b43legacy: Avoid packet losses in the dma worker code

This patch addresses a bug in the dma worker code that keeps draining
packets even when the hardware queues are full. In such cases packets
can not be passed down to the device and are erroneusly dropped by the
code. It is based on commit bad6919469662b7c92bc6353642aaaa777b36bac,
which fixes the same problem in b43.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 36 insertions, 29 deletions

diff --git a/drivers/net/wireless/b43legacy/dma.c b/drivers/net/wireless/b43legacy/dma.c
index c5535adf6991..aebef75a2c62 100644
--- a/drivers/net/wireless/b43legacy/dma.c
+++ b/drivers/net/wireless/b43legacy/dma.c
@@ -727,7 +727,6 @@ struct b43legacy_dmaring *b43legacy_setup_dmaring(struct b43legacy_wldev *dev,
 		} else
 			B43legacy_WARN_ON(1);
 	}
-	spin_lock_init(&ring->lock);
 #ifdef CONFIG_B43LEGACY_DEBUG
 	ring->last_injected_overflow = jiffies;
 #endif
@@ -1144,10 +1143,8 @@ int b43legacy_dma_tx(struct b43legacy_wldev *dev,
 {
 	struct b43legacy_dmaring *ring;
 	int err = 0;
-	unsigned long flags;
 
 	ring = priority_to_txring(dev, skb_get_queue_mapping(skb));
-	spin_lock_irqsave(&ring->lock, flags);
 	B43legacy_WARN_ON(!ring->tx);
 
 	if (unlikely(ring->stopped)) {
@@ -1157,16 +1154,14 @@ int b43legacy_dma_tx(struct b43legacy_wldev *dev,
 		 * For now, just refuse the transmit. */
 		if (b43legacy_debug(dev, B43legacy_DBG_DMAVERBOSE))
 			b43legacyerr(dev->wl, "Packet after queue stopped\n");
-		err = -ENOSPC;
-		goto out_unlock;
+		return -ENOSPC;
 	}
 
 	if (unlikely(WARN_ON(free_slots(ring) < SLOTS_PER_PACKET))) {
 		/* If we get here, we have a real error with the queue
 		 * full, but queues not stopped. */
 		b43legacyerr(dev->wl, "DMA queue overflow\n");
-		err = -ENOSPC;
-		goto out_unlock;
+		return -ENOSPC;
 	}
 
 	/* dma_tx_fragment might reallocate the skb, so invalidate pointers pointing
@@ -1176,25 +1171,23 @@ int b43legacy_dma_tx(struct b43legacy_wldev *dev,
 		/* Drop this packet, as we don't have the encryption key
 		 * anymore and must not transmit it unencrypted. */
 		dev_kfree_skb_any(skb);
-		err = 0;
-		goto out_unlock;
+		return 0;
 	}
 	if (unlikely(err)) {
 		b43legacyerr(dev->wl, "DMA tx mapping failure\n");
-		goto out_unlock;
+		return err;
 	}
 	if ((free_slots(ring) < SLOTS_PER_PACKET) ||
 	    should_inject_overflow(ring)) {
 		/* This TX ring is full. */
-		ieee80211_stop_queue(dev->wl->hw, txring_to_priority(ring));
+		unsigned int skb_mapping = skb_get_queue_mapping(skb);
+		ieee80211_stop_queue(dev->wl->hw, skb_mapping);
+		dev->wl->tx_queue_stopped[skb_mapping] = 1;
 		ring->stopped = 1;
 		if (b43legacy_debug(dev, B43legacy_DBG_DMAVERBOSE))
 			b43legacydbg(dev->wl, "Stopped TX ring %d\n",
 			       ring->index);
 	}
-out_unlock:
-	spin_unlock_irqrestore(&ring->lock, flags);
-
 	return err;
 }
 
@@ -1205,14 +1198,29 @@ void b43legacy_dma_handle_txstatus(struct b43legacy_wldev *dev,
 	struct b43legacy_dmadesc_meta *meta;
 	int retry_limit;
 	int slot;
+	int firstused;
 
 	ring = parse_cookie(dev, status->cookie, &slot);
 	if (unlikely(!ring))
 		return;
-	B43legacy_WARN_ON(!irqs_disabled());
-	spin_lock(&ring->lock);
-
 	B43legacy_WARN_ON(!ring->tx);
+
+	/* Sanity check: TX packets are processed in-order on one ring.
+	 * Check if the slot deduced from the cookie really is the first
+	 * used slot. */
+	firstused = ring->current_slot - ring->used_slots + 1;
+	if (firstused < 0)
+		firstused = ring->nr_slots + firstused;
+	if (unlikely(slot != firstused)) {
+		/* This possibly is a firmware bug and will result in
+		 * malfunction, memory leaks and/or stall of DMA functionality.
+		 */
+		b43legacydbg(dev->wl, "Out of order TX status report on DMA "
+			     "ring %d. Expected %d, but got %d\n",
+			     ring->index, firstused, slot);
+		return;
+	}
+
 	while (1) {
 		B43legacy_WARN_ON(!(slot >= 0 && slot < ring->nr_slots));
 		op32_idx2desc(ring, slot, &meta);
@@ -1285,14 +1293,21 @@ void b43legacy_dma_handle_txstatus(struct b43legacy_wldev *dev,
 	dev->stats.last_tx = jiffies;
 	if (ring->stopped) {
 		B43legacy_WARN_ON(free_slots(ring) < SLOTS_PER_PACKET);
-		ieee80211_wake_queue(dev->wl->hw, txring_to_priority(ring));
 		ring->stopped = 0;
+	}
+
+	if (dev->wl->tx_queue_stopped[ring->queue_prio]) {
+		dev->wl->tx_queue_stopped[ring->queue_prio] = 0;
+	} else {
+		/* If the driver queue is running wake the corresponding
+		 * mac80211 queue. */
+		ieee80211_wake_queue(dev->wl->hw, ring->queue_prio);
 		if (b43legacy_debug(dev, B43legacy_DBG_DMAVERBOSE))
 			b43legacydbg(dev->wl, "Woke up TX ring %d\n",
-			       ring->index);
+				     ring->index);
 	}
-
-	spin_unlock(&ring->lock);
+	/* Add work to the queue. */
+	ieee80211_queue_work(dev->wl->hw, &dev->wl->tx_work);
 }
 
 static void dma_rx(struct b43legacy_dmaring *ring,
@@ -1415,22 +1430,14 @@ void b43legacy_dma_rx(struct b43legacy_dmaring *ring)
 
 static void b43legacy_dma_tx_suspend_ring(struct b43legacy_dmaring *ring)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&ring->lock, flags);
 	B43legacy_WARN_ON(!ring->tx);
 	op32_tx_suspend(ring);
-	spin_unlock_irqrestore(&ring->lock, flags);
 }
 
 static void b43legacy_dma_tx_resume_ring(struct b43legacy_dmaring *ring)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&ring->lock, flags);
 	B43legacy_WARN_ON(!ring->tx);
 	op32_tx_resume(ring);
-	spin_unlock_irqrestore(&ring->lock, flags);
 }
 
 void b43legacy_dma_tx_suspend(struct b43legacy_wldev *dev)