iwlwifi: check control channel for pure 40MHz

for pure 40MHz mode, set the control channel location if provided, but not
like Mixed mode; if information is not provided, still allow 40MHz
operation.
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-core.c

@@ -826,9 +826,18 @@ void iwl_set_rxon_ht(struct iwl_priv *priv, struct iwl_ht_info *ht_info)
 			 RXON_FLG_CTRL_CHANNEL_LOC_HI_MSK);
 	if (iwl_is_fat_tx_allowed(priv, NULL)) {
 		/* pure 40 fat */
-		if (ht_info->ht_protection == IEEE80211_HT_OP_MODE_PROTECTION_20MHZ)
+		if (ht_info->ht_protection == IEEE80211_HT_OP_MODE_PROTECTION_20MHZ) {
 			rxon->flags |= RXON_FLG_CHANNEL_MODE_PURE_40;
-		else {
+			/* Note: control channel is opposite of extension channel */
+			switch (ht_info->extension_chan_offset) {
+			case IEEE80211_HT_PARAM_CHA_SEC_ABOVE:
+				rxon->flags &= ~RXON_FLG_CTRL_CHANNEL_LOC_HI_MSK;
+				break;
+			case IEEE80211_HT_PARAM_CHA_SEC_BELOW:
+				rxon->flags |= RXON_FLG_CTRL_CHANNEL_LOC_HI_MSK;
+				break;
+			}
+		} else {
 			/* Note: control channel is opposite of extension channel */
 			switch (ht_info->extension_chan_offset) {
 			case IEEE80211_HT_PARAM_CHA_SEC_ABOVE: