ath9k: save tsf in channel context

Save TSF in channel context for multiple operating channels.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Rajkumar Manoharan <rmanohar@qti.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/channel.c b/drivers/net/wireless/ath/ath9k/channel.c
index e3127b5..4a7691e 100644
--- a/drivers/net/wireless/ath/ath9k/channel.c
+++ b/drivers/net/wireless/ath/ath9k/channel.c
@@ -227,6 +227,11 @@
 
 		send_ps = true;
 		spin_lock_bh(&sc->chan_lock);
+
+		if (sc->cur_chan != &sc->offchannel.chan) {
+			getrawmonotonic(&sc->cur_chan->tsf_ts);
+			sc->cur_chan->tsf_val = ath9k_hw_gettsf64(sc->sc_ah);
+		}
 	}
 	sc->cur_chan = sc->next_chan;
 	sc->cur_chan->stopped = false;