IB/hfi1: Add the TID second leg ACK packet builder

This patch adds the TID packet builder for the responder side, which
contains the state machine to build TID RDMA ACK packet for either
TID RDMA WRITE DATA or TID RDMA RESYNC packets.
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Mitko Haralanov <mitko.haralanov@intel.com>
Signed-off-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/hfi1/tid_rdma.c

@@ -124,6 +124,9 @@ static void hfi1_mod_tid_reap_timer(struct rvt_qp *qp);
 static void hfi1_mod_tid_retry_timer(struct rvt_qp *qp);
 static int hfi1_stop_tid_retry_timer(struct rvt_qp *qp);
 static void hfi1_tid_retry_timeout(struct timer_list *t);
+static int make_tid_rdma_ack(struct rvt_qp *qp,
+			     struct ib_other_headers *ohdr,
+			     struct hfi1_pkt_state *ps);
 
 static u64 tid_rdma_opfn_encode(struct tid_rdma_params *p)
 {
@@ -4874,6 +4877,10 @@ int hfi1_make_tid_rdma_pkt(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
 
 	ohdr = &ps->s_txreq->phdr.hdr.ibh.u.oth;
 
+	if ((priv->s_flags & RVT_S_ACK_PENDING) &&
+	    make_tid_rdma_ack(qp, ohdr, ps))
+		return 1;
+
 	if (!(ib_rvt_state_ops[qp->state] & RVT_PROCESS_SEND_OK)) {
 		if (!(ib_rvt_state_ops[qp->state] & RVT_FLUSH_SEND))
 			goto bail;
@@ -5014,3 +5021,137 @@ int hfi1_make_tid_rdma_pkt(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
 	iowait_set_flag(&priv->s_iowait, IOWAIT_PENDING_TID);
 	return 0;
 }
+
+static int make_tid_rdma_ack(struct rvt_qp *qp,
+			     struct ib_other_headers *ohdr,
+			     struct hfi1_pkt_state *ps)
+{
+	struct rvt_ack_entry *e;
+	struct hfi1_qp_priv *qpriv = qp->priv;
+	struct hfi1_ibdev *dev = to_idev(qp->ibqp.device);
+	u32 hwords, next;
+	u32 len = 0;
+	u32 bth1 = 0, bth2 = 0;
+	int middle = 0;
+	u16 flow;
+	struct tid_rdma_request *req, *nreq;
+
+	/* Don't send an ACK if we aren't supposed to. */
+	if (!(ib_rvt_state_ops[qp->state] & RVT_PROCESS_RECV_OK))
+		goto bail;
+
+	/* header size in 32-bit words LRH+BTH = (8+12)/4. */
+	hwords = 5;
+
+	e = &qp->s_ack_queue[qpriv->r_tid_ack];
+	req = ack_to_tid_req(e);
+	/*
+	 * In the RESYNC case, we are exactly one segment past the
+	 * previously sent ack or at the previously sent NAK. So to send
+	 * the resync ack, we go back one segment (which might be part of
+	 * the previous request) and let the do-while loop execute again.
+	 * The advantage of executing the do-while loop is that any data
+	 * received after the previous ack is automatically acked in the
+	 * RESYNC ack. It turns out that for the do-while loop we only need
+	 * to pull back qpriv->r_tid_ack, not the segment
+	 * indices/counters. The scheme works even if the previous request
+	 * was not a TID WRITE request.
+	 */
+	if (qpriv->resync) {
+		if (!req->ack_seg || req->ack_seg == req->total_segs)
+			qpriv->r_tid_ack = !qpriv->r_tid_ack ?
+				rvt_size_atomic(&dev->rdi) :
+				qpriv->r_tid_ack - 1;
+		e = &qp->s_ack_queue[qpriv->r_tid_ack];
+		req = ack_to_tid_req(e);
+	}
+
+	/*
+	 * If we've sent all the ACKs that we can, we are done
+	 * until we get more segments...
+	 */
+	if (!qpriv->s_nak_state && !qpriv->resync &&
+	    req->ack_seg == req->comp_seg)
+		goto bail;
+
+	do {
+		/*
+		 * To deal with coalesced ACKs, the acked_tail pointer
+		 * into the flow array is used. The distance between it
+		 * and the clear_tail is the number of flows that are
+		 * being ACK'ed.
+		 */
+		req->ack_seg +=
+			/* Get up-to-date value */
+			CIRC_CNT(req->clear_tail, req->acked_tail,
+				 MAX_FLOWS);
+		/* Advance acked index */
+		req->acked_tail = req->clear_tail;
+
+		/*
+		 * req->clear_tail points to the segment currently being
+		 * received. So, when sending an ACK, the previous
+		 * segment is being ACK'ed.
+		 */
+		flow = CIRC_PREV(req->acked_tail, MAX_FLOWS);
+		if (req->ack_seg != req->total_segs)
+			break;
+		req->state = TID_REQUEST_COMPLETE;
+
+		next = qpriv->r_tid_ack + 1;
+		if (next > rvt_size_atomic(&dev->rdi))
+			next = 0;
+		qpriv->r_tid_ack = next;
+		if (qp->s_ack_queue[next].opcode != TID_OP(WRITE_REQ))
+			break;
+		nreq = ack_to_tid_req(&qp->s_ack_queue[next]);
+		if (!nreq->comp_seg || nreq->ack_seg == nreq->comp_seg)
+			break;
+
+		/* Move to the next ack entry now */
+		e = &qp->s_ack_queue[qpriv->r_tid_ack];
+		req = ack_to_tid_req(e);
+	} while (1);
+
+	/*
+	 * At this point qpriv->r_tid_ack == qpriv->r_tid_tail but e and
+	 * req could be pointing at the previous ack queue entry
+	 */
+	if (qpriv->s_nak_state ||
+	    (qpriv->resync &&
+	     !hfi1_tid_rdma_is_resync_psn(qpriv->r_next_psn_kdeth - 1) &&
+	     (cmp_psn(qpriv->r_next_psn_kdeth - 1,
+		      full_flow_psn(&req->flows[flow],
+				    req->flows[flow].flow_state.lpsn)) > 0))) {
+		/*
+		 * A NAK will implicitly acknowledge all previous TID RDMA
+		 * requests. Therefore, we NAK with the req->acked_tail
+		 * segment for the request at qpriv->r_tid_ack (same at
+		 * this point as the req->clear_tail segment for the
+		 * qpriv->r_tid_tail request)
+		 */
+		e = &qp->s_ack_queue[qpriv->r_tid_ack];
+		req = ack_to_tid_req(e);
+		flow = req->acked_tail;
+	}
+
+	hwords += hfi1_build_tid_rdma_write_ack(qp, e, ohdr, flow, &bth1,
+						&bth2);
+	len = 0;
+	qpriv->s_flags &= ~RVT_S_ACK_PENDING;
+	ps->s_txreq->hdr_dwords = hwords;
+	ps->s_txreq->sde = qpriv->s_sde;
+	ps->s_txreq->s_cur_size = len;
+	ps->s_txreq->ss = NULL;
+	hfi1_make_ruc_header(qp, ohdr, (TID_OP(ACK) << 24), bth1, bth2, middle,
+			     ps);
+	return 1;
+bail:
+	/*
+	 * Ensure s_rdma_ack_cnt changes are committed prior to resetting
+	 * RVT_S_RESP_PENDING
+	 */
+	smp_wmb();
+	qpriv->s_flags &= ~RVT_S_ACK_PENDING;
+	return 0;
+}