This series implements custom wake_tx_queue operations for ath11k and
ath12k drivers to prevent hardware ring overflow issues under heavy
traffic.

Without proper flow control, both drivers experience -ENOMEM errors
("failed to transmit frame -12") when the hardware TCL ring fills up.
Additionally, ath12k can hang under sustained high throughput. These
issues are more commonly observed in VMs with PCIe passthrough but
also occur on bare metal systems.

The implementation follows the pattern used in the iwlwifi driver,
checking hardware ring space before dequeuing packets from mac80211.
Per-txq locking via txq->drv_priv serializes peek and dequeue
operations for the same txq, preventing use-after-free races while
keeping different txqs fully parallel.

Testing shows stable operation with eliminated -ENOMEM errors, no hangs,
and improved throughput under heavy traffic conditions.

Jose Ignacio Tornos Martinez (3):
  mac80211: add ieee80211_tx_peek API
  wifi: ath11k: implement custom wake_tx_queue with flow control
  wifi: ath12k: implement custom wake_tx_queue with flow control

v3: Address the review comments from Tamizh Raja:
    - ath11k/ath12k: replace per-ring wake_tx_lock with per-txq spinlock via
      txq->drv_priv to fix race condition between ieee80211_tx_peek() and
      ieee80211_tx_dequeue() when multiple CPUs process the same txq
    - ath12k: fix MLO link selection in wake_tx_queue to use
      rcu_dereference(ahvif->link[link_id]) instead of deflink, matching
      the link selection logic in op_tx
v2: https://lore.kernel.org/all/20260715125017.277242-1-jtornosm@redhat.com/

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2.49.0