mt76: mt7615: do not always reset the dfs state setting the channel

mac80211/hostapd runs mt7615_set_channel with the same channel
parameters sending multiple rdd commands overwriting the previous ones.
This behaviour is causing tpt issues on dfs channels.
Fix the issue checking new channel freq/width with the running one.

Fixes: 5dabdf71e94e ("mt76: mt7615: add multiple wiphy support to the dfs support code")
Signed-off-by: Lorenzo Bianconi <[e-mail]>
Signed-off-by: Felix Fietkau <[e-mail]>

drivers/net/wireless/mediatek/mt76/mt7615/main.c

···
 	spin_unlock_bh(&dev->sta_poll_lock);
 }
 
+static void mt7615_init_dfs_state(struct mt7615_phy *phy)
+{
+	struct mt76_phy *mphy = phy->mt76;
+	struct ieee80211_hw *hw = mphy->hw;
+	struct cfg80211_chan_def *chandef = &hw->conf.chandef;
+
+	if (hw->conf.flags & IEEE80211_CONF_OFFCHANNEL)
+		return;
+
+	if (!(chandef->chan->flags & IEEE80211_CHAN_RADAR))
+		return;
+
+	if (mphy->chandef.chan->center_freq == chandef->chan->center_freq &&
+	    mphy->chandef.width == chandef->width)
+		return;
+
+	phy->dfs_state = -1;
+}
+
 static int mt7615_set_channel(struct mt7615_phy *phy)
 {
 	struct mt7615_dev *dev = phy->dev;
···
 	mutex_lock(&dev->mt76.mutex);
 	set_bit(MT76_RESET, &phy->mt76->state);
 
-	phy->dfs_state = -1;
+	mt7615_init_dfs_state(phy);
 	mt76_set_channel(phy->mt76);
 
 	ret = mt7615_mcu_set_chan_info(phy, MCU_EXT_CMD_CHANNEL_SWITCH);