[PATCH V2] rtl8187: Change rate-control feedback

[PATCH V2] rtl8187: Change rate-control feedback

[Larry Finger]

The driver for the RTL8187L chips returns IEEE80211_TX_STAT_ACK for all
packets, even if the maximum number of retries was exhausted. In addition
it fails to setup max_rates in the ieee80211_hw struct, This behavior
may be responsible for the problems noted in Bug 14168. As the bug is very
old, testers have not been found, and I do not have the case where the
indicated signal is less than -70 dBm.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Stable <stable@kernel.org>
---

V1 => V2: Protect against zero divide, and the case where the 16-bit retry
	  counter wraps to zero. The latter is unlikely, but tested for
	  completeness.
---

Index: wireless-testing/drivers/net/wireless/rtl818x/rtl8187/dev.c
===================================================================
--- wireless-testing.orig/drivers/net/wireless/rtl818x/rtl8187/dev.c
+++ wireless-testing/drivers/net/wireless/rtl818x/rtl8187/dev.c
@@ -869,23 +869,35 @@ static void rtl8187_work(struct work_str
 	/* The RTL8187 returns the retry count through register 0xFFFA. In
 	 * addition, it appears to be a cumulative retry count, not the
 	 * value for the current TX packet. When multiple TX entries are
-	 * queued, the retry count will be valid for the last one in the queue.
-	 * The "error" should not matter for purposes of rate setting. */
+	 * waiting in the queue, the retry count will be the total for all.
+	 * The "error" may matter for purposes of rate setting, but there is
+	 * no other choice with this hardware.
+	 */
 	struct rtl8187_priv *priv = container_of(work, struct rtl8187_priv,
 				    work.work);
 	struct ieee80211_tx_info *info;
 	struct ieee80211_hw *dev = priv->dev;
 	static u16 retry;
 	u16 tmp;
+	u16 avg_retry;
+	int length;
 
 	mutex_lock(&priv->conf_mutex);
 	tmp = rtl818x_ioread16(priv, (__le16 *)0xFFFA);
+	length = skb_queue_len(&priv->b_tx_status.queue);
+	if (unlikely(!length))
+		length = 1;
+	if (unlikely(tmp < retry))
+		tmp = retry;
+	avg_retry = (tmp - retry) / length;
 	while (skb_queue_len(&priv->b_tx_status.queue) > 0) {
 		struct sk_buff *old_skb;
 
 		old_skb = skb_dequeue(&priv->b_tx_status.queue);
 		info = IEEE80211_SKB_CB(old_skb);
-		info->status.rates[0].count = tmp - retry + 1;
+		info->status.rates[0].count = avg_retry + 1;
+		if (info->status.rates[0].count > RETRY_COUNT)
+			info->flags &= ~IEEE80211_TX_STAT_ACK;
 		ieee80211_tx_status_irqsafe(dev, old_skb);
 	}
 	retry = tmp;
@@ -931,8 +943,8 @@ static int rtl8187_start(struct ieee8021
 		rtl818x_iowrite32(priv, &priv->map->TX_CONF,
 				  RTL818X_TX_CONF_HW_SEQNUM |
 				  RTL818X_TX_CONF_DISREQQSIZE |
-				  (7 << 8  /* short retry limit */) |
-				  (7 << 0  /* long retry limit */) |
+				  (RETRY_COUNT << 8  /* short retry limit */) |
+				  (RETRY_COUNT << 0  /* long retry limit */) |
 				  (7 << 21 /* MAX TX DMA */));
 		rtl8187_init_urbs(dev);
 		rtl8187b_init_status_urb(dev);
@@ -1376,6 +1388,9 @@ static int __devinit rtl8187_probe(struc
 	dev->flags = IEEE80211_HW_HOST_BROADCAST_PS_BUFFERING |
 		     IEEE80211_HW_SIGNAL_DBM |
 		     IEEE80211_HW_RX_INCLUDES_FCS;
+	/* Initialize rate-control variables */
+	dev->max_rates = 1;
+	dev->max_rate_tries = RETRY_COUNT;
 
 	eeprom.data = dev;
 	eeprom.register_read = rtl8187_eeprom_register_read;
Index: wireless-testing/drivers/net/wireless/rtl818x/rtl8187/rtl8187.h
===================================================================
--- wireless-testing.orig/drivers/net/wireless/rtl818x/rtl8187/rtl8187.h
+++ wireless-testing/drivers/net/wireless/rtl818x/rtl8187/rtl8187.h
@@ -35,6 +35,8 @@
 #define RFKILL_MASK_8187_89_97	0x2
 #define RFKILL_MASK_8198	0x4
 
+#define RETRY_COUNT		7
+
 struct rtl8187_rx_info {
 	struct urb *urb;
 	struct ieee80211_hw *dev;

Re: [PATCH V2] rtl8187: Change rate-control feedback

[Hin-Tak Leung]

--- On Tue, 1/3/11, Larry Finger <Larry.Finger@lwfinger.net> wrote:

> The driver for the RTL8187L chips
> returns IEEE80211_TX_STAT_ACK for all
> packets, even if the maximum number of retries was
> exhausted. In addition
> it fails to setup max_rates in the ieee80211_hw struct,
> This behavior
> may be responsible for the problems noted in Bug 14168. As
> the bug is very
> old, testers have not been found, and I do not have the
> case where the
> indicated signal is less than -70 dBm.
> 
> Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
> Cc: Stable <stable@kernel.org>
> ---
> 
> V1 => V2: Protect against zero divide, and the case
> where the 16-bit retry
>       counter wraps to zero. The latter
> is unlikely, but tested for
>       completeness.

Acked-by: Hin-Tak Leung <htl10@users.sourceforge.net>

This may be style-thing - the meaning of some of the variables changes mid-routine. I think one alternative way (not necessarily better) is to unlock the mutex and return if length ==0, and something similiar to the register wrap-around?

I'm okay with this as is though.