[PATCH ath-next v2 8/9] wifi: ath11k: stop a scheduling round when the hardware refuses a frame

[Julius Bairaktaris <julius@bairaktaris.de>]

ath11k_dp_tx() returns -ENOSPC when the MSDU idr is exhausted and
-ENOMEM when no TCL descriptor is free on any ring, and the caller
answers both by freeing the frame. Inside a scheduling round that is a
loop: the next iteration pulls the next frame out of the same flow queue
and drops that one too, so a transient shortage costs the head of an
FQ-CoDel queue rather than the tail of a hardware one, and the frames it
discards are the ones the queue had already selected as most deserving
of the medium.

Return the error from the transmit path and end the round on it. The
round-robin over the remaining stations stops as well, since a shortage
that reaches this point is not specific to the station being served.

ath11k_dp_tx() also rejects a frame the hardware can never accept, with
-EINVAL or -EOPNOTSUPP; those describe the frame and not the ring, so the
round continues past them.

ath10k and mt76 end a round the same way when the hardware has no room.

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.9.0.1-02146-QCAHKSWPL_SILICONZ-1
Assisted-by: Claude:claude-opus-5
Signed-off-by: Julius Bairaktaris <julius@bairaktaris.de>
---
 drivers/net/wireless/ath/ath11k/mac.c | 34 ++++++++++++++++++++-------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/drivers/net/wireless/ath/ath11k/mac.c b/drivers/net/wireless/ath/ath11k/mac.c
index 996f421b6957..eb420fa0fd68 100644
--- a/drivers/net/wireless/ath/ath11k/mac.c
+++ b/drivers/net/wireless/ath/ath11k/mac.c
@@ -6499,9 +6499,9 @@ static int ath11k_mac_mgmt_tx(struct ath11k *ar, struct sk_buff *skb,
 	return 0;
 }
 
-static void ath11k_mac_op_tx(struct ieee80211_hw *hw,
-			     struct ieee80211_tx_control *control,
-			     struct sk_buff *skb)
+static int ath11k_mac_tx(struct ieee80211_hw *hw,
+			 struct ieee80211_tx_control *control,
+			 struct sk_buff *skb)
 {
 	struct ath11k_skb_cb *skb_cb = ATH11K_SKB_CB(skb);
 	struct ath11k *ar = hw->priv;
@@ -6533,7 +6533,7 @@ static void ath11k_mac_op_tx(struct ieee80211_hw *hw,
 				    ret);
 			ieee80211_free_txskb(ar->hw, skb);
 		}
-		return;
+		return ret;
 	}
 
 	if (control->sta)
@@ -6544,19 +6544,34 @@ static void ath11k_mac_op_tx(struct ieee80211_hw *hw,
 		ath11k_warn(ar->ab, "failed to transmit frame %d\n", ret);
 		ieee80211_free_txskb(ar->hw, skb);
 	}
+
+	return ret;
+}
+
+static void ath11k_mac_op_tx(struct ieee80211_hw *hw,
+			     struct ieee80211_tx_control *control,
+			     struct sk_buff *skb)
+{
+	ath11k_mac_tx(hw, control, skb);
 }
 
-static void ath11k_mac_tx_push_txq(struct ath11k *ar, struct ieee80211_txq *txq)
+static int ath11k_mac_tx_push_txq(struct ath11k *ar, struct ieee80211_txq *txq)
 {
 	struct ieee80211_tx_control control = { .sta = txq->sta };
 	struct sk_buff *skb;
+	int ret;
 
 	/* ieee80211_tx_dequeue() applies the airtime queue limit, so the burst
 	 * a station gets from one selection is bounded by the airtime already
 	 * in flight for it rather than by a frame count.
 	 */
-	while ((skb = ieee80211_tx_dequeue(ar->hw, txq)))
-		ath11k_mac_op_tx(ar->hw, &control, skb);
+	while ((skb = ieee80211_tx_dequeue(ar->hw, txq))) {
+		ret = ath11k_mac_tx(ar->hw, &control, skb);
+		if (unlikely(ret == -ENOSPC || ret == -ENOMEM))
+			return ret;
+	}
+
+	return 0;
 }
 
 static void ath11k_mac_schedule_txq(struct ath11k *ar, u8 ac)
@@ -6568,8 +6583,11 @@ static void ath11k_mac_schedule_txq(struct ath11k *ar, u8 ac)
 
 	ieee80211_txq_schedule_start(hw, ac);
 	while ((txq = ieee80211_next_txq(hw, ac))) {
-		ath11k_mac_tx_push_txq(ar, txq);
+		int ret = ath11k_mac_tx_push_txq(ar, txq);
+
 		ieee80211_return_txq(hw, txq, false);
+		if (unlikely(ret))
+			break;
 	}
 	ieee80211_txq_schedule_end(hw, ac);
 
-- 
2.53.0