ath9k: Update Beacon timers based on timestamp from the AP

Some APs seem to drift away from the expected TBTT (timestamp %
beacon_int_in_usec differs quite a bit from zero) which can result in
us waking up way too early to receive a Beacon frame. In order to work
around this, re-configure the Beacon timers after having received a
Beacon frame from the AP (i.e., when we know the offset between the
expected TBTT and the actual time the AP is sending out the Beacon
frame).

Signed-off-by: Jouni Malinen <jouni.malinen@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

3 files changed, 16 insertions, 1 deletions

diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index 0d4ac43f6d91..796a3adffea0 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -518,6 +518,7 @@ struct ath_rfkill {
 #define SC_OP_WAIT_FOR_CAB      BIT(16)
 #define SC_OP_WAIT_FOR_PSPOLL_DATA BIT(17)
 #define SC_OP_WAIT_FOR_TX_ACK   BIT(18)
+#define SC_OP_BEACON_SYNC       BIT(19)
 
 struct ath_bus_ops {
         void            (*read_cachesize)(struct ath_softc *sc, int *csz);
diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index 5759c9465029..61da08a1648c 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -487,7 +487,7 @@ static void ath9k_tasklet(unsigned long data)
                  * the next Beacon.
                  */
                 DPRINTF(sc, ATH_DBG_PS, "TSFOOR - Sync with next Beacon\n");
-                sc->sc_flags |= SC_OP_WAIT_FOR_BEACON;
+                sc->sc_flags |= SC_OP_WAIT_FOR_BEACON | SC_OP_BEACON_SYNC;
         }
 
         /* re-enable hardware interrupt */
@@ -914,6 +914,13 @@ static void ath9k_bss_assoc_info(struct ath_softc *sc,
                 if (avp->av_opmode == NL80211_IFTYPE_STATION) {
                         sc->curaid = bss_conf->aid;
                         ath9k_hw_write_associd(sc);
+
+                        /*
+                         * Request a re-configuration of Beacon related timers
+                         * on the receipt of the first Beacon frame (i.e.,
+                         * after time sync with the AP).
+                         */
+                        sc->sc_flags |= SC_OP_BEACON_SYNC;
                 }
 
                 /* Configure the beacon */
diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c
index 5e046b58ad93..5014a19b0f75 100644
--- a/drivers/net/wireless/ath/ath9k/recv.c
+++ b/drivers/net/wireless/ath/ath9k/recv.c
@@ -521,6 +521,13 @@ static void ath_rx_ps_beacon(struct ath_softc *sc, struct sk_buff *skb)
         if (memcmp(sc->curbssid, mgmt->bssid, ETH_ALEN) != 0)
                 return; /* not from our current AP */
 
+        if (sc->sc_flags & SC_OP_BEACON_SYNC) {
+                sc->sc_flags &= ~SC_OP_BEACON_SYNC;
+                DPRINTF(sc, ATH_DBG_PS, "Reconfigure Beacon timers based on "
+                        "timestamp from the AP\n");
+                ath_beacon_config(sc, NULL);
+        }
+
         if (!(sc->hw->conf.flags & IEEE80211_CONF_PS)) {
                 /* We are not in PS mode anymore; remain awake */
                 DPRINTF(sc, ATH_DBG_PS, "Not in PS mode anymore, remain "