IB/mthca: correct log2 calculation

Fix thinko in rd_atomic calculation: ffs(x) - 1 does not find the next
power of 2 -- it should be fls(x - 1).

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

diff --git a/drivers/infiniband/hw/mthca/mthca_qp.c b/drivers/infiniband/hw/mthca/mthca_qp.c
index c5c3d0e..84056a8 100644 (file)
--- a/drivers/infiniband/hw/mthca/mthca_qp.c
+++ b/drivers/infiniband/hw/mthca/mthca_qp.c
@@ -728,9 +728,9 @@ int mthca_modify_qp(struct ib_qp *ibqp, struct ib_qp_attr *attr, int attr_mask)
        }
 
        if (attr_mask & IB_QP_MAX_QP_RD_ATOMIC) {
-               qp_context->params1 |= cpu_to_be32(min(attr->max_rd_atomic ?
-                                                      ffs(attr->max_rd_atomic) - 1 : 0,
-                                                      7) << 21);
+               if (attr->max_rd_atomic)
+                       qp_context->params1 |=
+                               cpu_to_be32(fls(attr->max_rd_atomic - 1) << 21);
                qp_param->opt_param_mask |= cpu_to_be32(MTHCA_QP_OPTPAR_SRA_MAX);
        }
 
@@ -769,8 +769,6 @@ int mthca_modify_qp(struct ib_qp *ibqp, struct ib_qp_attr *attr, int attr_mask)
        }
 
        if (attr_mask & IB_QP_MAX_DEST_RD_ATOMIC) {
-               u8 rra_max;
-
                if (qp->resp_depth && !attr->max_dest_rd_atomic) {
                        /*
                         * Lowering our responder resources to zero.
@@ -798,13 +796,10 @@ int mthca_modify_qp(struct ib_qp *ibqp, struct ib_qp_attr *attr, int attr_mask)
                                                                MTHCA_QP_OPTPAR_RAE);
                }
 
-               for (rra_max = 0;
-                    1 << rra_max < attr->max_dest_rd_atomic &&
-                            rra_max < dev->qp_table.rdb_shift;
-                    ++rra_max)
-                       ; /* nothing */
+               if (attr->max_dest_rd_atomic)
+                       qp_context->params2 |=
+                               cpu_to_be32(fls(attr->max_dest_rd_atomic - 1) << 21);
 
-               qp_context->params2      |= cpu_to_be32(rra_max << 21);
                qp_param->opt_param_mask |= cpu_to_be32(MTHCA_QP_OPTPAR_RRA_MAX);
 
                qp->resp_depth = attr->max_dest_rd_atomic;