[PATCH] ipw2200: Exponential averaging for signal and noise Level

This patch replaces sliding averaging by exponential averaging for
reporting the wireless statistics for signal and noise level for ipw2200.
See details from: http://www.ces.clemson.edu/linux/ipw2200_averages.shtml

Signed-off-by: Bill Moss <bmoss@clemson.edu>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 22 insertions, 18 deletions

diff --git a/drivers/net/wireless/ipw2200.c b/drivers/net/wireless/ipw2200.c
index bca89cff85a6..a879edba5fac 100644
--- a/drivers/net/wireless/ipw2200.c
+++ b/drivers/net/wireless/ipw2200.c
@@ -3771,6 +3771,13 @@ static void inline average_init(struct average *avg)
         memset(avg, 0, sizeof(*avg));
 }
 
+#define DEPTH_RSSI 8
+#define DEPTH_NOISE 16
+static s16 exponential_average(s16 prev_avg, s16 val, u8 depth)
+{
+        return ((depth-1)*prev_avg +  val)/depth;
+}
+
 static void average_add(struct average *avg, s16 val)
 {
         avg->sum -= avg->entries[avg->pos];
@@ -3800,8 +3807,8 @@ static void ipw_reset_stats(struct ipw_priv *priv)
         priv->quality = 0;
 
         average_init(&priv->average_missed_beacons);
-        average_init(&priv->average_rssi);
-        average_init(&priv->average_noise);
+        priv->exp_avg_rssi = -60;
+        priv->exp_avg_noise = -85 + 0x100;
 
         priv->last_rate = 0;
         priv->last_missed_beacons = 0;
@@ -4008,7 +4015,7 @@ static void ipw_gather_stats(struct ipw_priv *priv)
         IPW_DEBUG_STATS("Tx quality   : %3d%% (%u errors, %u packets)\n",
                         tx_quality, tx_failures_delta, tx_packets_delta);
 
-        rssi = average_value(&priv->average_rssi);
+        rssi = priv->exp_avg_rssi;
         signal_quality =
             (100 *
              (priv->ieee->perfect_rssi - priv->ieee->worst_rssi) *
@@ -4023,7 +4030,7 @@ static void ipw_gather_stats(struct ipw_priv *priv)
         else if (signal_quality < 1)
                 signal_quality = 0;
 
-        IPW_DEBUG_STATS("Signal level : %3d%% (%d dBm)\n",
+        IPW_ERROR("Signal level : %3d%% (%d dBm)\n",
                         signal_quality, rssi);
 
         quality = min(beacon_quality,
@@ -4577,11 +4584,10 @@ static void ipw_rx_notification(struct ipw_priv *priv,
 
         case HOST_NOTIFICATION_NOISE_STATS:{
                         if (notif->size == sizeof(u32)) {
-                                priv->last_noise =
-                                    (u8) (le32_to_cpu(notif->u.noise.value) &
-                                          0xff);
-                                average_add(&priv->average_noise,
-                                            priv->last_noise);
+                                priv->exp_avg_noise =
+                                    exponential_average(priv->exp_avg_noise,
+                                    (u8) (le32_to_cpu(notif->u.noise.value) & 0xff),
+                                    DEPTH_NOISE);
                                 break;
                         }
 
@@ -7837,9 +7843,9 @@ static void ipw_rx(struct ipw_priv *priv)
                                 if (network_packet && priv->assoc_network) {
                                         priv->assoc_network->stats.rssi =
                                             stats.rssi;
-                                        average_add(&priv->average_rssi,
-                                                    stats.rssi);
-                                        priv->last_rx_rssi = stats.rssi;
+                                        priv->exp_avg_rssi =
+                                            exponential_average(priv->exp_avg_rssi,
+                                            stats.rssi, DEPTH_RSSI);
                                 }
 
                                 IPW_DEBUG_RX("Frame: len=%u\n",
@@ -9579,8 +9585,8 @@ static struct iw_statistics *ipw_get_wireless_stats(struct net_device *dev)
         }
 
         wstats->qual.qual = priv->quality;
-        wstats->qual.level = average_value(&priv->average_rssi);
-        wstats->qual.noise = average_value(&priv->average_noise);
+        wstats->qual.level = priv->exp_avg_rssi;
+        wstats->qual.noise = priv->exp_avg_noise;
         wstats->qual.updated = IW_QUAL_QUAL_UPDATED | IW_QUAL_LEVEL_UPDATED |
             IW_QUAL_NOISE_UPDATED | IW_QUAL_DBM;
 
diff --git a/drivers/net/wireless/ipw2200.h b/drivers/net/wireless/ipw2200.h
index 4b9804900702..1f2cab3f9944 100644
--- a/drivers/net/wireless/ipw2200.h
+++ b/drivers/net/wireless/ipw2200.h
@@ -1153,11 +1153,9 @@ struct ipw_priv {
         u32 config;
         u32 capability;
 
-        u8 last_rx_rssi;
-        u8 last_noise;
         struct average average_missed_beacons;
-        struct average average_rssi;
-        struct average average_noise;
+        s16 exp_avg_rssi;
+        s16 exp_avg_noise;
         u32 port_type;
         int rx_bufs_min;          /**< minimum number of bufs in Rx queue */
         int rx_pend_max;          /**< maximum pending buffers for one IRQ */