IB/ib_mthca: Pre-link receive WQEs in Tavor mode

We have recently discovered that Tavor mode requires each WQE in a
posted list of receive WQEs to have a valid NDA field at all times.
This requirement holds true for regular QPs as well as for SRQs.  This
patch prelinks the receive queue in a regular QP and keeps the free
list in SRQ always properly linked.

Signed-off-by: Eli Cohen <eli@mellanox.co.il>
Reviewed-by: Jack Morgenstein <jackm@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

2 files changed, 22 insertions, 14 deletions

diff --git a/drivers/infiniband/hw/mthca/mthca_qp.c b/drivers/infiniband/hw/mthca/mthca_qp.c
index 0e5461c65731..db5595bbf7f0 100644
--- a/drivers/infiniband/hw/mthca/mthca_qp.c
+++ b/drivers/infiniband/hw/mthca/mthca_qp.c
@@ -1175,6 +1175,7 @@ static int mthca_alloc_qp_common(struct mthca_dev *dev,
 {
         int ret;
         int i;
+        struct mthca_next_seg *next;
 
         qp->refcount = 1;
         init_waitqueue_head(&qp->wait);
@@ -1217,7 +1218,6 @@ static int mthca_alloc_qp_common(struct mthca_dev *dev,
         }
 
         if (mthca_is_memfree(dev)) {
-                struct mthca_next_seg *next;
                 struct mthca_data_seg *scatter;
                 int size = (sizeof (struct mthca_next_seg) +
                             qp->rq.max_gs * sizeof (struct mthca_data_seg)) / 16;
@@ -1240,6 +1240,13 @@ static int mthca_alloc_qp_common(struct mthca_dev *dev,
                                                     qp->sq.wqe_shift) +
                                                    qp->send_wqe_offset);
                 }
+        } else {
+                for (i = 0; i < qp->rq.max; ++i) {
+                        next = get_recv_wqe(qp, i);
+                        next->nda_op = htonl((((i + 1) % qp->rq.max) <<
+                                              qp->rq.wqe_shift) | 1);
+                }
+
         }
 
         qp->sq.last = get_send_wqe(qp, qp->sq.max - 1);
@@ -1863,7 +1870,6 @@ int mthca_tavor_post_receive(struct ib_qp *ibqp, struct ib_recv_wr *wr,
                 prev_wqe = qp->rq.last;
                 qp->rq.last = wqe;
 
-                ((struct mthca_next_seg *) wqe)->nda_op = 0;
                 ((struct mthca_next_seg *) wqe)->ee_nds =
                         cpu_to_be32(MTHCA_NEXT_DBD);
                 ((struct mthca_next_seg *) wqe)->flags = 0;
@@ -1885,9 +1891,6 @@ int mthca_tavor_post_receive(struct ib_qp *ibqp, struct ib_recv_wr *wr,
 
                 qp->wrid[ind] = wr->wr_id;
 
-                ((struct mthca_next_seg *) prev_wqe)->nda_op =
-                        cpu_to_be32((ind << qp->rq.wqe_shift) | 1);
-                wmb();
                 ((struct mthca_next_seg *) prev_wqe)->ee_nds =
                         cpu_to_be32(MTHCA_NEXT_DBD | size);
 
diff --git a/drivers/infiniband/hw/mthca/mthca_srq.c b/drivers/infiniband/hw/mthca/mthca_srq.c
index ec63adc1099c..a5ffff6e1026 100644
--- a/drivers/infiniband/hw/mthca/mthca_srq.c
+++ b/drivers/infiniband/hw/mthca/mthca_srq.c
@@ -175,9 +175,17 @@ static int mthca_alloc_srq_buf(struct mthca_dev *dev, struct mthca_pd *pd,
          * scatter list L_Keys to the sentry value of 0x100.
          */
         for (i = 0; i < srq->max; ++i) {
-                wqe = get_wqe(srq, i);
+                struct mthca_next_seg *next;
 
-                *wqe_to_link(wqe) = i < srq->max - 1 ? i + 1 : -1;
+                next = wqe = get_wqe(srq, i);
+
+                if (i < srq->max - 1) {
+                        *wqe_to_link(wqe) = i + 1;
+                        next->nda_op = htonl(((i + 1) << srq->wqe_shift) | 1);
+                } else {
+                        *wqe_to_link(wqe) = -1;
+                        next->nda_op = 0;
+                }
 
                 for (scatter = wqe + sizeof (struct mthca_next_seg);
                      (void *) scatter < wqe + (1 << srq->wqe_shift);
@@ -470,12 +478,15 @@ out:
 void mthca_free_srq_wqe(struct mthca_srq *srq, u32 wqe_addr)
 {
         int ind;
+        struct mthca_next_seg *last_free;
 
         ind = wqe_addr >> srq->wqe_shift;
 
         spin_lock(&srq->lock);
 
-        *wqe_to_link(get_wqe(srq, srq->last_free)) = ind;
+        last_free = get_wqe(srq, srq->last_free);
+        *wqe_to_link(last_free) = ind;
+        last_free->nda_op = htonl((ind << srq->wqe_shift) | 1);
         *wqe_to_link(get_wqe(srq, ind)) = -1;
         srq->last_free = ind;
 
@@ -516,7 +527,6 @@ int mthca_tavor_post_srq_recv(struct ib_srq *ibsrq, struct ib_recv_wr *wr,
                 prev_wqe  = srq->last;
                 srq->last = wqe;
 
-                ((struct mthca_next_seg *) wqe)->nda_op = 0;
                 ((struct mthca_next_seg *) wqe)->ee_nds = 0;
                 /* flags field will always remain 0 */
 
@@ -537,9 +547,6 @@ int mthca_tavor_post_srq_recv(struct ib_srq *ibsrq, struct ib_recv_wr *wr,
                 if (i < srq->max_gs)
                         mthca_set_data_seg_inval(wqe);
 
-                ((struct mthca_next_seg *) prev_wqe)->nda_op =
-                        cpu_to_be32((ind << srq->wqe_shift) | 1);
-                wmb();
                 ((struct mthca_next_seg *) prev_wqe)->ee_nds =
                         cpu_to_be32(MTHCA_NEXT_DBD);
 
@@ -613,8 +620,6 @@ int mthca_arbel_post_srq_recv(struct ib_srq *ibsrq, struct ib_recv_wr *wr,
                         break;
                 }
 
-                ((struct mthca_next_seg *) wqe)->nda_op =
-                        cpu_to_be32((next_ind << srq->wqe_shift) | 1);
                 ((struct mthca_next_seg *) wqe)->ee_nds = 0;
                 /* flags field will always remain 0 */