ath9k: Fix invalid noisefloor reading due to channel update

While switching b/w HT20/40, the current channel's nf values
are updated into history buffer. Since the current channel's
channel type, channel flag got updated before reading
nf value from hw. This channel type mismatch is causing invalid
readings when hw is on ht20 but getnf tries to read on extn chains.

Signed-off-by: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/main.c

@@ -1672,6 +1672,7 @@ static int ath9k_config(struct ieee80211_hw *hw, u32 changed)
 
 	if (changed & IEEE80211_CONF_CHANGE_CHANNEL) {
 		struct ieee80211_channel *curchan = hw->conf.channel;
+		struct ath9k_channel old_chan;
 		int pos = curchan->hw_value;
 		int old_pos = -1;
 		unsigned long flags;
@@ -1688,14 +1689,24 @@ static int ath9k_config(struct ieee80211_hw *hw, u32 changed)
 			"Set channel: %d MHz type: %d\n",
 			curchan->center_freq, conf->channel_type);
 
-		ath9k_cmn_update_ichannel(&sc->sc_ah->channels[pos],
-					  curchan, conf->channel_type);
-
 		/* update survey stats for the old channel before switching */
 		spin_lock_irqsave(&common->cc_lock, flags);
 		ath_update_survey_stats(sc);
 		spin_unlock_irqrestore(&common->cc_lock, flags);
 
+		/*
+		 * Preserve the current channel values, before updating
+		 * the same channel
+		 */
+		if (old_pos == pos) {
+			memcpy(&old_chan, &sc->sc_ah->channels[pos],
+				sizeof(struct ath9k_channel));
+			ah->curchan = &old_chan;
+		}
+
+		ath9k_cmn_update_ichannel(&sc->sc_ah->channels[pos],
+					  curchan, conf->channel_type);
+
 		/*
 		 * If the operating channel changes, change the survey in-use flags
 		 * along with it.