iwlwifi: don't switch to SGI if not supported by AP

This patch fixes SGI support. RS didn't look at the capabilities of the AP
before switching to SGI, this should lead to a stall in the traffic with an
AP that doesn't support SGI.
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Guy Cohen  <guy.cohen@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-4965-rs.c

@@ -1439,6 +1439,15 @@ static int rs_move_siso_to_other(struct iwl_priv *priv,
 			}
 			break;
 		case IWL_SISO_SWITCH_GI:
+			if (!tbl->is_fat &&
+				!(priv->current_ht_config.sgf &
+						HT_SHORT_GI_20MHZ))
+				break;
+			if (tbl->is_fat &&
+				!(priv->current_ht_config.sgf &
+						HT_SHORT_GI_40MHZ))
+				break;
+
 			IWL_DEBUG_RATE("LQ: SISO toggle SGI/NGI\n");
 
 			memcpy(search_tbl, tbl, sz);
@@ -1521,6 +1530,15 @@ static int rs_move_mimo_to_other(struct iwl_priv *priv,
 			break;
 
 		case IWL_MIMO_SWITCH_GI:
+			if (!tbl->is_fat &&
+				!(priv->current_ht_config.sgf &
+						HT_SHORT_GI_20MHZ))
+				break;
+			if (tbl->is_fat &&
+				!(priv->current_ht_config.sgf &
+						HT_SHORT_GI_40MHZ))
+				break;
+
 			IWL_DEBUG_RATE("LQ: MIMO toggle SGI/NGI\n");
 
 			/* Set up new search table for MIMO */

drivers/net/wireless/iwlwifi/iwl-dev.h

@@ -610,8 +610,8 @@ struct iwl_hw_params {
 #endif
 };
 
-#define HT_SHORT_GI_20MHZ_ONLY	(1 << 0)
-#define HT_SHORT_GI_40MHZ_ONLY	(1 << 1)
+#define HT_SHORT_GI_20MHZ	(1 << 0)
+#define HT_SHORT_GI_40MHZ	(1 << 1)
 
 
 #define IWL_RX_HDR(x) ((struct iwl4965_rx_frame_hdr *)(\

drivers/net/wireless/iwlwifi/iwl4965-base.c

@@ -700,9 +700,9 @@ static void iwl4965_ht_conf(struct iwl_priv *priv,
 	priv->ps_mode = (u8)((ht_conf->cap & IEEE80211_HT_CAP_MIMO_PS) >> 2);
 
 	if (ht_conf->cap & IEEE80211_HT_CAP_SGI_20)
-		iwl_conf->sgf |= 0x1;
+		iwl_conf->sgf |= HT_SHORT_GI_20MHZ;
 	if (ht_conf->cap & IEEE80211_HT_CAP_SGI_40)
-		iwl_conf->sgf |= 0x2;
+		iwl_conf->sgf |= HT_SHORT_GI_40MHZ;
 
 	iwl_conf->is_green_field = !!(ht_conf->cap & IEEE80211_HT_CAP_GRN_FLD);
 	iwl_conf->max_amsdu_size =