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>

4 files changed, 101 insertions, 79 deletions

diff --git a/drivers/net/wireless/ath/ath9k/hw.c b/drivers/net/wireless/ath/ath9k/hw.c
index 6bfac1ca07f..2fd62546187 100644
--- a/drivers/net/wireless/ath/ath9k/hw.c
+++ b/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;
 }
 
diff --git a/drivers/net/wireless/ath/ath9k/hw.h b/drivers/net/wireless/ath/ath9k/hw.h
index bfecde083a4..5cf0714f069 100644
--- a/drivers/net/wireless/ath/ath9k/hw.h
+++ b/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 {
diff --git a/drivers/net/wireless/ath/ath9k/init.c b/drivers/net/wireless/ath/ath9k/init.c
index d457cb3bd77..f388dcc8e46 100644
--- a/drivers/net/wireless/ath/ath9k/init.c
+++ b/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;
 
diff --git a/drivers/net/wireless/ath/ath9k/rc.c b/drivers/net/wireless/ath/ath9k/rc.c
index 8519452c95f..f5180d3d407 100644
--- a/drivers/net/wireless/ath/ath9k/rc.c
+++ b/drivers/net/wireless/ath/ath9k/rc.c
@@ -40,73 +40,75 @@ static const struct ath_rate_table ar5416_11na_ratetable = {
 		{ VALID, VALID, WLAN_RC_PHY_OFDM, 54000, /* 54 Mb */
 			29300, 7, 108, 4, 7, 7, 7, 7 },
 		{ VALID_2040, VALID_2040, WLAN_RC_PHY_HT_20_SS, 6500, /* 6.5 Mb */
-			6400, 0, 0, 0, 8, 24, 8, 24 },
+			6400, 0, 0, 0, 8, 25, 8, 25 },
 		{ VALID_20, VALID_20, WLAN_RC_PHY_HT_20_SS, 13000, /* 13 Mb */
-			12700, 1, 1, 2, 9, 25, 9, 25 },
+			12700, 1, 1, 2, 9, 26, 9, 26 },
 		{ VALID_20, VALID_20, WLAN_RC_PHY_HT_20_SS, 19500, /* 19.5 Mb */
-			18800, 2, 2, 2, 10, 26, 10, 26 },
+			18800, 2, 2, 2, 10, 27, 10, 27 },
 		{ VALID_20, VALID_20, WLAN_RC_PHY_HT_20_SS, 26000, /* 26 Mb */
-			25000, 3, 3, 4, 11, 27, 11, 27 },
+			25000, 3, 3, 4, 11, 28, 11, 28 },
 		{ VALID_20, VALID_20, WLAN_RC_PHY_HT_20_SS, 39000, /* 39 Mb */
-			36700, 4, 4, 4, 12, 28, 12, 28 },
+			36700, 4, 4, 4, 12, 29, 12, 29 },
 		{ INVALID, VALID_20, WLAN_RC_PHY_HT_20_SS, 52000, /* 52 Mb */
-			48100, 5, 5, 4, 13, 29, 13, 29 },
+			48100, 5, 5, 4, 13, 30, 13, 30 },
 		{ INVALID, VALID_20, WLAN_RC_PHY_HT_20_SS, 58500, /* 58.5 Mb */
-			53500, 6, 6, 4, 14, 30, 14, 30 },
+			53500, 6, 6, 4, 14, 31, 14, 31 },
 		{ INVALID, VALID_20, WLAN_RC_PHY_HT_20_SS, 65000, /* 65 Mb */
-			59000, 7, 7, 4, 15, 31, 15, 32 },
+			59000, 7, 7, 4, 15, 32, 15, 33 },
 		{ INVALID, INVALID, WLAN_RC_PHY_HT_20_DS, 13000, /* 13 Mb */
-			12700, 8, 8, 3, 16, 33, 16, 33 },
+			12700, 8, 8, 3, 16, 34, 16, 34 },
 		{ INVALID, INVALID, WLAN_RC_PHY_HT_20_DS, 26000, /* 26 Mb */
-			24800, 9, 9, 2, 17, 34, 17, 34 },
+			24800, 9, 9, 2, 17, 35, 17, 35 },
 		{ INVALID, INVALID, WLAN_RC_PHY_HT_20_DS, 39000, /* 39 Mb */
-			36600, 10, 10, 2, 18, 35, 18, 35 },
+			36600, 10, 10, 2, 18, 36, 18, 36 },
 		{ VALID_20, INVALID, WLAN_RC_PHY_HT_20_DS, 52000, /* 52 Mb */
-			48100, 11, 11, 4, 19, 36, 19, 36 },
+			48100, 11, 11, 4, 19, 37, 19, 37 },
 		{ VALID_20, INVALID, WLAN_RC_PHY_HT_20_DS, 78000, /* 78 Mb */
-			69500, 12, 12, 4, 20, 37, 20, 37 },
+			69500, 12, 12, 4, 20, 38, 20, 38 },
 		{ VALID_20, INVALID, WLAN_RC_PHY_HT_20_DS, 104000, /* 104 Mb */
-			89500, 13, 13, 4, 21, 38, 21, 38 },
+			89500, 13, 13, 4, 21, 39, 21, 39 },
 		{ VALID_20, INVALID, WLAN_RC_PHY_HT_20_DS, 117000, /* 117 Mb */
-			98900, 14, 14, 4, 22, 39, 22, 39 },
+			98900, 14, 14, 4, 22, 40, 22, 40 },
 		{ VALID_20, INVALID, WLAN_RC_PHY_HT_20_DS, 130000, /* 130 Mb */
-			108300, 15, 15, 4, 23, 40, 23, 41 },
+			108300, 15, 15, 4, 23, 41, 24, 42 },
+		{ VALID_20, INVALID, WLAN_RC_PHY_HT_20_DS_HGI, 144400, /* 144.4 Mb */
+			12000, 15, 15, 4, 23, 41, 24, 42 },
 		{ VALID_40, VALID_40, WLAN_RC_PHY_HT_40_SS, 13500, /* 13.5 Mb */
-			13200, 0, 0, 0, 8, 24, 24, 24 },
+			13200, 0, 0, 0, 8, 25, 25, 25 },
 		{ VALID_40, VALID_40, WLAN_RC_PHY_HT_40_SS, 27500, /* 27.0 Mb */
-			25900, 1, 1, 2, 9, 25, 25, 25 },
+			25900, 1, 1, 2, 9, 26, 26, 26 },
 		{ VALID_40, VALID_40, WLAN_RC_PHY_HT_40_SS, 40500, /* 40.5 Mb */
-			38600, 2, 2, 2, 10, 26, 26, 26 },
+			38600, 2, 2, 2, 10, 27, 27, 27 },
 		{ VALID_40, VALID_40, WLAN_RC_PHY_HT_40_SS, 54000, /* 54 Mb */
-			49800, 3, 3, 4, 11, 27, 27, 27 },
+			49800, 3, 3, 4, 11, 28, 28, 28 },
 		{ VALID_40, VALID_40, WLAN_RC_PHY_HT_40_SS, 81500, /* 81 Mb */
-			72200, 4, 4, 4, 12, 28, 28, 28 },
+			72200, 4, 4, 4, 12, 29, 29, 29 },
 		{ INVALID, VALID_40, WLAN_RC_PHY_HT_40_SS, 108000, /* 108 Mb */
-			92900, 5, 5, 4, 13, 29, 29, 29 },
+			92900, 5, 5, 4, 13, 30, 30, 30 },
 		{ INVALID, VALID_40, WLAN_RC_PHY_HT_40_SS, 121500, /* 121.5 Mb */
-			102700, 6, 6, 4, 14, 30, 30, 30 },
+			102700, 6, 6, 4, 14, 31, 31, 31 },
 		{ INVALID, VALID_40, WLAN_RC_PHY_HT_40_SS, 135000, /* 135 Mb */
-			112000, 7, 7, 4, 15, 31, 32, 32 },
+			112000, 7, 7, 4, 15, 32, 33, 33 },
 		{ INVALID, VALID_40, WLAN_RC_PHY_HT_40_SS_HGI, 150000, /* 150 Mb */
-			122000, 7, 7, 4, 15, 31, 32, 32 },
+			122000, 7, 7, 4, 15, 32, 33, 33 },
 		{ INVALID, INVALID, WLAN_RC_PHY_HT_40_DS, 27000, /* 27 Mb */
-			25800, 8, 8, 0, 16, 33, 33, 33 },
+			25800, 8, 8, 0, 16, 34, 34, 34 },
 		{ INVALID, INVALID, WLAN_RC_PHY_HT_40_DS, 54000, /* 54 Mb */
-			49800, 9, 9, 2, 17, 34, 34, 34 },
+			49800, 9, 9, 2, 17, 35, 35, 35 },
 		{ INVALID, INVALID, WLAN_RC_PHY_HT_40_DS, 81000, /* 81 Mb */
-			71900, 10, 10, 2, 18, 35, 35, 35 },
+			71900, 10, 10, 2, 18, 36, 36, 36 },
 		{ VALID_40, INVALID, WLAN_RC_PHY_HT_40_DS, 108000, /* 108 Mb */
-			92500, 11, 11, 4, 19, 36, 36, 36 },
+			92500, 11, 11, 4, 19, 37, 37, 37 },
 		{ VALID_40, INVALID, WLAN_RC_PHY_HT_40_DS, 162000, /* 162 Mb */
-			130300, 12, 12, 4, 20, 37, 37, 37 },
+			130300, 12, 12, 4, 20, 38, 38, 38 },
 		{ VALID_40, INVALID, WLAN_RC_PHY_HT_40_DS, 216000, /* 216 Mb */
-			162800, 13, 13, 4, 21, 38, 38, 38 },
+			162800, 13, 13, 4, 21, 39, 39, 39 },
 		{ VALID_40, INVALID, WLAN_RC_PHY_HT_40_DS, 243000, /* 243 Mb */
-			178200, 14, 14, 4, 22, 39, 39, 39 },
+			178200, 14, 14, 4, 22, 40, 40, 40 },
 		{ VALID_40, INVALID, WLAN_RC_PHY_HT_40_DS, 270000, /* 270 Mb */
-			192100, 15, 15, 4, 23, 40, 41, 41 },
+			192100, 15, 15, 4, 23, 41, 42, 42 },
 		{ VALID_40, INVALID, WLAN_RC_PHY_HT_40_DS_HGI, 300000, /* 300 Mb */
-			207000, 15, 15, 4, 23, 40, 41, 41 },
+			207000, 15, 15, 4, 23, 41, 42, 42 },
 	},
 	50,  /* probe interval */
 	WLAN_RC_HT_FLAG,  /* Phy rates allowed initially */
@@ -144,73 +146,75 @@ static const struct ath_rate_table ar5416_11ng_ratetable = {
 		{ VALID, VALID, WLAN_RC_PHY_OFDM, 54000, /* 54 Mb */
 			30900, 11, 108, 8, 11, 11, 11, 11 },
 		{ INVALID, INVALID, WLAN_RC_PHY_HT_20_SS, 6500, /* 6.5 Mb */
-			6400, 0, 0, 4, 12, 28, 12, 28 },
+			6400, 0, 0, 4, 12, 29, 12, 29 },
 		{ VALID_20, VALID_20, WLAN_RC_PHY_HT_20_SS, 13000, /* 13 Mb */
-			12700, 1, 1, 6, 13, 29, 13, 29 },
+			12700, 1, 1, 6, 13, 30, 13, 30 },
 		{ VALID_20, VALID_20, WLAN_RC_PHY_HT_20_SS, 19500, /* 19.5 Mb */
-			18800, 2, 2, 6, 14, 30, 14, 30 },
+			18800, 2, 2, 6, 14, 31, 14, 31 },
 		{ VALID_20, VALID_20, WLAN_RC_PHY_HT_20_SS, 26000, /* 26 Mb */
-			25000, 3, 3, 8, 15, 31, 15, 31 },
+			25000, 3, 3, 8, 15, 32, 15, 32 },
 		{ VALID_20, VALID_20, WLAN_RC_PHY_HT_20_SS, 39000, /* 39 Mb */
-			36700, 4, 4, 8, 16, 32, 16, 32 },
+			36700, 4, 4, 8, 16, 33, 16, 33 },
 		{ INVALID, VALID_20, WLAN_RC_PHY_HT_20_SS, 52000, /* 52 Mb */
-			48100, 5, 5, 8, 17, 33, 17, 33 },
+			48100, 5, 5, 8, 17, 34, 17, 34 },
 		{ INVALID,  VALID_20, WLAN_RC_PHY_HT_20_SS, 58500, /* 58.5 Mb */
-			53500, 6, 6, 8, 18, 34, 18, 34 },
+			53500, 6, 6, 8, 18, 35, 18, 35 },
 		{ INVALID, VALID_20, WLAN_RC_PHY_HT_20_SS, 65000, /* 65 Mb */
-			59000, 7, 7, 8, 19, 35, 19, 36 },
+			59000, 7, 7, 8, 19, 36, 19, 37 },
 		{ INVALID, INVALID, WLAN_RC_PHY_HT_20_DS, 13000, /* 13 Mb */
-			12700, 8, 8, 4, 20, 37, 20, 37 },
+			12700, 8, 8, 4, 20, 38, 20, 38 },
 		{ INVALID, INVALID, WLAN_RC_PHY_HT_20_DS, 26000, /* 26 Mb */
-			24800, 9, 9, 6, 21, 38, 21, 38 },
+			24800, 9, 9, 6, 21, 39, 21, 39 },
 		{ INVALID, INVALID, WLAN_RC_PHY_HT_20_DS, 39000, /* 39 Mb */
-			36600, 10, 10, 6, 22, 39, 22, 39 },
+			36600, 10, 10, 6, 22, 40, 22, 40 },
 		{ VALID_20, INVALID, WLAN_RC_PHY_HT_20_DS, 52000, /* 52 Mb */
-			48100, 11, 11, 8, 23, 40, 23, 40 },
+			48100, 11, 11, 8, 23, 41, 23, 41 },
 		{ VALID_20, INVALID, WLAN_RC_PHY_HT_20_DS, 78000, /* 78 Mb */
-			69500, 12, 12, 8, 24, 41, 24, 41 },
+			69500, 12, 12, 8, 24, 42, 24, 42 },
 		{ VALID_20, INVALID, WLAN_RC_PHY_HT_20_DS, 104000, /* 104 Mb */
-			89500, 13, 13, 8, 25, 42, 25, 42 },
+			89500, 13, 13, 8, 25, 43, 25, 43 },
 		{ VALID_20, INVALID, WLAN_RC_PHY_HT_20_DS, 117000, /* 117 Mb */
-			98900, 14, 14, 8, 26, 43, 26, 44 },
+			98900, 14, 14, 8, 26, 44, 26, 44 },
 		{ VALID_20, INVALID, WLAN_RC_PHY_HT_20_DS, 130000, /* 130 Mb */
-			108300, 15, 15, 8, 27, 44, 27, 45 },
+			108300, 15, 15, 8, 27, 45, 28, 46 },
+		{ VALID_20, INVALID, WLAN_RC_PHY_HT_20_DS_HGI, 144400, /* 130 Mb */
+			120000, 15, 15, 8, 27, 45, 28, 46 },
 		{ VALID_40, VALID_40, WLAN_RC_PHY_HT_40_SS, 13500, /* 13.5 Mb */
-			13200, 0, 0, 8, 12, 28, 28, 28 },
+			13200, 0, 0, 8, 12, 29, 29, 29 },
 		{ VALID_40, VALID_40, WLAN_RC_PHY_HT_40_SS, 27500, /* 27.0 Mb */
-			25900, 1, 1, 8, 13, 29, 29, 29 },
+			25900, 1, 1, 8, 13, 30, 30, 30 },
 		{ VALID_40, VALID_40, WLAN_RC_PHY_HT_40_SS, 40500, /* 40.5 Mb */
-			38600, 2, 2, 8, 14, 30, 30, 30 },
+			38600, 2, 2, 8, 14, 31, 31, 31 },
 		{ VALID_40, VALID_40, WLAN_RC_PHY_HT_40_SS, 54000, /* 54 Mb */
-			49800, 3, 3, 8,  15, 31, 31, 31 },
+			49800, 3, 3, 8,  15, 32, 32, 32 },
 		{ VALID_40, VALID_40, WLAN_RC_PHY_HT_40_SS, 81500, /* 81 Mb */
-			72200, 4, 4, 8, 16, 32, 32, 32 },
+			72200, 4, 4, 8, 16, 33, 33, 33 },
 		{ INVALID, VALID_40, WLAN_RC_PHY_HT_40_SS, 108000, /* 108 Mb */
-			92900, 5, 5, 8, 17, 33, 33, 33 },
+			92900, 5, 5, 8, 17, 34, 34, 34 },
 		{ INVALID,  VALID_40, WLAN_RC_PHY_HT_40_SS, 121500, /* 121.5 Mb */
-			102700, 6, 6, 8, 18, 34, 34, 34 },
+			102700, 6, 6, 8, 18, 35, 35, 35 },
 		{ INVALID, VALID_40, WLAN_RC_PHY_HT_40_SS, 135000, /* 135 Mb */
-			112000, 7, 7, 8, 19, 35, 36, 36 },
+			112000, 7, 7, 8, 19, 36, 37, 37 },
 		{ INVALID, VALID_40, WLAN_RC_PHY_HT_40_SS_HGI, 150000, /* 150 Mb */
-			122000, 7, 7, 8, 19, 35, 36, 36 },
+			122000, 7, 7, 8, 19, 36, 37, 37 },
 		{ INVALID, INVALID, WLAN_RC_PHY_HT_40_DS, 27000, /* 27 Mb */
-			25800, 8, 8, 8, 20, 37, 37, 37 },
+			25800, 8, 8, 8, 20, 38, 38, 38 },
 		{ INVALID, INVALID, WLAN_RC_PHY_HT_40_DS, 54000, /* 54 Mb */
-			49800, 9, 9, 8, 21, 38, 38, 38 },
+			49800, 9, 9, 8, 21, 39, 39, 39 },
 		{ INVALID, INVALID, WLAN_RC_PHY_HT_40_DS, 81000, /* 81 Mb */
-			71900, 10, 10, 8, 22, 39, 39, 39 },
+			71900, 10, 10, 8, 22, 40, 40, 40 },
 		{ VALID_40, INVALID, WLAN_RC_PHY_HT_40_DS, 108000, /* 108 Mb */
-			92500, 11, 11, 8, 23, 40, 40, 40 },
+			92500, 11, 11, 8, 23, 41, 41, 41 },
 		{ VALID_40, INVALID, WLAN_RC_PHY_HT_40_DS, 162000, /* 162 Mb */
-			130300, 12, 12, 8, 24, 41, 41, 41 },
+			130300, 12, 12, 8, 24, 42, 42, 42 },
 		{ VALID_40, INVALID, WLAN_RC_PHY_HT_40_DS, 216000, /* 216 Mb */
-			162800, 13, 13, 8, 25, 42, 42, 42 },
+			162800, 13, 13, 8, 25, 43, 43, 43 },
 		{ VALID_40, INVALID, WLAN_RC_PHY_HT_40_DS, 243000, /* 243 Mb */
-			178200, 14, 14, 8, 26, 43, 43, 43 },
+			178200, 14, 14, 8, 26, 44, 44, 44 },
 		{ VALID_40, INVALID, WLAN_RC_PHY_HT_40_DS, 270000, /* 270 Mb */
-			192100, 15, 15, 8, 27, 44, 45, 45 },
+			192100, 15, 15, 8, 27, 45, 46, 46 },
 		{ VALID_40, INVALID, WLAN_RC_PHY_HT_40_DS_HGI, 300000, /* 300 Mb */
-			207000, 15, 15, 8, 27, 44, 45, 45 },
+			207000, 15, 15, 8, 27, 45, 46, 46 },
 	},
 	50,  /* probe interval */
 	WLAN_RC_HT_FLAG,  /* Phy rates allowed initially */
@@ -1193,7 +1197,7 @@ static void ath_rc_init(struct ath_softc *sc,
 }
 
 static u8 ath_rc_build_ht_caps(struct ath_softc *sc, struct ieee80211_sta *sta,
-			       bool is_cw40, bool is_sgi40)
+			       bool is_cw40, bool is_sgi)
 {
 	u8 caps = 0;
 
@@ -1206,8 +1210,9 @@ static u8 ath_rc_build_ht_caps(struct ath_softc *sc, struct ieee80211_sta *sta,
 		}
 		if (is_cw40)
 			caps |= WLAN_RC_40_FLAG;
-		if (is_sgi40)
+		if (is_sgi)
 			caps |= WLAN_RC_SGI_FLAG;
+
 	}
 
 	return caps;
@@ -1300,7 +1305,7 @@ static void ath_rate_init(void *priv, struct ieee80211_supported_band *sband,
 	struct ath_softc *sc = priv;
 	struct ath_rate_priv *ath_rc_priv = priv_sta;
 	const struct ath_rate_table *rate_table;
-	bool is_cw40, is_sgi40;
+	bool is_cw40, is_sgi = false;
 	int i, j = 0;
 
 	for (i = 0; i < sband->n_bitrates; i++) {
@@ -1323,7 +1328,11 @@ static void ath_rate_init(void *priv, struct ieee80211_supported_band *sband,
 	}
 
 	is_cw40 = sta->ht_cap.cap & IEEE80211_HT_CAP_SUP_WIDTH_20_40;
-	is_sgi40 = sta->ht_cap.cap & IEEE80211_HT_CAP_SGI_40;
+
+	if (is_cw40)
+		is_sgi = sta->ht_cap.cap & IEEE80211_HT_CAP_SGI_40;
+	else if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_SGI_20)
+		is_sgi = sta->ht_cap.cap & IEEE80211_HT_CAP_SGI_20;
 
 	/* Choose rate table first */
 
@@ -1336,7 +1345,7 @@ static void ath_rate_init(void *priv, struct ieee80211_supported_band *sband,
 		rate_table = hw_rate_table[sc->cur_rate_mode];
 	}
 
-	ath_rc_priv->ht_cap = ath_rc_build_ht_caps(sc, sta, is_cw40, is_sgi40);
+	ath_rc_priv->ht_cap = ath_rc_build_ht_caps(sc, sta, is_cw40, is_sgi);
 	ath_rc_init(sc, priv_sta, sband, sta, rate_table);
 }
 
@@ -1347,10 +1356,10 @@ static void ath_rate_update(void *priv, struct ieee80211_supported_band *sband,
 	struct ath_softc *sc = priv;
 	struct ath_rate_priv *ath_rc_priv = priv_sta;
 	const struct ath_rate_table *rate_table = NULL;
-	bool oper_cw40 = false, oper_sgi40;
+	bool oper_cw40 = false, oper_sgi;
 	bool local_cw40 = (ath_rc_priv->ht_cap & WLAN_RC_40_FLAG) ?
 		true : false;
-	bool local_sgi40 = (ath_rc_priv->ht_cap & WLAN_RC_SGI_FLAG) ?
+	bool local_sgi = (ath_rc_priv->ht_cap & WLAN_RC_SGI_FLAG) ?
 		true : false;
 
 	/* FIXME: Handle AP mode later when we support CWM */
@@ -1363,15 +1372,21 @@ static void ath_rate_update(void *priv, struct ieee80211_supported_band *sband,
 		    oper_chan_type == NL80211_CHAN_HT40PLUS)
 			oper_cw40 = true;
 
-		oper_sgi40 = (sta->ht_cap.cap & IEEE80211_HT_CAP_SGI_40) ?
-			true : false;
+		if (oper_cw40)
+			oper_sgi = (sta->ht_cap.cap & IEEE80211_HT_CAP_SGI_40) ?
+				   true : false;
+		else if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_SGI_20)
+			oper_sgi = (sta->ht_cap.cap & IEEE80211_HT_CAP_SGI_20) ?
+				   true : false;
+		else
+			oper_sgi = false;
 
-		if ((local_cw40 != oper_cw40) || (local_sgi40 != oper_sgi40)) {
+		if ((local_cw40 != oper_cw40) || (local_sgi != oper_sgi)) {
 			rate_table = ath_choose_rate_table(sc, sband->band,
 						   sta->ht_cap.ht_supported,
 						   oper_cw40);
 			ath_rc_priv->ht_cap = ath_rc_build_ht_caps(sc, sta,
-						   oper_cw40, oper_sgi40);
+						   oper_cw40, oper_sgi);
 			ath_rc_init(sc, priv_sta, sband, sta, rate_table);
 
 			ath_print(ath9k_hw_common(sc->sc_ah), ATH_DBG_CONFIG,