mt76: mt7915: optimize mt7915_mac_sta_poll

Since DMA completion does not imply tx completion, it makes more sense to
poll for airtime from mt7915_mac_tx_free.
Reduce the runtime of the function by moving all items from dev->sta_poll_list
to a local list once and process any stations that were added afterwards
on the next run
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7915/dma.c

@@ -95,7 +95,6 @@ static int mt7915_poll_tx(struct napi_struct *napi, int budget)
 	dev = container_of(napi, struct mt7915_dev, mt76.tx_napi);
 
 	mt7915_tx_cleanup(dev);
-	mt7915_mac_sta_poll(dev);
 
 	tasklet_schedule(&dev->mt76.tx_tasklet);
 

drivers/net/wireless/mediatek/mt76/mt7915/mac.c

@@ -97,7 +97,7 @@ static u32 mt7915_mac_wtbl_lmac_addr(struct mt7915_dev *dev, u16 wcid)
 }
 
 /* TODO: use txfree airtime info to avoid runtime accessing in the long run */
-void mt7915_mac_sta_poll(struct mt7915_dev *dev)
+static void mt7915_mac_sta_poll(struct mt7915_dev *dev)
 {
 	static const u8 ac_to_tid[] = {
 		[IEEE80211_AC_BE] = 0,
@@ -114,8 +114,13 @@ void mt7915_mac_sta_poll(struct mt7915_dev *dev)
 	struct ieee80211_sta *sta;
 	struct mt7915_sta *msta;
 	u32 tx_time[IEEE80211_NUM_ACS], rx_time[IEEE80211_NUM_ACS];
+	LIST_HEAD(sta_poll_list);
 	int i;
 
+	spin_lock_bh(&dev->sta_poll_lock);
+	list_splice_init(&dev->sta_poll_list, &sta_poll_list);
+	spin_unlock_bh(&dev->sta_poll_lock);
+
 	rcu_read_lock();
 
 	while (true) {
@@ -124,11 +129,11 @@ void mt7915_mac_sta_poll(struct mt7915_dev *dev)
 		u16 idx;
 
 		spin_lock_bh(&dev->sta_poll_lock);
-		if (list_empty(&dev->sta_poll_list)) {
+		if (list_empty(&sta_poll_list)) {
 			spin_unlock_bh(&dev->sta_poll_lock);
 			break;
 		}
-		msta = list_first_entry(&dev->sta_poll_list,
+		msta = list_first_entry(&sta_poll_list,
 					struct mt7915_sta, poll_list);
 		list_del_init(&msta->poll_list);
 		spin_unlock_bh(&dev->sta_poll_lock);
@@ -929,6 +934,8 @@ void mt7915_mac_tx_free(struct mt7915_dev *dev, struct sk_buff *skb)
 		mt76_put_txwi(mdev, txwi);
 	}
 	dev_kfree_skb(skb);
+
+	mt7915_mac_sta_poll(dev);
 }
 
 void mt7915_tx_complete_skb(struct mt76_dev *mdev, enum mt76_txq_id qid,

drivers/net/wireless/mediatek/mt76/mt7915/mt7915.h

@@ -436,7 +436,6 @@ mt7915_l2_rmw(struct mt7915_dev *dev, u32 addr, u32 mask, u32 val)
 bool mt7915_mac_wtbl_update(struct mt7915_dev *dev, int idx, u32 mask);
 void mt7915_mac_reset_counters(struct mt7915_phy *phy);
 void mt7915_mac_cca_stats_reset(struct mt7915_phy *phy);
-void mt7915_mac_sta_poll(struct mt7915_dev *dev);
 void mt7915_mac_write_txwi(struct mt7915_dev *dev, __le32 *txwi,
 			   struct sk_buff *skb, struct mt76_wcid *wcid,
 			   struct ieee80211_key_conf *key, bool beacon);