[PATCH ath-next v4 7/9] wifi: ath11k: charge received airtime to the station deficit

[Julius Bairaktaris]

That's true, I will incorporate a fix in v5.
Thanks for looking into it!

Julius

Am Di., 29. Sept. 2026 um 16:11 Uhr schrieb Tamizh Raja
<tamizh.raja at oss.qualcomm.com>:
>
> On Tue, Sep 8, 2026 at 7:23 PM Julius Bairaktaris <julius at bairaktaris.de> wrote:
> >
> > mac80211's airtime scheduler is configured to account both directions:
> > local->airtime_flags is AIRTIME_USE_TX | AIRTIME_USE_RX, and
> > ieee80211_sta_register_airtime() adds the received airtime to the same
> > deficit the transmit side subtracts from. ath11k passes zero for it, so
> > an access point serving a station that mostly uploads charges that
> > station nothing for the medium it occupies, and the deficit that decides
> > whose queue is served next describes half the traffic.
> >
> > Register the duration the hardware reports for each received PPDU. It
> > arrives in the RXPCU PPDU end TLV on the monitor status ring, which is
> > subscribed for every radio, and ath11k already accumulates it as the
> > station's rx_duration. Charging it once per PPDU matches what the
> > transmit side registers, whereas an estimate rebuilt per MSDU counts the
> > preamble and the interframe space once for every subframe of an
> > aggregate.
> >
> > The PPDU end user stats TLV that names the TID is not in the default
> > monitor status filter, so the airtime is charged to best effort, the
> > access category the deficit arbitrates the bulk of the traffic in. The
>
> This means the resulting fairness accounting is only an approximation
> and can leave VO/VI deficits
> uncharged while accumulating all received airtime against BE
>
> > call is made after ab->base_lock is dropped, under the rcu read lock the
> > loop holds, as the tx completion path does; base_lock is contended by
> > every tx completion. A PPDU from a peer with no station entry is not
> > charged to anyone.
> >
> > Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.9.0.1-02146-QCAHKSWPL_SILICONZ-1
> >
> > Assisted-by: Claude:claude-opus-5
> > Signed-off-by: Julius Bairaktaris <julius at bairaktaris.de>
> > ---
> >  drivers/net/wireless/ath/ath11k/dp_rx.c | 15 +++++++++++++++
> >  1 file changed, 15 insertions(+)
> >
> > diff --git a/drivers/net/wireless/ath/ath11k/dp_rx.c b/drivers/net/wireless/ath/ath11k/dp_rx.c
> > index 68472e1e748a..a7b9bb295728 100644
> > --- a/drivers/net/wireless/ath/ath11k/dp_rx.c
> > +++ b/drivers/net/wireless/ath/ath11k/dp_rx.c
> > @@ -5270,6 +5270,7 @@ int ath11k_dp_rx_process_mon_status(struct ath11k_base *ab, int mac_id,
> >         struct sk_buff_head skb_list;
> >         struct ath11k_peer *peer;
> >         struct ath11k_sta *arsta;
> > +       struct ieee80211_sta *sta;
> >         int num_buffs_reaped = 0;
> >         u32 rx_buf_sz;
> >         u16 log_type;
> > @@ -5324,6 +5325,7 @@ int ath11k_dp_rx_process_mon_status(struct ath11k_base *ab, int mac_id,
> >                         continue;
> >                 }
> >
> > +               sta = NULL;
> >                 rcu_read_lock();
> >                 spin_lock_bh(&ab->base_lock);
> >                 peer = ath11k_peer_find_by_id(ab, ppdu_info->peer_id);
> > @@ -5337,12 +5339,25 @@ int ath11k_dp_rx_process_mon_status(struct ath11k_base *ab, int mac_id,
> >
> >                 arsta = ath11k_sta_to_arsta(peer->sta);
> >                 ath11k_dp_rx_update_peer_stats(arsta, ppdu_info);
> > +               sta = peer->sta;
> >
> >                 if (ath11k_debugfs_is_pktlog_peer_valid(ar, peer->addr))
> >                         trace_ath11k_htt_rxdesc(ar, skb->data, log_type, rx_buf_sz);
> >
> >  next_skb:
> >                 spin_unlock_bh(&ab->base_lock);
> > +
> > +               /* The airtime a station spends transmitting is taken from
> > +                * the others, so its deficit is charged for it too, with the
> > +                * duration the hardware measured for the whole PPDU, as on
> > +                * the transmit side. The TLV that names the TID is not in
> > +                * the default monitor status filter, so the charge goes to
> > +                * BE. Outside base_lock, which tx completion contends for;
> > +                * sta is held by the rcu read lock.
> > +                */
> > +               if (sta && ppdu_info->rx_duration)
> > +                       ieee80211_sta_register_airtime(sta, 0, 0,
> > +                                                      ppdu_info->rx_duration);
> >                 rcu_read_unlock();
> >
> >                 dev_kfree_skb_any(skb);
> > --
> > 2.53.0
> >
> >
>
>
> --
> - Tamizh.