Index: sys/dev/ath/ath_hal/ar5416/ar5416_xmit.c
===================================================================
--- sys/dev/ath/ath_hal/ar5416/ar5416_xmit.c	(revision 257209)
+++ sys/dev/ath/ath_hal/ar5416/ar5416_xmit.c	(working copy)
@@ -27,6 +27,8 @@
 #include "ar5416/ar5416phy.h"
 #include "ar5416/ar5416desc.h"
 
+#define TU_TO_USEC(_tu)         ((_tu) << 10)
+
 /*
  * Stop transmit on the specified queue
  */
@@ -1039,7 +1041,40 @@
 					ah->ah_config.ah_dma_beacon_response_time)
 				- ah->ah_config.ah_additional_swba_backoff) * 1024;
 			OS_REG_WRITE(ah, AR_QRDYTIMECFG(q), value | AR_Q_RDYTIMECFG_ENA);
+		} else {
+			int value;
+			/*
+			 * NB: don't set default ready time if driver
+			 * has explicitly specified something.  This is
+			 * here solely for backwards compatibility.
+			 */
+			/*
+			 * XXX for now, hard-code a CAB interval of 70%
+			 * XXX of the total beacon interval.
+			 *
+			 * XXX This keeps Merlin and later based MACs
+			 * XXX quite a bit happier (stops stuck beacons,
+			 * XXX which I gather is because of such a long
+			 * XXX cabq time.)
+			 */
+			value = (ahp->ah_beaconInterval * 70 / 100)
+				- (ah->ah_config.ah_sw_beacon_response_time
+				+ ah->ah_config.ah_dma_beacon_response_time)
+				- ah->ah_config.ah_additional_swba_backoff;
+			/*
+			 * XXX Ensure it isn't too low - nothing lower
+			 * XXX than 10 TU
+			 */
+			if (value < 10)
+				value = 10;
+			HALDEBUG(ah, HAL_DEBUG_TXQUEUE,
+			    "%s: defaulting to rdytime = %d uS\n",
+			    __func__, value);
+			OS_REG_WRITE(ah, AR_QRDYTIMECFG(q),
+			    SM(TU_TO_USEC(value), AR_Q_RDYTIMECFG_INT) |
+			    AR_Q_RDYTIMECFG_ENA);
 		}
+
 		dmisc |= SM(AR_D_MISC_ARB_LOCKOUT_CNTRL_GLOBAL,
 			    AR_D_MISC_ARB_LOCKOUT_CNTRL);
 		break;