iwlwifi: report the rate index as an MCS rate number

If transmit in HT rate, report the rate index as an MCS rate number
instead of an index. so "iw" can display correct BitRate
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-agn-rs.c

@@ -270,6 +270,8 @@ const static struct iwl_rate_mcs_info iwl_rate_mcs[IWL_RATE_COUNT] = {
   {"60", "64QAM 5/6"}
 };
 
+#define MCS_INDEX_PER_STREAM	(8)
+
 static inline u8 rs_extract_rate(u32 rate_n_flags)
 {
 	return (u8)(rate_n_flags & 0xFF);
@@ -2518,12 +2520,33 @@ static void rs_get_rate(void *priv_r, struct ieee80211_sta *sta, void *priv_sta,
 		}
 	}
 
+	if (lq_sta->last_rate_n_flags & RATE_MCS_HT_MSK) {
+		rate_idx -= IWL_FIRST_OFDM_RATE;
+		/* 6M and 9M shared same MCS index */
+		rate_idx = (rate_idx > 0) ? (rate_idx - 1) : 0;
+		if (rs_extract_rate(lq_sta->last_rate_n_flags) >=
+		    IWL_RATE_MIMO3_6M_PLCP)
+			rate_idx = rate_idx + (2 * MCS_INDEX_PER_STREAM);
+		else if (rs_extract_rate(lq_sta->last_rate_n_flags) >=
+			 IWL_RATE_MIMO2_6M_PLCP)
+			rate_idx = rate_idx + MCS_INDEX_PER_STREAM;
+		info->control.rates[0].flags = IEEE80211_TX_RC_MCS;
+		if (lq_sta->last_rate_n_flags & RATE_MCS_SGI_MSK)
+			info->control.rates[0].flags |= IEEE80211_TX_RC_SHORT_GI;
+		if (lq_sta->last_rate_n_flags & RATE_MCS_DUP_MSK)
+			info->control.rates[0].flags |= IEEE80211_TX_RC_DUP_DATA;
+		if (lq_sta->last_rate_n_flags & RATE_MCS_FAT_MSK)
+			info->control.rates[0].flags |= IEEE80211_TX_RC_40_MHZ_WIDTH;
+		if (lq_sta->last_rate_n_flags & RATE_MCS_GF_MSK)
+			info->control.rates[0].flags |= IEEE80211_TX_RC_GREEN_FIELD;
+	} else {
 		if (rate_idx < 0 || rate_idx > IWL_RATE_COUNT)
 			rate_idx = rate_lowest_index(sband, sta);
 		else if (sband->band == IEEE80211_BAND_5GHZ)
 			rate_idx -= IWL_FIRST_OFDM_RATE;
-
+	}
 	info->control.rates[0].idx = rate_idx;
+
 }
 
 static void *rs_alloc_sta(void *priv_rate, struct ieee80211_sta *sta,