b43: avoid packet losses in the dma worker code.

Following Rafal request, we verified that on "modern" CPUs using one
or more workers is equivalent. Here is patch V3 that addresses the
packet loss bug in the dma engine using only one worker.

-------

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.

This problem was already discussed here

http://www.mail-archive.com/b43-dev@lists.infradead.org/msg01413.html

and acknowledged by Michael.

Number of hardware queues is now defined in b43.h (B43_QOS_QUEUE_NUM).

Acknowledgements to Riccardo Paolillo <riccardo.paolillo@gmail.com> and
Michele Orru <michele.orru@hotmail.it>

Signed-off-by: Francesco Gringoli <francesco.gringoli@ing.unibs.it>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 40 insertions, 15 deletions

diff --git a/drivers/net/wireless/b43/main.c b/drivers/net/wireless/b43/main.c
index 5634d9a..989f654 100644
--- a/drivers/net/wireless/b43/main.c
+++ b/drivers/net/wireless/b43/main.c
@@ -3378,6 +3378,7 @@ static void b43_tx_work(struct work_struct *work)
 	struct b43_wl *wl = container_of(work, struct b43_wl, tx_work);
 	struct b43_wldev *dev;
 	struct sk_buff *skb;
+	int queue_num;
 	int err = 0;
 
 	mutex_lock(&wl->mutex);
@@ -3387,15 +3388,26 @@ static void b43_tx_work(struct work_struct *work)
 		return;
 	}
 
-	while (skb_queue_len(&wl->tx_queue)) {
-		skb = skb_dequeue(&wl->tx_queue);
+	for (queue_num = 0; queue_num < B43_QOS_QUEUE_NUM; queue_num++) {
+		while (skb_queue_len(&wl->tx_queue[queue_num])) {
+			skb = skb_dequeue(&wl->tx_queue[queue_num]);
+			if (b43_using_pio_transfers(dev))
+				err = b43_pio_tx(dev, skb);
+			else
+				err = b43_dma_tx(dev, skb);
+			if (err == -ENOSPC) {
+				wl->tx_queue_stopped[queue_num] = 1;
+				ieee80211_stop_queue(wl->hw, queue_num);
+				skb_queue_head(&wl->tx_queue[queue_num], skb);
+				break;
+			}
+			if (unlikely(err))
+				dev_kfree_skb(skb); /* Drop it */
+			err = 0;
+		}
 
-		if (b43_using_pio_transfers(dev))
-			err = b43_pio_tx(dev, skb);
-		else
-			err = b43_dma_tx(dev, skb);
-		if (unlikely(err))
-			dev_kfree_skb(skb); /* Drop it */
+		if (!err)
+			wl->tx_queue_stopped[queue_num] = 0;
 	}
 
 #if B43_DEBUG
@@ -3416,8 +3428,12 @@ static void b43_op_tx(struct ieee80211_hw *hw,
 	}
 	B43_WARN_ON(skb_shinfo(skb)->nr_frags);
 
-	skb_queue_tail(&wl->tx_queue, skb);
-	ieee80211_queue_work(wl->hw, &wl->tx_work);
+	skb_queue_tail(&wl->tx_queue[skb->queue_mapping], skb);
+	if (!wl->tx_queue_stopped[skb->queue_mapping]) {
+		ieee80211_queue_work(wl->hw, &wl->tx_work);
+	} else {
+		ieee80211_stop_queue(wl->hw, skb->queue_mapping);
+	}
 }
 
 static void b43_qos_params_upload(struct b43_wldev *dev,
@@ -4147,6 +4163,7 @@ static struct b43_wldev * b43_wireless_core_stop(struct b43_wldev *dev)
 	struct b43_wl *wl;
 	struct b43_wldev *orig_dev;
 	u32 mask;
+	int queue_num;
 
 	if (!dev)
 		return NULL;
@@ -4199,9 +4216,11 @@ redo:
 	mask = b43_read32(dev, B43_MMIO_GEN_IRQ_MASK);
 	B43_WARN_ON(mask != 0xFFFFFFFF && mask);
 
-	/* Drain the TX queue */
-	while (skb_queue_len(&wl->tx_queue))
-		dev_kfree_skb(skb_dequeue(&wl->tx_queue));
+	/* Drain all TX queues. */
+	for (queue_num = 0; queue_num < B43_QOS_QUEUE_NUM; queue_num++) {
+		while (skb_queue_len(&wl->tx_queue[queue_num]))
+			dev_kfree_skb(skb_dequeue(&wl->tx_queue[queue_num]));
+	}
 
 	b43_mac_suspend(dev);
 	b43_leds_exit(dev);
@@ -5245,6 +5264,7 @@ static struct b43_wl *b43_wireless_init(struct b43_bus_dev *dev)
 	struct ieee80211_hw *hw;
 	struct b43_wl *wl;
 	char chip_name[6];
+	int queue_num;
 
 	hw = ieee80211_alloc_hw(sizeof(*wl), &b43_hw_ops);
 	if (!hw) {
@@ -5264,7 +5284,7 @@ static struct b43_wl *b43_wireless_init(struct b43_bus_dev *dev)
 		BIT(NL80211_IFTYPE_WDS) |
 		BIT(NL80211_IFTYPE_ADHOC);
 
-	hw->queues = modparam_qos ? 4 : 1;
+	hw->queues = modparam_qos ? B43_QOS_QUEUE_NUM : 1;
 	wl->mac80211_initially_registered_queues = hw->queues;
 	hw->max_rates = 2;
 	SET_IEEE80211_DEV(hw, dev->dev);
@@ -5281,7 +5301,12 @@ static struct b43_wl *b43_wireless_init(struct b43_bus_dev *dev)
 	INIT_WORK(&wl->beacon_update_trigger, b43_beacon_update_trigger_work);
 	INIT_WORK(&wl->txpower_adjust_work, b43_phy_txpower_adjust_work);
 	INIT_WORK(&wl->tx_work, b43_tx_work);
-	skb_queue_head_init(&wl->tx_queue);
+
+	/* Initialize queues and flags. */
+	for (queue_num = 0; queue_num < B43_QOS_QUEUE_NUM; queue_num++) {
+		skb_queue_head_init(&wl->tx_queue[queue_num]);
+		wl->tx_queue_stopped[queue_num] = 0;
+	}
 
 	snprintf(chip_name, ARRAY_SIZE(chip_name),
 		 (dev->chip_id > 0x9999) ? "%d" : "%04X", dev->chip_id);