[PATCH ath-next v3 8/9] wifi: ath11k: stop a scheduling round when the hardware refuses a frame

[Julius Bairaktaris]

ath11k_dp_tx() returns -ENOSPC when the MSDU idr is exhausted and -ENOMEM
when no TCL descriptor is free on any ring or a DMA mapping fails, 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.

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, and every frame with -ESHUTDOWN while a firmware
crash is being flushed; those describe the frame or the device 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 at bairaktaris.de>
---
 drivers/net/wireless/ath/ath11k/mac.c | 41 ++++++++++++++++++++-------
 1 file changed, 30 insertions(+), 11 deletions(-)

diff --git a/drivers/net/wireless/ath/ath11k/mac.c b/drivers/net/wireless/ath/ath11k/mac.c
index 150b3a1a9c19..2a70a9c58235 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)
@@ -6544,20 +6544,36 @@ 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 itself, so a
-	 * selection ends where that limit binds, where the hardware queue is
-	 * stopped, or when the queue empties, as the generic handler does
-	 * today.
+	 * selection ends where the airtime queue limit binds, where the
+	 * hardware queue is stopped, or when the queue empties, as the generic
+	 * handler does today, and additionally when the hardware refuses a
+	 * frame.
 	 */
-	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)
@@ -6569,8 +6585,11 @@ 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