IB/mthca: fix posting of send lists of length >= 255 on mem-free HCAs

On mem-free HCAs, when posting a long list of send requests, a
doorbell must be rung every 255 requests.  Add code to handle this.

Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

2 files changed, 31 insertions, 3 deletions

diff --git a/drivers/infiniband/hw/mthca/mthca_qp.c b/drivers/infiniband/hw/mthca/mthca_qp.c
index f9c8eb9845c9..7450550db736 100644
--- a/drivers/infiniband/hw/mthca/mthca_qp.c
+++ b/drivers/infiniband/hw/mthca/mthca_qp.c
@@ -1822,6 +1822,7 @@ int mthca_arbel_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
 {
         struct mthca_dev *dev = to_mdev(ibqp->device);
         struct mthca_qp *qp = to_mqp(ibqp);
+        __be32 doorbell[2];
         void *wqe;
         void *prev_wqe;
         unsigned long flags;
@@ -1841,6 +1842,34 @@ int mthca_arbel_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
         ind = qp->sq.head & (qp->sq.max - 1);
 
         for (nreq = 0; wr; ++nreq, wr = wr->next) {
+                if (unlikely(nreq == MTHCA_ARBEL_MAX_WQES_PER_SEND_DB)) {
+                        nreq = 0;
+
+                        doorbell[0] = cpu_to_be32((MTHCA_ARBEL_MAX_WQES_PER_SEND_DB << 24) |
+                                                  ((qp->sq.head & 0xffff) << 8) |
+                                                  f0 | op0);
+                        doorbell[1] = cpu_to_be32((qp->qpn << 8) | size0);
+
+                        qp->sq.head += MTHCA_ARBEL_MAX_WQES_PER_SEND_DB;
+                        size0 = 0;
+
+                        /*
+                         * Make sure that descriptors are written before
+                         * doorbell record.
+                         */
+                        wmb();
+                        *qp->sq.db = cpu_to_be32(qp->sq.head & 0xffff);
+
+                        /*
+                         * Make sure doorbell record is written before we
+                         * write MMIO send doorbell.
+                         */
+                        wmb();
+                        mthca_write64(doorbell,
+                                      dev->kar + MTHCA_SEND_DOORBELL,
+                                      MTHCA_GET_DOORBELL_LOCK(&dev->doorbell_lock));
+                }
+
                 if (mthca_wq_overflow(&qp->sq, nreq, qp->ibqp.send_cq)) {
                         mthca_err(dev, "SQ %06x full (%u head, %u tail,"
                                         " %d max, %d nreq)\n", qp->qpn,
@@ -2017,8 +2046,6 @@ int mthca_arbel_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
 
 out:
         if (likely(nreq)) {
-                __be32 doorbell[2];
-
                 doorbell[0] = cpu_to_be32((nreq << 24)                  |
                                           ((qp->sq.head & 0xffff) << 8) |
                                           f0 | op0);
diff --git a/drivers/infiniband/hw/mthca/mthca_wqe.h b/drivers/infiniband/hw/mthca/mthca_wqe.h
index 73f1c0b9021e..e7d2c1e86199 100644
--- a/drivers/infiniband/hw/mthca/mthca_wqe.h
+++ b/drivers/infiniband/hw/mthca/mthca_wqe.h
@@ -50,7 +50,8 @@ enum {
 
 enum {
         MTHCA_INVAL_LKEY                        = 0x100,
-        MTHCA_TAVOR_MAX_WQES_PER_RECV_DB        = 256
+        MTHCA_TAVOR_MAX_WQES_PER_RECV_DB        = 256,
+        MTHCA_ARBEL_MAX_WQES_PER_SEND_DB        = 255
 };
 
 struct mthca_next_seg {