ath9k: fix extending the rx timestamp with the hardware TSF

AR5416 and all newer chipsets use a 32 bit rx timestamp, so there
is no need to keep the 15 bit timestamp extending logic around.

This patch removes ath9k_hw_extend_tsf (replaced by a call to
ath9k_hw_gettsf64), and reduces the frequency of TSF reads, which
can improve performance in some cases.

This change also has the side effect of making rx timestamps
more accurate.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/hw.c

@@ -2616,21 +2616,6 @@ void ath9k_hw_set_tsfadjust(struct ath_hw *ah, u32 setting)
 }
 EXPORT_SYMBOL(ath9k_hw_set_tsfadjust);
 
-/*
- *  Extend 15-bit time stamp from rx descriptor to
- *  a full 64-bit TSF using the current h/w TSF.
-*/
-u64 ath9k_hw_extend_tsf(struct ath_hw *ah, u32 rstamp)
-{
-	u64 tsf;
-
-	tsf = ath9k_hw_gettsf64(ah);
-	if ((tsf & 0x7fff) < rstamp)
-		tsf -= 0x8000;
-	return (tsf & ~0x7fff) | rstamp;
-}
-EXPORT_SYMBOL(ath9k_hw_extend_tsf);
-
 void ath9k_hw_set11nmac2040(struct ath_hw *ah)
 {
 	struct ieee80211_conf *conf = &ath9k_hw_common(ah)->hw->conf;

drivers/net/wireless/ath/ath9k/hw.h

@@ -894,7 +894,6 @@ u64 ath9k_hw_gettsf64(struct ath_hw *ah);
 void ath9k_hw_settsf64(struct ath_hw *ah, u64 tsf64);
 void ath9k_hw_reset_tsf(struct ath_hw *ah);
 void ath9k_hw_set_tsfadjust(struct ath_hw *ah, u32 setting);
-u64 ath9k_hw_extend_tsf(struct ath_hw *ah, u32 rstamp);
 void ath9k_hw_init_global_settings(struct ath_hw *ah);
 void ath9k_hw_set11nmac2040(struct ath_hw *ah);
 void ath9k_hw_beaconinit(struct ath_hw *ah, u32 next_beacon, u32 beacon_period);

drivers/net/wireless/ath/ath9k/recv.c

@@ -1002,8 +1002,6 @@ static int ath9k_rx_skb_preprocess(struct ath_common *common,
 				   struct ieee80211_rx_status *rx_status,
 				   bool *decrypt_error)
 {
-	struct ath_hw *ah = common->ah;
-
 	memset(rx_status, 0, sizeof(struct ieee80211_rx_status));
 
 	/*
@@ -1018,7 +1016,6 @@ static int ath9k_rx_skb_preprocess(struct ath_common *common,
 	if (ath9k_process_rate(common, hw, rx_stats, rx_status))
 		return -EINVAL;
 
-	rx_status->mactime = ath9k_hw_extend_tsf(ah, rx_stats->rs_tstamp);
 	rx_status->band = hw->conf.channel->band;
 	rx_status->freq = hw->conf.channel->center_freq;
 	rx_status->signal = ATH_DEFAULT_NOISE_FLOOR + rx_stats->rs_rssi;
@@ -1100,6 +1097,8 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
 	bool edma = !!(ah->caps.hw_caps & ATH9K_HW_CAP_EDMA);
 	int dma_type;
 	u8 rx_status_len = ah->caps.rx_status_len;
+	u64 tsf = 0;
+	u32 tsf_lower = 0;
 
 	if (edma)
 		dma_type = DMA_BIDIRECTIONAL;
@@ -1109,6 +1108,9 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
 	qtype = hp ? ATH9K_RX_QUEUE_HP : ATH9K_RX_QUEUE_LP;
 	spin_lock_bh(&sc->rx.rxbuflock);
 
+	tsf = ath9k_hw_gettsf64(ah);
+	tsf_lower = tsf & 0xffffffff;
+
 	do {
 		/* If handling rx interrupt and flush is in progress => exit */
 		if ((sc->sc_flags & SC_OP_RXFLUSH) && (flush == 0))
@@ -1141,6 +1143,15 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
 		if (flush)
 			goto requeue;
 
+		rxs->mactime = (tsf & ~0xffffffffULL) | rs.rs_tstamp;
+		if (rs.rs_tstamp > tsf_lower &&
+		    unlikely(rs.rs_tstamp - tsf_lower > 0x10000000))
+			rxs->mactime -= 0x100000000ULL;
+
+		if (rs.rs_tstamp < tsf_lower &&
+		    unlikely(tsf_lower - rs.rs_tstamp > 0x10000000))
+			rxs->mactime += 0x100000000ULL;
+
 		retval = ath9k_rx_skb_preprocess(common, hw, hdr, &rs,
 						 rxs, &decrypt_error);
 		if (retval)