zd1211rw: Fix TX status reporting in order to have proper rate control

First, we reduce the number of hardware retries to 0 (ie 2 real retries
for each rate). Next, when we report the retries to mac80211, we always
report a retry count of 1 (it seems to be 2 in fact, but using 2 seems
to lead to wrong performance for some reason). We use a state machine to
determine the real fate of a packet based on the 802.11 ACK and what the
Zydas hardware is saying when a real retry occurs. The real retry rates
are encoded in a static array. It has been tested with both zd1211 and
zd1211b hardware. Of course, since the Zydas hardware is not reporting
retries accurately, we are just doing our best in order to get the best
performance (ie higher throughput).

Signed-off-by: Benoit PAPILLAULT <benoit.papillault@free.fr>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 182 insertions, 20 deletions

diff --git a/drivers/net/wireless/zd1211rw/zd_mac.c b/drivers/net/wireless/zd1211rw/zd_mac.c
index 6d666359a42..8a243732c51 100644
--- a/drivers/net/wireless/zd1211rw/zd_mac.c
+++ b/drivers/net/wireless/zd1211rw/zd_mac.c
@@ -88,6 +88,34 @@ static const struct ieee80211_rate zd_rates[] = {
 	  .flags = 0 },
 };
 
+/*
+ * Zydas retry rates table. Each line is listed in the same order as
+ * in zd_rates[] and contains all the rate used when a packet is sent
+ * starting with a given rates. Let's consider an example :
+ *
+ * "11 Mbits : 4, 3, 2, 1, 0" means :
+ * - packet is sent using 4 different rates
+ * - 1st rate is index 3 (ie 11 Mbits)
+ * - 2nd rate is index 2 (ie 5.5 Mbits)
+ * - 3rd rate is index 1 (ie 2 Mbits)
+ * - 4th rate is index 0 (ie 1 Mbits)
+ */
+
+static const struct tx_retry_rate zd_retry_rates[] = {
+	{ /*  1 Mbits */	1, { 0 }},
+	{ /*  2 Mbits */	2, { 1,  0 }},
+	{ /*  5.5 Mbits */	3, { 2,  1, 0 }},
+	{ /* 11 Mbits */	4, { 3,  2, 1, 0 }},
+	{ /*  6 Mbits */	5, { 4,  3, 2, 1, 0 }},
+	{ /*  9 Mbits */	6, { 5,  4, 3, 2, 1, 0}},
+	{ /* 12 Mbits */	5, { 6,  3, 2, 1, 0 }},
+	{ /* 18 Mbits */	6, { 7,  6, 3, 2, 1, 0 }},
+	{ /* 24 Mbits */	6, { 8,  6, 3, 2, 1, 0 }},
+	{ /* 36 Mbits */	7, { 9,  8, 6, 3, 2, 1, 0 }},
+	{ /* 48 Mbits */	8, {10,  9, 8, 6, 3, 2, 1, 0 }},
+	{ /* 54 Mbits */	9, {11, 10, 9, 8, 6, 3, 2, 1, 0 }}
+};
+
 static const struct ieee80211_channel zd_channels[] = {
 	{ .center_freq = 2412, .hw_value = 1 },
 	{ .center_freq = 2417, .hw_value = 2 },
@@ -282,7 +310,7 @@ static void zd_op_stop(struct ieee80211_hw *hw)
 }
 
 /**
- * tx_status - reports tx status of a packet if required
+ * zd_mac_tx_status - reports tx status of a packet if required
  * @hw - a &struct ieee80211_hw pointer
  * @skb - a sk-buffer
  * @flags: extra flags to set in the TX status info
@@ -295,15 +323,49 @@ static void zd_op_stop(struct ieee80211_hw *hw)
  *
  * If no status information has been requested, the skb is freed.
  */
-static void tx_status(struct ieee80211_hw *hw, struct sk_buff *skb,
-		      int ackssi, bool success)
+static void zd_mac_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb,
+		      int ackssi, struct tx_status *tx_status)
 {
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	int i;
+	int success = 1, retry = 1;
+	int first_idx;
+	const struct tx_retry_rate *retries;
 
 	ieee80211_tx_info_clear_status(info);
 
-	if (success)
+	if (tx_status) {
+		success = !tx_status->failure;
+		retry = tx_status->retry + success;
+	}
+
+	if (success) {
+		/* success */
 		info->flags |= IEEE80211_TX_STAT_ACK;
+	} else {
+		/* failure */
+		info->flags &= ~IEEE80211_TX_STAT_ACK;
+	}
+
+	first_idx = info->status.rates[0].idx;
+	ZD_ASSERT(0<=first_idx && first_idx<ARRAY_SIZE(zd_retry_rates));
+	retries = &zd_retry_rates[first_idx];
+	ZD_ASSERT(0<=retry && retry<=retries->count);
+
+	info->status.rates[0].idx = retries->rate[0];
+	info->status.rates[0].count = 1; // (retry > 1 ? 2 : 1);
+
+	for (i=1; i<IEEE80211_TX_MAX_RATES-1 && i<retry; i++) {
+		info->status.rates[i].idx = retries->rate[i];
+		info->status.rates[i].count = 1; // ((i==retry-1) && success ? 1:2);
+	}
+	for (; i<IEEE80211_TX_MAX_RATES && i<retry; i++) {
+		info->status.rates[i].idx = retries->rate[retry-1];
+		info->status.rates[i].count = 1; // (success ? 1:2);
+	}
+	if (i<IEEE80211_TX_MAX_RATES)
+		info->status.rates[i].idx = -1; /* terminate */
+
 	info->status.ack_signal = ackssi;
 	ieee80211_tx_status_irqsafe(hw, skb);
 }
@@ -316,16 +378,79 @@ static void tx_status(struct ieee80211_hw *hw, struct sk_buff *skb,
  * transferred. The first frame from the tx queue, will be selected and
  * reported as error to the upper layers.
  */
-void zd_mac_tx_failed(struct ieee80211_hw *hw)
+void zd_mac_tx_failed(struct urb *urb)
 {
-	struct sk_buff_head *q = &zd_hw_mac(hw)->ack_wait_queue;
+	struct ieee80211_hw * hw = zd_usb_to_hw(urb->context);
+	struct zd_mac *mac = zd_hw_mac(hw);
+	struct sk_buff_head *q = &mac->ack_wait_queue;
 	struct sk_buff *skb;
+	struct tx_status *tx_status = (struct tx_status *)urb->transfer_buffer;
+	unsigned long flags;
+	int success = !tx_status->failure;
+	int retry = tx_status->retry + success;
+	int found = 0;
+	int i, position = 0;
 
-	skb = skb_dequeue(q);
-	if (skb == NULL)
-		return;
+	q = &mac->ack_wait_queue;
+	spin_lock_irqsave(&q->lock, flags);
+
+	skb_queue_walk(q, skb) {
+		struct ieee80211_hdr *tx_hdr;
+		struct ieee80211_tx_info *info;
+		int first_idx, final_idx;
+		const struct tx_retry_rate *retries;
+		u8 final_rate;
+
+		position ++;
+
+		/* if the hardware reports a failure and we had a 802.11 ACK
+		 * pending, then we skip the first skb when searching for a
+		 * matching frame */
+		if (tx_status->failure && mac->ack_pending &&
+		    skb_queue_is_first(q, skb)) {
+			continue;
+		}
+
+		tx_hdr = (struct ieee80211_hdr *)skb->data;
+
+		/* we skip all frames not matching the reported destination */
+		if (unlikely(memcmp(tx_hdr->addr1, tx_status->mac, ETH_ALEN))) {
+			continue;
+		}
+
+		/* we skip all frames not matching the reported final rate */
 
-	tx_status(hw, skb, 0, 0);
+		info = IEEE80211_SKB_CB(skb);
+		first_idx = info->status.rates[0].idx;
+		ZD_ASSERT(0<=first_idx && first_idx<ARRAY_SIZE(zd_retry_rates));
+		retries = &zd_retry_rates[first_idx];
+		if (retry < 0 || retry > retries->count) {
+			continue;
+		}
+
+		ZD_ASSERT(0<=retry && retry<=retries->count);
+		final_idx = retries->rate[retry-1];
+		final_rate = zd_rates[final_idx].hw_value;
+
+		if (final_rate != tx_status->rate) {
+			continue;
+		}
+
+		found = 1;
+		break;
+	}
+
+	if (found) {
+		for (i=1; i<=position; i++) {
+			skb = __skb_dequeue(q);
+			zd_mac_tx_status(hw, skb,
+					 mac->ack_pending ? mac->ack_signal : 0,
+					 i == position ? tx_status : NULL);
+			mac->ack_pending = 0;
+		}
+	}
+
+	spin_unlock_irqrestore(&q->lock, flags);
 }
 
 /**
@@ -342,18 +467,27 @@ void zd_mac_tx_to_dev(struct sk_buff *skb, int error)
 {
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 	struct ieee80211_hw *hw = info->rate_driver_data[0];
+	struct zd_mac *mac = zd_hw_mac(hw);
+
+	ieee80211_tx_info_clear_status(info);
 
 	skb_pull(skb, sizeof(struct zd_ctrlset));
 	if (unlikely(error ||
 	    (info->flags & IEEE80211_TX_CTL_NO_ACK))) {
-		tx_status(hw, skb, 0, !error);
+		/*
+		 * FIXME : do we need to fill in anything ?
+		 */
+		ieee80211_tx_status_irqsafe(hw, skb);
 	} else {
-		struct sk_buff_head *q =
-			&zd_hw_mac(hw)->ack_wait_queue;
+		struct sk_buff_head *q = &mac->ack_wait_queue;
 
 		skb_queue_tail(q, skb);
-		while (skb_queue_len(q) > ZD_MAC_MAX_ACK_WAITERS)
-			zd_mac_tx_failed(hw);
+		while (skb_queue_len(q) > ZD_MAC_MAX_ACK_WAITERS) {
+			zd_mac_tx_status(hw, skb_dequeue(q),
+					 mac->ack_pending ? mac->ack_signal : 0,
+					 NULL);
+			mac->ack_pending = 0;
+		}
 	}
 }
 
@@ -606,27 +740,47 @@ fail:
 static int filter_ack(struct ieee80211_hw *hw, struct ieee80211_hdr *rx_hdr,
 		      struct ieee80211_rx_status *stats)
 {
+	struct zd_mac *mac = zd_hw_mac(hw);
 	struct sk_buff *skb;
 	struct sk_buff_head *q;
 	unsigned long flags;
+	int found = 0;
+	int i, position = 0;
 
 	if (!ieee80211_is_ack(rx_hdr->frame_control))
 		return 0;
 
-	q = &zd_hw_mac(hw)->ack_wait_queue;
+	q = &mac->ack_wait_queue;
 	spin_lock_irqsave(&q->lock, flags);
 	skb_queue_walk(q, skb) {
 		struct ieee80211_hdr *tx_hdr;
 
+		position ++;
+
+		if (mac->ack_pending && skb_queue_is_first(q, skb))
+		    continue;
+
 		tx_hdr = (struct ieee80211_hdr *)skb->data;
 		if (likely(!memcmp(tx_hdr->addr2, rx_hdr->addr1, ETH_ALEN)))
 		{
-			__skb_unlink(skb, q);
-			tx_status(hw, skb, stats->signal, 1);
-			goto out;
+			found = 1;
+			break;
 		}
 	}
-out:
+
+	if (found) {
+		for (i=1; i<position; i++) {
+			skb = __skb_dequeue(q);
+			zd_mac_tx_status(hw, skb,
+					 mac->ack_pending ? mac->ack_signal : 0,
+					 NULL);
+			mac->ack_pending = 0;
+		}
+
+		mac->ack_pending = 1;
+		mac->ack_signal = stats->signal;
+	}
+
 	spin_unlock_irqrestore(&q->lock, flags);
 	return 1;
 }
@@ -709,6 +863,7 @@ int zd_mac_rx(struct ieee80211_hw *hw, const u8 *buffer, unsigned int length)
 		skb_reserve(skb, 2);
 	}
 
+	/* FIXME : could we avoid this big memcpy ? */
 	memcpy(skb_put(skb, length), buffer, length);
 
 	memcpy(IEEE80211_SKB_RXCB(skb), &stats, sizeof(stats));
@@ -999,7 +1154,14 @@ struct ieee80211_hw *zd_mac_alloc_hw(struct usb_interface *intf)
 	hw->queues = 1;
 	hw->extra_tx_headroom = sizeof(struct zd_ctrlset);
 
+	/*
+	 * Tell mac80211 that we support multi rate retries
+	 */
+	hw->max_rates = IEEE80211_TX_MAX_RATES;
+	hw->max_rate_tries = 18;	/* 9 rates * 2 retries/rate */
+
 	skb_queue_head_init(&mac->ack_wait_queue);
+	mac->ack_pending = 0;
 
 	zd_chip_init(&mac->chip, hw, intf);
 	housekeeping_init(mac);