wifi: mt76: mt7915: fix mt7915_mac_set_timing()

Correct mac timiing settings for different hardware generations.
This improves 40-60Mbps performance.

Fixes: 9aac2969 ("mt76: mt7915: update mac timing settings")
Reported-By: Carson Vandegriffe <carson.vandegriffe@candelatech.com>
Tested-by: Chad Monroe <chad.monroe@smartrg.com>
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

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

@@ -1153,7 +1153,7 @@ void mt7915_mac_set_timing(struct mt7915_phy *phy)
 		  FIELD_PREP(MT_TIMEOUT_VAL_CCA, 48);
 	u32 ofdm = FIELD_PREP(MT_TIMEOUT_VAL_PLCP, 60) |
 		   FIELD_PREP(MT_TIMEOUT_VAL_CCA, 28);
-	int offset;
+	int eifs_ofdm = 360, sifs = 10, offset;
 	bool a_band = !(phy->mt76->chandef.chan->band == NL80211_BAND_2GHZ);
 
 	if (!test_bit(MT76_STATE_RUNNING, &phy->mt76->state))
@@ -1171,17 +1171,26 @@ void mt7915_mac_set_timing(struct mt7915_phy *phy)
 	reg_offset = FIELD_PREP(MT_TIMEOUT_VAL_PLCP, offset) |
 		     FIELD_PREP(MT_TIMEOUT_VAL_CCA, offset);
 
+	if (!is_mt7915(&dev->mt76)) {
+		if (!a_band) {
+			mt76_wr(dev, MT_TMAC_ICR1(phy->band_idx),
+				FIELD_PREP(MT_IFS_EIFS_CCK, 314));
+			eifs_ofdm = 78;
+		} else {
+			eifs_ofdm = 84;
+		}
+	} else if (a_band) {
+		sifs = 16;
+	}
+
 	mt76_wr(dev, MT_TMAC_CDTR(phy->band_idx), cck + reg_offset);
 	mt76_wr(dev, MT_TMAC_ODTR(phy->band_idx), ofdm + reg_offset);
 	mt76_wr(dev, MT_TMAC_ICR0(phy->band_idx),
-		FIELD_PREP(MT_IFS_EIFS_OFDM, a_band ? 84 : 78) |
+		FIELD_PREP(MT_IFS_EIFS_OFDM, eifs_ofdm) |
 		FIELD_PREP(MT_IFS_RIFS, 2) |
-		FIELD_PREP(MT_IFS_SIFS, 10) |
+		FIELD_PREP(MT_IFS_SIFS, sifs) |
 		FIELD_PREP(MT_IFS_SLOT, phy->slottime));
 
-	mt76_wr(dev, MT_TMAC_ICR1(phy->band_idx),
-		FIELD_PREP(MT_IFS_EIFS_CCK, 314));
-
 	if (phy->slottime < 20 || a_band)
 		val = MT7915_CFEND_RATE_DEFAULT;
 	else