nimble/ll: Simplify SyncInfo calculation

This simplifies calculation of SyncInfo used in AUX_ADV_IND and
LL_PERIODIC_SYNC_IND to use the same code in both cases.

In case of LL Control PDU we do not "rewind" connsm to find proper
connection event but instead "advance" padv event the same way as it was
done for AUX_ADV_IND PDU.

Author: andrzej-kaczmarek

nimble/controller/include/controller/ble_ll_conn.h

@@ -448,10 +448,15 @@ void ble_ll_conn_chan_map_update(void);
 /* required for unit testing */
 uint8_t ble_ll_conn_calc_dci(struct ble_ll_conn_sm *conn, uint16_t latency);
 
-/* used to get anchor point for connection event specified */
-void ble_ll_conn_get_anchor(struct ble_ll_conn_sm *connsm, uint16_t conn_event,
+/* get current event counter and anchor point */
+void ble_ll_conn_anchor_get(struct ble_ll_conn_sm *connsm, uint16_t *event_cntr,
                             uint32_t *anchor, uint8_t *anchor_usecs);
 
+/* get anchor point for specified connection event */
+void ble_ll_conn_anchor_event_cntr_get(struct ble_ll_conn_sm *connsm,
+                                       uint16_t event_cntr, uint32_t *anchor,
+                                       uint8_t *anchor_usecs);
+
 #if MYNEWT_VAL(BLE_LL_ROLE_CENTRAL)
 int ble_ll_conn_move_anchor(struct ble_ll_conn_sm *connsm, uint16_t offset);
 #endif

nimble/controller/src/ble_ll_adv.c

@@ -643,83 +643,73 @@ ble_ll_adv_pdu_make(uint8_t *dptr, void *pducb_arg, uint8_t *hdr_byte)
 #if MYNEWT_VAL(BLE_LL_CFG_FEAT_LL_PERIODIC_ADV)
 static void
 ble_ll_adv_put_syncinfo(struct ble_ll_adv_sm *advsm,
-                        struct ble_ll_conn_sm *connsm, uint8_t *conn_event_cnt,
+                        struct ble_ll_conn_sm *connsm, uint8_t *conn_event_cntr,
                         uint8_t *dptr)
 {
-#if MYNEWT_VAL(BLE_LL_CFG_FEAT_LL_PERIODIC_ADV_SYNC_TRANSFER)
-    uint16_t conn_cnt;
-#endif
-    unsigned int event_cnt_off = 0;
-    uint32_t offset = 0;
-    uint32_t itvl_us;
+    uint32_t offset_us;
+    uint32_t offset;
     uint32_t anchor_ticks;
     uint8_t anchor_rem_us;
-    uint8_t units;
+#if MYNEWT_VAL(BLE_LL_CFG_FEAT_LL_PERIODIC_ADV_SYNC_TRANSFER)
+    uint16_t anchor_event_cntr;
+#endif
+    uint32_t event_start;
+    uint8_t event_start_us;
+    uint32_t event_cntr_offset = 0;
 
     if (connsm) {
 #if MYNEWT_VAL(BLE_LL_CFG_FEAT_LL_PERIODIC_ADV_SYNC_TRANSFER)
-        anchor_ticks = connsm->anchor_point;
-        anchor_rem_us = connsm->anchor_point_usecs;
-        conn_cnt = connsm->event_cntr;
-
-        /* get anchor for conn event that is before periodic_adv_event_start_time */
-        while (LL_TMR_GT(anchor_ticks, advsm->padv_event_start)) {
-            ble_ll_conn_get_anchor(connsm, --conn_cnt, &anchor_ticks, &anchor_rem_us);
-        }
-
-        offset = ble_ll_tmr_t2u(advsm->padv_event_start - anchor_ticks);
-        offset -= anchor_rem_us;
-        offset += advsm->padv_event_start_rem_us;
+        ble_ll_conn_anchor_get(connsm, &anchor_event_cntr,
+                               &anchor_ticks, &anchor_rem_us);
 
         /* connEventCount */
-        put_le16(conn_event_cnt, conn_cnt);
+        put_le16(conn_event_cntr, anchor_event_cntr);
+#else
+        BLE_LL_ASSERT(0);
 #endif
     } else {
-        anchor_ticks = advsm->padv_event_start;
-        anchor_rem_us = advsm->padv_event_start_rem_us;
-        itvl_us = advsm->periodic_adv_itvl * BLE_LL_ADV_PERIODIC_ITVL;
-
-        /* Get periodic event that is past AUX start time (so that we always
-         * provide valid offset if it is not too far in future). This can
-         * happen if advertising event is interleaved with periodic advertising
-         * event (when chaining).
-         */
-        while (LL_TMR_GEQ(AUX_CURRENT(advsm)->start_time, anchor_ticks)) {
-            ble_ll_tmr_add(&anchor_ticks, &anchor_rem_us, itvl_us);
-            event_cnt_off++;
-        }
+        anchor_ticks = AUX_CURRENT(advsm)->start_time;
+        anchor_rem_us = 0;
+    }
 
-        /* We always schedule aux with 0 rem_us so no need to include it here */
-        offset = ble_ll_tmr_t2u(anchor_ticks - AUX_CURRENT(advsm)->start_time);
-        offset += anchor_rem_us;
+    event_start = advsm->padv_event_start;
+    event_start_us = advsm->padv_event_start_rem_us;
+
+    /* Find padv event that is past anchor item */
+    while (LL_TMR_LEQ(event_start, anchor_ticks)) {
+        ble_ll_tmr_add(&event_start, &event_start_us, advsm->padv_itvl_us);
+        event_cntr_offset++;
     }
 
+    offset_us = ble_ll_tmr_t2u(event_start - anchor_ticks);
+    offset_us += event_start_us;
+    offset_us -= anchor_rem_us;
+
     /* Sync Packet Offset (13 bits), Offset Units (1 bit), Offset Adjust (1 bit),
      * RFU (1 bit)
      */
-    if (offset > 245700) {
-        units = 0x20;
-        offset = offset / 300;
-
+    if (offset_us > 245700) {
+        offset = offset_us / 300;
         if (offset >= 0x2000) {
             if (connsm) {
                 offset -= 0x2000;
-                units |= 0x40;
+                /* Offset Units = 1, Offset Adjust = 1 */
+                offset |= 0x6000;
             } else {
-                /* not able to represent time in offset */
                 offset = 0;
-                units = 0x00;
-                event_cnt_off = 0;
+                event_cntr_offset = 0;
             }
+        } else {
+            /* Offset Units = 1, Offset Adjust = 0 */
+            offset |= 0x2000;
         }
 
     } else {
-        units = 0x00;
-        offset = offset / 30;
+        offset = offset_us / 30;
+        /* Offset Units = 0, Offset Adjust = 0 */
     }
 
-    dptr[0] = (offset & 0x000000ff);
-    dptr[1] = ((offset >> 8) & 0x0000001f) | units;
+    put_le16(&dptr[0], offset);
 
     /* Interval (2 bytes) */
     put_le16(&dptr[2], advsm->periodic_adv_itvl);
@@ -743,7 +733,7 @@ ble_ll_adv_put_syncinfo(struct ble_ll_adv_sm *advsm,
     dptr[15] = (uint8_t)(advsm->periodic_crcinit >> 16);
 
     /* Event Counter (2 bytes) */
-    put_le16(&dptr[16], advsm->periodic_event_cntr + event_cnt_off);
+    put_le16(&dptr[16], advsm->periodic_event_cntr + event_cntr_offset);
 }
 #endif
 

nimble/controller/src/ble_ll_conn.c

@@ -2275,10 +2275,20 @@ ble_ll_conn_end(struct ble_ll_conn_sm *connsm, uint8_t ble_err)
                        connsm->event_cntr, (uint32_t)ble_err);
 }
 
-#if MYNEWT_VAL(BLE_LL_CFG_FEAT_LL_PERIODIC_ADV_SYNC_TRANSFER)
 void
-ble_ll_conn_get_anchor(struct ble_ll_conn_sm *connsm, uint16_t conn_event,
+ble_ll_conn_anchor_get(struct ble_ll_conn_sm *connsm, uint16_t *event_cntr,
                        uint32_t *anchor, uint8_t *anchor_usecs)
+{
+    *event_cntr = connsm->event_cntr;
+    *anchor = connsm->anchor_point;
+    *anchor_usecs = connsm->anchor_point_usecs;
+}
+
+#if MYNEWT_VAL(BLE_LL_CFG_FEAT_LL_PERIODIC_ADV_SYNC_TRANSFER)
+void
+ble_ll_conn_anchor_event_cntr_get(struct ble_ll_conn_sm *connsm,
+                                  uint16_t event_cntr, uint32_t *anchor,
+                                  uint8_t *anchor_usecs)
 {
     uint32_t itvl;
 
@@ -2287,11 +2297,11 @@ ble_ll_conn_get_anchor(struct ble_ll_conn_sm *connsm, uint16_t conn_event,
     *anchor = connsm->anchor_point;
     *anchor_usecs = connsm->anchor_point_usecs;
 
-    if ((int16_t)(conn_event - connsm->event_cntr) < 0) {
-        itvl *= connsm->event_cntr - conn_event;
+    if ((int16_t)(event_cntr - connsm->event_cntr) < 0) {
+        itvl *= connsm->event_cntr - event_cntr;
         ble_ll_tmr_sub(anchor, anchor_usecs, itvl);
     } else {
-        itvl *= conn_event - connsm->event_cntr;
+        itvl *= event_cntr - connsm->event_cntr;
         ble_ll_tmr_add(anchor, anchor_usecs, itvl);
     }
 }

nimble/controller/src/ble_ll_sync.c

@@ -2094,17 +2094,17 @@ ble_ll_sync_periodic_ind(struct ble_ll_conn_sm *connsm,
 
     /* get anchor for specified conn event */
     conn_event_count = get_le16(sync_ind + 20);
-    ble_ll_conn_get_anchor(connsm, conn_event_count, &sm->anchor_point,
-                           &sm->anchor_point_usecs);
+    ble_ll_conn_anchor_event_cntr_get(connsm, conn_event_count, &sm->anchor_point,
+                                      &sm->anchor_point_usecs);
 
     /* Set last anchor point */
     sm->last_anchor_point = sm->anchor_point - (last_pa_diff * sm->itvl_ticks);
 
     /* calculate extra window widening */
     sync_conn_event_count = get_le16(sync_ind + 32);
     sca = sync_ind[24] >> 5;
-    ble_ll_conn_get_anchor(connsm, sync_conn_event_count, &sync_anchor,
-                           &sync_anchor_usecs);
+    ble_ll_conn_anchor_event_cntr_get(connsm, sync_conn_event_count, &sync_anchor,
+                                      &sync_anchor_usecs);
     ww_adjust = ble_ll_utils_calc_window_widening(connsm->anchor_point,
                                                   sync_anchor, sca);
 
@@ -2155,7 +2155,7 @@ ble_ll_sync_put_syncinfo(struct ble_ll_sync_sm *syncsm,
 
     /* get anchor for conn event that is before periodic_adv_event_start_time */
     while (LL_TMR_GT(anchor, syncsm->anchor_point)) {
-        ble_ll_conn_get_anchor(connsm, --conn_cnt, &anchor, &anchor_usecs);
+        ble_ll_conn_anchor_event_cntr_get(connsm, --conn_cnt, &anchor, &anchor_usecs);
     }
 
     offset = ble_ll_tmr_t2u(syncsm->anchor_point - anchor);