mt76: improve signal strength reporting

Instead of just taking the maximum per-chain signal strength values,
add an approximation for the sum of the combined signal.
This should more accurately reflect the real signal strength, especially
if the per-chain signal strength values are close to each other
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mac80211.c

@@ -932,6 +932,35 @@ void mt76_wcid_key_setup(struct mt76_dev *dev, struct mt76_wcid *wcid,
 }
 EXPORT_SYMBOL(mt76_wcid_key_setup);
 
+static int
+mt76_rx_signal(struct mt76_rx_status *status)
+{
+	s8 *chain_signal = status->chain_signal;
+	int signal = -128;
+	u8 chains;
+
+	for (chains = status->chains; chains; chains >>= 1, chain_signal++) {
+		int cur, diff;
+
+		if (!(chains & BIT(0)))
+			continue;
+
+		cur = *chain_signal;
+		if (cur > signal)
+			swap(cur, signal);
+
+		diff = signal - cur;
+		if (diff == 0)
+			signal += 3;
+		else if (diff <= 2)
+			signal += 2;
+		else if (diff <= 6)
+			signal += 1;
+	}
+
+	return signal;
+}
+
 static void
 mt76_rx_convert(struct mt76_dev *dev, struct sk_buff *skb,
 		struct ieee80211_hw **hw,
@@ -960,6 +989,9 @@ mt76_rx_convert(struct mt76_dev *dev, struct sk_buff *skb,
 	status->ampdu_reference = mstat.ampdu_ref;
 	status->device_timestamp = mstat.timestamp;
 	status->mactime = mstat.timestamp;
+	status->signal = mt76_rx_signal(&mstat);
+	if (status->signal <= -128)
+		status->flag |= RX_FLAG_NO_SIGNAL_VAL;
 
 	if (ieee80211_is_beacon(hdr->frame_control) ||
 	    ieee80211_is_probe_resp(hdr->frame_control))

drivers/net/wireless/mediatek/mt76/mt7603/mac.c

@@ -643,11 +643,6 @@ mt7603_mac_fill_rx(struct mt7603_dev *dev, struct sk_buff *skb)
 		status->chain_signal[1] = FIELD_GET(MT_RXV4_IB_RSSI1, rxdg3) +
 					  dev->rssi_offset[1];
 
-		status->signal = status->chain_signal[0];
-		if (status->chains & BIT(1))
-			status->signal = max(status->signal,
-					     status->chain_signal[1]);
-
 		if (FIELD_GET(MT_RXV1_FRAME_MODE, rxdg0) == 1)
 			status->bw = RATE_INFO_BW_40;
 

drivers/net/wireless/mediatek/mt76/mt7615/mac.c

@@ -576,15 +576,6 @@ static int mt7615_mac_fill_rx(struct mt7615_dev *dev, struct sk_buff *skb)
 		status->chain_signal[1] = to_rssi(MT_RXV4_RCPI1, rxdg3);
 		status->chain_signal[2] = to_rssi(MT_RXV4_RCPI2, rxdg3);
 		status->chain_signal[3] = to_rssi(MT_RXV4_RCPI3, rxdg3);
-		status->signal = status->chain_signal[0];
-
-		for (i = 1; i < hweight8(mphy->antenna_mask); i++) {
-			if (!(status->chains & BIT(i)))
-				continue;
-
-			status->signal = max(status->signal,
-					     status->chain_signal[i]);
-		}
 
 		mt7615_mac_fill_tm_rx(mphy->priv, rxd);
 

drivers/net/wireless/mediatek/mt76/mt76x02_mac.c

@@ -860,9 +860,7 @@ int mt76x02_mac_process_rx(struct mt76x02_dev *dev, struct sk_buff *skb,
 		status->chain_signal[1] = mt76x02_mac_get_rssi(dev,
 							       rxwi->rssi[1],
 							       1);
-		signal = max_t(s8, signal, status->chain_signal[1]);
 	}
-	status->signal = signal;
 	status->freq = dev->mphy.chandef.chan->center_freq;
 	status->band = dev->mphy.chandef.chan->band;
 

drivers/net/wireless/mediatek/mt76/mt7915/mac.c

@@ -593,7 +593,7 @@ mt7915_mac_fill_rx(struct mt7915_dev *dev, struct sk_buff *skb)
 	u16 seq_ctrl = 0;
 	u8 qos_ctl = 0;
 	__le16 fc = 0;
-	int i, idx;
+	int idx;
 
 	memset(status, 0, sizeof(*status));
 
@@ -753,15 +753,6 @@ mt7915_mac_fill_rx(struct mt7915_dev *dev, struct sk_buff *skb)
 		status->chain_signal[1] = to_rssi(MT_PRXV_RCPI1, v1);
 		status->chain_signal[2] = to_rssi(MT_PRXV_RCPI2, v1);
 		status->chain_signal[3] = to_rssi(MT_PRXV_RCPI3, v1);
-		status->signal = status->chain_signal[0];
-
-		for (i = 1; i < hweight8(mphy->antenna_mask); i++) {
-			if (!(status->chains & BIT(i)))
-				continue;
-
-			status->signal = max(status->signal,
-					     status->chain_signal[i]);
-		}
 
 		/* RXD Group 5 - C-RXV */
 		if (rxd1 & MT_RXD1_NORMAL_GROUP_5) {

drivers/net/wireless/mediatek/mt76/mt7921/mac.c

@@ -670,9 +670,6 @@ mt7921_mac_fill_rx(struct mt7921_dev *dev, struct sk_buff *skb)
 					     status->chain_signal[i]);
 		}
 
-		if (status->signal == -128)
-			status->flag |= RX_FLAG_NO_SIGNAL_VAL;
-
 		stbc = FIELD_GET(MT_PRXV_STBC, v0);
 		gi = FIELD_GET(MT_PRXV_SGI, v0);
 		cck = false;