wifi: mt76: mt7921: add mt7921_mutex_acquire at mt7921_[start, stop]_ap

Add mt7921_mutex_acquire at mt7921_[start, stop]_ap to fix the race
with the context holding dev->muxtex and the driver might access the
device in low power state.

Fixes: 9d958b60 ("mt76: mt7921: fix command timeout in AP stop period")
Tested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7921/main.c

@@ -1526,17 +1526,23 @@ mt7921_start_ap(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 	struct mt7921_dev *dev = mt7921_hw_dev(hw);
 	int err;
 
+	mt7921_mutex_acquire(dev);
+
 	err = mt76_connac_mcu_uni_add_bss(phy->mt76, vif, &mvif->sta.wcid,
 					  true);
 	if (err)
-		return err;
+		goto out;
 
 	err = mt7921_mcu_set_bss_pm(dev, vif, true);
 	if (err)
-		return err;
+		goto out;
+
+	err = mt7921_mcu_sta_update(dev, NULL, vif, true,
+				    MT76_STA_INFO_STATE_NONE);
+out:
+	mt7921_mutex_release(dev);
 
-	return mt7921_mcu_sta_update(dev, NULL, vif, true,
-				     MT76_STA_INFO_STATE_NONE);
+	return err;
 }
 
 static void
@@ -1548,11 +1554,16 @@ mt7921_stop_ap(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 	struct mt7921_dev *dev = mt7921_hw_dev(hw);
 	int err;
 
+	mt7921_mutex_acquire(dev);
+
 	err = mt7921_mcu_set_bss_pm(dev, vif, false);
 	if (err)
-		return;
+		goto out;
 
 	mt76_connac_mcu_uni_add_bss(phy->mt76, vif, &mvif->sta.wcid, false);
+
+out:
+	mt7921_mutex_release(dev);
 }
 
 const struct ieee80211_ops mt7921_ops = {