mt76x2: convert between per-chain tx power and combined output

Using both chains adds max. 3 dBm. A similar worst-case calculation is
being used in ath9k as well to ensure that the hardware stays within
regulatory limits
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/mediatek/mt76/mt76x2_init.c

@@ -785,6 +785,9 @@ mt76x2_init_txpower(struct mt76x2_dev *dev,
 		chan->max_power = mt76x2_get_max_rate_power(&t) +
 				  target_power;
 		chan->max_power /= 2;
+
+		/* convert to combined output power on 2x2 devices */
+		chan->max_power += 3;
 	}
 }
 

drivers/net/wireless/mediatek/mt76/mt76x2_main.c

@@ -155,6 +155,9 @@ mt76x2_config(struct ieee80211_hw *hw, u32 changed)
 	if (changed & IEEE80211_CONF_CHANGE_POWER) {
 		dev->txpower_conf = hw->conf.power_level * 2;
 
+		/* convert to per-chain power for 2x2 devices */
+		dev->txpower_conf -= 6;
+
 		if (test_bit(MT76_STATE_RUNNING, &dev->mt76.state)) {
 			mt76x2_phy_set_txpower(dev);
 			mt76x2_tx_set_txpwr_auto(dev, dev->txpower_conf);
@@ -437,6 +440,10 @@ mt76x2_get_txpower(struct ieee80211_hw *hw, struct ieee80211_vif *vif, int *dbm)
 	struct mt76x2_dev *dev = hw->priv;
 
 	*dbm = dev->txpower_cur / 2;
+
+	/* convert from per-chain power to combined output on 2x2 devices */
+	*dbm += 3;
+
 	return 0;
 }