ath10k: report estimated frame transmit airtime to improve fairness

The airtime of a transmitted frame will be estimated from last used tx rate
which the firmware reports with the peer stats feature
(WMI_SERVICE_PEER_STATS). The airtime is computed on the tx path and it
will be reported to mac80211 upon tx completion.

This change is based on Kan's orginal commit in Chromium tree
("CHROMIUM: ath10k: Implementing airtime fairness based TX scheduler")
ref: https://chromium-review.googlesource.com/588190

Tested on QCA4019 with firmware version 10.4-3.2.1.1-00015
Tested on QCA9984 with firmware version 10.4-3.9.0.1-00005

Signed-off-by: Kan Yan <kyan@google.com>
[rmanohar@codeaurora.org: ported only the airtime computation]
Signed-off-by: Rajkumar Manoharan <rmanohar@codeaurora.org>
[toke@redhat.com: Rebase to mac80211-next, add test note]
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

4 files changed, 61 insertions, 3 deletions

diff --git a/drivers/net/wireless/ath/ath10k/core.h b/drivers/net/wireless/ath/ath10k/core.h
index 4b730eec88d2..59958664dde4 100644
--- a/drivers/net/wireless/ath/ath10k/core.h
+++ b/drivers/net/wireless/ath/ath10k/core.h
@@ -126,6 +126,7 @@ struct ath10k_skb_cb {
         u8 flags;
         u8 eid;
         u16 msdu_id;
+        u16 airtime_est;
         struct ieee80211_vif *vif;
         struct ieee80211_txq *txq;
 } __packed;
@@ -498,6 +499,7 @@ struct ath10k_sta {
         u16 peer_id;
         struct rate_info txrate;
         struct ieee80211_tx_info tx_info;
+        u32 last_tx_bitrate;
 
         struct work_struct update_wk;
         u64 rx_duration;
diff --git a/drivers/net/wireless/ath/ath10k/htt_rx.c b/drivers/net/wireless/ath/ath10k/htt_rx.c
index 98c525189087..77f494d52ec3 100644
--- a/drivers/net/wireless/ath/ath10k/htt_rx.c
+++ b/drivers/net/wireless/ath/ath10k/htt_rx.c
@@ -3080,6 +3080,7 @@ ath10k_update_per_peer_tx_stats(struct ath10k *ar,
 
         arsta->txrate.nss = txrate.nss;
         arsta->txrate.bw = ath10k_bw_to_mac80211_bw(txrate.bw);
+        arsta->last_tx_bitrate = cfg80211_calculate_bitrate(&arsta->txrate);
         if (sgi)
                 arsta->txrate.flags |= RATE_INFO_FLAGS_SHORT_GI;
 
diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
index 0d5215da410a..88c7b58c9e2f 100644
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -3544,7 +3544,7 @@ static void ath10k_tx_h_add_p2p_noa_ie(struct ath10k *ar,
 static void ath10k_mac_tx_h_fill_cb(struct ath10k *ar,
                                     struct ieee80211_vif *vif,
                                     struct ieee80211_txq *txq,
-                                    struct sk_buff *skb)
+                                    struct sk_buff *skb, u16 airtime)
 {
         struct ieee80211_hdr *hdr = (void *)skb->data;
         struct ath10k_skb_cb *cb = ATH10K_SKB_CB(skb);
@@ -3561,6 +3561,7 @@ static void ath10k_mac_tx_h_fill_cb(struct ath10k *ar,
 
         cb->vif = vif;
         cb->txq = txq;
+        cb->airtime_est = airtime;
 }
 
 bool ath10k_mac_tx_frm_has_freq(struct ath10k *ar)
@@ -3948,6 +3949,49 @@ static bool ath10k_mac_tx_can_push(struct ieee80211_hw *hw,
         return false;
 }
 
+/* Return estimated airtime in microsecond, which is calculated using last
+ * reported TX rate. This is just a rough estimation because host driver has no
+ * knowledge of the actual transmit rate, retries or aggregation. If actual
+ * airtime can be reported by firmware, then delta between estimated and actual
+ * airtime can be adjusted from deficit.
+ */
+#define IEEE80211_ATF_OVERHEAD          100     /* IFS + some slot time */
+#define IEEE80211_ATF_OVERHEAD_IFS      16      /* IFS only */
+static u16 ath10k_mac_update_airtime(struct ath10k *ar,
+                                     struct ieee80211_txq *txq,
+                                     struct sk_buff *skb)
+{
+        struct ath10k_sta *arsta;
+        u32 pktlen;
+        u16 airtime = 0;
+
+        if (!txq || !txq->sta)
+                return airtime;
+
+        spin_lock_bh(&ar->data_lock);
+        arsta = (struct ath10k_sta *)txq->sta->drv_priv;
+
+        pktlen = skb->len + 38; /* Assume MAC header 30, SNAP 8 for most case */
+        if (arsta->last_tx_bitrate) {
+                /* airtime in us, last_tx_bitrate in 100kbps */
+                airtime = (pktlen * 8 * (1000 / 100))
+                                / arsta->last_tx_bitrate;
+                /* overhead for media access time and IFS */
+                airtime += IEEE80211_ATF_OVERHEAD_IFS;
+        } else {
+                /* This is mostly for throttle excessive BC/MC frames, and the
+                 * airtime/rate doesn't need be exact. Airtime of BC/MC frames
+                 * in 2G get some discount, which helps prevent very low rate
+                 * frames from being blocked for too long.
+                 */
+                airtime = (pktlen * 8 * (1000 / 100)) / 60; /* 6M */
+                airtime += IEEE80211_ATF_OVERHEAD;
+        }
+        spin_unlock_bh(&ar->data_lock);
+
+        return airtime;
+}
+
 int ath10k_mac_tx_push_txq(struct ieee80211_hw *hw,
                            struct ieee80211_txq *txq)
 {
@@ -3963,6 +4007,7 @@ int ath10k_mac_tx_push_txq(struct ieee80211_hw *hw,
         size_t skb_len;
         bool is_mgmt, is_presp;
         int ret;
+        u16 airtime;
 
         spin_lock_bh(&ar->htt.tx_lock);
         ret = ath10k_htt_tx_inc_pending(htt);
@@ -3980,7 +4025,8 @@ int ath10k_mac_tx_push_txq(struct ieee80211_hw *hw,
                 return -ENOENT;
         }
 
-        ath10k_mac_tx_h_fill_cb(ar, vif, txq, skb);
+        airtime = ath10k_mac_update_airtime(ar, txq, skb);
+        ath10k_mac_tx_h_fill_cb(ar, vif, txq, skb, airtime);
 
         skb_len = skb->len;
         txmode = ath10k_mac_tx_h_get_txmode(ar, vif, sta, skb);
@@ -4247,8 +4293,10 @@ static void ath10k_mac_op_tx(struct ieee80211_hw *hw,
         bool is_mgmt;
         bool is_presp;
         int ret;
+        u16 airtime;
 
-        ath10k_mac_tx_h_fill_cb(ar, vif, txq, skb);
+        airtime = ath10k_mac_update_airtime(ar, txq, skb);
+        ath10k_mac_tx_h_fill_cb(ar, vif, txq, skb, airtime);
 
         txmode = ath10k_mac_tx_h_get_txmode(ar, vif, sta, skb);
         txpath = ath10k_mac_tx_h_get_txpath(ar, skb, txmode);
@@ -8604,6 +8652,9 @@ int ath10k_mac_register(struct ath10k *ar)
                 wiphy_ext_feature_set(ar->hw->wiphy,
                                       NL80211_EXT_FEATURE_ACK_SIGNAL_SUPPORT);
 
+        if (ath10k_peer_stats_enabled(ar))
+                wiphy_ext_feature_set(ar->hw->wiphy,
+                                      NL80211_EXT_FEATURE_AIRTIME_FAIRNESS);
         /*
          * on LL hardware queues are managed entirely by the FW
          * so we only advertise to mac we can do the queues thing
diff --git a/drivers/net/wireless/ath/ath10k/txrx.c b/drivers/net/wireless/ath/ath10k/txrx.c
index f13d88906b5a..44c13b884603 100644
--- a/drivers/net/wireless/ath/ath10k/txrx.c
+++ b/drivers/net/wireless/ath/ath10k/txrx.c
@@ -95,6 +95,10 @@ int ath10k_txrx_tx_unref(struct ath10k_htt *htt,
                 wake_up(&htt->empty_tx_wq);
         spin_unlock_bh(&htt->tx_lock);
 
+        if (txq && txq->sta)
+                ieee80211_sta_register_airtime(txq->sta, txq->tid,
+                                               skb_cb->airtime_est, 0);
+
         if (ar->bus_param.dev_type != ATH10K_DEV_TYPE_HL)
                 dma_unmap_single(dev, skb_cb->paddr, msdu->len, DMA_TO_DEVICE);