dmaengine: bcm-sba-raid: Reduce locking context in sba_alloc_request()

We don't require to hold "sba->reqs_lock" for long-time
in sba_alloc_request() because lock protection is not
required when initializing members of "struct sba_request".
Signed-off-by: Anup Patel <anup.patel@broadcom.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/bcm-sba-raid.c

@@ -207,11 +207,16 @@ static struct sba_request *sba_alloc_request(struct sba_device *sba)
 	struct sba_request *req = NULL;
 
 	spin_lock_irqsave(&sba->reqs_lock, flags);
-
 	req = list_first_entry_or_null(&sba->reqs_free_list,
 				       struct sba_request, node);
 	if (req) {
 		list_move_tail(&req->node, &sba->reqs_alloc_list);
+		sba->reqs_free_count--;
+	}
+	spin_unlock_irqrestore(&sba->reqs_lock, flags);
+	if (!req)
+		return NULL;
+
 	req->state = SBA_REQUEST_STATE_ALLOCED;
 	req->fence = false;
 	req->first = req;
@@ -219,12 +224,7 @@ static struct sba_request *sba_alloc_request(struct sba_device *sba)
 	req->next_count = 1;
 	atomic_set(&req->next_pending_count, 1);
 
-		sba->reqs_free_count--;
-
 	dma_async_tx_descriptor_init(&req->tx, &sba->dma_chan);
-	}
-
-	spin_unlock_irqrestore(&sba->reqs_lock, flags);
 
 	return req;
 }