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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
9df86e2e70 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>
This commit is contained in:
David Gnedt 2011-01-30 20:10:46 +01:00 committed by John W. Linville
parent 172710bf83
commit e7332a4144
1 changed files with 12 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
drivers/net/wireless/wl1251/tx.c
View File

@ -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 */