isci: cleanup/optimize pool implementation

The circ_buf macros are ~6% faster, as measured by perf, because they take
advantage of power-of-two math assumptions i.e. no test and branch for
rollover. Their semantics are clearer than the hidden side effects in pool.h
(like sci_pool_get() which hides an assignment).

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

4 files changed, 56 insertions, 231 deletions

diff --git a/drivers/scsi/isci/host.c b/drivers/scsi/isci/host.c
index 41a7c50..343655b 100644
--- a/drivers/scsi/isci/host.c
+++ b/drivers/scsi/isci/host.c
@@ -52,6 +52,7 @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
+#include <linux/circ_buf.h>
 #include <linux/device.h>
 #include <scsi/sas.h>
 #include "host.h"
@@ -1054,6 +1055,33 @@ 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)
 {
@@ -1069,9 +1097,11 @@ static enum sci_status scic_controller_start(struct scic_sds_controller *scic,
 	}
 
 	/* Build the TCi free pool */
-	sci_pool_initialize(scic->tci_pool);
+	BUILD_BUG_ON(SCI_MAX_IO_REQUESTS > 1 << sizeof(ihost->tci_pool[0]) * 8);
+	ihost->tci_head = 0;
+	ihost->tci_tail = 0;
 	for (index = 0; index < scic->task_context_entries; index++)
-		sci_pool_put(scic->tci_pool, index);
+		isci_tci_free(ihost, index);
 
 	/* Build the RNi free pool */
 	scic_sds_remote_node_table_initialize(
@@ -3063,18 +3093,17 @@ enum sci_task_status scic_controller_start_task(
  * 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)
+u16 scic_controller_allocate_io_tag(struct scic_sds_controller *scic)
 {
-	u16 task_context;
-	u16 sequence_count;
-
-	if (!sci_pool_empty(scic->tci_pool)) {
-		sci_pool_get(scic->tci_pool, task_context);
+	struct isci_host *ihost = scic_to_ihost(scic);
+	u16 tci;
+	u16 seq;
 
-		sequence_count = scic->io_request_sequence[task_context];
+	if (isci_tci_space(ihost)) {
+		tci = isci_tci_alloc(ihost);
+		seq = scic->io_request_sequence[tci];
 
-		return scic_sds_io_tag_construct(sequence_count, task_context);
+		return scic_sds_io_tag_construct(seq, tci);
 	}
 
 	return SCI_CONTROLLER_INVALID_IO_TAG;
@@ -3105,10 +3134,10 @@ u16 scic_controller_allocate_io_tag(
  * 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)
+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 sequence;
 	u16 index;
 
@@ -3117,18 +3146,16 @@ enum sci_status scic_controller_free_io_tag(
 	sequence = scic_sds_io_tag_get_sequence(io_tag);
 	index    = scic_sds_io_tag_get_index(io_tag);
 
-	if (!sci_pool_full(scic->tci_pool)) {
-		if (sequence == scic->io_request_sequence[index]) {
-			scic_sds_io_sequence_increment(
-				scic->io_request_sequence[index]);
+	/* prevent tail from passing head */
+	if (isci_tci_active(ihost) == 0)
+		return SCI_FAILURE_INVALID_IO_TAG;
 
-			sci_pool_put(scic->tci_pool, index);
+	if (sequence == scic->io_request_sequence[index]) {
+		scic_sds_io_sequence_increment(scic->io_request_sequence[index]);
 
-			return SCI_SUCCESS;
-		}
-	}
+		isci_tci_free(ihost, index);
 
+		return SCI_SUCCESS;
+	}
 	return SCI_FAILURE_INVALID_IO_TAG;
 }
-
-
diff --git a/drivers/scsi/isci/host.h b/drivers/scsi/isci/host.h
index 74035004..c61a9fa 100644
--- a/drivers/scsi/isci/host.h
+++ b/drivers/scsi/isci/host.h
@@ -57,7 +57,6 @@
 
 #include "remote_device.h"
 #include "phy.h"
-#include "pool.h"
 #include "isci.h"
 #include "remote_node_table.h"
 #include "registers.h"
@@ -180,11 +179,6 @@ struct scic_sds_controller {
 	struct scic_remote_node_table available_remote_nodes;
 
 	/**
-	 * This field is the TCi pool used to manage the task context index.
-	 */
-	SCI_POOL_CREATE(tci_pool, u16, SCI_MAX_IO_REQUESTS);
-
-	/**
 	 * This filed is the struct scic_power_control data used to controll when direct
 	 * attached devices can consume power.
 	 */
@@ -310,6 +304,10 @@ struct scic_sds_controller {
 
 struct isci_host {
 	struct scic_sds_controller sci;
+	u16 tci_head;
+	u16 tci_tail;
+	u16 tci_pool[SCI_MAX_IO_REQUESTS];
+
 	union scic_oem_parameters oem_parameters;
 
 	int id; /* unique within a given pci device */
@@ -423,8 +421,6 @@ enum scic_sds_controller_states {
 	SCIC_FAILED,
 };
 
-
-
 /**
  * struct isci_pci_info - This class represents the pci function containing the
  *    controllers. Depending on PCI SKU, there could be up to 2 controllers in
diff --git a/drivers/scsi/isci/isci.h b/drivers/scsi/isci/isci.h
index 714ed92..84ba533 100644
--- a/drivers/scsi/isci/isci.h
+++ b/drivers/scsi/isci/isci.h
@@ -112,6 +112,7 @@ static inline void check_sizes(void)
 	BUILD_BUG_ON_NOT_POWER_OF_2(SCU_MAX_UNSOLICITED_FRAMES);
 	BUILD_BUG_ON_NOT_POWER_OF_2(SCU_MAX_COMPLETION_QUEUE_ENTRIES);
 	BUILD_BUG_ON(SCU_MAX_UNSOLICITED_FRAMES > SCU_ABSOLUTE_MAX_UNSOLICITED_FRAMES);
+	BUILD_BUG_ON_NOT_POWER_OF_2(SCI_MAX_IO_REQUESTS);
 }
 
 /**
diff --git a/drivers/scsi/isci/pool.h b/drivers/scsi/isci/pool.h
deleted file mode 100644
index 016ec83..0000000
--- a/drivers/scsi/isci/pool.h
+++ /dev/null
@@ -1,199 +0,0 @@
-/*
- * This file is provided under a dual BSD/GPLv2 license.  When using or
- * redistributing this file, you may do so under either license.
- *
- * GPL LICENSE SUMMARY
- *
- * Copyright(c) 2008 - 2011 Intel Corporation. All rights reserved.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of version 2 of the GNU General Public License as
- * published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
- * The full GNU General Public License is included in this distribution
- * in the file called LICENSE.GPL.
- *
- * BSD LICENSE
- *
- * Copyright(c) 2008 - 2011 Intel Corporation. All rights reserved.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- *   * Redistributions of source code must retain the above copyright
- *     notice, this list of conditions and the following disclaimer.
- *   * Redistributions in binary form must reproduce the above copyright
- *     notice, this list of conditions and the following disclaimer in
- *     the documentation and/or other materials provided with the
- *     distribution.
- *   * Neither the name of Intel Corporation nor the names of its
- *     contributors may be used to endorse or promote products derived
- *     from this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-/**
- * This file contains the interface to the pool class. This class allows two
- *    different two different priority tasks to insert and remove items from
- *    the free pool. The user of the pool is expected to evaluate the pool
- *    condition empty before a get operation and pool condition full before a
- *    put operation. Methods Provided: - sci_pool_create() -
- *    sci_pool_initialize() - sci_pool_empty() - sci_pool_full() -
- *    sci_pool_get() - sci_pool_put()
- *
- *
- */
-
-#ifndef _SCI_POOL_H_
-#define _SCI_POOL_H_
-
-/**
- * SCI_POOL_INCREMENT() -
- *
- * Private operation for the pool
- */
-#define SCI_POOL_INCREMENT(pool, index) \
-	(((index) + 1) == (pool).size ? 0 : (index) + 1)
-
-/**
- * SCI_POOL_CREATE() -
- *
- * This creates a pool structure of pool_name. The members in the pool are of
- * type with number of elements equal to size.
- */
-#define SCI_POOL_CREATE(pool_name, type, pool_size) \
-	struct \
-	{ \
-		u32 size; \
-		u32 get; \
-		u32 put; \
-		type array[(pool_size) + 1]; \
-	} pool_name
-
-
-/**
- * sci_pool_empty() -
- *
- * This macro evaluates the pool and returns true if the pool is empty. If the
- * pool is empty the user should not perform any get operation on the pool.
- */
-#define sci_pool_empty(pool) \
-	((pool).get == (pool).put)
-
-/**
- * sci_pool_full() -
- *
- * This macro evaluates the pool and returns true if the pool is full.  If the
- * pool is full the user should not perform any put operation.
- */
-#define sci_pool_full(pool) \
-	(SCI_POOL_INCREMENT(pool, (pool).put) == (pool).get)
-
-/**
- * sci_pool_size() -
- *
- * This macro returns the size of the pool created.  The internal size of the
- * pool is actually 1 larger then necessary in order to ensure get and put
- * pointers can be written simultaneously by different users.  As a result,
- * this macro subtracts 1 from the internal size
- */
-#define sci_pool_size(pool) \
-	((pool).size - 1)
-
-/**
- * sci_pool_count() -
- *
- * This macro indicates the number of elements currently contained in the pool.
- */
-#define sci_pool_count(pool) \
-	(\
-		sci_pool_empty((pool)) \
-		? 0 \
-		: (\
-			sci_pool_full((pool)) \
-			? sci_pool_size((pool)) \
-			: (\
-				(pool).get > (pool).put \
-				? ((pool).size - (pool).get + (pool).put) \
-				: ((pool).put - (pool).get) \
-				) \
-			) \
-	)
-
-/**
- * sci_pool_initialize() -
- *
- * This macro initializes the pool to an empty condition.
- */
-#define sci_pool_initialize(pool) \
-	{ \
-		(pool).size = (sizeof((pool).array) / sizeof((pool).array[0])); \
-		(pool).get = 0; \
-		(pool).put = 0; \
-	}
-
-/**
- * sci_pool_get() -
- *
- * This macro will get the next free element from the pool. This should only be
- * called if the pool is not empty.
- */
-#define sci_pool_get(pool, my_value) \
-	{ \
-		(my_value) = (pool).array[(pool).get]; \
-		(pool).get = SCI_POOL_INCREMENT((pool), (pool).get); \
-	}
-
-/**
- * sci_pool_put() -
- *
- * This macro will put the value into the pool. This should only be called if
- * the pool is not full.
- */
-#define sci_pool_put(pool, value) \
-	{ \
-		(pool).array[(pool).put] = (value); \
-		(pool).put = SCI_POOL_INCREMENT((pool), (pool).put); \
-	}
-
-/**
- * sci_pool_erase() -
- *
- * This macro will search the pool and remove any elements in the pool matching
- * the supplied value. This method can only be utilized on pools
- */
-#define sci_pool_erase(pool, type, value) \
-	{ \
-		type tmp_value;	\
-		u32 index; \
-		u32 element_count = sci_pool_count((pool)); \
- \
-		for (index = 0; index < element_count; index++) {	\
-			sci_pool_get((pool), tmp_value); \
-			if (tmp_value != (value)) \
-				sci_pool_put((pool), tmp_value); \
-		} \
-	}
-
-#endif /* _SCI_POOL_H_ */