[PATCH v4 0/4] ath11k/ath12k: implement TX flow control

[Jose Ignacio Tornos Martinez <jtornosm@redhat.com>]

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,
adapted for ath11k/ath12k hardware ring architecture, checking
hardware ring space before dequeuing packets from mac80211.

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

Jose Ignacio Tornos Martinez (4):
  wifi: ath11k: use queue mapping for WCN6750 ring selection
  wifi: ath11k/ath12k: remove skb parameter from get_ring_selector
  wifi: ath11k: implement custom wake_tx_queue with flow control
  wifi: ath12k: implement custom wake_tx_queue with flow control

v4: Address feedback from Johannes Berg:
  - Drop the ieee80211_tx_peek() mac80211 patch entirely due to the
    commented concerns.
  - Redesign as a consequence of dropping the peek API:
    - Patch 1: switch WCN6750 from skb_get_hash() to skb_get_queue_mapping()
      as a preparatory step, since the AC value is all that is needed.
      This aligns with the approach already used by ath12k WCN7850
      (which has the same ring count).
    - Patch 2: Instead of peeking the skb to call get_ring_selector(skb),
      pass txq->ac directly via get_ring_selector(u8 ac). This is safe
      because mac80211 guarantees skb_get_queue_mapping(skb) == txq->ac for
      any skb dequeued from a given txq.
    - Patch 3 and 4: adapt tx flow control to the new approach.
v3: https://lore.kernel.org/all/20260720070852.206495-1-jtornosm@redhat.com/
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2.49.0