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@@ -0,0 +1,272 @@
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+From: Manikanta Pubbisetty <[email protected]>
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+Date: Wed, 11 Jul 2018 00:12:53 +0530
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+Subject: [PATCH] mac80211: add stop/start logic for software TXQs
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+
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+Sometimes, it is required to stop the transmissions momentarily and
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+resume it later; stopping the txqs becomes very critical in scenarios where
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+the packet transmission has to be ceased completely. For example, during
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+the hardware restart, during off channel operations,
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+when initiating CSA(upon detecting a radar on the DFS channel), etc.
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+
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+The TX queue stop/start logic in mac80211 works well in stopping the TX
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+when drivers make use of netdev queues, i.e, when Qdiscs in network layer
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+take care of traffic scheduling. Since the devices implementing
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+wake_tx_queue can run without Qdiscs, packets will be handed to mac80211
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+directly without queueing them in the netdev queues.
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+
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+Also, mac80211 does not invoke any of the
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+netif_stop_*/netif_wake_* APIs if wake_tx_queue is implemented.
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+Since the queues are not stopped in this case, transmissions can continue
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+and this will impact negatively on the operation of the wireless device.
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+
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+For example,
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+During hardware restart, we stop the netdev queues so that packets are
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+not sent to the driver. Since ath10k implements wake_tx_queue,
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+TX queues will not be stopped and packets might reach the hardware while
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+it is restarting; this can make hardware unresponsive and the only
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+possible option for recovery is to reboot the entire system.
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+
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+There is another problem to this, it is observed that the packets
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+were sent on the DFS channel for a prolonged duration after radar
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+detection impacting the channel closing time.
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+
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+We can still invoke netif stop/wake APIs when wake_tx_queue is implemented
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+but this could lead to packet drops in network layer; adding stop/start
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+logic for software TXQs in mac80211 instead makes more sense; the change
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+proposed adds the same in mac80211.
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+
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+Signed-off-by: Manikanta Pubbisetty <[email protected]>
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+Signed-off-by: Johannes Berg <[email protected]>
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+---
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+
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+--- a/include/net/mac80211.h
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++++ b/include/net/mac80211.h
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+@@ -1504,6 +1504,8 @@ enum ieee80211_vif_flags {
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+ * @drv_priv: data area for driver use, will always be aligned to
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+ * sizeof(void \*).
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+ * @txq: the multicast data TX queue (if driver uses the TXQ abstraction)
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++ * @txqs_stopped: per AC flag to indicate that intermediate TXQs are stopped,
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++ * protected by fq->lock.
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+ */
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+ struct ieee80211_vif {
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+ enum nl80211_iftype type;
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+@@ -1528,6 +1530,8 @@ struct ieee80211_vif {
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+
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+ unsigned int probe_req_reg;
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+
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++ bool txqs_stopped[IEEE80211_NUM_ACS];
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++
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+ /* must be last */
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+ u8 drv_priv[0] __aligned(sizeof(void *));
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+ };
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+--- a/net/mac80211/ieee80211_i.h
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++++ b/net/mac80211/ieee80211_i.h
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+@@ -818,6 +818,7 @@ enum txq_info_flags {
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+ IEEE80211_TXQ_STOP,
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+ IEEE80211_TXQ_AMPDU,
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+ IEEE80211_TXQ_NO_AMSDU,
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++ IEEE80211_TXQ_STOP_NETIF_TX,
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+ };
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+
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+ /**
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+@@ -1226,6 +1227,7 @@ struct ieee80211_local {
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+
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+ struct sk_buff_head pending[IEEE80211_MAX_QUEUES];
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+ struct tasklet_struct tx_pending_tasklet;
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++ struct tasklet_struct wake_txqs_tasklet;
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+
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+ atomic_t agg_queue_stop[IEEE80211_MAX_QUEUES];
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+
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+@@ -2039,6 +2041,7 @@ void ieee80211_txq_remove_vlan(struct ie
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+ struct ieee80211_sub_if_data *sdata);
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+ void ieee80211_fill_txq_stats(struct cfg80211_txq_stats *txqstats,
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+ struct txq_info *txqi);
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++void ieee80211_wake_txqs(unsigned long data);
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+ void ieee80211_send_auth(struct ieee80211_sub_if_data *sdata,
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+ u16 transaction, u16 auth_alg, u16 status,
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+ const u8 *extra, size_t extra_len, const u8 *bssid,
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+--- a/net/mac80211/main.c
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++++ b/net/mac80211/main.c
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+@@ -686,6 +686,10 @@ struct ieee80211_hw *ieee80211_alloc_hw_
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+ tasklet_init(&local->tx_pending_tasklet, ieee80211_tx_pending,
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+ (unsigned long)local);
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+
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++ if (ops->wake_tx_queue)
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++ tasklet_init(&local->wake_txqs_tasklet, ieee80211_wake_txqs,
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++ (unsigned long)local);
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++
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+ tasklet_init(&local->tasklet,
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+ ieee80211_tasklet_handler,
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+ (unsigned long) local);
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+--- a/net/mac80211/tx.c
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++++ b/net/mac80211/tx.c
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+@@ -3482,13 +3482,19 @@ struct sk_buff *ieee80211_tx_dequeue(str
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+ struct ieee80211_tx_info *info;
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+ struct ieee80211_tx_data tx;
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+ ieee80211_tx_result r;
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+- struct ieee80211_vif *vif;
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++ struct ieee80211_vif *vif = txq->vif;
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+
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+ spin_lock_bh(&fq->lock);
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+
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+- if (test_bit(IEEE80211_TXQ_STOP, &txqi->flags))
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++ if (test_bit(IEEE80211_TXQ_STOP, &txqi->flags) ||
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++ test_bit(IEEE80211_TXQ_STOP_NETIF_TX, &txqi->flags))
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+ goto out;
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+
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++ if (vif->txqs_stopped[ieee80211_ac_from_tid(txq->tid)]) {
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++ set_bit(IEEE80211_TXQ_STOP_NETIF_TX, &txqi->flags);
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++ goto out;
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++ }
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++
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+ /* Make sure fragments stay together. */
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+ skb = __skb_dequeue(&txqi->frags);
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+ if (skb)
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+@@ -3583,6 +3589,7 @@ begin:
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+ }
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+
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+ IEEE80211_SKB_CB(skb)->control.vif = vif;
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++
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+ out:
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+ spin_unlock_bh(&fq->lock);
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+
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+--- a/net/mac80211/util.c
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++++ b/net/mac80211/util.c
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+@@ -240,6 +240,99 @@ __le16 ieee80211_ctstoself_duration(stru
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+ }
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+ EXPORT_SYMBOL(ieee80211_ctstoself_duration);
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+
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++static void __ieee80211_wake_txqs(struct ieee80211_sub_if_data *sdata, int ac)
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++{
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++ struct ieee80211_local *local = sdata->local;
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++ struct ieee80211_vif *vif = &sdata->vif;
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++ struct fq *fq = &local->fq;
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++ struct ps_data *ps = NULL;
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++ struct txq_info *txqi;
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++ struct sta_info *sta;
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++ int i;
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++
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++ spin_lock_bh(&fq->lock);
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++
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++ if (sdata->vif.type == NL80211_IFTYPE_AP)
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++ ps = &sdata->bss->ps;
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++
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++ sdata->vif.txqs_stopped[ac] = false;
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++
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++ list_for_each_entry_rcu(sta, &local->sta_list, list) {
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++ if (sdata != sta->sdata)
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++ continue;
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++
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++ for (i = 0; i < ARRAY_SIZE(sta->sta.txq); i++) {
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++ struct ieee80211_txq *txq = sta->sta.txq[i];
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++
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++ txqi = to_txq_info(txq);
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++
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++ if (ac != txq->ac)
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++ continue;
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++
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++ if (!test_and_clear_bit(IEEE80211_TXQ_STOP_NETIF_TX,
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++ &txqi->flags))
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++ continue;
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++
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++ spin_unlock_bh(&fq->lock);
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++ drv_wake_tx_queue(local, txqi);
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++ spin_lock_bh(&fq->lock);
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++ }
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++ }
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++
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++ if (!vif->txq)
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++ goto out;
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++
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++ txqi = to_txq_info(vif->txq);
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++
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++ if (!test_and_clear_bit(IEEE80211_TXQ_STOP_NETIF_TX, &txqi->flags) ||
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++ (ps && atomic_read(&ps->num_sta_ps)) || ac != vif->txq->ac)
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++ goto out;
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++
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++ spin_unlock_bh(&fq->lock);
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++
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++ drv_wake_tx_queue(local, txqi);
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++ return;
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++out:
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++ spin_unlock_bh(&fq->lock);
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++}
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++
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++void ieee80211_wake_txqs(unsigned long data)
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++{
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++ struct ieee80211_local *local = (struct ieee80211_local *)data;
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++ struct ieee80211_sub_if_data *sdata;
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++ int n_acs = IEEE80211_NUM_ACS;
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++ unsigned long flags;
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++ int i;
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++
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++ rcu_read_lock();
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++ spin_lock_irqsave(&local->queue_stop_reason_lock, flags);
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++
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++ if (local->hw.queues < IEEE80211_NUM_ACS)
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++ n_acs = 1;
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++
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++ for (i = 0; i < local->hw.queues; i++) {
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++ if (local->queue_stop_reasons[i])
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++ continue;
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++
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++ spin_unlock_irqrestore(&local->queue_stop_reason_lock, flags);
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++ list_for_each_entry_rcu(sdata, &local->interfaces, list) {
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++ int ac;
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++
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++ for (ac = 0; ac < n_acs; ac++) {
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++ int ac_queue = sdata->vif.hw_queue[ac];
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++
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++ if (ac_queue == i ||
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++ sdata->vif.cab_queue == i)
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++ __ieee80211_wake_txqs(sdata, ac);
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++ }
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++ }
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++ spin_lock_irqsave(&local->queue_stop_reason_lock, flags);
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++ }
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++
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++ spin_unlock_irqrestore(&local->queue_stop_reason_lock, flags);
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++ rcu_read_unlock();
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++}
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++
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+ void ieee80211_propagate_queue_wake(struct ieee80211_local *local, int queue)
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+ {
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+ struct ieee80211_sub_if_data *sdata;
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+@@ -308,6 +401,9 @@ static void __ieee80211_wake_queue(struc
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+ rcu_read_unlock();
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+ } else
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+ tasklet_schedule(&local->tx_pending_tasklet);
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++
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++ if (local->ops->wake_tx_queue)
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++ tasklet_schedule(&local->wake_txqs_tasklet);
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+ }
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+
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+ void ieee80211_wake_queue_by_reason(struct ieee80211_hw *hw, int queue,
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+@@ -351,9 +447,6 @@ static void __ieee80211_stop_queue(struc
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+ if (__test_and_set_bit(reason, &local->queue_stop_reasons[queue]))
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+ return;
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+
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+- if (local->ops->wake_tx_queue)
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+- return;
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+-
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+ if (local->hw.queues < IEEE80211_NUM_ACS)
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+ n_acs = 1;
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+
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+@@ -366,8 +459,15 @@ static void __ieee80211_stop_queue(struc
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+
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+ for (ac = 0; ac < n_acs; ac++) {
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+ if (sdata->vif.hw_queue[ac] == queue ||
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+- sdata->vif.cab_queue == queue)
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+- netif_stop_subqueue(sdata->dev, ac);
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++ sdata->vif.cab_queue == queue) {
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++ if (!local->ops->wake_tx_queue) {
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++ netif_stop_subqueue(sdata->dev, ac);
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++ continue;
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++ }
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++ spin_lock(&local->fq.lock);
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++ sdata->vif.txqs_stopped[ac] = true;
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++ spin_unlock(&local->fq.lock);
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++ }
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+ }
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+ }
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+ rcu_read_unlock();
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Felix Fietkau