_SHIFT) |
-			 (scic_sds_port_get_index(target_port) <<
-			  SCU_CONTEXT_COMMAND_LOGICAL_PORT_SHIFT) |
-			  ISCI_TAG_TCI(sds_request->io_tag));
-	} else {
-		/*
-		 * Build the task context now since we have already read
-		 * the data
-		 *
-		 * I/O tag index is not assigned because we have to wait
-		 * until we get a TCi
-		 */
-		sds_request->post_context =
-			(SCU_CONTEXT_COMMAND_REQUEST_TYPE_POST_TC |
-			 (scic_sds_controller_get_protocol_engine_group(
-							owning_controller) <<
-			  SCU_CONTEXT_COMMAND_PROTOCOL_ENGINE_GROUP_SHIFT) |
-			 (scic_sds_port_get_index(target_port) <<
-			  SCU_CONTEXT_COMMAND_LOGICAL_PORT_SHIFT));
-	}
+	sds_request->post_context = (SCU_CONTEXT_COMMAND_REQUEST_TYPE_POST_TC |
+				     (scic_sds_controller_get_protocol_engine_group(controller) <<
+				      SCU_CONTEXT_COMMAND_PROTOCOL_ENGINE_GROUP_SHIFT) |
+				     (scic_sds_port_get_index(target_port) <<
+				      SCU_CONTEXT_COMMAND_LOGICAL_PORT_SHIFT) |
+				     ISCI_TAG_TCI(sds_request->io_tag));
 
 	/*
 	 * Copy the physical address for the command buffer to the
@@ -302,14 +280,11 @@ static void scu_ssp_reqeust_construct_task_context(
  * @sci_req:
  *
  */
-static void scu_ssp_io_request_construct_task_context(
-	struct scic_sds_request *sci_req,
-	enum dma_data_direction dir,
-	u32 len)
+static void scu_ssp_io_request_construct_task_context(struct scic_sds_request *sci_req,
+						      enum dma_data_direction dir,
+						      u32 len)
 {
-	struct scu_task_context *task_context;
-
-	task_context = scic_sds_request_get_task_context(sci_req);
+	struct scu_task_context *task_context = sci_req->tc;
 
 	scu_ssp_reqeust_construct_task_context(sci_req, task_context);
 
@@ -347,12 +322,9 @@ static void scu_ssp_io_request_construct_task_context(
  *    constructed.
  *
  */
-static void scu_ssp_task_request_construct_task_context(
-	struct scic_sds_request *sci_req)
+static void scu_ssp_task_request_construct_task_context(struct scic_sds_request *sci_req)
 {
-	struct scu_task_context *task_context;
-
-	task_context = scic_sds_request_get_task_context(sci_req);
+	struct scu_task_context *task_context = sci_req->tc;
 
 	scu_ssp_reqeust_construct_task_context(sci_req, task_context);
 
@@ -421,35 +393,12 @@ static void scu_sata_reqeust_construct_task_context(
 	/* Set the first word of the H2D REG FIS */
 	task_context->type.words[0] = *(u32 *)&sci_req->stp.cmd;
 
-	if (sci_req->was_tag_assigned_by_user) {
-		/*
-		 * Build the task context now since we have already read
-		 * the data
-		 */
-		sci_req->post_context =
-			(SCU_CONTEXT_COMMAND_REQUEST_TYPE_POST_TC |
-			 (scic_sds_controller_get_protocol_engine_group(
-							controller) <<
-			  SCU_CONTEXT_COMMAND_PROTOCOL_ENGINE_GROUP_SHIFT) |
-			 (scic_sds_port_get_index(target_port) <<
-			  SCU_CONTEXT_COMMAND_LOGICAL_PORT_SHIFT) |
-			  ISCI_TAG_TCI(sci_req->io_tag));
-	} else {
-		/*
-		 * Build the task context now since we have already read
-		 * the data.
-		 * I/O tag index is not assigned because we have to wait
-		 * until we get a TCi.
-		 */
-		sci_req->post_context =
-			(SCU_CONTEXT_COMMAND_REQUEST_TYPE_POST_TC |
-			 (scic_sds_controller_get_protocol_engine_group(
-							controller) <<
-			  SCU_CONTEXT_COMMAND_PROTOCOL_ENGINE_GROUP_SHIFT) |
-			 (scic_sds_port_get_index(target_port) <<
-			  SCU_CONTEXT_COMMAND_LOGICAL_PORT_SHIFT));
-	}
-
+	sci_req->post_context = (SCU_CONTEXT_COMMAND_REQUEST_TYPE_POST_TC |
+				 (scic_sds_controller_get_protocol_engine_group(controller) <<
+				  SCU_CONTEXT_COMMAND_PROTOCOL_ENGINE_GROUP_SHIFT) |
+				 (scic_sds_port_get_index(target_port) <<
+				  SCU_CONTEXT_COMMAND_LOGICAL_PORT_SHIFT) |
+				 ISCI_TAG_TCI(sci_req->io_tag));
 	/*
 	 * Copy the physical address for the command buffer to the SCU Task
 	 * Context. We must offset the command buffer by 4 bytes because the
@@ -467,22 +416,9 @@ static void scu_sata_reqeust_construct_task_context(
 	task_context->response_iu_lower = 0;
 }
 
-
-
-/**
- * scu_stp_raw_request_construct_task_context -
- * @sci_req: This parameter specifies the STP request object for which to
- *    construct a RAW command frame task context.
- * @task_context: This parameter specifies the SCU specific task context buffer
- *    to construct.
- *
- * This method performs the operations common to all SATA/STP requests
- * utilizing the raw frame method. none
- */
-static void scu_stp_raw_request_construct_task_context(struct scic_sds_stp_request *stp_req,
-						       struct scu_task_context *task_context)
+static void scu_stp_raw_request_construct_task_context(struct scic_sds_request *sci_req)
 {
-	struct scic_sds_request *sci_req = to_sci_req(stp_req);
+	struct scu_task_context *task_context = sci_req->tc;
 
 	scu_sata_reqeust_construct_task_context(sci_req, task_context);
 
@@ -500,8 +436,7 @@ scic_sds_stp_pio_request_construct(struct scic_sds_request *sci_req,
 	struct scic_sds_stp_request *stp_req = &sci_req->stp.req;
 	struct scic_sds_stp_pio_request *pio = &stp_req->type.pio;
 
-	scu_stp_raw_request_construct_task_context(stp_req,
-						   sci_req->task_context_buffer);
+	scu_stp_raw_request_construct_task_context(sci_req);
 
 	pio->current_transfer_bytes = 0;
 	pio->ending_error = 0;
@@ -512,13 +447,10 @@ scic_sds_stp_pio_request_construct(struct scic_sds_request *sci_req,
 
 	if (copy_rx_frame) {
 		scic_sds_request_build_sgl(sci_req);
-		/* Since the IO request copy of the TC contains the same data as
-		 * the actual TC this pointer is vaild for either.
-		 */
-		pio->request_current.sgl_pair = &sci_req->task_context_buffer->sgl_pair_ab;
+		pio->request_current.sgl_index = 0;
 	} else {
 		/* The user does not want the data copied to the SGL buffer location */
-		pio->request_current.sgl_pair = NULL;
+		pio->request_current.sgl_index = -1;
 	}
 
 	return SCI_SUCCESS;
@@ -541,7 +473,7 @@ static void scic_sds_stp_optimized_request_construct(struct scic_sds_request *sc
 						     u32 len,
 						     enum dma_data_direction dir)
 {
-	struct scu_task_context *task_context = sci_req->task_context_buffer;
+	struct scu_task_context *task_context = sci_req->tc;
 
 	/* Build the STP task context structure */
 	scu_sata_reqeust_construct_task_context(sci_req, task_context);
@@ -587,8 +519,7 @@ scic