package/kernel/mac80211/patches/312-ath9k-Correct-TSF-adjustment-to-align-the-beacon-tim.patch

   1 From: Benjamin Berg <benjamin.berg@open-mesh.com>
   2 Date: Mon, 4 Jul 2016 14:37:20 +0200
   3 Subject: [PATCH] ath9k: Correct TSF adjustment to align the beacon time
   4  correctly
   5
   6 Beacons were not send out at (timestamp % beacon_time == 0) for interfaces
   7 other than the primary one. To send out beacons with the correct timestamp
   8 according to 10.1.3.2 of the 802.11 standard the tsf_adjustment has to be
   9 set to the negative time difference instead of positive. This way the
  10 later beacons get corrected to have a lower (and similar) timestamp with
  11 regard to the beacon from slot 0.
  12
  13 I am not aware about any issues that have been caused by this.
  14
  15 Signed-off-by: Benjamin Berg <benjamin.berg@open-mesh.com>
  16 ---
  17
  18 --- a/drivers/net/wireless/ath/ath9k/beacon.c
  19 +++ b/drivers/net/wireless/ath/ath9k/beacon.c
  20 @@ -279,17 +279,21 @@ static void ath9k_set_tsfadjust(struct a
  21         struct ath_common *common = ath9k_hw_common(sc->sc_ah);
  22         struct ath_vif *avp = (void *)vif->drv_priv;
  23         struct ath_beacon_config *cur_conf = &avp->chanctx->beacon;
  24 -       u32 tsfadjust;
  25 +       s64 tsfadjust;
  26
  27         if (avp->av_bslot == 0)
  28                 return;
  29
  30 +       /* tsf_adjust is added to the TSF value. We send out the beacon late,
  31 +        * so need to adjust the TSF starting point to be later in time (i.e.
  32 +        * the theoretical first beacon has a TSF of 0 after correction).
  33 +        */
  34         tsfadjust = cur_conf->beacon_interval * avp->av_bslot;
  35 -       tsfadjust = TU_TO_USEC(tsfadjust) / ATH_BCBUF;
  36 +       tsfadjust = -TU_TO_USEC(tsfadjust) / ATH_BCBUF;
  37         avp->tsf_adjust = cpu_to_le64(tsfadjust);
  38
  39 -       ath_dbg(common, CONFIG, "tsfadjust is: %llu for bslot: %d\n",
  40 -               (unsigned long long)tsfadjust, avp->av_bslot);
  41 +       ath_dbg(common, CONFIG, "tsfadjust is: %lld for bslot: %d\n",
  42 +               (signed long long)tsfadjust, avp->av_bslot);
  43  }
  44
  45  bool ath9k_csa_is_finished(struct ath_softc *sc, struct ieee80211_vif *vif)