ath9k: check for Rx-STBC flag and pass it to ieee80211

This patch make use of STBC flag in DMA RX descriptor.
Only devices after ar9280 can provide this information.

If card support it we will set HAVE_STBC flag, to show
clint programm thet STBC is supported but not received.
Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -21,6 +21,7 @@
 #include <linux/ath9k_platform.h>
 #include <linux/module.h>
 #include <linux/relay.h>
+#include <net/ieee80211_radiotap.h>
 
 #include "ath9k.h"
 
@@ -766,9 +767,14 @@ void ath9k_set_hw_capab(struct ath_softc *sc, struct ieee80211_hw *hw)
 		IEEE80211_HW_REPORTS_TX_ACK_STATUS |
 		IEEE80211_HW_SUPPORTS_RC_TABLE;
 
-	if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_HT)
+	if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_HT) {
 		hw->flags |= IEEE80211_HW_AMPDU_AGGREGATION;
 
+		if (AR_SREV_9280_20_OR_LATER(ah))
+			hw->radiotap_mcs_details |=
+				IEEE80211_RADIOTAP_MCS_HAVE_STBC;
+	}
+
 	if (AR_SREV_9160_10_OR_LATER(sc->sc_ah) || ath9k_modparam_nohwcrypt)
 		hw->flags |= IEEE80211_HW_MFP_CAPABLE;
 

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

@@ -593,6 +593,11 @@ int ath9k_hw_rxprocdesc(struct ath_hw *ah, struct ath_desc *ds,
 		(ads.ds_rxstatus3 & AR_GI) ? RX_FLAG_SHORT_GI : 0;
 	rs->flag |=
 		(ads.ds_rxstatus3 & AR_2040) ? RX_FLAG_40MHZ : 0;
+	if (AR_SREV_9280_20_OR_LATER(ah))
+		rs->flag |=
+			(ads.ds_rxstatus3 & AR_STBC) ?
+				/* we can only Nss=1 STBC */
+				(1 << RX_FLAG_STBC_SHIFT) : 0;
 
 	if (ads.ds_rxstatus8 & AR_PreDelimCRCErr)
 		rs->rs_flags |= ATH9K_RX_DELIM_CRC_PRE;

drivers/net/wireless/ath/ath9k/mac.h

@@ -534,7 +534,8 @@ struct ar5416_desc {
 #define AR_2040             0x00000002
 #define AR_Parallel40       0x00000004
 #define AR_Parallel40_S     2
-#define AR_RxStatusRsvd30   0x000000f8
+#define AR_STBC             0x00000008 /* on ar9280 and later */
+#define AR_RxStatusRsvd30   0x000000f0
 #define AR_RxAntenna	    0xffffff00
 #define AR_RxAntenna_S	    8