wifi: mt76: use atomic iface iteration for pre-TBTT work

In addition to the previous series I posted, over time I'd
also like to get rid of the iflist_mtx in mac80211. That
isn't easy now since lots of places use iteration and would
have to be audited, but even a cursory look suggests that
mt76 might be more problematic than most since holding the
wiphy lock for the latency-sensitive pre-TBTT work could be
an issue.

Convert the pre-TBTT work to use atomic iteration and then
sending the device commands outside of it.

Signed-off-by: Johannes Berg <[e-mail]>
Signed-off-by: Felix Fietkau <[e-mail]>

drivers/net/wireless/mediatek/mt76/mt76x02_beacon.c

···
 void
 mt76x02_update_beacon_iter(void *priv, u8 *mac, struct ieee80211_vif *vif)
 {
-	struct mt76x02_dev *dev = (struct mt76x02_dev *)priv;
+	struct beacon_bc_data *data = priv;
+	struct mt76x02_dev *dev = data->dev;
 	struct mt76x02_vif *mvif = (struct mt76x02_vif *)vif->drv_priv;
 	struct sk_buff *skb = NULL;
 
···
 	if (!skb)
 		return;
 
-	mt76x02_mac_set_beacon(dev, skb);
+	__skb_queue_tail(&data->q, skb);
 }
 EXPORT_SYMBOL_GPL(mt76x02_update_beacon_iter);
 
···
 			    int max_nframes)
 {
 	int i, nframes;
-
-	data->dev = dev;
-	__skb_queue_head_init(&data->q);
 
 	do {
 		nframes = skb_queue_len(&data->q);

drivers/net/wireless/mediatek/mt76/mt76x02_mmio.c

···
 	struct mt76x02_dev *dev = from_tasklet(dev, t, mt76.pre_tbtt_tasklet);
 	struct mt76_dev *mdev = &dev->mt76;
 	struct mt76_queue *q = dev->mphy.q_tx[MT_TXQ_PSD];
-	struct beacon_bc_data data = {};
+	struct beacon_bc_data data = {
+		.dev = dev,
+	};
 	struct sk_buff *skb;
 	int i;
 
 	if (mt76_hw(dev)->conf.flags & IEEE80211_CONF_OFFCHANNEL)
 		return;
+
+	__skb_queue_head_init(&data.q);
 
 	mt76x02_resync_beacon_timer(dev);
 
···
 
 	ieee80211_iterate_active_interfaces_atomic(mt76_hw(dev),
 		IEEE80211_IFACE_ITER_RESUME_ALL,
-		mt76x02_update_beacon_iter, dev);
+		mt76x02_update_beacon_iter, &data);
+
+	while ((skb = __skb_dequeue(&data.q)) != NULL)
+		mt76x02_mac_set_beacon(dev, skb);
 
 	mt76_wr(dev, MT_BCN_BYPASS_MASK,
 		0xff00 | ~(0xff00 >> dev->beacon_data_count));

drivers/net/wireless/mediatek/mt76/mt76x02_usb_core.c

···
 {
 	struct mt76x02_dev *dev =
 		container_of(work, struct mt76x02_dev, pre_tbtt_work);
-	struct beacon_bc_data data = {};
+	struct beacon_bc_data data = {
+		.dev = dev,
+	};
 	struct sk_buff *skb;
 	int nbeacons;
 
···
 	if (mt76_hw(dev)->conf.flags & IEEE80211_CONF_OFFCHANNEL)
 		return;
 
+	__skb_queue_head_init(&data.q);
+
 	mt76x02_resync_beacon_timer(dev);
 
 	/* Prevent corrupt transmissions during update */
 	mt76_set(dev, MT_BCN_BYPASS_MASK, 0xffff);
 	dev->beacon_data_count = 0;
 
-	ieee80211_iterate_active_interfaces(mt76_hw(dev),
+	ieee80211_iterate_active_interfaces_atomic(mt76_hw(dev),
 		IEEE80211_IFACE_ITER_RESUME_ALL,
-		mt76x02_update_beacon_iter, dev);
+		mt76x02_update_beacon_iter, &data);
+
+	while ((skb = __skb_dequeue(&data.q)) != NULL)
+		mt76x02_mac_set_beacon(dev, skb);
 
 	mt76_csa_check(&dev->mt76);