iwlagn: Enable/disable PS poll based on RSSI and BT coex traffic state

WiFi throughput drops drastically when BT is turned on, BT and WiFi
are simultaneously transmitting/receiving traffic. This is particularly true
when BT has higher priority over WiFi, and hence the device defers TX frames.
The AP assumes that the channel is bad and reduces the data rate, implying
longer airtime, which exacerbates the problem further, resulting ultimately
in what is popularly called the "death-spiral" phenomenon. The use of PS-poll
in such scenarios guarantees a low but consistent throughput.

Since the death-spiral phenomenon is observed only when the RSSI is low, use
PS-poll only when RSSI is low and disable when high, with a known hysterisis.

This feature specifies the high and low thresholds and implements the
callbacks registered with mac80211, which will be called when threshold events
occur.

iwlwifi: dynamic pspoll: optimize rssi monitor code

Signed-off-by: Meenakshi Venkataraman <meenakshi.venkataraman@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-agn.c b/drivers/net/wireless/iwlwifi/iwl-agn.c
index 3a4fca14fef8..cbd8d101f6f8 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn.c
+++ b/drivers/net/wireless/iwlwifi/iwl-agn.c
@@ -2015,11 +2015,18 @@ int iwl_alive_start(struct iwl_priv *priv)
         if (priv->cfg->bt_params &&
             priv->cfg->bt_params->advanced_bt_coexist) {
                 /* Configure Bluetooth device coexistence support */
+                if (priv->cfg->bt_params->bt_sco_disable)
+                        priv->bt_enable_pspoll = false;
+                else
+                        priv->bt_enable_pspoll = true;
+
                 priv->bt_valid = IWLAGN_BT_ALL_VALID_MSK;
                 priv->kill_ack_mask = IWLAGN_BT_KILL_ACK_MASK_DEFAULT;
                 priv->kill_cts_mask = IWLAGN_BT_KILL_CTS_MASK_DEFAULT;
                 iwlagn_send_advance_bt_config(priv);
                 priv->bt_valid = IWLAGN_BT_VALID_ENABLE_FLAGS;
+                priv->cur_rssi_ctx = NULL;
+
                 iwlagn_send_prio_tbl(priv);
 
                 /* FIXME: w/a to force change uCode BT state machine */
@@ -2102,6 +2109,8 @@ static void __iwl_down(struct iwl_priv *priv)
 
         /* reset BT coex data */
         priv->bt_status = 0;
+        priv->cur_rssi_ctx = NULL;
+        priv->bt_is_sco = 0;
         if (priv->cfg->bt_params)
                 priv->bt_traffic_load =
                          priv->cfg->bt_params->bt_init_traffic_load;
@@ -2277,6 +2286,7 @@ static void iwlagn_prepare_restart(struct iwl_priv *priv)
         u8 bt_ci_compliance;
         u8 bt_load;
         u8 bt_status;
+        bool bt_is_sco;
 
         lockdep_assert_held(&priv->mutex);
 
@@ -2297,6 +2307,7 @@ static void iwlagn_prepare_restart(struct iwl_priv *priv)
         bt_ci_compliance = priv->bt_ci_compliance;
         bt_load = priv->bt_traffic_load;
         bt_status = priv->bt_status;
+        bt_is_sco = priv->bt_is_sco;
 
         __iwl_down(priv);
 
@@ -2304,6 +2315,7 @@ static void iwlagn_prepare_restart(struct iwl_priv *priv)
         priv->bt_ci_compliance = bt_ci_compliance;
         priv->bt_traffic_load = bt_load;
         priv->bt_status = bt_status;
+        priv->bt_is_sco = bt_is_sco;
 }
 
 static void iwl_bg_restart(struct work_struct *data)
@@ -3330,6 +3342,29 @@ static void iwl_uninit_drv(struct iwl_priv *priv)
         kfree(priv->beacon_cmd);
 }
 
+void iwl_mac_rssi_callback(struct ieee80211_hw *hw,
+                           enum ieee80211_rssi_event rssi_event)
+{
+        struct iwl_priv *priv = hw->priv;
+
+        mutex_lock(&priv->mutex);
+
+        if (priv->cfg->bt_params &&
+                        priv->cfg->bt_params->advanced_bt_coexist) {
+                if (rssi_event == RSSI_EVENT_LOW)
+                        priv->bt_enable_pspoll = true;
+                else if (rssi_event == RSSI_EVENT_HIGH)
+                        priv->bt_enable_pspoll = false;
+
+                iwlagn_send_advance_bt_config(priv);
+        } else {
+                IWL_DEBUG_MAC80211(priv, "Advanced BT coex disabled,"
+                                "ignoring RSSI callback\n");
+        }
+
+        mutex_unlock(&priv->mutex);
+}
+
 struct ieee80211_ops iwlagn_hw_ops = {
         .tx = iwlagn_mac_tx,
         .start = iwlagn_mac_start,
@@ -3355,6 +3390,7 @@ struct ieee80211_ops iwlagn_hw_ops = {
         .cancel_remain_on_channel = iwl_mac_cancel_remain_on_channel,
         .offchannel_tx = iwl_mac_offchannel_tx,
         .offchannel_tx_cancel_wait = iwl_mac_offchannel_tx_cancel_wait,
+        .rssi_callback = iwl_mac_rssi_callback,
         CFG80211_TESTMODE_CMD(iwl_testmode_cmd)
         CFG80211_TESTMODE_DUMP(iwl_testmode_dump)
 };