rt2x00: Improve TX status handling for BlockAckReq frames

Since rt2800 hardware isn't capable of reporting the TX status of
BlockAckReq frames implement the TX status handling of BARs in
rt2x00lib. We keep track of all BARs that are send out and try to
match incoming BAs to the appropriate BARs. This allows us to report a
more or less accurate TX status for BAR frames which in turn improves
BA session stability.

This is loosley based on Christian Lamparter's patch for carl9170
"carl9170: fix HT peer BA session corruption".

We have to walk the list of pending BARs for every rx'red BA even
though most BAs don't belong to any of these BARs as they are just
acknowledging an AMPDU. To keep that overhead low use RCU which allows
us to walk the list of pending BARs without the need to acquire a lock.
This however requires us to _copy_ relevant information from the BAR
(RA, TA, control field, start sequence number) into our BAR list entry.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Tested-by: Andreas Hartmann <andihartmann@01019freenet.de>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 100 insertions, 1 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2x00dev.c b/drivers/net/wireless/rt2x00/rt2x00dev.c
index 44f8b3f3cbed..b40a53857498 100644
--- a/drivers/net/wireless/rt2x00/rt2x00dev.c
+++ b/drivers/net/wireless/rt2x00/rt2x00dev.c
@@ -271,6 +271,50 @@ void rt2x00lib_dmadone(struct queue_entry *entry)
 }
 EXPORT_SYMBOL_GPL(rt2x00lib_dmadone);
 
+static inline int rt2x00lib_txdone_bar_status(struct queue_entry *entry)
+{
+	struct rt2x00_dev *rt2x00dev = entry->queue->rt2x00dev;
+	struct ieee80211_bar *bar = (void *) entry->skb->data;
+	struct rt2x00_bar_list_entry *bar_entry;
+	int ret;
+
+	if (likely(!ieee80211_is_back_req(bar->frame_control)))
+		return 0;
+
+	/*
+	 * Unlike all other frames, the status report for BARs does
+	 * not directly come from the hardware as it is incapable of
+	 * matching a BA to a previously send BAR. The hardware will
+	 * report all BARs as if they weren't acked at all.
+	 *
+	 * Instead the RX-path will scan for incoming BAs and set the
+	 * block_acked flag if it sees one that was likely caused by
+	 * a BAR from us.
+	 *
+	 * Remove remaining BARs here and return their status for
+	 * TX done processing.
+	 */
+	ret = 0;
+	rcu_read_lock();
+	list_for_each_entry_rcu(bar_entry, &rt2x00dev->bar_list, list) {
+		if (bar_entry->entry != entry)
+			continue;
+
+		spin_lock_bh(&rt2x00dev->bar_list_lock);
+		/* Return whether this BAR was blockacked or not */
+		ret = bar_entry->block_acked;
+		/* Remove the BAR from our checklist */
+		list_del_rcu(&bar_entry->list);
+		spin_unlock_bh(&rt2x00dev->bar_list_lock);
+		kfree_rcu(bar_entry, head);
+
+		break;
+	}
+	rcu_read_unlock();
+
+	return ret;
+}
+
 void rt2x00lib_txdone(struct queue_entry *entry,
 		      struct txdone_entry_desc *txdesc)
 {
@@ -324,9 +368,12 @@ void rt2x00lib_txdone(struct queue_entry *entry,
 	rt2x00debug_dump_frame(rt2x00dev, DUMP_FRAME_TXDONE, entry->skb);
 
 	/*
-	 * Determine if the frame has been successfully transmitted.
+	 * Determine if the frame has been successfully transmitted and
+	 * remove BARs from our check list while checking for their
+	 * TX status.
 	 */
 	success =
+	    rt2x00lib_txdone_bar_status(entry) ||
 	    test_bit(TXDONE_SUCCESS, &txdesc->flags) ||
 	    test_bit(TXDONE_UNKNOWN, &txdesc->flags);
 
@@ -491,6 +538,50 @@ static void rt2x00lib_sleep(struct work_struct *work)
 				 IEEE80211_CONF_CHANGE_PS);
 }
 
+static void rt2x00lib_rxdone_check_ba(struct rt2x00_dev *rt2x00dev,
+				      struct sk_buff *skb,
+				      struct rxdone_entry_desc *rxdesc)
+{
+	struct rt2x00_bar_list_entry *entry;
+	struct ieee80211_bar *ba = (void *)skb->data;
+
+	if (likely(!ieee80211_is_back(ba->frame_control)))
+		return;
+
+	if (rxdesc->size < sizeof(*ba) + FCS_LEN)
+		return;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(entry, &rt2x00dev->bar_list, list) {
+
+		if (ba->start_seq_num != entry->start_seq_num)
+			continue;
+
+#define TID_CHECK(a, b) (						\
+	((a) & cpu_to_le16(IEEE80211_BAR_CTRL_TID_INFO_MASK)) ==	\
+	((b) & cpu_to_le16(IEEE80211_BAR_CTRL_TID_INFO_MASK)))		\
+
+		if (!TID_CHECK(ba->control, entry->control))
+			continue;
+
+#undef TID_CHECK
+
+		if (compare_ether_addr(ba->ra, entry->ta))
+			continue;
+
+		if (compare_ether_addr(ba->ta, entry->ra))
+			continue;
+
+		/* Mark BAR since we received the according BA */
+		spin_lock_bh(&rt2x00dev->bar_list_lock);
+		entry->block_acked = 1;
+		spin_unlock_bh(&rt2x00dev->bar_list_lock);
+		break;
+	}
+	rcu_read_unlock();
+
+}
+
 static void rt2x00lib_rxdone_check_ps(struct rt2x00_dev *rt2x00dev,
 				      struct sk_buff *skb,
 				      struct rxdone_entry_desc *rxdesc)
@@ -674,6 +765,12 @@ void rt2x00lib_rxdone(struct queue_entry *entry, gfp_t gfp)
 	rt2x00lib_rxdone_check_ps(rt2x00dev, entry->skb, &rxdesc);
 
 	/*
+	 * Check for incoming BlockAcks to match to the BlockAckReqs
+	 * we've send out.
+	 */
+	rt2x00lib_rxdone_check_ba(rt2x00dev, entry->skb, &rxdesc);
+
+	/*
 	 * Update extra components
 	 */
 	rt2x00link_update_stats(rt2x00dev, entry->skb, &rxdesc);
@@ -1183,6 +1280,8 @@ int rt2x00lib_probe_dev(struct rt2x00_dev *rt2x00dev)
 
 	spin_lock_init(&rt2x00dev->irqmask_lock);
 	mutex_init(&rt2x00dev->csr_mutex);
+	INIT_LIST_HEAD(&rt2x00dev->bar_list);
+	spin_lock_init(&rt2x00dev->bar_list_lock);
 
 	set_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags);