4 files changed, 30 insertions, 2 deletions

diff --git a/drivers/infiniband/hw/mthca/mthca_dev.h b/drivers/infiniband/hw/mthca/mthca_dev.h
index 49d0eae5518a..4c1dcb4c1822 100644
--- a/drivers/infiniband/hw/mthca/mthca_dev.h
+++ b/drivers/infiniband/hw/mthca/mthca_dev.h
@@ -151,6 +151,7 @@ struct mthca_limits {
         int      reserved_qps;
         int      num_srqs;
         int      max_srq_wqes;
+        int      max_srq_sge;
         int      reserved_srqs;
         int      num_eecs;
         int      reserved_eecs;
@@ -507,6 +508,7 @@ void mthca_free_srq(struct mthca_dev *dev, struct mthca_srq *srq);
 int mthca_modify_srq(struct ib_srq *ibsrq, struct ib_srq_attr *attr,
                      enum ib_srq_attr_mask attr_mask);
 int mthca_query_srq(struct ib_srq *srq, struct ib_srq_attr *srq_attr);
+int mthca_max_srq_sge(struct mthca_dev *dev);
 void mthca_srq_event(struct mthca_dev *dev, u32 srqn,
                      enum ib_event_type event_type);
 void mthca_free_srq_wqe(struct mthca_srq *srq, u32 wqe_addr);
diff --git a/drivers/infiniband/hw/mthca/mthca_main.c b/drivers/infiniband/hw/mthca/mthca_main.c
index 7e9c97b09404..9b9ff7bff357 100644
--- a/drivers/infiniband/hw/mthca/mthca_main.c
+++ b/drivers/infiniband/hw/mthca/mthca_main.c
@@ -191,6 +191,7 @@ static int __devinit mthca_dev_lim(struct mthca_dev *mdev, struct mthca_dev_lim
         mdev->limits.reserved_srqs      = dev_lim->reserved_srqs;
         mdev->limits.reserved_eecs      = dev_lim->reserved_eecs;
         mdev->limits.max_desc_sz        = dev_lim->max_desc_sz;
+        mdev->limits.max_srq_sge        = mthca_max_srq_sge(mdev);
         /*
          * Subtract 1 from the limit because we need to allocate a
          * spare CQE so the HCA HW can tell the difference between an
diff --git a/drivers/infiniband/hw/mthca/mthca_provider.c b/drivers/infiniband/hw/mthca/mthca_provider.c
index 2c250bc11c33..565a24b1756f 100644
--- a/drivers/infiniband/hw/mthca/mthca_provider.c
+++ b/drivers/infiniband/hw/mthca/mthca_provider.c
@@ -106,7 +106,7 @@ static int mthca_query_device(struct ib_device *ibdev,
         props->max_res_rd_atom     = props->max_qp_rd_atom * props->max_qp;
         props->max_srq             = mdev->limits.num_srqs - mdev->limits.reserved_srqs;
         props->max_srq_wr          = mdev->limits.max_srq_wqes;
-        props->max_srq_sge         = mdev->limits.max_sg;
+        props->max_srq_sge         = mdev->limits.max_srq_sge;
         props->local_ca_ack_delay  = mdev->limits.local_ca_ack_delay;
         props->atomic_cap          = mdev->limits.flags & DEV_LIM_FLAG_ATOMIC ?
                                         IB_ATOMIC_HCA : IB_ATOMIC_NONE;
diff --git a/drivers/infiniband/hw/mthca/mthca_srq.c b/drivers/infiniband/hw/mthca/mthca_srq.c
index 2dd3aea05341..adcaf85355ae 100644
--- a/drivers/infiniband/hw/mthca/mthca_srq.c
+++ b/drivers/infiniband/hw/mthca/mthca_srq.c
@@ -192,7 +192,7 @@ int mthca_alloc_srq(struct mthca_dev *dev, struct mthca_pd *pd,
 
         /* Sanity check SRQ size before proceeding */
         if (attr->max_wr  > dev->limits.max_srq_wqes ||
-            attr->max_sge > dev->limits.max_sg)
+            attr->max_sge > dev->limits.max_srq_sge)
                 return -EINVAL;
 
         srq->max      = attr->max_wr;
@@ -660,6 +660,31 @@ int mthca_arbel_post_srq_recv(struct ib_srq *ibsrq, struct ib_recv_wr *wr,
         return err;
 }
 
+int mthca_max_srq_sge(struct mthca_dev *dev)
+{
+        if (mthca_is_memfree(dev))
+                return dev->limits.max_sg;
+
+        /*
+         * SRQ allocations are based on powers of 2 for Tavor,
+         * (although they only need to be multiples of 16 bytes).
+         *
+         * Therefore, we need to base the max number of sg entries on
+         * the largest power of 2 descriptor size that is <= to the
+         * actual max WQE descriptor size, rather than return the
+         * max_sg value given by the firmware (which is based on WQE
+         * sizes as multiples of 16, not powers of 2).
+         *
+         * If SRQ implementation is changed for Tavor to be based on
+         * multiples of 16, the calculation below can be deleted and
+         * the FW max_sg value returned.
+         */
+        return min_t(int, dev->limits.max_sg,
+                     ((1 << (fls(dev->limits.max_desc_sz) - 1)) -
+                      sizeof (struct mthca_next_seg)) /
+                     sizeof (struct mthca_data_seg));
+}
+
 int __devinit mthca_init_srq_table(struct mthca_dev *dev)
 {
         int err;