mac80211: minstrel: Change expected throughput unit back to Kbps

BugLink: http://bugs.launchpad.net/bugs/1558330

commit 212c5a5e upstream.

The change from cur_tp to the function
minstrel_get_tp_avg/minstrel_ht_get_tp_avg changed the unit used for the
current throughput. For example in minstrel_ht the correct
conversion between them would be:

    mrs->cur_tp / 10 == minstrel_ht_get_tp_avg(..).

This factor 10 must also be included in the calculation of
minstrel_get_expected_throughput and minstrel_ht_get_expected_throughput to
return values with the unit [Kbps] instead of [10Kbps]. Otherwise routing
algorithms like B.A.T.M.A.N. V will make incorrect decision based on these
values. Its kernel based implementation expects expected_throughput always
to have the unit [Kbps] and not sometimes [10Kbps] and sometimes [Kbps].

The same requirement has iw or olsrdv2's nl80211 based statistics module
which retrieve the same data via NL80211_STA_INFO_TX_BITRATE.

Fixes: 6a27b2c4 ("mac80211: restructure per-rate throughput calculation into function")
Signed-off-by: Sven Eckelmann <sven@open-mesh.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

net/mac80211/rc80211_minstrel.c

@@ -711,7 +711,7 @@ static u32 minstrel_get_expected_throughput(void *priv_sta)
 	 * computing cur_tp
 	 */
 	tmp_mrs = &mi->r[idx].stats;
-	tmp_cur_tp = minstrel_get_tp_avg(&mi->r[idx], tmp_mrs->prob_ewma);
+	tmp_cur_tp = minstrel_get_tp_avg(&mi->r[idx], tmp_mrs->prob_ewma) * 10;
 	tmp_cur_tp = tmp_cur_tp * 1200 * 8 / 1024;
 
 	return tmp_cur_tp;

net/mac80211/rc80211_minstrel_ht.c

@@ -1334,7 +1334,8 @@ static u32 minstrel_ht_get_expected_throughput(void *priv_sta)
 	prob = mi->groups[i].rates[j].prob_ewma;
 
 	/* convert tp_avg from pkt per second in kbps */
-	tp_avg = minstrel_ht_get_tp_avg(mi, i, j, prob) * AVG_PKT_SIZE * 8 / 1024;
+	tp_avg = minstrel_ht_get_tp_avg(mi, i, j, prob) * 10;
+	tp_avg = tp_avg * AVG_PKT_SIZE * 8 / 1024;
 
 	return tp_avg;
 }