rt2x00: Use correct TBTT_SYNC config in AP mode

This seems to fix problems with some powersaving clients since a
positive value in TBTT_SYNC_CFG_TBTT_ADJUST introduces beacon skew,
which is not wanted in AP mode.

Also update the rest of the TBTT_SYNC config according to the
legacy drivers in AP mode.
Signed-off-by: NHelmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: NIvo van Doorn <IvDoorn@gmail.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2800lib.c

@@ -1245,6 +1245,25 @@ void rt2800_config_intf(struct rt2x00_dev *rt2x00dev, struct rt2x00_intf *intf,
 		rt2800_register_read(rt2x00dev, BCN_TIME_CFG, &reg);
 		rt2x00_set_field32(&reg, BCN_TIME_CFG_TSF_SYNC, conf->sync);
 		rt2800_register_write(rt2x00dev, BCN_TIME_CFG, reg);
+
+		if (conf->sync == TSF_SYNC_AP_NONE) {
+			/*
+			 * Tune beacon queue transmit parameters for AP mode
+			 */
+			rt2800_register_read(rt2x00dev, TBTT_SYNC_CFG, &reg);
+			rt2x00_set_field32(&reg, TBTT_SYNC_CFG_BCN_CWMIN, 0);
+			rt2x00_set_field32(&reg, TBTT_SYNC_CFG_BCN_AIFSN, 1);
+			rt2x00_set_field32(&reg, TBTT_SYNC_CFG_BCN_EXP_WIN, 32);
+			rt2x00_set_field32(&reg, TBTT_SYNC_CFG_TBTT_ADJUST, 0);
+			rt2800_register_write(rt2x00dev, TBTT_SYNC_CFG, reg);
+		} else {
+			rt2800_register_read(rt2x00dev, TBTT_SYNC_CFG, &reg);
+			rt2x00_set_field32(&reg, TBTT_SYNC_CFG_BCN_CWMIN, 4);
+			rt2x00_set_field32(&reg, TBTT_SYNC_CFG_BCN_AIFSN, 2);
+			rt2x00_set_field32(&reg, TBTT_SYNC_CFG_BCN_EXP_WIN, 32);
+			rt2x00_set_field32(&reg, TBTT_SYNC_CFG_TBTT_ADJUST, 16);
+			rt2800_register_write(rt2x00dev, TBTT_SYNC_CFG, reg);
+		}
 	}
 
 	if (flags & CONFIG_UPDATE_MAC) {