[PATCH] mt7601u: remove warning when avg_rssi is zero

[Stanislaw Gruszka]

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: b305a6ab0247 ("mt7601u: use EWMA to calculate avg_rssi")
Reported-by: Adam Borowski <kilob...@angband.pl>
Signed-off-by: Stanislaw Gruszka <sgrus...@redhat.com>
---
 drivers/net/wireless/mediatek/mt7601u/phy.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt7601u/phy.c 
b/drivers/net/wireless/mediatek/mt7601u/phy.c
index d440c550bdb1..3ffc8d19285b 100644
--- a/drivers/net/wireless/mediatek/mt7601u/phy.c
+++ b/drivers/net/wireless/mediatek/mt7601u/phy.c
@@ -985,13 +985,15 @@ 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);
-- 
1.9.3