wifi: mac80211: support initialising current S1G short beacon index

Introduce the sb_count variable which tracks the number of
beacon intervals until the next long beacon. To initialise this
value, we find the current short beacon index into this period
which represents the number of short beacons left to send before
the next long beacon. We use the same TSF value used to initialise
the DTIM count to ensure the short beacon count and DTIM count
are in sync as its common for the long beacon period and DTIM period
to be equivalent.

Signed-off-by: Lachlan Hodges <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

1 files changed, 28 insertions, 3 deletions

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 0d85a382746f..32f1bc5908c5 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -3913,10 +3913,8 @@ int ieee80211_parse_p2p_noa(const struct ieee80211_p2p_noa_attr *attr,
 }
 EXPORT_SYMBOL(ieee80211_parse_p2p_noa);
 
-void ieee80211_recalc_dtim(struct ieee80211_local *local,
-			   struct ieee80211_sub_if_data *sdata)
+void ieee80211_recalc_dtim(struct ieee80211_sub_if_data *sdata, u64 tsf)
 {
-	u64 tsf = drv_get_tsf(local, sdata);
 	u64 dtim_count = 0;
 	u32 beacon_int = sdata->vif.bss_conf.beacon_int * 1024;
 	u8 dtim_period = sdata->vif.bss_conf.dtim_period;
@@ -3954,6 +3952,33 @@ void ieee80211_recalc_dtim(struct ieee80211_local *local,
 	ps->dtim_count = dtim_count;
 }
 
+/*
+ * Given a long beacon period, calculate the current index into
+ * that period to determine the number of TSBTTs until the next TBTT.
+ * It is completely valid to have a short beacon period that differs
+ * from the dtim period (i.e a TBTT thats not a DTIM).
+ */
+void ieee80211_recalc_sb_count(struct ieee80211_sub_if_data *sdata, u64 tsf)
+{
+	u32 sb_idx;
+	struct ps_data *ps = &sdata->bss->ps;
+	u8 lb_period = sdata->vif.bss_conf.s1g_long_beacon_period;
+	u32 beacon_int = sdata->vif.bss_conf.beacon_int * 1024;
+
+	/* No mesh / IBSS support for short beaconing */
+	if (tsf == -1ULL || !lb_period ||
+	    (sdata->vif.type != NL80211_IFTYPE_AP &&
+	     sdata->vif.type != NL80211_IFTYPE_AP_VLAN))
+		return;
+
+	/* find the current TSBTT index in our lb_period */
+	do_div(tsf, beacon_int);
+	sb_idx = do_div(tsf, lb_period);
+
+	/* num TSBTTs until the next TBTT */
+	ps->sb_count = sb_idx ? lb_period - sb_idx : 0;
+}
+
 static u8 ieee80211_chanctx_radar_detect(struct ieee80211_local *local,
 					 struct ieee80211_chanctx *ctx)
 {