[PATCH v2 09/16] dmaengine: bcm-sba-raid: Improve sba_issue_pending() run duration

[Anup Patel]

The pending sba_request list can become very long in real-life usage
(e.g. setting up RAID array) which can cause sba_issue_pending() to
run for long duration.

This patch adds common sba_process_deferred_requests() to process
few completed and pending requests so that it finishes in short
duration. We use this common sba_process_deferred_requests() in
both sba_issue_pending() and sba_receive_message().

Signed-off-by: Anup Patel <anup.patel@xxxxxxxxxxxx>
---
 drivers/dma/bcm-sba-raid.c | 234 ++++++++++++++++++++++++---------------------
 1 file changed, 125 insertions(+), 109 deletions(-)

diff --git a/drivers/dma/bcm-sba-raid.c b/drivers/dma/bcm-sba-raid.c
index af6cc8e..f6616da 100644
--- a/drivers/dma/bcm-sba-raid.c
+++ b/drivers/dma/bcm-sba-raid.c
@@ -277,38 +277,28 @@ static void _sba_free_request(struct sba_device *sba,
 		sba->reqs_fence = false;
 }
 
-static void sba_received_request(struct sba_request *req)
+/* Note: Must be called with sba->reqs_lock held */
+static void _sba_complete_request(struct sba_device *sba,
+				  struct sba_request *req)
 {
-	unsigned long flags;
-	struct sba_device *sba = req->sba;
-
-	spin_lock_irqsave(&sba->reqs_lock, flags);
+	lockdep_assert_held(&sba->reqs_lock);
 	req->flags &= ~SBA_REQUEST_STATE_MASK;
-	req->flags |= SBA_REQUEST_STATE_RECEIVED;
-	list_move_tail(&req->node, &sba->reqs_received_list);
-	spin_unlock_irqrestore(&sba->reqs_lock, flags);
+	req->flags |= SBA_REQUEST_STATE_COMPLETED;
+	list_move_tail(&req->node, &sba->reqs_completed_list);
+	if (list_empty(&sba->reqs_active_list))
+		sba->reqs_fence = false;
 }
 
-static void sba_complete_chained_requests(struct sba_request *req)
+/* Note: Must be called with sba->reqs_lock held */
+static void _sba_received_request(struct sba_device *sba,
+				  struct sba_request *req)
 {
-	unsigned long flags;
-	struct sba_request *nreq;
-	struct sba_device *sba = req->sba;
-
-	spin_lock_irqsave(&sba->reqs_lock, flags);
-
+	lockdep_assert_held(&sba->reqs_lock);
 	req->flags &= ~SBA_REQUEST_STATE_MASK;
-	req->flags |= SBA_REQUEST_STATE_COMPLETED;
-	list_move_tail(&req->node, &sba->reqs_completed_list);
-	list_for_each_entry(nreq, &req->next, next) {
-		nreq->flags &= ~SBA_REQUEST_STATE_MASK;
-		nreq->flags |= SBA_REQUEST_STATE_COMPLETED;
-		list_move_tail(&nreq->node, &sba->reqs_completed_list);
-	}
+	req->flags |= SBA_REQUEST_STATE_RECEIVED;
+	list_move_tail(&req->node, &sba->reqs_received_list);
 	if (list_empty(&sba->reqs_active_list))
 		sba->reqs_fence = false;
-
-	spin_unlock_irqrestore(&sba->reqs_lock, flags);
 }
 
 static void sba_free_chained_requests(struct sba_request *req)
@@ -386,26 +376,6 @@ static void sba_cleanup_pending_requests(struct sba_device *sba)
 	spin_unlock_irqrestore(&sba->reqs_lock, flags);
 }
 
-/* ====== DMAENGINE callbacks ===== */
-
-static void sba_free_chan_resources(struct dma_chan *dchan)
-{
-	/*
-	 * Channel resources are pre-alloced so we just free-up
-	 * whatever we can so that we can re-use pre-alloced
-	 * channel resources next time.
-	 */
-	sba_cleanup_nonpending_requests(to_sba_device(dchan));
-}
-
-static int sba_device_terminate_all(struct dma_chan *dchan)
-{
-	/* Cleanup all pending requests */
-	sba_cleanup_pending_requests(to_sba_device(dchan));
-
-	return 0;
-}
-
 static int sba_send_mbox_request(struct sba_device *sba,
 				 struct sba_request *req)
 {
@@ -431,17 +401,27 @@ static int sba_send_mbox_request(struct sba_device *sba,
 	return 0;
 }
 
-static void sba_issue_pending(struct dma_chan *dchan)
+static void sba_process_deferred_requests(struct sba_device *sba)
 {
 	int ret;
+	u32 count;
 	unsigned long flags;
-	struct sba_request *req, *req1;
-	struct sba_device *sba = to_sba_device(dchan);
+	struct sba_request *req;
+	struct dma_async_tx_descriptor *tx;
 
 	spin_lock_irqsave(&sba->reqs_lock, flags);
 
-	/* Process all pending request */
-	list_for_each_entry_safe(req, req1, &sba->reqs_pending_list, node) {
+	/* Count pending requests */
+	count = 0;
+	list_for_each_entry(req, &sba->reqs_pending_list, node)
+		count++;
+
+	/* Process pending requests */
+	while (!list_empty(&sba->reqs_pending_list) && count) {
+		/* Get the first pending request */
+		req = list_first_entry(&sba->reqs_pending_list,
+				       struct sba_request, node);
+
 		/* Try to make request active */
 		if (!_sba_active_request(sba, req))
 			break;
@@ -456,11 +436,102 @@ static void sba_issue_pending(struct dma_chan *dchan)
 			_sba_pending_request(sba, req);
 			break;
 		}
+
+		count--;
+	}
+
+	/* Count completed requests */
+	count = 0;
+	list_for_each_entry(req, &sba->reqs_completed_list, node)
+		count++;
+
+	/* Process completed requests */
+	while (!list_empty(&sba->reqs_completed_list) && count) {
+		req = list_first_entry(&sba->reqs_completed_list,
+					struct sba_request, node);
+		list_del_init(&req->node);
+		tx = &req->tx;
+
+		spin_unlock_irqrestore(&sba->reqs_lock, flags);
+
+		WARN_ON(tx->cookie < 0);
+		if (tx->cookie > 0) {
+			dma_cookie_complete(tx);
+			dmaengine_desc_get_callback_invoke(tx, NULL);
+			dma_descriptor_unmap(tx);
+			tx->callback = NULL;
+			tx->callback_result = NULL;
+		}
+
+		dma_run_dependencies(tx);
+
+		spin_lock_irqsave(&sba->reqs_lock, flags);
+
+		/* If waiting for 'ack' then move to completed list */
+		if (!async_tx_test_ack(&req->tx))
+			_sba_complete_request(sba, req);
+		else
+			_sba_free_request(sba, req);
+
+		count--;
 	}
 
+	/* Re-check pending and completed work */
+	count = 0;
+	if (!list_empty(&sba->reqs_pending_list) ||
+	    !list_empty(&sba->reqs_completed_list))
+		count = 1;
+
 	spin_unlock_irqrestore(&sba->reqs_lock, flags);
 }
 
+static void sba_process_received_request(struct sba_device *sba,
+					 struct sba_request *req)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&sba->reqs_lock, flags);
+
+	/* Mark request as received */
+	_sba_received_request(sba, req);
+
+	/* Update request */
+	if (!atomic_dec_return(&req->first->next_pending_count))
+		_sba_complete_request(sba, req->first);
+	if (req->first != req)
+		_sba_free_request(sba, req);
+
+	spin_unlock_irqrestore(&sba->reqs_lock, flags);
+}
+
+/* ====== DMAENGINE callbacks ===== */
+
+static void sba_free_chan_resources(struct dma_chan *dchan)
+{
+	/*
+	 * Channel resources are pre-alloced so we just free-up
+	 * whatever we can so that we can re-use pre-alloced
+	 * channel resources next time.
+	 */
+	sba_cleanup_nonpending_requests(to_sba_device(dchan));
+}
+
+static int sba_device_terminate_all(struct dma_chan *dchan)
+{
+	/* Cleanup all pending requests */
+	sba_cleanup_pending_requests(to_sba_device(dchan));
+
+	return 0;
+}
+
+static void sba_issue_pending(struct dma_chan *dchan)
+{
+	struct sba_device *sba = to_sba_device(dchan);
+
+	/* Process deferred requests */
+	sba_process_deferred_requests(sba);
+}
+
 static dma_cookie_t sba_tx_submit(struct dma_async_tx_descriptor *tx)
 {
 	unsigned long flags;
@@ -1382,40 +1453,10 @@ sba_prep_dma_pq(struct dma_chan *dchan, dma_addr_t *dst, dma_addr_t *src,
 
 /* ====== Mailbox callbacks ===== */
 
-static void sba_dma_tx_actions(struct sba_request *req)
-{
-	struct dma_async_tx_descriptor *tx = &req->tx;
-
-	WARN_ON(tx->cookie < 0);
-
-	if (tx->cookie > 0) {
-		dma_cookie_complete(tx);
-
-		/*
-		 * Call the callback (must not sleep or submit new
-		 * operations to this channel)
-		 */
-		if (tx->callback)
-			tx->callback(tx->callback_param);
-
-		dma_descriptor_unmap(tx);
-	}
-
-	/* Run dependent operations */
-	dma_run_dependencies(tx);
-
-	/* If waiting for 'ack' then move to completed list */
-	if (!async_tx_test_ack(&req->tx))
-		sba_complete_chained_requests(req);
-	else
-		sba_free_chained_requests(req);
-}
-
 static void sba_receive_message(struct mbox_client *cl, void *msg)
 {
-	unsigned long flags;
 	struct brcm_message *m = msg;
-	struct sba_request *req = m->ctx, *req1;
+	struct sba_request *req = m->ctx;
 	struct sba_device *sba = req->sba;
 
 	/* Error count if message has error */
@@ -1423,36 +1464,11 @@ static void sba_receive_message(struct mbox_client *cl, void *msg)
 		dev_err(sba->dev, "%s got message with error %d",
 			dma_chan_name(&sba->dma_chan), m->error);
 
-	/* Mark request as received */
-	sba_received_request(req);
-
-	/* Wait for all chained requests to be completed */
-	if (atomic_dec_return(&req->first->next_pending_count))
-		goto done;
-
-	/* Point to first request */
-	req = req->first;
-
-	/* Update request */
-	if (req->flags & SBA_REQUEST_STATE_RECEIVED)
-		sba_dma_tx_actions(req);
-	else
-		sba_free_chained_requests(req);
-
-	spin_lock_irqsave(&sba->reqs_lock, flags);
-
-	/* Re-check all completed request waiting for 'ack' */
-	list_for_each_entry_safe(req, req1, &sba->reqs_completed_list, node) {
-		spin_unlock_irqrestore(&sba->reqs_lock, flags);
-		sba_dma_tx_actions(req);
-		spin_lock_irqsave(&sba->reqs_lock, flags);
-	}
-
-	spin_unlock_irqrestore(&sba->reqs_lock, flags);
+	/* Process received request */
+	sba_process_received_request(sba, req);
 
-done:
-	/* Try to submit pending request */
-	sba_issue_pending(&sba->dma_chan);
+	/* Process deferred requests */
+	sba_process_deferred_requests(sba);
 }
 
 /* ====== Platform driver routines ===== */
-- 
2.7.4