mt76: mt7615: add support for per-chain signal strength reporting

Fill in RX status->chain_signal to avoid empty value.
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

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

@@ -13,6 +13,11 @@
 #include "../dma.h"
 #include "mac.h"
 
+static inline s8 to_rssi(u32 field, u32 rxv)
+{
+	return (FIELD_GET(field, rxv) - 220) / 2;
+}
+
 static struct mt76_wcid *mt7615_rx_get_wcid(struct mt7615_dev *dev,
 					    u8 idx, bool unicast)
 {
@@ -120,6 +125,7 @@ int mt7615_mac_fill_rx(struct mt7615_dev *dev, struct sk_buff *skb)
 	if (rxd0 & MT_RXD0_NORMAL_GROUP_3) {
 		u32 rxdg0 = le32_to_cpu(rxd[0]);
 		u32 rxdg1 = le32_to_cpu(rxd[1]);
+		u32 rxdg3 = le32_to_cpu(rxd[3]);
 		u8 stbc = FIELD_GET(MT_RXV1_HT_STBC, rxdg0);
 		bool cck = false;
 
@@ -169,7 +175,21 @@ int mt7615_mac_fill_rx(struct mt7615_dev *dev, struct sk_buff *skb)
 
 		status->enc_flags |= RX_ENC_FLAG_STBC_MASK * stbc;
 
-		/* TODO: RSSI */
+		status->chains = dev->mt76.antenna_mask;
+		status->chain_signal[0] = to_rssi(MT_RXV4_RCPI0, rxdg3);
+		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(dev->mt76.antenna_mask); i++) {
+			if (!(status->chains & BIT(i)))
+				continue;
+
+			status->signal = max(status->signal,
+					     status->chain_signal[i]);
+		}
+
 		rxd += 6;
 		if ((u8 *)rxd - skb->data >= skb->len)
 			return -EINVAL;

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

@@ -98,6 +98,11 @@ enum rx_pkt_type {
 #define MT_RXV2_GROUP_ID		GENMASK(26, 21)
 #define MT_RXV2_LENGTH			GENMASK(20, 0)
 
+#define MT_RXV4_RCPI3			GENMASK(31, 24)
+#define MT_RXV4_RCPI2			GENMASK(23, 16)
+#define MT_RXV4_RCPI1			GENMASK(15, 8)
+#define MT_RXV4_RCPI0			GENMASK(7, 0)
+
 enum tx_header_format {
 	MT_HDR_FORMAT_802_3,
 	MT_HDR_FORMAT_CMD,