wl1251: Fix queue stopping/waking for TX path

This patch was adapted from 06f7bc7db79fabe6b2ec16eff0f59e4acc21eb72
(from linus's linux-2.6 tree of kernel.org)

here's the original message:
    The queue stopping/waking functionality was broken in a way that could
    cause huge latencies in TX transfers and even cause the TX to stall in the
    right circumstances. Correct these problems.

Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@no-log.org>
Acked-by: Kalle Valo <kvalo@adurom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

3 files changed, 24 insertions, 13 deletions

diff --git a/drivers/net/wireless/wl12xx/wl1251.h b/drivers/net/wireless/wl12xx/wl1251.h
index 9bc4fea3315..e113d4c1fb3 100644
--- a/drivers/net/wireless/wl12xx/wl1251.h
+++ b/drivers/net/wireless/wl12xx/wl1251.h
@@ -272,6 +272,8 @@ struct wl1251 {
         int irq;
         bool use_eeprom;
 
+        spinlock_t wl_lock;
+
         enum wl1251_state state;
         struct mutex mutex;
 
@@ -399,7 +401,8 @@ void wl1251_disable_interrupts(struct wl1251 *wl);
 
 #define WL1251_DEFAULT_POWER_LEVEL 20
 
-#define WL1251_TX_QUEUE_MAX_LENGTH 20
+#define WL1251_TX_QUEUE_LOW_WATERMARK  10
+#define WL1251_TX_QUEUE_HIGH_WATERMARK 25
 
 #define WL1251_DEFAULT_BEACON_INT 100
 #define WL1251_DEFAULT_DTIM_PERIOD 1
diff --git a/drivers/net/wireless/wl12xx/wl1251_main.c b/drivers/net/wireless/wl12xx/wl1251_main.c
index f9d9ad620cc..faf221ca3f4 100644
--- a/drivers/net/wireless/wl12xx/wl1251_main.c
+++ b/drivers/net/wireless/wl12xx/wl1251_main.c
@@ -375,6 +375,7 @@ out:
 static int wl1251_op_tx(struct ieee80211_hw *hw, struct sk_buff *skb)
 {
         struct wl1251 *wl = hw->priv;
+        unsigned long flags;
 
         skb_queue_tail(&wl->tx_queue, skb);
 
@@ -389,16 +390,13 @@ static int wl1251_op_tx(struct ieee80211_hw *hw, struct sk_buff *skb)
          * The workqueue is slow to process the tx_queue and we need stop
          * the queue here, otherwise the queue will get too long.
          */
-        if (skb_queue_len(&wl->tx_queue) >= WL1251_TX_QUEUE_MAX_LENGTH) {
+        if (skb_queue_len(&wl->tx_queue) >= WL1251_TX_QUEUE_HIGH_WATERMARK) {
                 wl1251_debug(DEBUG_TX, "op_tx: tx_queue full, stop queues");
-                ieee80211_stop_queues(wl->hw);
 
-                /*
-                 * FIXME: this is racy, the variable is not properly
-                 * protected. Maybe fix this by removing the stupid
-                 * variable altogether and checking the real queue state?
-                 */
+                spin_lock_irqsave(&wl->wl_lock, flags);
+                ieee80211_stop_queues(wl->hw);
                 wl->tx_queue_stopped = true;
+                spin_unlock_irqrestore(&wl->wl_lock, flags);
         }
 
         return NETDEV_TX_OK;
diff --git a/drivers/net/wireless/wl12xx/wl1251_tx.c b/drivers/net/wireless/wl12xx/wl1251_tx.c
index 6d618fb1fd9..388492a7f41 100644
--- a/drivers/net/wireless/wl12xx/wl1251_tx.c
+++ b/drivers/net/wireless/wl12xx/wl1251_tx.c
@@ -320,11 +320,6 @@ void wl1251_tx_work(struct work_struct *work)
 
                 ret = wl1251_tx_frame(wl, skb);
                 if (ret == -EBUSY) {
-                        /* firmware buffer is full, stop queues */
-                        wl1251_debug(DEBUG_TX, "tx_work: fw buffer full, "
-                                     "stop queues");
-                        ieee80211_stop_queues(wl->hw);
-                        wl->tx_queue_stopped = true;
                         skb_queue_head(&wl->tx_queue, skb);
                         goto out;
                 } else if (ret < 0) {
@@ -447,6 +442,7 @@ void wl1251_tx_complete(struct wl1251 *wl)
 {
         int i, result_index, num_complete = 0;
         struct tx_result result[FW_TX_CMPLT_BLOCK_SIZE], *result_ptr;
+        unsigned long flags;
 
         if (unlikely(wl->state != WL1251_STATE_ON))
                 return;
@@ -475,6 +471,20 @@ void wl1251_tx_complete(struct wl1251 *wl)
                 }
         }
 
+        if (wl->tx_queue_stopped
+            &&
+            skb_queue_len(&wl->tx_queue) <= WL1251_TX_QUEUE_LOW_WATERMARK){
+
+                /* firmware buffer 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 */
         if (num_complete) {
                 /*