iw_cxgb4: Fix cxgb4 arm CQ logic w/IB_CQ_REPORT_MISSED_EVENTS

Current cxgb4 arm CQ logic ignores IB_CQ_REPORT_MISSED_EVENTS for
request completion notification on a CQ. Due to this ib_poll_handler()
assumes all events polled and avoids further iopoll scheduling.

This patch adds logic to cxgb4 ib_req_notify_cq() handler to check if
CQ is not empty and return accordingly. Based on the return value of
ib_req_notify_cq() handler, ib_poll_handler() will schedule a run of
iopoll handler.
Signed-off-by: Potnuri Bharat Teja <bharat@chelsio.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/cxgb4/cq.c

@@ -1016,15 +1016,15 @@ int c4iw_resize_cq(struct ib_cq *cq, int cqe, struct ib_udata *udata)
 int c4iw_arm_cq(struct ib_cq *ibcq, enum ib_cq_notify_flags flags)
 {
 	struct c4iw_cq *chp;
-	int ret;
+	int ret = 0;
 	unsigned long flag;
 
 	chp = to_c4iw_cq(ibcq);
 	spin_lock_irqsave(&chp->lock, flag);
-	ret = t4_arm_cq(&chp->cq,
+	t4_arm_cq(&chp->cq,
 		  (flags & IB_CQ_SOLICITED_MASK) == IB_CQ_SOLICITED);
+	if (flags & IB_CQ_REPORT_MISSED_EVENTS)
+		ret = t4_cq_notempty(&chp->cq);
 	spin_unlock_irqrestore(&chp->lock, flag);
-	if (ret && !(flags & IB_CQ_REPORT_MISSED_EVENTS))
-		ret = 0;
 	return ret;
 }

drivers/infiniband/hw/cxgb4/t4.h

@@ -634,6 +634,11 @@ static inline int t4_valid_cqe(struct t4_cq *cq, struct t4_cqe *cqe)
 	return (CQE_GENBIT(cqe) == cq->gen);
 }
 
+static inline int t4_cq_notempty(struct t4_cq *cq)
+{
+	return cq->sw_in_use || t4_valid_cqe(cq, &cq->queue[cq->cidx]);
+}
+
 static inline int t4_next_hw_cqe(struct t4_cq *cq, struct t4_cqe **cqe)
 {
 	int ret;