ath9k: Fix chainmask selection for AR9462

Force chain 1 to be used for CCK rates since the target power
table stored in EEPROM is too high to transmit with both chains.
This is needed to avoid regulatory violation.
Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -173,6 +173,8 @@ void ath_descdma_cleanup(struct ath_softc *sc, struct ath_descdma *dd,
 
 #define ATH_AN_2_TID(_an, _tidno)  (&(_an)->tid[(_tidno)])
 
+#define IS_CCK_RATE(rate) ((rate >= 0x18) && (rate <= 0x1e))
+
 #define ATH_TX_COMPLETE_POLL_INT	1000
 
 enum ATH_AGGR_STATUS {

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

@@ -1820,10 +1820,14 @@ u8 ath_txchainmask_reduction(struct ath_softc *sc, u8 chainmask, u32 rate)
 {
 	struct ath_hw *ah = sc->sc_ah;
 	struct ath9k_channel *curchan = ah->curchan;
+
 	if ((ah->caps.hw_caps & ATH9K_HW_CAP_APM) &&
 	    (curchan->channelFlags & CHANNEL_5GHZ) &&
 	    (chainmask == 0x7) && (rate < 0x90))
 		return 0x3;
+	else if (AR_SREV_9462(ah) && ath9k_hw_btcoex_is_enabled(ah) &&
+		 IS_CCK_RATE(rate))
+		return 0x2;
 	else
 		return chainmask;
 }