[PATCH] IPoIB: fix static rate calculation
Correct and simplify calculation of static rate. We need to round up the
quotient of (local_rate - path_rate) / path_rate. To round up we add
(path_rate - 1) to the numerator, so the quotient simplifies to (local_rate -
1) / path_rate.
No idea how I came up with the old formula.
Signed-off-by: Roland Dreier <roland@topspin.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
index f46932d..70208c3 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
@@ -258,13 +258,12 @@
.traffic_class = mcast->mcmember.traffic_class
}
};
+ int path_rate = ib_sa_rate_enum_to_int(mcast->mcmember.rate);
av.grh.dgid = mcast->mcmember.mgid;
- if (ib_sa_rate_enum_to_int(mcast->mcmember.rate) > 0)
- av.static_rate = (2 * priv->local_rate -
- ib_sa_rate_enum_to_int(mcast->mcmember.rate) - 1) /
- (priv->local_rate ? priv->local_rate : 1);
+ if (path_rate > 0 && priv->local_rate > path_rate)
+ av.static_rate = (priv->local_rate - 1) / path_rate;
ipoib_dbg_mcast(priv, "static_rate %d for local port %dX, mcmember %dX\n",
av.static_rate, priv->local_rate,