Commit 9804b98d authored by Bruno Randolf's avatar Bruno Randolf Committed by David S. Miller
Browse files

ath5k: better beacon timer calculation

update ath5k_beacon_update_timers() for better beacon timer calculation in a
variety of situations. most important is the possibility to call it with the
timestamp of a received beacon, when we detected that a HW merge has happened
and we need to reconfigure the beacon timers based on that.

we call this from the mac80211 callback reset_tsf now instead of beacon_update,
and there will be more use of it in the next patch.

drivers/net/wireless/ath5k/base.c:      Changes-licensed-under: 3-Clause-BSD
Signed-off-by: default avatarBruno Randolf <>
Signed-off-by: default avatarJohn W. Linville <>
parent e535c1ac
......@@ -290,6 +290,7 @@ static int ath5k_beacon_setup(struct ath5k_softc *sc,
struct ieee80211_tx_control *ctl);
static void ath5k_beacon_send(struct ath5k_softc *sc);
static void ath5k_beacon_config(struct ath5k_softc *sc);
static void ath5k_beacon_update_timers(struct ath5k_softc *sc, u64 bc_tsf);
static inline u64 ath5k_extend_tsf(struct ath5k_hw *ah, u32 rstamp)
......@@ -1984,34 +1985,102 @@ ath5k_beacon_send(struct ath5k_softc *sc)
* ath5k_beacon_update_timers - update beacon timers
* @sc: struct ath5k_softc pointer we are operating on
* @bc_tsf: the timestamp of the beacon. 0 to reset the TSF. -1 to perform a
* beacon timer update based on the current HW TSF.
* Calculate the next target beacon transmit time (TBTT) based on the timestamp
* of a received beacon or the current local hardware TSF and write it to the
* beacon timer registers.
* This is called in a variety of situations, e.g. when a beacon is received,
* when a HW merge has been detected, but also when an new IBSS is created or
* when we otherwise know we have to update the timers, but we keep it in this
* function to have it all together in one place.
static void
ath5k_beacon_update_timers(struct ath5k_softc *sc)
ath5k_beacon_update_timers(struct ath5k_softc *sc, u64 bc_tsf)
struct ath5k_hw *ah = sc->ah;
u32 uninitialized_var(nexttbtt), intval, tsftu;
u64 tsf;
u32 nexttbtt, intval, hw_tu, bc_tu;
u64 hw_tsf;
intval = sc->bintval & AR5K_BEACON_PERIOD;
if (WARN_ON(!intval))
/* current TSF converted to TU */
tsf = ath5k_hw_get_tsf64(ah);
tsftu = TSF_TO_TU(tsf);
/* beacon TSF converted to TU */
bc_tu = TSF_TO_TU(bc_tsf);
* Pull nexttbtt forward to reflect the current
* TSF. Add one intval otherwise the timespan
* can be too short for ibss merges.
nexttbtt = tsftu + 2 * intval;
/* current TSF converted to TU */
hw_tsf = ath5k_hw_get_tsf64(ah);
hw_tu = TSF_TO_TU(hw_tsf);
"hw tsftu %u nexttbtt %u intval %u\n", tsftu, nexttbtt, intval);
#define FUDGE 3
/* we use FUDGE to make sure the next TBTT is ahead of the current TU */
if (bc_tsf == -1) {
* no beacons received, called internally.
* just need to refresh timers based on HW TSF.
nexttbtt = roundup(hw_tu + FUDGE, intval);
} else if (bc_tsf == 0) {
* no beacon received, probably called by ath5k_reset_tsf().
* reset TSF to start with 0.
nexttbtt = intval;
} else if (bc_tsf > hw_tsf) {
* beacon received, SW merge happend but HW TSF not yet updated.
* not possible to reconfigure timers yet, but next time we
* receive a beacon with the same BSSID, the hardware will
* automatically update the TSF and then we need to reconfigure
* the timers.
"need to wait for HW TSF sync\n");
} else {
* most important case for beacon synchronization between STA.
* beacon received and HW TSF has been already updated by HW.
* update next TBTT based on the TSF of the beacon, but make
* sure it is ahead of our local TSF timer.
nexttbtt = bc_tu + roundup(hw_tu + FUDGE - bc_tu, intval);
#undef FUDGE
intval |= AR5K_BEACON_ENA;
ath5k_hw_init_beacon(ah, nexttbtt, intval);
* debugging output last in order to preserve the time critical aspect
* of this function
if (bc_tsf == -1)
"reconfigured timers based on HW TSF\n");
else if (bc_tsf == 0)
"reset HW TSF and timers\n");
"updated timers based on beacon TSF\n");
"bc_tsf %llx hw_tsf %llx bc_tu %u hw_tu %u nexttbtt %u\n",
bc_tsf, hw_tsf, bc_tu, hw_tu, nexttbtt);
ATH5K_DBG_UNLIMIT(sc, ATH5K_DEBUG_BEACON, "intval %u %s %s\n",
intval & AR5K_BEACON_ENA ? "AR5K_BEACON_ENA" : "",
......@@ -2045,7 +2114,6 @@ ath5k_beacon_config(struct ath5k_softc *sc)
* only once here.
if (!ath5k_hw_hasveol(ah))
sc->imask |= AR5K_INT_SWBA;
......@@ -2795,7 +2863,14 @@ ath5k_reset_tsf(struct ieee80211_hw *hw)
struct ath5k_softc *sc = hw->priv;
* in IBSS mode we need to update the beacon timers too.
* this will also reset the TSF if we call it with 0
if (sc->opmode == IEEE80211_IF_TYPE_IBSS)
ath5k_beacon_update_timers(sc, 0);
static int
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