iwlwifi: mvm: choose an initial tx rate based on rssi conditions

Improve the initial tx rate and antenna selection to be based on
the rssi of the last rx. This avoids starting at the lowest legacy
rate always and requiring more tx traffic to "climb" up the rates.
Since this option might cause trouble in certain setups, allow to
disable it by default.

Signed-off-by: Eyal Shapira <eyalx.shapira@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

1 files changed, 108 insertions, 23 deletions

diff --git a/drivers/net/wireless/iwlwifi/mvm/rs.c b/drivers/net/wireless/iwlwifi/mvm/rs.c
index f77dfe4df07..d179a8eb50d 100644
--- a/drivers/net/wireless/iwlwifi/mvm/rs.c
+++ b/drivers/net/wireless/iwlwifi/mvm/rs.c
@@ -2288,6 +2288,110 @@ out:
 	lq_sta->last_txrate_idx = index;
 }
 
+struct rs_init_rate_info {
+	s8 rssi;
+	u8 rate_idx;
+};
+
+static const struct rs_init_rate_info rs_init_rates_24ghz[] = {
+	{ -60, IWL_RATE_54M_INDEX },
+	{ -64, IWL_RATE_48M_INDEX },
+	{ -68, IWL_RATE_36M_INDEX },
+	{ -80, IWL_RATE_24M_INDEX },
+	{ -84, IWL_RATE_18M_INDEX },
+	{ -85, IWL_RATE_12M_INDEX },
+	{ -86, IWL_RATE_11M_INDEX },
+	{ -88, IWL_RATE_5M_INDEX  },
+	{ -90, IWL_RATE_2M_INDEX  },
+	{ S8_MIN, IWL_RATE_1M_INDEX },
+};
+
+static const struct rs_init_rate_info rs_init_rates_5ghz[] = {
+	{ -60, IWL_RATE_54M_INDEX },
+	{ -64, IWL_RATE_48M_INDEX },
+	{ -72, IWL_RATE_36M_INDEX },
+	{ -80, IWL_RATE_24M_INDEX },
+	{ -84, IWL_RATE_18M_INDEX },
+	{ -85, IWL_RATE_12M_INDEX },
+	{ -87, IWL_RATE_9M_INDEX  },
+	{ S8_MIN, IWL_RATE_6M_INDEX },
+};
+
+/* Choose an initial legacy rate and antenna to use based on the RSSI
+ * of last Rx
+ */
+static void rs_get_initial_rate(struct iwl_mvm *mvm,
+				struct iwl_lq_sta *lq_sta,
+				enum ieee80211_band band,
+				struct rs_rate *rate)
+{
+	int i, nentries;
+	s8 best_rssi = S8_MIN;
+	u8 best_ant = ANT_NONE;
+	u8 valid_tx_ant = mvm->fw->valid_tx_ant;
+	const struct rs_init_rate_info *initial_rates;
+
+	for (i = 0; i < ARRAY_SIZE(lq_sta->pers.chain_signal); i++) {
+		if (!(lq_sta->pers.chains & BIT(i)))
+			continue;
+
+		if (lq_sta->pers.chain_signal[i] > best_rssi) {
+			best_rssi = lq_sta->pers.chain_signal[i];
+			best_ant = BIT(i);
+		}
+	}
+
+	IWL_DEBUG_RATE(mvm, "Best ANT: %s Best RSSI: %d\n",
+		       rs_pretty_ant(best_ant), best_rssi);
+
+	if (best_ant != ANT_A && best_ant != ANT_B)
+		rate->ant = first_antenna(valid_tx_ant);
+	else
+		rate->ant = best_ant;
+
+	rate->sgi = false;
+	rate->ldpc = false;
+	rate->bw = RATE_MCS_CHAN_WIDTH_20;
+
+	rate->index = find_first_bit(&lq_sta->active_legacy_rate,
+				     BITS_PER_LONG);
+
+	if (band == IEEE80211_BAND_5GHZ) {
+		rate->type = LQ_LEGACY_A;
+		initial_rates = rs_init_rates_5ghz;
+		nentries = ARRAY_SIZE(rs_init_rates_5ghz);
+	} else {
+		rate->type = LQ_LEGACY_G;
+		initial_rates = rs_init_rates_24ghz;
+		nentries = ARRAY_SIZE(rs_init_rates_24ghz);
+	}
+
+	if (IWL_MVM_RS_RSSI_BASED_INIT_RATE) {
+		for (i = 0; i < nentries; i++) {
+			int rate_idx = initial_rates[i].rate_idx;
+			if ((best_rssi >= initial_rates[i].rssi) &&
+			    (BIT(rate_idx) & lq_sta->active_legacy_rate)) {
+				rate->index = rate_idx;
+				break;
+			}
+		}
+	}
+
+	IWL_DEBUG_RATE(mvm, "rate_idx %d ANT %s\n", rate->index,
+		       rs_pretty_ant(rate->ant));
+}
+
+/* Save info about RSSI of last Rx */
+void rs_update_last_rssi(struct iwl_mvm *mvm,
+			 struct iwl_lq_sta *lq_sta,
+			 struct ieee80211_rx_status *rx_status)
+{
+	lq_sta->pers.chains = rx_status->chains;
+	lq_sta->pers.chain_signal[0] = rx_status->chain_signal[0];
+	lq_sta->pers.chain_signal[1] = rx_status->chain_signal[1];
+	lq_sta->pers.chain_signal[2] = rx_status->chain_signal[2];
+}
+
 /**
  * rs_initialize_lq - Initialize a station's hardware rate table
  *
@@ -2310,17 +2414,11 @@ static void rs_initialize_lq(struct iwl_mvm *mvm,
 {
 	struct iwl_scale_tbl_info *tbl;
 	struct rs_rate *rate;
-	int i;
 	u8 active_tbl = 0;
-	u8 valid_tx_ant;
 
 	if (!sta || !lq_sta)
 		return;
 
-	i = lq_sta->last_txrate_idx;
-
-	valid_tx_ant = mvm->fw->valid_tx_ant;
-
 	if (!lq_sta->search_better_tbl)
 		active_tbl = lq_sta->active_tbl;
 	else
@@ -2329,18 +2427,8 @@ static void rs_initialize_lq(struct iwl_mvm *mvm,
 	tbl = &(lq_sta->lq_info[active_tbl]);
 	rate = &tbl->rate;
 
-	if ((i < 0) || (i >= IWL_RATE_COUNT))
-		i = 0;
-
-	rate->index = i;
-	rate->ant = first_antenna(valid_tx_ant);
-	rate->sgi = false;
-	rate->ldpc = false;
-	rate->bw = RATE_MCS_CHAN_WIDTH_20;
-	if (band == IEEE80211_BAND_5GHZ)
-		rate->type = LQ_LEGACY_A;
-	else
-		rate->type = LQ_LEGACY_G;
+	rs_get_initial_rate(mvm, lq_sta, band, rate);
+	lq_sta->last_txrate_idx = rate->index;
 
 	WARN_ON_ONCE(rate->ant != ANT_A && rate->ant != ANT_B);
 	if (rate->ant == ANT_A)
@@ -2397,6 +2485,8 @@ static void *rs_alloc_sta(void *mvm_rate, struct ieee80211_sta *sta,
 	lq_sta->pers.dbg_fixed_rate = 0;
 	lq_sta->pers.dbg_fixed_txp_reduction = TPC_INVALID;
 #endif
+	lq_sta->pers.chains = 0;
+	memset(lq_sta->pers.chain_signal, 0, sizeof(lq_sta->pers.chain_signal));
 
 	return &sta_priv->lq_sta;
 }
@@ -2630,11 +2720,6 @@ void iwl_mvm_rs_rate_init(struct iwl_mvm *mvm, struct ieee80211_sta *sta,
 
 	/* as default allow aggregation for all tids */
 	lq_sta->tx_agg_tid_en = IWL_AGG_ALL_TID;
-
-	/* Set last_txrate_idx to lowest rate */
-	lq_sta->last_txrate_idx = rate_lowest_index(sband, sta);
-	if (sband->band == IEEE80211_BAND_5GHZ)
-		lq_sta->last_txrate_idx += IWL_FIRST_OFDM_RATE;
 	lq_sta->is_agg = 0;
 #ifdef CONFIG_IWLWIFI_DEBUGFS
 	iwl_mvm_reset_frame_stats(mvm, &mvm->drv_rx_stats);