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, 104 insertions, 2 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-agn-lib.c b/drivers/net/wireless/iwlwifi/iwl-agn-lib.c
index 94f6d606866..eb2be0d3048 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn-lib.c
+++ b/drivers/net/wireless/iwlwifi/iwl-agn-lib.c
@@ -1634,9 +1634,11 @@ void iwlagn_send_advance_bt_config(struct iwl_priv *priv)
 	} else {
 		basic.flags = IWLAGN_BT_FLAG_COEX_MODE_3W <<
 					IWLAGN_BT_FLAG_COEX_MODE_SHIFT;
-		if (priv->cfg->bt_params &&
-		    priv->cfg->bt_params->bt_sco_disable)
+
+		if (!priv->bt_enable_pspoll)
 			basic.flags |= IWLAGN_BT_FLAG_SYNC_2_BT_DISABLE;
+		else
+			basic.flags &= ~IWLAGN_BT_FLAG_SYNC_2_BT_DISABLE;
 
 		if (priv->bt_ch_announce)
 			basic.flags |= IWLAGN_BT_FLAG_CHANNEL_INHIBITION;
@@ -1671,6 +1673,84 @@ void iwlagn_send_advance_bt_config(struct iwl_priv *priv)
 
 }
 
+void iwlagn_bt_adjust_rssi_monitor(struct iwl_priv *priv, bool rssi_ena)
+{
+	struct iwl_rxon_context *ctx, *found_ctx = NULL;
+	bool found_ap = false;
+
+	lockdep_assert_held(&priv->mutex);
+
+	/* Check whether AP or GO mode is active. */
+	if (rssi_ena) {
+		for_each_context(priv, ctx) {
+			if (ctx->vif && ctx->vif->type == NL80211_IFTYPE_AP &&
+			    iwl_is_associated_ctx(ctx)) {
+				found_ap = true;
+				break;
+			}
+		}
+	}
+
+	/*
+	 * If disable was received or If GO/AP mode, disable RSSI
+	 * measurements.
+	 */
+	if (!rssi_ena || found_ap) {
+		if (priv->cur_rssi_ctx) {
+			ctx = priv->cur_rssi_ctx;
+			ieee80211_disable_rssi_reports(ctx->vif);
+			priv->cur_rssi_ctx = NULL;
+		}
+		return;
+	}
+
+	/*
+	 * If rssi measurements need to be enabled, consider all cases now.
+	 * Figure out how many contexts are active.
+	 */
+	for_each_context(priv, ctx) {
+		if (ctx->vif && ctx->vif->type == NL80211_IFTYPE_STATION &&
+		    iwl_is_associated_ctx(ctx)) {
+			found_ctx = ctx;
+			break;
+		}
+	}
+
+	/*
+	 * rssi monitor already enabled for the correct interface...nothing
+	 * to do.
+	 */
+	if (found_ctx == priv->cur_rssi_ctx)
+		return;
+
+	/*
+	 * Figure out if rssi monitor is currently enabled, and needs
+	 * to be changed. If rssi monitor is already enabled, disable
+	 * it first else just enable rssi measurements on the
+	 * interface found above.
+	 */
+	if (priv->cur_rssi_ctx) {
+		ctx = priv->cur_rssi_ctx;
+		if (ctx->vif)
+			ieee80211_disable_rssi_reports(ctx->vif);
+	}
+
+	priv->cur_rssi_ctx = found_ctx;
+
+	if (!found_ctx)
+		return;
+
+	ieee80211_enable_rssi_reports(found_ctx->vif,
+			IWLAGN_BT_PSP_MIN_RSSI_THRESHOLD,
+			IWLAGN_BT_PSP_MAX_RSSI_THRESHOLD);
+}
+
+static bool iwlagn_bt_traffic_is_sco(struct iwl_bt_uart_msg *uart_msg)
+{
+	return BT_UART_MSG_FRAME3SCOESCO_MSK & uart_msg->frame3 >>
+			BT_UART_MSG_FRAME3SCOESCO_POS;
+}
+
 static void iwlagn_bt_traffic_change_work(struct work_struct *work)
 {
 	struct iwl_priv *priv =
@@ -1732,10 +1812,30 @@ static void iwlagn_bt_traffic_change_work(struct work_struct *work)
 				ieee80211_request_smps(ctx->vif, smps_request);
 		}
 	}
+
+	/*
+	 * Dynamic PS poll related functionality. Adjust RSSI measurements if
+	 * necessary.
+	 */
+	iwlagn_bt_coex_rssi_monitor(priv);
 out:
 	mutex_unlock(&priv->mutex);
 }
 
+/*
+ * If BT sco traffic, and RSSI monitor is enabled, move measurements to the
+ * correct interface or disable it if this is the last interface to be
+ * removed.
+ */
+void iwlagn_bt_coex_rssi_monitor(struct iwl_priv *priv)
+{
+	if (priv->bt_is_sco &&
+	    priv->bt_traffic_load == IWL_BT_COEX_TRAFFIC_LOAD_CONTINUOUS)
+		iwlagn_bt_adjust_rssi_monitor(priv, true);
+	else
+		iwlagn_bt_adjust_rssi_monitor(priv, false);
+}
+
 static void iwlagn_print_uartmsg(struct iwl_priv *priv,
 				struct iwl_bt_uart_msg *uart_msg)
 {
@@ -1851,6 +1951,8 @@ void iwlagn_bt_coex_profile_notif(struct iwl_priv *priv,
 	iwlagn_print_uartmsg(priv, uart_msg);
 
 	priv->last_bt_traffic_load = priv->bt_traffic_load;
+	priv->bt_is_sco = iwlagn_bt_traffic_is_sco(uart_msg);
+
 	if (priv->iw_mode != NL80211_IFTYPE_ADHOC) {
 		if (priv->bt_status != coex->bt_status ||
 		    priv->last_bt_traffic_load != coex->bt_traffic_load) {