[PATCH][2/3] IPoIB: fix static rate calculation

Roland Dreier
2005-04-01T03:59:01Z

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>

--- linux-export.orig/drivers/infiniband/ulp/ipoib/ipoib_main.c 2005-03-31 19:06:47.984714505 -0800
+++ linux-export/drivers/infiniband/ulp/ipoib/ipoib_main.c 2005-03-31 19:26:39.094134171 -0800
@@ -302,11 +302,10 @@
.sl = pathrec->sl,
.port_num = priv->port
};
+ int path_rate = ib_sa_rate_enum_to_int(pathrec->rate);

- if (ib_sa_rate_enum_to_int(pathrec->rate) > 0)
- av.static_rate = (2 * priv->local_rate -
- ib_sa_rate_enum_to_int(pathrec->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(priv, "static_rate %d for local port %dX, path %dX\n",
av.static_rate, priv->local_rate,
--- linux-export.orig/drivers/infiniband/ulp/ipoib/ipoib_multicast.c 2005-03-31 19:07:01.877698296 -0800
+++ linux-export/drivers/infiniband/ulp/ipoib/ipoib_multicast.c 2005-03-31 19:26:03.861782487 -0800
@@ -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,