rt2x00: Fix HT40 operation in rt2800.

Closer inspection of the legacy Ralink driver reveals that in case of HT40+
or HT40- we must adjust the frequency settings that we program to the device.
Implement the same adjustment in the rt2x00 code.

With this HT40 seems to work for all devices supported by rt2800pci and
rt2800usb.
Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>

drivers/net/wireless/rt2x00/rt2800lib.c

@@ -2531,11 +2531,8 @@ int rt2800_probe_hw_mode(struct rt2x00_dev *rt2x00dev)
 	else
 		spec->ht.ht_supported = false;
 
-	/*
-	 * Don't set IEEE80211_HT_CAP_SUP_WIDTH_20_40 for now as it causes
-	 * reception problems with HT40 capable 11n APs
-	 */
 	spec->ht.cap =
+	    IEEE80211_HT_CAP_SUP_WIDTH_20_40 |
 	    IEEE80211_HT_CAP_GRN_FLD |
 	    IEEE80211_HT_CAP_SGI_20 |
 	    IEEE80211_HT_CAP_SGI_40 |

drivers/net/wireless/rt2x00/rt2x00config.c

@@ -170,23 +170,27 @@ void rt2x00lib_config(struct rt2x00_dev *rt2x00dev,
 		      unsigned int ieee80211_flags)
 {
 	struct rt2x00lib_conf libconf;
+	u16 hw_value;
 
 	memset(&libconf, 0, sizeof(libconf));
 
 	libconf.conf = conf;
 
 	if (ieee80211_flags & IEEE80211_CONF_CHANGE_CHANNEL) {
-		if (conf_is_ht40(conf))
+		if (conf_is_ht40(conf)) {
 			__set_bit(CONFIG_CHANNEL_HT40, &rt2x00dev->flags);
-		else
+			hw_value = rt2x00ht_center_channel(rt2x00dev, conf);
+		} else {
 			__clear_bit(CONFIG_CHANNEL_HT40, &rt2x00dev->flags);
+			hw_value = conf->channel->hw_value;
+		}
 
 		memcpy(&libconf.rf,
-		       &rt2x00dev->spec.channels[conf->channel->hw_value],
+		       &rt2x00dev->spec.channels[hw_value],
 		       sizeof(libconf.rf));
 
 		memcpy(&libconf.channel,
-		       &rt2x00dev->spec.channels_info[conf->channel->hw_value],
+		       &rt2x00dev->spec.channels_info[hw_value],
 		       sizeof(libconf.channel));
 	}
 

drivers/net/wireless/rt2x00/rt2x00ht.c

@@ -84,3 +84,31 @@ void rt2x00ht_create_tx_descriptor(struct queue_entry *entry,
 	else
 		txdesc->txop = TXOP_HTTXOP;
 }
+
+u16 rt2x00ht_center_channel(struct rt2x00_dev *rt2x00dev,
+			    struct ieee80211_conf *conf)
+{
+	struct hw_mode_spec *spec = &rt2x00dev->spec;
+	int center_channel;
+	u16 i;
+
+	/*
+	 * Initialize center channel to current channel.
+	 */
+	center_channel = spec->channels[conf->channel->hw_value].channel;
+
+	/*
+	 * Adjust center channel to HT40+ and HT40- operation.
+	 */
+	if (conf_is_ht40_plus(conf))
+		center_channel += 2;
+	else if (conf_is_ht40_minus(conf))
+		center_channel -= (center_channel == 14) ? 1 : 2;
+
+	for (i = 0; i < spec->num_channels; i++)
+		if (spec->channels[i].channel == center_channel)
+			return i;
+
+	WARN_ON(1);
+	return conf->channel->hw_value;
+}

drivers/net/wireless/rt2x00/rt2x00lib.h

@@ -367,12 +367,21 @@ static inline void rt2x00crypto_rx_insert_iv(struct sk_buff *skb,
 void rt2x00ht_create_tx_descriptor(struct queue_entry *entry,
 				   struct txentry_desc *txdesc,
 				   const struct rt2x00_rate *hwrate);
+
+u16 rt2x00ht_center_channel(struct rt2x00_dev *rt2x00dev,
+			    struct ieee80211_conf *conf);
 #else
 static inline void rt2x00ht_create_tx_descriptor(struct queue_entry *entry,
 						 struct txentry_desc *txdesc,
 						 const struct rt2x00_rate *hwrate)
 {
 }
+
+static inline u16 rt2x00ht_center_channel(struct rt2x00_dev *rt2x00dev,
+					  struct ieee80211_conf *conf)
+{
+	return conf->channel->hw_value;
+}
 #endif /* CONFIG_RT2X00_LIB_HT */
 
 /*