1 files changed, 25 insertions, 25 deletions

diff --git a/drivers/net/wireless/ath9k/beacon.c b/drivers/net/wireless/ath9k/beacon.c
index 039c78136c50..3fd1b86a9b39 100644
--- a/drivers/net/wireless/ath9k/beacon.c
+++ b/drivers/net/wireless/ath9k/beacon.c
@@ -153,6 +153,8 @@ static struct ath_buf *ath_beacon_generate(struct ieee80211_hw *hw,
         bf->bf_mpdu = skb;
         if (skb == NULL)
                 return NULL;
+        ((struct ieee80211_mgmt *)skb->data)->u.beacon.timestamp =
+                avp->tsf_adjust;
 
         info = IEEE80211_SKB_CB(skb);
         if (info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ) {
@@ -253,7 +255,6 @@ int ath_beacon_alloc(struct ath_wiphy *aphy, struct ieee80211_vif *vif)
 {
         struct ath_softc *sc = aphy->sc;
         struct ath_vif *avp;
-        struct ieee80211_hdr *hdr;
         struct ath_buf *bf;
         struct sk_buff *skb;
         __le64 tstamp;
@@ -316,42 +317,33 @@ int ath_beacon_alloc(struct ath_wiphy *aphy, struct ieee80211_vif *vif)
 
         tstamp = ((struct ieee80211_mgmt *)skb->data)->u.beacon.timestamp;
         sc->beacon.bc_tstamp = le64_to_cpu(tstamp);
-
-        /*
-         * Calculate a TSF adjustment factor required for
-         * staggered beacons.  Note that we assume the format
-         * of the beacon frame leaves the tstamp field immediately
-         * following the header.
-         */
+        /* Calculate a TSF adjustment factor required for staggered beacons. */
         if (avp->av_bslot > 0) {
                 u64 tsfadjust;
-                __le64 val;
                 int intval;
 
                 intval = sc->hw->conf.beacon_int ?
                         sc->hw->conf.beacon_int : ATH_DEFAULT_BINTVAL;
 
                 /*
-                 * The beacon interval is in TU's; the TSF in usecs.
-                 * We figure out how many TU's to add to align the
-                 * timestamp then convert to TSF units and handle
-                 * byte swapping before writing it in the frame.
-                 * The hardware will then add this each time a beacon
-                 * frame is sent.  Note that we align vif's 1..N
-                 * and leave vif 0 untouched.  This means vap 0
-                 * has a timestamp in one beacon interval while the
-                 * others get a timestamp aligned to the next interval.
+                 * Calculate the TSF offset for this beacon slot, i.e., the
+                 * number of usecs that need to be added to the timestamp field
+                 * in Beacon and Probe Response frames. Beacon slot 0 is
+                 * processed at the correct offset, so it does not require TSF
+                 * adjustment. Other slots are adjusted to get the timestamp
+                 * close to the TBTT for the BSS.
                  */
-                tsfadjust = (intval * (ATH_BCBUF - avp->av_bslot)) / ATH_BCBUF;
-                val = cpu_to_le64(tsfadjust << 10);     /* TU->TSF */
+                tsfadjust = intval * avp->av_bslot / ATH_BCBUF;
+                avp->tsf_adjust = cpu_to_le64(TU_TO_USEC(tsfadjust));
 
                 DPRINTF(sc, ATH_DBG_BEACON,
                         "stagger beacons, bslot %d intval %u tsfadjust %llu\n",
                         avp->av_bslot, intval, (unsigned long long)tsfadjust);
 
-                hdr = (struct ieee80211_hdr *)skb->data;
-                memcpy(&hdr[1], &val, sizeof(val));
-        }
+                ((struct ieee80211_mgmt *)skb->data)->u.beacon.timestamp =
+                        avp->tsf_adjust;
+        } else
+                avp->tsf_adjust = cpu_to_le64(0);
 
         bf->bf_mpdu = skb;
         bf->bf_buf_addr = bf->bf_dmacontext =
@@ -447,8 +439,16 @@ void ath_beacon_tasklet(unsigned long data)
         tsf = ath9k_hw_gettsf64(ah);
         tsftu = TSF_TO_TU(tsf>>32, tsf);
         slot = ((tsftu % intval) * ATH_BCBUF) / intval;
-        vif = sc->beacon.bslot[(slot + 1) % ATH_BCBUF];
-        aphy = sc->beacon.bslot_aphy[(slot + 1) % ATH_BCBUF];
+        /*
+         * Reverse the slot order to get slot 0 on the TBTT offset that does
+         * not require TSF adjustment and other slots adding
+         * slot/ATH_BCBUF * beacon_int to timestamp. For example, with
+         * ATH_BCBUF = 4, we process beacon slots as follows: 3 2 1 0 3 2 1 ..
+         * and slot 0 is at correct offset to TBTT.
+         */
+        slot = ATH_BCBUF - slot - 1;
+        vif = sc->beacon.bslot[slot];
+        aphy = sc->beacon.bslot_aphy[slot];
 
         DPRINTF(sc, ATH_DBG_BEACON,
                 "slot %d [tsf %llu tsftu %u intval %u] vif %p\n",