int ieee80211_cs_headroom(struct ieee80211_local *local,
                          struct cfg80211_crypto_settings *crypto,
                          enum nl80211_iftype iftype);
+void ieee80211_recalc_dtim(struct ieee80211_local *local,
+                          struct ieee80211_sub_if_data *sdata);
 
 #ifdef CONFIG_MAC80211_NOINLINE
 #define debug_noinline noinline
 
                return -ENOMEM;
        }
 
+       ieee80211_recalc_dtim(local, sdata);
        ieee80211_bss_info_change_notify(sdata, changed);
 
        netif_carrier_on(sdata->dev);
 
        return ret;
 }
 EXPORT_SYMBOL(ieee80211_parse_p2p_noa);
+
+void ieee80211_recalc_dtim(struct ieee80211_local *local,
+                          struct ieee80211_sub_if_data *sdata)
+{
+       u64 tsf = drv_get_tsf(local, sdata);
+       u64 dtim_count = 0;
+       u16 beacon_int = sdata->vif.bss_conf.beacon_int * 1024;
+       u8 dtim_period = sdata->vif.bss_conf.dtim_period;
+       struct ps_data *ps;
+       u8 bcns_from_dtim;
+
+       if (tsf == -1ULL || !beacon_int || !dtim_period)
+               return;
+
+       if (sdata->vif.type == NL80211_IFTYPE_AP ||
+           sdata->vif.type == NL80211_IFTYPE_AP_VLAN) {
+               if (!sdata->bss)
+                       return;
+
+               ps = &sdata->bss->ps;
+       } else if (ieee80211_vif_is_mesh(&sdata->vif)) {
+               ps = &sdata->u.mesh.ps;
+       } else {
+               return;
+       }
+
+       /*
+        * actually finds last dtim_count, mac80211 will update in
+        * __beacon_add_tim().
+        * dtim_count = dtim_period - (tsf / bcn_int) % dtim_period
+        */
+       do_div(tsf, beacon_int);
+       bcns_from_dtim = do_div(tsf, dtim_period);
+       /* just had a DTIM */
+       if (!bcns_from_dtim)
+               dtim_count = 0;
+       else
+               dtim_count = dtim_period - bcns_from_dtim;
+
+       ps->dtim_count = dtim_count;
+}