ath9k: enable dynack using set_coverage_class codepath

Enable ACK timeout estimation algorithm if set_coverage_class routine has been
called with negative coverage_class parameter. Dynack is automatically disabled
setting valid value for coverage class
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -1876,6 +1876,20 @@ static int ath9k_get_survey(struct ieee80211_hw *hw, int idx,
 	return 0;
 }
 
+static void ath9k_enable_dynack(struct ath_softc *sc)
+{
+#ifdef CONFIG_ATH9K_DYNACK
+	u32 rfilt;
+	struct ath_hw *ah = sc->sc_ah;
+
+	ath_dynack_reset(ah);
+
+	ah->dynack.enabled = true;
+	rfilt = ath_calcrxfilter(sc);
+	ath9k_hw_setrxfilter(ah, rfilt);
+#endif
+}
+
 static void ath9k_set_coverage_class(struct ieee80211_hw *hw,
 				     s16 coverage_class)
 {
@@ -1886,11 +1900,22 @@ static void ath9k_set_coverage_class(struct ieee80211_hw *hw,
 		return;
 
 	mutex_lock(&sc->mutex);
-	ah->coverage_class = coverage_class;
 
-	ath9k_ps_wakeup(sc);
-	ath9k_hw_init_global_settings(ah);
-	ath9k_ps_restore(sc);
+	if (coverage_class >= 0) {
+		ah->coverage_class = coverage_class;
+		if (ah->dynack.enabled) {
+			u32 rfilt;
+
+			ah->dynack.enabled = false;
+			rfilt = ath_calcrxfilter(sc);
+			ath9k_hw_setrxfilter(ah, rfilt);
+		}
+		ath9k_ps_wakeup(sc);
+		ath9k_hw_init_global_settings(ah);
+		ath9k_ps_restore(sc);
+	} else if (!ah->dynack.enabled) {
+		ath9k_enable_dynack(sc);
+	}
 
 	mutex_unlock(&sc->mutex);
 }