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,