mirror of https://github.com/proski/madwifi
Improved slottime and acktimeout/ctstimeout computations
Needs field testing git-svn-id: http://madwifi-project.org/svn/madwifi/trunk@3870 0192ed92-7a03-0410-a25b-9323aeb14dbd
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benoit
parent
b327291039
commit
a729fef8c6
127
ath/if_ath.c
127
ath/if_ath.c
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@ -4284,26 +4284,88 @@ ath_mode_init(struct net_device *dev)
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rfilt, mfilt[0], mfilt[1]);
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}
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static inline int
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ath_slottime2timeout(struct ath_softc *sc, int slottime)
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/* returns aSIFSTime based on current channel settings */
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static int
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ath_default_sifs(struct ath_softc *sc)
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{
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/* IEEE 802.11 2007 9.2.8 says the ACK timeout shall be SIFSTime +
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* slot time (+ PHY RX start delay). HAL seems to use a constant of 8
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/* Turbo mode. FIXME : what is the correct value? */
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if (sc->sc_dturbo || (sc->sc_curchan.privFlags & CHANNEL_ST))
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return 8;
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if (sc->sc_curchan.channelFlags & CHANNEL_2GHZ) {
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/* default : 802.11b or 802.11g with short/long slot time */
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return 10;
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} else if (sc->sc_curchan.channelFlags & CHANNEL_5GHZ) {
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/* 802.11a/10MHz (half rates) */
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if (sc->sc_curchan.channelFlags & CHANNEL_HALF)
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return 64;
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/* 802.11a/5MHz (quarter rates) */
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if (sc->sc_curchan.channelFlags & CHANNEL_QUARTER)
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return 32;
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/* default : 802.11a/20MHz */
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return 16;
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}
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/* incorrect value for channelFlags, returns a default value */
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return 10;
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}
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static inline int
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ath_slottime2timeout(struct ath_softc *sc, int aSlotTime)
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{
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/* IEEE 802.11-2007 9.2.8 says the ACK timeout shall be aSIFSTime +
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* aSlotTime (+ aPHY-RX-START-Delay). HAL seems to use a constant of 8
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* for OFDM overhead and 18 for CCK overhead.
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*
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* XXX: Update based on emperical evidence (potentially save 15us per
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* timeout). */
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if (((sc->sc_curchan.channelFlags & IEEE80211_CHAN_A) ==
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IEEE80211_CHAN_A) ||
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(((sc->sc_curchan.channelFlags & IEEE80211_CHAN_108G) ==
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IEEE80211_CHAN_108G) &&
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(sc->sc_ic.ic_flags & IEEE80211_F_SHSLOT)))
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/* Short slot time: 802.11a, and 802.11g turbo in turbo mode
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* with short slot time. */
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return slottime + 8;
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else
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/* Constant for CCK MIB processing time. */
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return slottime + 18;
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*/
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int aSIFSTime;
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aSIFSTime = ath_default_sifs(sc);
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/* FIXME : we neglect aPHY-RX-START-Delay */
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return aSIFSTime + aSlotTime;
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}
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/* returns aSlotTime in us based on the current channel settings. This value
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* does not take into account air propagation time */
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static int
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ath_default_slottime(struct ath_softc *sc)
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{
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struct ieee80211com *ic = &sc->sc_ic;
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/* Turbo mode */
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if (sc->sc_dturbo || (sc->sc_curchan.privFlags & CHANNEL_ST))
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return 6;
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if (sc->sc_curchan.channelFlags & CHANNEL_2GHZ) {
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/* 802.11g with short slot time */
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if (ic->ic_flags & IEEE80211_F_SHSLOT)
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return 9;
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/* default : 802.11b or 802.11g with long slot time */
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return 20;
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} else if (sc->sc_curchan.channelFlags & CHANNEL_5GHZ) {
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/* 802.11a/10MHz (half rates) */
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if (sc->sc_curchan.channelFlags & CHANNEL_HALF)
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return 13;
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/* 802.11a/5MHz (quarter rates) */
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if (sc->sc_curchan.channelFlags & CHANNEL_QUARTER)
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return 21;
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/* default : 802.11a/20MHz */
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return 9;
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}
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/* incorrect value for channelFlags, returns a default value */
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return 20;
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}
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static inline int
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@ -4337,22 +4399,19 @@ ath_getctstimeout(struct ath_softc *sc)
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}
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/*
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* Set the slot time based on the current setting.
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* Set the slot time, ACK timeout, CTS timeout HW registers based on the
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* current setting.
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*/
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static inline void
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ath_setslottime(struct ath_softc *sc)
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{
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struct ieee80211com *ic = &sc->sc_ic;
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struct ath_hal *ah = sc->sc_ah;
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if (sc->sc_slottimeconf > 0) /* manual override */
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ath_hal_setslottime(ah, sc->sc_slottimeconf);
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else if (sc->sc_dturbo || (sc->sc_curchan.privFlags & CHANNEL_ST))
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ath_hal_setslottime(ah, HAL_SLOT_TIME_6);
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else if (ic->ic_flags & IEEE80211_F_SHSLOT)
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ath_hal_setslottime(ah, HAL_SLOT_TIME_9);
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else
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ath_hal_setslottime(ah, HAL_SLOT_TIME_20);
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ath_hal_setslottime(ah, ath_default_slottime(sc));
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sc->sc_updateslot = OK;
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ath_setacktimeout(sc);
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ath_setctstimeout(sc);
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@ -10535,18 +10594,14 @@ ath_estimate_max_distance(struct ath_softc *sc)
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static inline int
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ath_distance2slottime(struct ath_softc *sc, int distance)
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{
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/* Allowance for air propagation (roundtrip time) should be at least
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* 5us per the standards.
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*
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* So let's set a minimum distance to accomodate this:
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* roundtrip time = ((distance / speed_of_light) * 2)
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* distance = ((time * 300 ) / 2) or ((5 * 300) / 2) = 750 m */
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int rtdist = distance * 2;
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/* IEEE 802.11-2007 10.4.3.2 defines aAirPropagationTime as being
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* twice the propagation time for a signal to cross the maximum
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* distance */
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int c = 299; /* Speed of light in vacuum in m/us. */
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/* IEEE 802.11 2007 10l.4.3.2. In us. */
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int aAirPropagation = MAX(5, howmany(rtdist, c));
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/* XXX: RX/TX turnaround & MAC delay. */
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return ath_ccatime(sc) + aAirPropagation;
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/* IEEE 802.11 2007 10.4.3.2. In us. */
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int aAirPropagationTime = (distance * 2) / c;
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return ath_default_slottime(sc) + aAirPropagationTime;
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}
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static inline int
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