[PATCH] rt2x00: Implement SW diversity

When mac80211 indicates that the default antenna setup
should be used _and_ that this default setup is SW_DIVERSITY.

This requires sampling and storing the RSSI per antenna
and check once every 2 seconds to determine if the RSSI
has changed significantly. Once this is the case we should sample
the other antenna for a short period and evaluate if
we need to swap antenna or not.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 135 insertions, 3 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2x00dev.c b/drivers/net/wireless/rt2x00/rt2x00dev.c
index 0f824b27f1e..360f03ae17a 100644
--- a/drivers/net/wireless/rt2x00/rt2x00dev.c
+++ b/drivers/net/wireless/rt2x00/rt2x00dev.c
@@ -193,6 +193,133 @@ void rt2x00lib_toggle_rx(struct rt2x00_dev *rt2x00dev, enum dev_state state)
                 rt2x00lib_start_link_tuner(rt2x00dev);
 }
 
+static void rt2x00lib_evaluate_antenna_sample(struct rt2x00_dev *rt2x00dev)
+{
+        enum antenna rx = rt2x00dev->link.ant.active.rx;
+        enum antenna tx = rt2x00dev->link.ant.active.tx;
+        int sample_a =
+            rt2x00_get_link_ant_rssi_history(&rt2x00dev->link, ANTENNA_A);
+        int sample_b =
+            rt2x00_get_link_ant_rssi_history(&rt2x00dev->link, ANTENNA_B);
+
+        /*
+         * We are done sampling. Now we should evaluate the results.
+         */
+        rt2x00dev->link.ant.flags &= ~ANTENNA_MODE_SAMPLE;
+
+        /*
+         * During the last period we have sampled the RSSI
+         * from both antenna's. It now is time to determine
+         * which antenna demonstrated the best performance.
+         * When we are already on the antenna with the best
+         * performance, then there really is nothing for us
+         * left to do.
+         */
+        if (sample_a == sample_b)
+                return;
+
+        if (rt2x00dev->link.ant.flags & ANTENNA_RX_DIVERSITY) {
+                if (sample_a > sample_b && rx == ANTENNA_B)
+                        rx = ANTENNA_A;
+                else if (rx == ANTENNA_A)
+                        rx = ANTENNA_B;
+        }
+
+        if (rt2x00dev->link.ant.flags & ANTENNA_TX_DIVERSITY) {
+                if (sample_a > sample_b && tx == ANTENNA_B)
+                        tx = ANTENNA_A;
+                else if (tx == ANTENNA_A)
+                        tx = ANTENNA_B;
+        }
+
+        rt2x00lib_config_antenna(rt2x00dev, rx, tx);
+}
+
+static void rt2x00lib_evaluate_antenna_eval(struct rt2x00_dev *rt2x00dev)
+{
+        enum antenna rx = rt2x00dev->link.ant.active.rx;
+        enum antenna tx = rt2x00dev->link.ant.active.tx;
+        int rssi_curr = rt2x00_get_link_ant_rssi(&rt2x00dev->link);
+        int rssi_old = rt2x00_update_ant_rssi(&rt2x00dev->link, rssi_curr);
+
+        /*
+         * Legacy driver indicates that we should swap antenna's
+         * when the difference in RSSI is greater that 5. This
+         * also should be done when the RSSI was actually better
+         * then the previous sample.
+         * When the difference exceeds the threshold we should
+         * sample the rssi from the other antenna to make a valid
+         * comparison between the 2 antennas.
+         */
+        if ((rssi_curr - rssi_old) > -5 || (rssi_curr - rssi_old) < 5)
+                return;
+
+        rt2x00dev->link.ant.flags |= ANTENNA_MODE_SAMPLE;
+
+        if (rt2x00dev->link.ant.flags & ANTENNA_RX_DIVERSITY)
+                rx = (rx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;
+
+        if (rt2x00dev->link.ant.flags & ANTENNA_TX_DIVERSITY)
+                tx = (tx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;
+
+        rt2x00lib_config_antenna(rt2x00dev, rx, tx);
+}
+
+static void rt2x00lib_evaluate_antenna(struct rt2x00_dev *rt2x00dev)
+{
+        /*
+         * Determine if software diversity is enabled for
+         * either the TX or RX antenna (or both).
+         * Always perform this check since within the link
+         * tuner interval the configuration might have changed.
+         */
+        rt2x00dev->link.ant.flags &= ~ANTENNA_RX_DIVERSITY;
+        rt2x00dev->link.ant.flags &= ~ANTENNA_TX_DIVERSITY;
+
+        if (rt2x00dev->hw->conf.antenna_sel_rx == 0 &&
+            rt2x00dev->default_ant.rx != ANTENNA_SW_DIVERSITY)
+                rt2x00dev->link.ant.flags |= ANTENNA_RX_DIVERSITY;
+        if (rt2x00dev->hw->conf.antenna_sel_tx == 0 &&
+            rt2x00dev->default_ant.tx != ANTENNA_SW_DIVERSITY)
+                rt2x00dev->link.ant.flags |= ANTENNA_TX_DIVERSITY;
+
+        if (!(rt2x00dev->link.ant.flags & ANTENNA_RX_DIVERSITY) &&
+            !(rt2x00dev->link.ant.flags & ANTENNA_TX_DIVERSITY)) {
+                rt2x00dev->link.ant.flags &= ~ANTENNA_MODE_SAMPLE;
+                return;
+        }
+
+        /*
+         * If we have only sampled the data over the last period
+         * we should now harvest the data. Otherwise just evaluate
+         * the data. The latter should only be performed once
+         * every 2 seconds.
+         */
+        if (rt2x00dev->link.ant.flags & ANTENNA_MODE_SAMPLE)
+                rt2x00lib_evaluate_antenna_sample(rt2x00dev);
+        else if (rt2x00dev->link.count & 1)
+                rt2x00lib_evaluate_antenna_eval(rt2x00dev);
+}
+
+static void rt2x00lib_update_link_stats(struct link *link, int rssi)
+{
+        int avg_rssi = rssi;
+
+        /*
+         * Update global RSSI
+         */
+        if (link->qual.avg_rssi)
+                avg_rssi = MOVING_AVERAGE(link->qual.avg_rssi, rssi, 8);
+        link->qual.avg_rssi = avg_rssi;
+
+        /*
+         * Update antenna RSSI
+         */
+        if (link->ant.rssi_ant)
+                rssi = MOVING_AVERAGE(link->ant.rssi_ant, rssi, 8);
+        link->ant.rssi_ant = rssi;
+}
+
 static void rt2x00lib_precalculate_link_signal(struct link_qual *qual)
 {
         if (qual->rx_failed || qual->rx_success)
@@ -261,7 +388,6 @@ static void rt2x00lib_link_tuner(struct work_struct *work)
          * Update statistics.
          */
         rt2x00dev->ops->lib->link_stats(rt2x00dev, &rt2x00dev->link.qual);
-
         rt2x00dev->low_level_stats.dot11FCSErrorCount +=
             rt2x00dev->link.qual.rx_failed;
 
@@ -273,6 +399,11 @@ static void rt2x00lib_link_tuner(struct work_struct *work)
                 rt2x00dev->ops->lib->link_tuner(rt2x00dev);
 
         /*
+         * Evaluate antenna setup.
+         */
+        rt2x00lib_evaluate_antenna(rt2x00dev);
+
+        /*
          * Precalculate a portion of the link signal which is
          * in based on the tx/rx success/failure counters.
          */
@@ -426,14 +557,15 @@ void rt2x00lib_rxdone(struct data_entry *entry, struct sk_buff *skb,
                 }
         }
 
-        rt2x00_update_link_rssi(&rt2x00dev->link, desc->rssi);
+        rt2x00lib_update_link_stats(&rt2x00dev->link, desc->rssi);
         rt2x00dev->link.qual.rx_success++;
+
         rx_status->rate = val;
         rx_status->signal =
             rt2x00lib_calculate_link_signal(rt2x00dev, desc->rssi);
         rx_status->ssi = desc->rssi;
         rx_status->flag = desc->flags;
-        rx_status->antenna = rt2x00dev->link.active_ant.rx;
+        rx_status->antenna = rt2x00dev->link.ant.active.rx;
 
         /*
          * Send frame to mac80211