IB/mlx5: Fix reported max SGE calculation

Add the 512 bytes limit of RDMA READ and the size of remote
address to the max SGE calculation.

Fixes: e126ba97dba9 ('mlx5: Add driver for Mellanox Connect-IB adapters')
Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
index 16ac41d..46facd3 100644
--- a/drivers/infiniband/hw/mlx5/main.c
+++ b/drivers/infiniband/hw/mlx5/main.c
@@ -496,6 +496,7 @@ static int mlx5_ib_query_device(struct ib_device *ibdev,
 	struct mlx5_ib_dev *dev = to_mdev(ibdev);
 	struct mlx5_core_dev *mdev = dev->mdev;
 	int err = -ENOMEM;
+	int max_sq_desc;
 	int max_rq_sg;
 	int max_sq_sg;
 	u64 min_page_size = 1ull << MLX5_CAP_GEN(mdev, log_pg_sz);
@@ -618,9 +619,10 @@ static int mlx5_ib_query_device(struct ib_device *ibdev,
 	props->max_qp_wr	   = 1 << MLX5_CAP_GEN(mdev, log_max_qp_sz);
 	max_rq_sg =  MLX5_CAP_GEN(mdev, max_wqe_sz_rq) /
 		     sizeof(struct mlx5_wqe_data_seg);
-	max_sq_sg = (MLX5_CAP_GEN(mdev, max_wqe_sz_sq) -
-		     sizeof(struct mlx5_wqe_ctrl_seg)) /
-		     sizeof(struct mlx5_wqe_data_seg);
+	max_sq_desc = min_t(int, MLX5_CAP_GEN(mdev, max_wqe_sz_sq), 512);
+	max_sq_sg = (max_sq_desc - sizeof(struct mlx5_wqe_ctrl_seg) -
+		     sizeof(struct mlx5_wqe_raddr_seg)) /
+		sizeof(struct mlx5_wqe_data_seg);
 	props->max_sge = min(max_rq_sg, max_sq_sg);
 	props->max_sge_rd	   = MLX5_MAX_SGE_RD;
 	props->max_cq		   = 1 << MLX5_CAP_GEN(mdev, log_max_cq);