ath9k: Enable Short GI in 20 Mhz for ar9287 and later chips

This patch enables short GI rx at all rates and tx at mcs15
for 20 Mhz channel width also.
Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -2234,6 +2234,9 @@ int ath9k_hw_fill_cap_info(struct ath_hw *ah)
 	if (AR_SREV_9300_20_OR_LATER(ah))
 		pCap->hw_caps |= ATH9K_HW_CAP_RAC_SUPPORTED;
 
+	if (AR_SREV_9287_10_OR_LATER(ah))
+		pCap->hw_caps |= ATH9K_HW_CAP_SGI_20;
+
 	return 0;
 }
 

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

@@ -199,6 +199,7 @@ enum ath9k_hw_caps {
 	ATH9K_HW_CAP_RAC_SUPPORTED		= BIT(18),
 	ATH9K_HW_CAP_LDPC			= BIT(19),
 	ATH9K_HW_CAP_FASTCLOCK			= BIT(20),
+	ATH9K_HW_CAP_SGI_20			= BIT(21),
 };
 
 enum ath9k_capability_type {

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

@@ -208,6 +208,9 @@ static void setup_ht_cap(struct ath_softc *sc,
 	if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_LDPC)
 		ht_info->cap |= IEEE80211_HT_CAP_LDPC_CODING;
 
+	if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_SGI_20)
+		ht_info->cap |= IEEE80211_HT_CAP_SGI_20;
+
 	ht_info->ampdu_factor = IEEE80211_HT_MAX_AMPDU_64K;
 	ht_info->ampdu_density = IEEE80211_HT_MPDU_DENSITY_8;