wl1251: fix queue stopping/waking for TX path

The queue stopping/waking functionality was broken in a way that could
cause the TX to stall if the right circumstances are met.

The problem was caused by tx_work, which is scheduled on each TX operation.
If the firmware buffer is full, tx_work does nothing. In combinition with
stopped queues or non-continues transfers, tx_work is never scheduled again.
Moreover the low watermark introduced by
9df86e2e702c6d5547aced7f241addd2d698bb11 never takes effect because of some
old code.

Solve this by scheduling tx_work every time tx_queue is non-empty and
firmware buffer is freed on tx_complete.

This also solves a possible but unlikely case: If less frames than the high
watermark are queued, but more than firmware buffer can hold. This results
in queues staying awake but the only scheduled tx_work doesn't transfer all
frames, so the remaining frames are stuck in the queue until more frames
get queued and tx_work is scheduled again.

Signed-off-by: David Gnedt <david.gnedt@davizone.at>
Acked-by: Kalle Valo <kvalo@adurom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 12 insertions, 36 deletions

diff --git a/drivers/net/wireless/wl1251/tx.c b/drivers/net/wireless/wl1251/tx.c
index 554b4f9a3d3e..10112de55493 100644
--- a/drivers/net/wireless/wl1251/tx.c
+++ b/drivers/net/wireless/wl1251/tx.c
@@ -368,7 +368,7 @@ static void wl1251_tx_packet_cb(struct wl1251 *wl,
 {
         struct ieee80211_tx_info *info;
         struct sk_buff *skb;
-        int hdrlen, ret;
+        int hdrlen;
         u8 *frame;
 
         skb = wl->tx_frames[result->id];
@@ -407,40 +407,12 @@ static void wl1251_tx_packet_cb(struct wl1251 *wl,
         ieee80211_tx_status(wl->hw, skb);
 
         wl->tx_frames[result->id] = NULL;
-
-        if (wl->tx_queue_stopped) {
-                wl1251_debug(DEBUG_TX, "cb: queue was stopped");
-
-                skb = skb_dequeue(&wl->tx_queue);
-
-                /* The skb can be NULL because tx_work might have been
-                   scheduled before the queue was stopped making the
-                   queue empty */
-
-                if (skb) {
-                        ret = wl1251_tx_frame(wl, skb);
-                        if (ret == -EBUSY) {
-                                /* firmware buffer is still full */
-                                wl1251_debug(DEBUG_TX, "cb: fw buffer "
-                                             "still full");
-                                skb_queue_head(&wl->tx_queue, skb);
-                                return;
-                        } else if (ret < 0) {
-                                dev_kfree_skb(skb);
-                                return;
-                        }
-                }
-
-                wl1251_debug(DEBUG_TX, "cb: waking queues");
-                ieee80211_wake_queues(wl->hw);
-                wl->tx_queue_stopped = false;
-        }
 }
 
 /* Called upon reception of a TX complete interrupt */
 void wl1251_tx_complete(struct wl1251 *wl)
 {
-        int i, result_index, num_complete = 0;
+        int i, result_index, num_complete = 0, queue_len;
         struct tx_result result[FW_TX_CMPLT_BLOCK_SIZE], *result_ptr;
         unsigned long flags;
 
@@ -471,18 +443,22 @@ void wl1251_tx_complete(struct wl1251 *wl)
                 }
         }
 
-        if (wl->tx_queue_stopped
-            &&
-            skb_queue_len(&wl->tx_queue) <= WL1251_TX_QUEUE_LOW_WATERMARK){
+        queue_len = skb_queue_len(&wl->tx_queue);
 
-                /* firmware buffer has space, restart queues */
+        if ((num_complete > 0) && (queue_len > 0)) {
+                /* firmware buffer has space, reschedule tx_work */
+                wl1251_debug(DEBUG_TX, "tx_complete: reschedule tx_work");
+                ieee80211_queue_work(wl->hw, &wl->tx_work);
+        }
+
+        if (wl->tx_queue_stopped &&
+            queue_len <= WL1251_TX_QUEUE_LOW_WATERMARK) {
+                /* tx_queue has space, restart queues */
                 wl1251_debug(DEBUG_TX, "tx_complete: waking queues");
                 spin_lock_irqsave(&wl->wl_lock, flags);
                 ieee80211_wake_queues(wl->hw);
                 wl->tx_queue_stopped = false;
                 spin_unlock_irqrestore(&wl->wl_lock, flags);
-                ieee80211_queue_work(wl->hw, &wl->tx_work);
-
         }
 
         /* Every completed frame needs to be acknowledged */