ath9k: AR9280 PCI devices must serialize IO as well

Cc: stable@kernel.org
Signed-off-by: NLuis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath9k/hw.c

@@ -687,7 +687,8 @@ static struct ath_hal *ath9k_hw_do_attach(u16 devid, struct ath_softc *sc,
 	}
 
 	if (ah->ah_config.serialize_regmode == SER_REG_MODE_AUTO) {
-		if (ah->ah_macVersion == AR_SREV_VERSION_5416_PCI) {
+		if (ah->ah_macVersion == AR_SREV_VERSION_5416_PCI ||
+		    (AR_SREV_9280(ah) && !ah->ah_isPciExpress)) {
 			ah->ah_config.serialize_regmode =
 				SER_REG_MODE_ON;
 		} else {