[PATCH 2/2] wifi: ath12k: implement custom wake_tx_queue with flow control

[Jeff Johnson]

On 7/10/2026 8:54 AM, Jose Ignacio Tornos Martinez wrote:
> Under heavy traffic, ath12k can hang and experiences -ENOMEM errors
> ("failed to transmit frame -12") when the hardware TCL ring fills up.
> This issue is more commonly observed in VMs with PCIe passthrough but
> also occurs on bare metal systems.
> 
> Implement a custom wake_tx_queue operation that:
> 
> 1. Checks hardware ring space before dequeuing packets from mac80211
> 2. Uses per-packet locking to serialize ring access and prevent races
> 3. Syncs with hardware state to get accurate free slot count
> 4. Returns early during firmware crash in the same way as other tx paths
> 
> This approach follows the pattern used in the iwlwifi driver, adapted
> for ath12k's hardware ring architecture.
> 
> This prevents hangs, eliminates -ENOMEM errors, and improves throughput
> by optimizing resource usage and preventing unnecessary packet drops.
> 
> Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm at redhat.com>

Just based upon the description I doubt this will be accepted. The ath12k
datapath team is striving to have a lockless fastpath, so adding new locks is
problematic. I've BCC'ed the internal developers list so that the team knows
to give more constructive feedback.

/jeff