ath9k_htc: Fix beacon miss under heavy load

Transmission of beacons becomes erratic when TX load
is high, since the latency involved in the generation
of a SWBA interrupt on the target to the actual sending
of a beacon is quite high for USB devices.

Fix this by adjusting the beacon response time.

Signed-off-by: Sujith Manoharan <Sujith.Manoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/htc.h

@@ -358,6 +358,13 @@ struct ath_led {
 
 #define BSTUCK_THRESHOLD 10
 
+/*
+ * Adjust these when the max. no of beaconing interfaces is
+ * increased.
+ */
+#define DEFAULT_SWBA_RESPONSE 40 /* in TUs */
+#define MIN_SWBA_RESPONSE     10 /* in TUs */
+
 struct htc_beacon_config {
 	struct ieee80211_vif *bslot[ATH9K_HTC_MAX_BCN_VIF];
 	u16 beacon_interval;

drivers/net/wireless/ath/ath9k/htc_drv_beacon.c

@@ -198,6 +198,15 @@ static void ath9k_htc_beacon_config_ap(struct ath9k_htc_priv *priv,
 	intval /= ATH9K_HTC_MAX_BCN_VIF;
 	nexttbtt = intval;
 
+	/*
+	 * To reduce beacon misses under heavy TX load,
+	 * set the beacon response time to a larger value.
+	 */
+	if (intval > DEFAULT_SWBA_RESPONSE)
+		priv->ah->config.sw_beacon_response_time = DEFAULT_SWBA_RESPONSE;
+	else
+		priv->ah->config.sw_beacon_response_time = MIN_SWBA_RESPONSE;
+
 	if (priv->op_flags & OP_TSF_RESET) {
 		ath9k_hw_reset_tsf(priv->ah);
 		priv->op_flags &= ~OP_TSF_RESET;
@@ -216,9 +225,10 @@ static void ath9k_htc_beacon_config_ap(struct ath9k_htc_priv *priv,
 		imask |= ATH9K_INT_SWBA;
 
 	ath_dbg(common, ATH_DBG_CONFIG,
-		"AP Beacon config, intval: %d, nexttbtt: %u "
+		"AP Beacon config, intval: %d, nexttbtt: %u, resp_time: %d "
 		"imask: 0x%x\n",
-		bss_conf->beacon_interval, nexttbtt, imask);
+		bss_conf->beacon_interval, nexttbtt,
+		priv->ah->config.sw_beacon_response_time, imask);
 
 	ath9k_htc_beaconq_config(priv);
 
@@ -252,12 +262,22 @@ static void ath9k_htc_beacon_config_adhoc(struct ath9k_htc_priv *priv,
 		nexttbtt += intval;
 	} while (nexttbtt < tsftu);
 
+	/*
+	 * Only one IBSS interfce is allowed.
+	 */
+	if (intval > DEFAULT_SWBA_RESPONSE)
+		priv->ah->config.sw_beacon_response_time = DEFAULT_SWBA_RESPONSE;
+	else
+		priv->ah->config.sw_beacon_response_time = MIN_SWBA_RESPONSE;
+
 	if (priv->op_flags & OP_ENABLE_BEACON)
 		imask |= ATH9K_INT_SWBA;
 
 	ath_dbg(common, ATH_DBG_CONFIG,
-		"IBSS Beacon config, intval: %d, nexttbtt: %u, imask: 0x%x\n",
-		bss_conf->beacon_interval, nexttbtt, imask);
+		"IBSS Beacon config, intval: %d, nexttbtt: %u, "
+		"resp_time: %d, imask: 0x%x\n",
+		bss_conf->beacon_interval, nexttbtt,
+		priv->ah->config.sw_beacon_response_time, imask);
 
 	WMI_CMD(WMI_DISABLE_INTR_CMDID);
 	ath9k_hw_beaconinit(priv->ah, TU_TO_USEC(nexttbtt), TU_TO_USEC(intval));
@@ -317,6 +337,7 @@ static void ath9k_htc_send_buffered(struct ath9k_htc_priv *priv,
 static void ath9k_htc_send_beacon(struct ath9k_htc_priv *priv,
 				  int slot)
 {
+	struct ath_common *common = ath9k_hw_common(priv->ah);
 	struct ieee80211_vif *vif;
 	struct ath9k_htc_vif *avp;
 	struct tx_beacon_header beacon_hdr;
@@ -325,6 +346,7 @@ static void ath9k_htc_send_beacon(struct ath9k_htc_priv *priv,
 	struct ieee80211_mgmt *mgmt;
 	struct sk_buff *beacon;
 	u8 *tx_fhdr;
+	int ret;
 
 	memset(&beacon_hdr, 0, sizeof(struct tx_beacon_header));
 	memset(&tx_ctl, 0, sizeof(struct ath9k_htc_tx_ctl));
@@ -367,7 +389,14 @@ static void ath9k_htc_send_beacon(struct ath9k_htc_priv *priv,
 	tx_fhdr = skb_push(beacon, sizeof(beacon_hdr));
 	memcpy(tx_fhdr, (u8 *) &beacon_hdr, sizeof(beacon_hdr));
 
-	htc_send(priv->htc, beacon, priv->beacon_ep, &tx_ctl);
+	ret = htc_send(priv->htc, beacon, priv->beacon_ep, &tx_ctl);
+	if (ret != 0) {
+		if (ret == -ENOMEM) {
+			ath_dbg(common, ATH_DBG_BSTUCK,
+				"Failed to send beacon, no free TX buffer\n");
+		}
+		dev_kfree_skb_any(beacon);
+	}
 
 	spin_unlock_bh(&priv->beacon_lock);
 }