iwlwifi: rs: option to easily disable Tx MIMO

The current TLC isn't optimized for low latency and some devices
have issues with MIMO. This kind of combo creates latency issues.
Allow to temporarily disable MIMO for tests in order to solve
the latency issues without the added complexity of MIMO.

Signed-off-by: Eyal Shapira <eyalx.shapira@intel.com>
Signed-off-by: Arik Nemtsov <arikx.nemtsov@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

drivers/net/wireless/iwlwifi/mvm/constants.h

@@ -95,5 +95,6 @@
 #define IWL_MVM_FW_MCAST_FILTER_PASS_ALL	0
 #define IWL_MVM_QUOTA_THRESHOLD			8
 #define IWL_MVM_RS_RSSI_BASED_INIT_RATE         0
+#define IWL_MVM_RS_DISABLE_MIMO			0
 
 #endif /* __MVM_CONSTANTS_H */

drivers/net/wireless/iwlwifi/mvm/rs.c

@@ -2684,6 +2684,9 @@ void iwl_mvm_rs_rate_init(struct iwl_mvm *mvm, struct ieee80211_sta *sta,
 			lq_sta->ldpc = true;
 	}
 
+	if (IWL_MVM_RS_DISABLE_MIMO)
+		lq_sta->active_mimo2_rate = 0;
+
 	lq_sta->max_legacy_rate_idx = find_last_bit(&lq_sta->active_legacy_rate,
 						    BITS_PER_LONG);
 	lq_sta->max_siso_rate_idx = find_last_bit(&lq_sta->active_siso_rate,