--- a/drivers/net/wireless/ath/ath5k/mac80211-ops.c
+++ b/drivers/net/wireless/ath/ath5k/mac80211-ops.c
@@ -86,13 +86,8 @@ ath5k_add_interface(struct ieee80211_hw 
 		goto end;
 	}
 
-	/* Don't allow other interfaces if one ad-hoc is configured.
-	 * TODO: Fix the problems with ad-hoc and multiple other interfaces.
-	 * We would need to operate the HW in ad-hoc mode to allow TSF updates
-	 * for the IBSS, but this breaks with additional AP or STA interfaces
-	 * at the moment. */
-	if (ah->num_adhoc_vifs ||
-	    (ah->nvifs && vif->type == NL80211_IFTYPE_ADHOC)) {
+	/* Don't allow more than one ad-hoc interface */
+	if (ah->num_adhoc_vifs && vif->type == NL80211_IFTYPE_ADHOC) {
 		ATH5K_ERR(ah, "Only one single ad-hoc interface is allowed.\n");
 		ret = -ELNRNG;
 		goto end;
--- a/drivers/net/wireless/ath/ath5k/base.c
+++ b/drivers/net/wireless/ath/ath5k/base.c
@@ -1937,7 +1937,7 @@ ath5k_beacon_send(struct ath5k_hw *ah)
 	}
 
 	if ((ah->opmode == NL80211_IFTYPE_AP && ah->num_ap_vifs +
-			ah->num_mesh_vifs > 1) ||
+			ah->num_adhoc_vifs + ah->num_mesh_vifs > 1) ||
 			ah->opmode == NL80211_IFTYPE_MESH_POINT) {
 		u64 tsf = ath5k_hw_get_tsf64(ah);
 		u32 tsftu = TSF_TO_TU(tsf);
@@ -2023,7 +2023,7 @@ ath5k_beacon_update_timers(struct ath5k_
 
 	intval = ah->bintval & AR5K_BEACON_PERIOD;
 	if (ah->opmode == NL80211_IFTYPE_AP && ah->num_ap_vifs
-		+ ah->num_mesh_vifs > 1) {
+		+ ah->num_adhoc_vifs + ah->num_mesh_vifs > 1) {
 		intval /= ATH_BCBUF;	/* staggered multi-bss beacons */
 		if (intval < 15)
 			ATH5K_WARN(ah, "intval %u is too low, min 15\n",
@@ -2490,6 +2490,7 @@ static const struct ieee80211_iface_limi
 				 BIT(NL80211_IFTYPE_MESH_POINT) |
 #endif
 				 BIT(NL80211_IFTYPE_AP) },
+	{ .max = 1,	.types = BIT(NL80211_IFTYPE_ADHOC) },
 };
 
 static const struct ieee80211_iface_combination if_comb = {
