wifi: mt76: mt7915: add back 160MHz channel width support for MT7915

A number of users reported that this support was working fine before
it got removed. Add it back, but leave out the unsupported 80+80 mode.

Fixes: ac922bd ("wifi: mt76: mt7915: remove BW160 and BW80+80 support")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230301163739.52314-1-nbd@nbd.name

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

@@ -383,7 +383,6 @@ mt7915_init_wiphy(struct mt7915_phy *phy)
 	ieee80211_hw_set(hw, SUPPORTS_RX_DECAP_OFFLOAD);
 	ieee80211_hw_set(hw, SUPPORTS_MULTI_BSSID);
 	ieee80211_hw_set(hw, WANT_MONITOR_VIF);
-	ieee80211_hw_set(hw, SUPPORTS_VHT_EXT_NSS_BW);
 
 	hw->max_tx_fragments = 4;
 
@@ -396,26 +395,38 @@ mt7915_init_wiphy(struct mt7915_phy *phy)
 	}
 
 	if (phy->mt76->cap.has_5ghz) {
+		struct ieee80211_sta_vht_cap *vht_cap;
+
+		vht_cap = &phy->mt76->sband_5g.sband.vht_cap;
 		phy->mt76->sband_5g.sband.ht_cap.cap |=
 			IEEE80211_HT_CAP_LDPC_CODING |
 			IEEE80211_HT_CAP_MAX_AMSDU;
 		phy->mt76->sband_5g.sband.ht_cap.ampdu_density =
 			IEEE80211_HT_MPDU_DENSITY_4;
 
 		if (is_mt7915(&dev->mt76)) {
-			phy->mt76->sband_5g.sband.vht_cap.cap |=
+			vht_cap->cap |=
 				IEEE80211_VHT_CAP_MAX_MPDU_LENGTH_7991 |
 				IEEE80211_VHT_CAP_MAX_A_MPDU_LENGTH_EXPONENT_MASK;
+
+			if (!dev->dbdc_support)
+				vht_cap->cap |=
+					IEEE80211_VHT_CAP_SHORT_GI_160 |
+					IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_160MHZ |
+					FIELD_PREP(IEEE80211_VHT_CAP_EXT_NSS_BW_MASK, 1);
 		} else {
-			phy->mt76->sband_5g.sband.vht_cap.cap |=
+			vht_cap->cap |=
 				IEEE80211_VHT_CAP_MAX_MPDU_LENGTH_11454 |
 				IEEE80211_VHT_CAP_MAX_A_MPDU_LENGTH_EXPONENT_MASK;
 
 			/* mt7916 dbdc with 2g 2x2 bw40 and 5g 2x2 bw160c */
-			phy->mt76->sband_5g.sband.vht_cap.cap |=
+			vht_cap->cap |=
 				IEEE80211_VHT_CAP_SHORT_GI_160 |
 				IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_160MHZ;
 		}
+
+		if (!is_mt7915(&dev->mt76) || !dev->dbdc_support)
+			ieee80211_hw_set(hw, SUPPORTS_VHT_EXT_NSS_BW);
 	}
 
 	mt76_set_stream_caps(phy->mt76, true);
@@ -841,9 +852,13 @@ mt7915_set_stream_he_txbf_caps(struct mt7915_phy *phy,
 	int sts = hweight8(phy->mt76->chainmask);
 	u8 c, sts_160 = sts;
 
-	/* mt7915 doesn't support bw160 */
-	if (is_mt7915(&dev->mt76))
-		sts_160 = 0;
+	/* Can do 1/2 of STS in 160Mhz mode for mt7915 */
+	if (is_mt7915(&dev->mt76)) {
+		if (!dev->dbdc_support)
+			sts_160 /= 2;
+		else
+			sts_160 = 0;
+	}
 
 #ifdef CONFIG_MAC80211_MESH
 	if (vif == NL80211_IFTYPE_MESH_POINT)
@@ -944,10 +959,15 @@ mt7915_init_he_caps(struct mt7915_phy *phy, enum nl80211_band band,
 	int i, idx = 0, nss = hweight8(phy->mt76->antenna_mask);
 	u16 mcs_map = 0;
 	u16 mcs_map_160 = 0;
-	u8 nss_160 = nss;
+	u8 nss_160;
 
-	/* Can't do 160MHz with mt7915 */
-	if (is_mt7915(&dev->mt76))
+	if (!is_mt7915(&dev->mt76))
+		nss_160 = nss;
+	else if (!dev->dbdc_support)
+		/* Can do 1/2 of NSS streams in 160Mhz mode for mt7915 */
+		nss_160 = nss / 2;
+	else
+		/* Can't do 160MHz with mt7915 dbdc */
 		nss_160 = 0;
 
 	for (i = 0; i < 8; i++) {