ath10k: improve wake_tx_queue ops performance

txqs_lock is interfering with wake_tx_queue submitting more frames.
so queues don't get filled in and don't keep firmware/hardware busy
enough. This change helps to reduce the txqs_lock contention and
wake_tx_queue() blockage to being possible in txrx_unref().

To reduce turn around time of wake_tx_queue ops and to maintain fairness
among all txqs, the callback is updated to push first txq alone from
pending list for every wake_tx_queue call. Remaining txqs will be
processed later upon tx completion.

Below improvements are observed in push-only mode and validated on
IPQ4019 platform. With this change, in AP mode ~10Mbps increase is
observed in downlink (AP -> STA) traffic and approx. 5-10% of CPU
usage is reduced.

Major improvement is observed in 1-hop Mesh mode topology in 11ACVHT80.
Compared to Infra mode, CPU overhead is higher in Mesh mode due to path
lookup and no fast-xmit support. So reducing spin lock contention is
helping in Mesh.

             TOT       +change
           --------    --------
TCP DL     545 Mbps    595 Mbps
TCP UL     555 Mbps    585 Mbps
Signed-off-by: Rajkumar Manoharan <rmanohar@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath10k/mac.c

@@ -4100,13 +4100,29 @@ static void ath10k_mac_op_wake_tx_queue(struct ieee80211_hw *hw,
 {
 	struct ath10k *ar = hw->priv;
 	struct ath10k_txq *artxq = (void *)txq->drv_priv;
+	struct ieee80211_txq *f_txq;
+	struct ath10k_txq *f_artxq;
+	int ret = 0;
+	int max = 16;
 
 	spin_lock_bh(&ar->txqs_lock);
 	if (list_empty(&artxq->list))
 		list_add_tail(&artxq->list, &ar->txqs);
+
+	f_artxq = list_first_entry(&ar->txqs, struct ath10k_txq, list);
+	f_txq = container_of((void *)f_artxq, struct ieee80211_txq, drv_priv);
+	list_del_init(&f_artxq->list);
+
+	while (ath10k_mac_tx_can_push(hw, f_txq) && max--) {
+		ret = ath10k_mac_tx_push_txq(hw, f_txq);
+		if (ret)
+			break;
+	}
+	if (ret != -ENOENT)
+		list_add_tail(&f_artxq->list, &ar->txqs);
 	spin_unlock_bh(&ar->txqs_lock);
 
-	ath10k_mac_tx_push_pending(ar);
+	ath10k_htt_tx_txq_update(hw, f_txq);
 	ath10k_htt_tx_txq_update(hw, txq);
 }