mt7601u: fix tx status reporting contexts

mac80211 requires that rx path does not run concurrently with
tx status reporting.  Since rx path is run in driver tasklet,
tx status cannot be reported directly from interrupt context
(there would be no way to lock it out).

Add tasklet for tx and move all possible code from irq handler
there.

Note: tx tasklet is needed because workqueue is queued very
      rarely and that kills TCP performance.

Signed-off-by: Jakub Kicinski <kubakici@wp.pl>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

1 files changed, 26 insertions, 4 deletions

diff --git a/drivers/net/wireless/mediatek/mt7601u/dma.c b/drivers/net/wireless/mediatek/mt7601u/dma.c
index fb183e369d92..63c485443a38 100644
--- a/drivers/net/wireless/mediatek/mt7601u/dma.c
+++ b/drivers/net/wireless/mediatek/mt7601u/dma.c
@@ -236,23 +236,42 @@ static void mt7601u_complete_tx(struct urb *urb)
 	skb = q->e[q->start].skb;
 	trace_mt_tx_dma_done(dev, skb);
 
-	mt7601u_tx_status(dev, skb);
+	__skb_queue_tail(&dev->tx_skb_done, skb);
+	tasklet_schedule(&dev->tx_tasklet);
 
 	if (q->used == q->entries - q->entries / 8)
 		ieee80211_wake_queue(dev->hw, skb_get_queue_mapping(skb));
 
 	q->start = (q->start + 1) % q->entries;
 	q->used--;
+out:
+	spin_unlock_irqrestore(&dev->tx_lock, flags);
+}
 
-	if (urb->status)
-		goto out;
+static void mt7601u_tx_tasklet(unsigned long data)
+{
+	struct mt7601u_dev *dev = (struct mt7601u_dev *) data;
+	struct sk_buff_head skbs;
+	unsigned long flags;
+
+	__skb_queue_head_init(&skbs);
+
+	spin_lock_irqsave(&dev->tx_lock, flags);
 
 	set_bit(MT7601U_STATE_MORE_STATS, &dev->state);
 	if (!test_and_set_bit(MT7601U_STATE_READING_STATS, &dev->state))
 		queue_delayed_work(dev->stat_wq, &dev->stat_work,
 				   msecs_to_jiffies(10));
-out:
+
+	skb_queue_splice_init(&dev->tx_skb_done, &skbs);
+
 	spin_unlock_irqrestore(&dev->tx_lock, flags);
+
+	while (!skb_queue_empty(&skbs)) {
+		struct sk_buff *skb = __skb_dequeue(&skbs);
+
+		mt7601u_tx_status(dev, skb);
+	}
 }
 
 static int mt7601u_dma_submit_tx(struct mt7601u_dev *dev,
@@ -475,6 +494,7 @@ int mt7601u_dma_init(struct mt7601u_dev *dev)
 {
 	int ret = -ENOMEM;
 
+	tasklet_init(&dev->tx_tasklet, mt7601u_tx_tasklet, (unsigned long) dev);
 	tasklet_init(&dev->rx_tasklet, mt7601u_rx_tasklet, (unsigned long) dev);
 
 	ret = mt7601u_alloc_tx(dev);
@@ -502,4 +522,6 @@ void mt7601u_dma_cleanup(struct mt7601u_dev *dev)
 
 	mt7601u_free_rx(dev);
 	mt7601u_free_tx(dev);
+
+	tasklet_kill(&dev->tx_tasklet);
 }