mt7601u: remove warning when avg_rssi is zero

It turned out that we can run calibration without already received
frames with RSSI data. In such case just don't update AGC register
and don't print the warning.

Fixes: b305a6a ("mt7601u: use EWMA to calculate avg_rssi")
Reported-by: Adam Borowski <[email protected]>
Signed-off-by: Stanislaw Gruszka <[email protected]>
Acked-by: Jakub Kicinski <[email protected]>
Signed-off-by: Kalle Valo <[email protected]>

Author: Stanislaw Gruszka

drivers/net/wireless/mediatek/mt7601u/phy.c

@@ -986,13 +986,15 @@ static void mt7601u_agc_tune(struct mt7601u_dev *dev)
 	 */
 	spin_lock_bh(&dev->con_mon_lock);
 	avg_rssi = ewma_rssi_read(&dev->avg_rssi);
-	WARN_ON_ONCE(avg_rssi == 0);
+	spin_unlock_bh(&dev->con_mon_lock);
+	if (avg_rssi == 0)
+		return;
+
 	avg_rssi = -avg_rssi;
 	if (avg_rssi <= -70)
 		val -= 0x20;
 	else if (avg_rssi <= -60)
 		val -= 0x10;
-	spin_unlock_bh(&dev->con_mon_lock);
 
 	if (val != mt7601u_bbp_rr(dev, 66))
 		mt7601u_bbp_wr(dev, 66, val);