ionic: use index not pointer for queue tracking

Use index counters rather than pointers for tracking head
and tail in the queues to save a little memory and to perhaps
slightly faster queue processing.

Signed-off-by: Shannon Nelson <snelson@pensando.io>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 23 insertions, 17 deletions

diff --git a/drivers/net/ethernet/pensando/ionic/ionic_dev.c b/drivers/net/ethernet/pensando/ionic/ionic_dev.c
index 25cf376f3b40..3645673b4b18 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_dev.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_dev.c
@@ -482,7 +482,7 @@ int ionic_cq_init(struct ionic_lif *lif, struct ionic_cq *cq,
 	cq->bound_intr = intr;
 	cq->num_descs = num_descs;
 	cq->desc_size = desc_size;
-	cq->tail = cq->info;
+	cq->tail_idx = 0;
 	cq->done_color = 1;
 
 	cur = cq->info;
@@ -522,15 +522,18 @@ unsigned int ionic_cq_service(struct ionic_cq *cq, unsigned int work_to_do,
 			      ionic_cq_cb cb, ionic_cq_done_cb done_cb,
 			      void *done_arg)
 {
+	struct ionic_cq_info *cq_info;
 	unsigned int work_done = 0;
 
 	if (work_to_do == 0)
 		return 0;
 
-	while (cb(cq, cq->tail)) {
-		if (cq->tail->last)
+	cq_info = &cq->info[cq->tail_idx];
+	while (cb(cq, cq_info)) {
+		if (cq->tail_idx == cq->num_descs - 1)
 			cq->done_color = !cq->done_color;
-		cq->tail = cq->tail->next;
+		cq->tail_idx = (cq->tail_idx + 1) & (cq->num_descs - 1);
+		cq_info = &cq->info[cq->tail_idx];
 		DEBUG_STATS_CQE_CNT(cq);
 
 		if (++work_done >= work_to_do)
@@ -565,8 +568,8 @@ int ionic_q_init(struct ionic_lif *lif, struct ionic_dev *idev,
 	q->num_descs = num_descs;
 	q->desc_size = desc_size;
 	q->sg_desc_size = sg_desc_size;
-	q->tail = q->info;
-	q->head = q->tail;
+	q->tail_idx = 0;
+	q->head_idx = 0;
 	q->pid = pid;
 
 	snprintf(q->name, sizeof(q->name), "L%d-%s%u", lif->index, name, index);
@@ -614,19 +617,22 @@ void ionic_q_post(struct ionic_queue *q, bool ring_doorbell, ionic_desc_cb cb,
 		  void *cb_arg)
 {
 	struct device *dev = q->lif->ionic->dev;
+	struct ionic_desc_info *desc_info;
 	struct ionic_lif *lif = q->lif;
 
-	q->head->cb = cb;
-	q->head->cb_arg = cb_arg;
-	q->head = q->head->next;
+	desc_info = &q->info[q->head_idx];
+	desc_info->cb = cb;
+	desc_info->cb_arg = cb_arg;
+
+	q->head_idx = (q->head_idx + 1) & (q->num_descs - 1);
 
 	dev_dbg(dev, "lif=%d qname=%s qid=%d qtype=%d p_index=%d ringdb=%d\n",
 		q->lif->index, q->name, q->hw_type, q->hw_index,
-		q->head->index, ring_doorbell);
+		q->head_idx, ring_doorbell);
 
 	if (ring_doorbell)
 		ionic_dbell_ring(lif->kern_dbpage, q->hw_type,
-				 q->dbval | q->head->index);
+				 q->dbval | q->head_idx);
 }
 
 static bool ionic_q_is_posted(struct ionic_queue *q, unsigned int pos)
@@ -634,8 +640,8 @@ static bool ionic_q_is_posted(struct ionic_queue *q, unsigned int pos)
 	unsigned int mask, tail, head;
 
 	mask = q->num_descs - 1;
-	tail = q->tail->index;
-	head = q->head->index;
+	tail = q->tail_idx;
+	head = q->head_idx;
 
 	return ((pos - tail) & mask) < ((head - tail) & mask);
 }
@@ -648,18 +654,18 @@ void ionic_q_service(struct ionic_queue *q, struct ionic_cq_info *cq_info,
 	void *cb_arg;
 
 	/* check for empty queue */
-	if (q->tail->index == q->head->index)
+	if (q->tail_idx == q->head_idx)
 		return;
 
 	/* stop index must be for a descriptor that is not yet completed */
 	if (unlikely(!ionic_q_is_posted(q, stop_index)))
 		dev_err(q->lif->ionic->dev,
 			"ionic stop is not posted %s stop %u tail %u head %u\n",
-			q->name, stop_index, q->tail->index, q->head->index);
+			q->name, stop_index, q->tail_idx, q->head_idx);
 
 	do {
-		desc_info = q->tail;
-		q->tail = desc_info->next;
+		desc_info = &q->info[q->tail_idx];
+		q->tail_idx = (q->tail_idx + 1) & (q->num_descs - 1);
 
 		cb = desc_info->cb;
 		cb_arg = desc_info->cb_arg;