mt76: fix A-MPDU density handling

The hardware requirements for A-MPDU density are entirely on the tx side,
not the rx side. Because of that, the IE value should stay at 0 and the
minimum value should instead be enforced in WTBL/TXWI

MT7615 has no restrictions here
Signed-off-by: Felix Fietkau <nbd@nbd.name>

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

@@ -198,7 +198,6 @@ mt76_init_sband(struct mt76_dev *dev, struct mt76_sband *msband,
 
 	ht_cap->mcs.tx_params = IEEE80211_HT_MCS_TX_DEFINED;
 	ht_cap->ampdu_factor = IEEE80211_HT_MAX_AMPDU_64K;
-	ht_cap->ampdu_density = IEEE80211_HT_MPDU_DENSITY_4;
 
 	mt76_init_stream_cap(dev, sband, vht);
 

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

@@ -318,11 +318,16 @@ void mt7603_wtbl_update_cap(struct mt7603_dev *dev, struct ieee80211_sta *sta)
 {
 	struct mt7603_sta *msta = (struct mt7603_sta *)sta->drv_priv;
 	int idx = msta->wcid.idx;
+	u8 ampdu_density;
 	u32 addr;
 	u32 val;
 
 	addr = mt7603_wtbl1_addr(idx);
 
+	ampdu_density = sta->ht_cap.ampdu_density;
+	if (ampdu_density < IEEE80211_HT_MPDU_DENSITY_4)
+		ampdu_density = IEEE80211_HT_MPDU_DENSITY_4;
+
 	val = mt76_rr(dev, addr + 2 * 4);
 	val &= MT_WTBL1_W2_KEY_TYPE | MT_WTBL1_W2_ADMISSION_CONTROL;
 	val |= FIELD_PREP(MT_WTBL1_W2_AMPDU_FACTOR, sta->ht_cap.ampdu_factor) |

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

@@ -409,6 +409,7 @@ void mt76x02_mac_write_txwi(struct mt76x02_dev *dev, struct mt76x02_txwi *txwi,
 		txwi->ack_ctl |= MT_TXWI_ACK_CTL_NSEQ;
 	if ((info->flags & IEEE80211_TX_CTL_AMPDU) && sta) {
 		u8 ba_size = IEEE80211_MIN_AMPDU_BUF;
+		u8 ampdu_density = sta->ht_cap.ampdu_density;
 
 		ba_size <<= sta->ht_cap.ampdu_factor;
 		ba_size = min_t(int, 63, ba_size - 1);
@@ -416,9 +417,11 @@ void mt76x02_mac_write_txwi(struct mt76x02_dev *dev, struct mt76x02_txwi *txwi,
 			ba_size = 0;
 		txwi->ack_ctl |= FIELD_PREP(MT_TXWI_ACK_CTL_BA_WINDOW, ba_size);
 
+		if (ampdu_density < IEEE80211_HT_MPDU_DENSITY_4)
+			ampdu_density = IEEE80211_HT_MPDU_DENSITY_4;
+
 		txwi_flags |= MT_TXWI_FLAGS_AMPDU |
-			 FIELD_PREP(MT_TXWI_FLAGS_MPDU_DENSITY,
-				    sta->ht_cap.ampdu_density);
+			 FIELD_PREP(MT_TXWI_FLAGS_MPDU_DENSITY, ampdu_density);
 	}
 
 	if (ieee80211_is_probe_resp(hdr->frame_control) ||