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-ring locking serializes ring access while allowing TX completions
to run, preventing deadlocks.

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

v2: Address feedback from Zhi-Jun You:
    - Add ieee80211_tx_peek() API in mac80211 to peek at the next frame
      without dequeuing, enabling accurate ring selection before dequeue
    - Use get_ring_selector() on the peeked skb to determine the exact
      target ring matching dp_tx, fixing ring mismatch on multi-ring
      platforms (ipq8074, wcn6750, qcn9274, wcn7850)
    Address feedback from Tamizh Chelvam Raja:
    - Fix ath12k radio assignment: obtain ar from txq->vif through the
      arvif chain instead of ah->radio flexible array
    Move CRASH_FLUSH check inside the TX loop 
v1: https://lore.kernel.org/all/20260710155443.1761760-1-jtornosm@redhat.com/
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2.49.0