Re: [RFC PATCH] ath11k: add ath11k_mac_op_flush_sta to properly flush pending packets

[Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>]

On 10/7/2025 1:41 PM, Florian Maurer wrote:
> When a STA is marked as no longer authorized, if the driver doesn't
> implement flush_sta(), mac80211 calls ieee80211_flush_queues() to
> flush hardware queues to avoid sending unencrypted frames.
> 
> This has became a problem for ath11k because ieee80211_flush_queues()
> will stop all traffic and call ath11k_flush, which waits until the
> whole HW queue is empty. In a busy environment this will trigger a
> timeout warning and stalls other STAs.
> 
> Fix this by implementing flush_sta method using WMI command to flush
> frames of a specific STA.
> Flushed frames will be marked as discard in tx complete indication.
> 
> warning print "ath11k c000000.wifi: failed to flush transmit queue 0"
> was observed on various openwrt devices, and is fixed through this patch.
> 
> Signed-off-by: Florian Maurer <f.maurer@outlook.de>
> Tested-by: Florian Maurer  <f.maurer@outlook.de>
> Co-authored-by: Benjamin Berg <benjamin@sipsolutions.net>
> Tested-by: Flole <flole@flole.de>
> ---
> We tested this patch and it solved the problem of flushing the transmit
> queues taking too long when the AP is busy.
> We did not confirm if this flush is implemented to guarantee that no
> unencrypted frames are sent out on station removal.
> Could someone with more knowledge about the firmware behavior check
> wether this approach is feasible or if a different approach should be
> taken.
> It is not clear to me if the approach taken in "wifi: ath10k: Flush
> only requested txq in ath10k_flush()" might be better.
> https://lore.kernel.org/linux-wireless/01d859e8e574a1f5d0b916333fe0b5cda859af9b.1732293922.git.repk@triplefau.lt/
> 
> Regards
> Florian
> 
>   drivers/net/wireless/ath/ath11k/mac.c | 19 +++++++++++++++++++
>   1 file changed, 19 insertions(+)
> 
> diff --git a/drivers/net/wireless/ath/ath11k/mac.c b/drivers/net/wireless/ath/ath11k/mac.c
> index 106e2530b64e..a94649edd4ed 100644
> --- a/drivers/net/wireless/ath/ath11k/mac.c
> +++ b/drivers/net/wireless/ath/ath11k/mac.c
> @@ -8330,6 +8330,24 @@ static void ath11k_mac_op_flush(struct ieee80211_hw *hw, struct ieee80211_vif *v
>   	ath11k_mac_flush_tx_complete(ar);
>   }
>   
> +static void ath11k_mac_op_flush_sta(struct ieee80211_hw *hw,
> +							struct ieee80211_vif *vif,
> +			    			struct ieee80211_sta *sta)
> +{
> +	struct ath11k_vif *arvif = (void *)vif->drv_priv;
> +	struct ath11k *ar = hw->priv;
> +	struct peer_flush_params params = {
> +		.peer_tid_bitmap = 0xFF,

The recommendation from the firmware developers is that all 32-bit has to be sent
in WMI_PEER_FLUSH_TIDS_CMDID for both AP and STA mode, otherwise some of the tid
queues may still have pending packets. Firmware does the intersection and gracefully
ignores the inactive tid queues when all the bits are set. We may need to check the
firmware crash dump to understand the issue with 0xffffffff bitmap.

Vasanth