iwlwifi: mvm: Use CS tx block bit for AP/GO

An AP/GO may perform the channel switch slightly before its stations.
This scenario may result in packet loss, since the transmission may start
before the client is actually on a new channel. In order to prevent
potential packet loss disable tx to all the stations when the channel
switch flow starts. Clear the disable_tx bit when a station is seen on a
target channel, or after IWL_MVM_CS_UNBLOCK_TX_TIMEOUT beacons on a new
channel. In addition call ieee80211_sta_block_awake in order to inform
mac80211 that the frames for this station should be buffered.

Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

7 files changed, 136 insertions, 3 deletions

diff --git a/drivers/net/wireless/iwlwifi/mvm/mac-ctxt.c b/drivers/net/wireless/iwlwifi/mvm/mac-ctxt.c
index a176d008dab1..96b9cf8137e7 100644
--- a/drivers/net/wireless/iwlwifi/mvm/mac-ctxt.c
+++ b/drivers/net/wireless/iwlwifi/mvm/mac-ctxt.c
@@ -1237,6 +1237,7 @@ int iwl_mvm_rx_beacon_notif(struct iwl_mvm *mvm,
         struct iwl_rx_packet *pkt = rxb_addr(rxb);
         struct iwl_mvm_tx_resp *beacon_notify_hdr;
         struct ieee80211_vif *csa_vif;
+        struct ieee80211_vif *tx_blocked_vif;
         u64 tsf;
 
         lockdep_assert_held(&mvm->mutex);
@@ -1267,6 +1268,30 @@ int iwl_mvm_rx_beacon_notif(struct iwl_mvm *mvm,
         if (unlikely(csa_vif && csa_vif->csa_active))
                 iwl_mvm_csa_count_down(mvm, csa_vif, mvm->ap_last_beacon_gp2);
 
+        tx_blocked_vif = rcu_dereference_protected(mvm->csa_tx_blocked_vif,
+                                                lockdep_is_held(&mvm->mutex));
+        if (unlikely(tx_blocked_vif)) {
+                struct iwl_mvm_vif *mvmvif =
+                        iwl_mvm_vif_from_mac80211(tx_blocked_vif);
+
+                /*
+                 * The channel switch is started and we have blocked the
+                 * stations. If this is the first beacon (the timeout wasn't
+                 * set), set the unblock timeout, otherwise countdown
+                 */
+                if (!mvm->csa_tx_block_bcn_timeout)
+                        mvm->csa_tx_block_bcn_timeout =
+                                IWL_MVM_CS_UNBLOCK_TX_TIMEOUT;
+                else
+                        mvm->csa_tx_block_bcn_timeout--;
+
+                /* Check if the timeout is expired, and unblock tx */
+                if (mvm->csa_tx_block_bcn_timeout == 0) {
+                        iwl_mvm_modify_all_sta_disable_tx(mvm, mvmvif, false);
+                        RCU_INIT_POINTER(mvm->csa_tx_blocked_vif, NULL);
+                }
+        }
+
         return 0;
 }
 
diff --git a/drivers/net/wireless/iwlwifi/mvm/mac80211.c b/drivers/net/wireless/iwlwifi/mvm/mac80211.c
index 4a0350fc4b4e..5ed6fb32087c 100644
--- a/drivers/net/wireless/iwlwifi/mvm/mac80211.c
+++ b/drivers/net/wireless/iwlwifi/mvm/mac80211.c
@@ -1614,6 +1614,11 @@ static void iwl_mvm_stop_ap_ibss(struct ieee80211_hw *hw,
                 RCU_INIT_POINTER(mvm->csa_vif, NULL);
         }
 
+        if (rcu_access_pointer(mvm->csa_tx_blocked_vif) == vif) {
+                RCU_INIT_POINTER(mvm->csa_tx_blocked_vif, NULL);
+                mvm->csa_tx_block_bcn_timeout = 0;
+        }
+
         mvmvif->ap_ibss_active = false;
         mvm->ap_last_beacon_gp2 = 0;
 
@@ -2491,6 +2496,12 @@ static void __iwl_mvm_unassign_vif_chanctx(struct iwl_mvm *mvm,
                 if (!vif->csa_active || !mvmvif->ap_ibss_active)
                         goto out;
 
+                /* Set CS bit on all the stations */
+                iwl_mvm_modify_all_sta_disable_tx(mvm, mvmvif, true);
+
+                /* Save blocked iface, the timeout is set on the next beacon */
+                rcu_assign_pointer(mvm->csa_tx_blocked_vif, vif);
+
                 mvmvif->ap_ibss_active = false;
                 break;
         case NL80211_IFTYPE_STATION:
diff --git a/drivers/net/wireless/iwlwifi/mvm/mvm.h b/drivers/net/wireless/iwlwifi/mvm/mvm.h
index db496c5c73fc..7b308c4834f6 100644
--- a/drivers/net/wireless/iwlwifi/mvm/mvm.h
+++ b/drivers/net/wireless/iwlwifi/mvm/mvm.h
@@ -95,6 +95,12 @@
  */
 #define IWL_MVM_CHANNEL_SWITCH_MARGIN 4
 
+/*
+ * Number of beacons to transmit on a new channel until we unblock tx to
+ * the stations, even if we didn't identify them on a new channel
+ */
+#define IWL_MVM_CS_UNBLOCK_TX_TIMEOUT 3
+
 enum iwl_mvm_tx_fifo {
         IWL_MVM_TX_FIFO_BK = 0,
         IWL_MVM_TX_FIFO_BE,
@@ -671,6 +677,8 @@ struct iwl_mvm {
         bool ps_disabled;
 
         struct ieee80211_vif __rcu *csa_vif;
+        struct ieee80211_vif __rcu *csa_tx_blocked_vif;
+        u8 csa_tx_block_bcn_timeout;
 
         /* system time of last beacon (for AP/GO interface) */
         u32 ap_last_beacon_gp2;
diff --git a/drivers/net/wireless/iwlwifi/mvm/rx.c b/drivers/net/wireless/iwlwifi/mvm/rx.c
index cf7276967acd..4b98987fc413 100644
--- a/drivers/net/wireless/iwlwifi/mvm/rx.c
+++ b/drivers/net/wireless/iwlwifi/mvm/rx.c
@@ -259,6 +259,23 @@ int iwl_mvm_rx_rx_mpdu(struct iwl_mvm *mvm, struct iwl_rx_cmd_buffer *rxb,
         memset(&rx_status, 0, sizeof(rx_status));
 
         /*
+         * We have tx blocked stations (with CS bit). If we heard frames from
+         * a blocked station on a new channel we can TX to it again.
+         */
+        if (unlikely(mvm->csa_tx_block_bcn_timeout)) {
+                struct ieee80211_sta *sta;
+
+                rcu_read_lock();
+
+                sta = ieee80211_find_sta(
+                        rcu_dereference(mvm->csa_tx_blocked_vif), hdr->addr2);
+                if (sta)
+                        iwl_mvm_sta_modify_disable_tx_ap(mvm, sta, false);
+
+                rcu_read_unlock();
+        }
+
+        /*
          * drop the packet if it has failed being decrypted by HW
          */
         if (iwl_mvm_set_mac80211_rx_flag(mvm, hdr, &rx_status, rx_pkt_status)) {
diff --git a/drivers/net/wireless/iwlwifi/mvm/sta.c b/drivers/net/wireless/iwlwifi/mvm/sta.c
index d3a6cf7558eb..812813964847 100644
--- a/drivers/net/wireless/iwlwifi/mvm/sta.c
+++ b/drivers/net/wireless/iwlwifi/mvm/sta.c
@@ -1468,3 +1468,57 @@ void iwl_mvm_sta_modify_disable_tx(struct iwl_mvm *mvm,
         if (ret)
                 IWL_ERR(mvm, "Failed to send ADD_STA command (%d)\n", ret);
 }
+
+void iwl_mvm_sta_modify_disable_tx_ap(struct iwl_mvm *mvm,
+                                      struct ieee80211_sta *sta,
+                                      bool disable)
+{
+        struct iwl_mvm_sta *mvm_sta = iwl_mvm_sta_from_mac80211(sta);
+
+        spin_lock_bh(&mvm_sta->lock);
+
+        if (mvm_sta->disable_tx == disable) {
+                spin_unlock_bh(&mvm_sta->lock);
+                return;
+        }
+
+        mvm_sta->disable_tx = disable;
+
+        /*
+         * Tell mac80211 to start/stop queueing tx for this station,
+         * but don't stop queueing if there are still pending frames
+         * for this station.
+         */
+        if (disable || !atomic_read(&mvm->pending_frames[mvm_sta->sta_id]))
+                ieee80211_sta_block_awake(mvm->hw, sta, disable);
+
+        iwl_mvm_sta_modify_disable_tx(mvm, mvm_sta, disable);
+
+        spin_unlock_bh(&mvm_sta->lock);
+}
+
+void iwl_mvm_modify_all_sta_disable_tx(struct iwl_mvm *mvm,
+                                       struct iwl_mvm_vif *mvmvif,
+                                       bool disable)
+{
+        struct ieee80211_sta *sta;
+        struct iwl_mvm_sta *mvm_sta;
+        int i;
+
+        lockdep_assert_held(&mvm->mutex);
+
+        /* Block/unblock all the stations of the given mvmvif */
+        for (i = 0; i < IWL_MVM_STATION_COUNT; i++) {
+                sta = rcu_dereference_protected(mvm->fw_id_to_mac_id[i],
+                                                lockdep_is_held(&mvm->mutex));
+                if (IS_ERR_OR_NULL(sta))
+                        continue;
+
+                mvm_sta = iwl_mvm_sta_from_mac80211(sta);
+                if (mvm_sta->mac_id_n_color !=
+                    FW_CMD_ID_AND_COLOR(mvmvif->id, mvmvif->color))
+                        continue;
+
+                iwl_mvm_sta_modify_disable_tx_ap(mvm, sta, disable);
+        }
+}
diff --git a/drivers/net/wireless/iwlwifi/mvm/sta.h b/drivers/net/wireless/iwlwifi/mvm/sta.h
index 10c1a5352651..3b1c8bd6cb54 100644
--- a/drivers/net/wireless/iwlwifi/mvm/sta.h
+++ b/drivers/net/wireless/iwlwifi/mvm/sta.h
@@ -73,6 +73,7 @@
 #include "rs.h"
 
 struct iwl_mvm;
+struct iwl_mvm_vif;
 
 /**
  * DOC: station table - introduction
@@ -295,6 +296,7 @@ static inline u16 iwl_mvm_tid_queued(struct iwl_mvm_tid_data *tid_data)
  * @tid_data: per tid data. Look at %iwl_mvm_tid_data.
  * @tx_protection: reference counter for controlling the Tx protection.
  * @tt_tx_protection: is thermal throttling enable Tx protection?
+ * @disable_tx: is tx to this STA disabled?
  *
  * When mac80211 creates a station it reserves some space (hw->sta_data_size)
  * in the structure for use by driver. This structure is placed in that
@@ -317,6 +319,8 @@ struct iwl_mvm_sta {
         /* Temporary, until the new TLC will control the Tx protection */
         s8 tx_protection;
         bool tt_tx_protection;
+
+        bool disable_tx;
 };
 
 static inline struct iwl_mvm_sta *
@@ -406,5 +410,11 @@ int iwl_mvm_drain_sta(struct iwl_mvm *mvm, struct iwl_mvm_sta *mvmsta,
                       bool drain);
 void iwl_mvm_sta_modify_disable_tx(struct iwl_mvm *mvm,
                                    struct iwl_mvm_sta *mvmsta, bool disable);
+void iwl_mvm_sta_modify_disable_tx_ap(struct iwl_mvm *mvm,
+                                      struct ieee80211_sta *sta,
+                                      bool disable);
+void iwl_mvm_modify_all_sta_disable_tx(struct iwl_mvm *mvm,
+                                       struct iwl_mvm_vif *mvmvif,
+                                       bool disable);
 
 #endif /* __sta_h__ */
diff --git a/drivers/net/wireless/iwlwifi/mvm/tx.c b/drivers/net/wireless/iwlwifi/mvm/tx.c
index fa87a4ba25ec..f5c0982d297c 100644
--- a/drivers/net/wireless/iwlwifi/mvm/tx.c
+++ b/drivers/net/wireless/iwlwifi/mvm/tx.c
@@ -727,13 +727,21 @@ static void iwl_mvm_rx_tx_cmd_single(struct iwl_mvm *mvm,
                 goto out;
 
         if (mvmsta && mvmsta->vif->type == NL80211_IFTYPE_AP) {
+
                 /*
-                 * If there are no pending frames for this STA, notify
-                 * mac80211 that this station can go to sleep in its
+                 * If there are no pending frames for this STA and
+                 * the tx to this station is not disabled, notify
+                 * mac80211 that this station can now wake up in its
                  * STA table.
                  * If mvmsta is not NULL, sta is valid.
                  */
-                ieee80211_sta_block_awake(mvm->hw, sta, false);
+
+                spin_lock_bh(&mvmsta->lock);
+
+                if (!mvmsta->disable_tx)
+                        ieee80211_sta_block_awake(mvm->hw, sta, false);
+
+                spin_unlock_bh(&mvmsta->lock);
         }
 
         if (PTR_ERR(sta) == -EBUSY || PTR_ERR(sta) == -ENOENT) {