nimble/ll: Add ISO sync feedback over HCI

This adds optional synchronization feedback over HCI for ISO. See syscfg
descrption for details.

nimble/controller/src/ble_ll_iso_big.c

@@ -144,6 +144,10 @@ struct ble_ll_iso_big {
 
  struct ble_ll_iso_bis_q bis_q;
 
+#if MYNEWT_VAL(BLE_LL_ISO_HCI_FEEDBACK_INTERVAL_MS)
+ uint32_t last_feedback;
+#endif
+
  uint8_t cstf : 1;
  uint8_t cssn : 4;
  uint8_t control_active : 3;
@@ -398,8 +402,16 @@ ble_ll_iso_big_event_done(struct ble_ll_iso_big *big)
 {
  struct ble_ll_iso_bis *bis;
  struct ble_hci_ev *hci_ev;
+#if MYNEWT_VAL(BLE_LL_ISO_HCI_FEEDBACK_INTERVAL_MS)
+ struct ble_hci_ev *fb_hci_ev = NULL;
+ struct ble_hci_ev_vs *fb_hci_ev_vs;
+ struct ble_hci_vs_subev_iso_hci_feedback *fb_hci_subev = NULL;
+ uint16_t exp;
+ uint32_t now;
+#endif
  struct ble_hci_ev_num_comp_pkts *hci_ev_ncp;
  int num_completed_pkt;
+ int idx;
  int rc;
 
  ble_ll_rfmgmt_release();
@@ -417,18 +429,49 @@ ble_ll_iso_big_event_done(struct ble_ll_iso_big *big)
  hci_ev_ncp->count = 0;
  }
 
+#if MYNEWT_VAL(BLE_LL_ISO_HCI_FEEDBACK_INTERVAL_MS)
+ now = os_time_get();
+ if (OS_TIME_TICK_GEQ(now, big->last_feedback +
+ os_time_ms_to_ticks32(MYNEWT_VAL(BLE_LL_ISO_HCI_FEEDBACK_INTERVAL_MS)))) {
+ fb_hci_ev = ble_transport_alloc_evt(1);
+ if (fb_hci_ev) {
+ fb_hci_ev->opcode = BLE_HCI_EVCODE_VS;
+ fb_hci_ev->length = sizeof(*fb_hci_ev_vs) + sizeof(*fb_hci_subev);
+ fb_hci_ev_vs = (void *)fb_hci_ev->data;
+ fb_hci_ev_vs->id = BLE_HCI_VS_SUBEV_ISO_HCI_FEEDBACK;
+ fb_hci_subev = (void *)fb_hci_ev_vs->data;
+ fb_hci_subev->big_handle = big->handle;
+ fb_hci_subev->count = 0;
+ }
+ }
+#endif
+
  STAILQ_FOREACH(bis, &big->bis_q, bis_q_next) {
  num_completed_pkt = ble_ll_isoal_mux_event_done(&bis->mux);
  if (hci_ev && num_completed_pkt) {
- hci_ev_ncp->completed[hci_ev_ncp->count].handle =
-   htole16(bis->conn_handle);
- hci_ev_ncp->completed[hci_ev_ncp->count].packets =
- htole16(num_completed_pkt + bis->num_completed_pkt);
+ idx = hci_ev_ncp->count++;
+ hci_ev_ncp->completed[idx].handle = htole16(bis->conn_handle);
+ hci_ev_ncp->completed[idx].packets = htole16(num_completed_pkt +
+   bis->num_completed_pkt);
  bis->num_completed_pkt = 0;
- hci_ev_ncp->count++;
  } else {
  bis->num_completed_pkt += num_completed_pkt;
  }
+
+#if MYNEWT_VAL(BLE_LL_ISO_HCI_FEEDBACK_INTERVAL_MS)
+ if (fb_hci_ev) {
+ /* Expected SDUs in queue after an event -> host should send
+ * sdu_per_interval SDUs until next event so there are sdu_per_event
+ * SDUs queued at next event. Feedback value is the difference between
+ * expected and actual SDUs count.
+ */
+ exp = bis->mux.sdu_per_event - bis->mux.sdu_per_interval;
+ idx = fb_hci_subev->count++;
+ fb_hci_subev->feedback[idx].handle = htole16(bis->conn_handle);
+ fb_hci_subev->feedback[idx].sdu_per_interval = bis->mux.sdu_per_interval;
+ fb_hci_subev->feedback[idx].diff = (int8_t)(bis->mux.sdu_q_len - exp);
+ }
+#endif
  }
 
  if (hci_ev) {
@@ -441,6 +484,15 @@ ble_ll_iso_big_event_done(struct ble_ll_iso_big *big)
  }
  }
 
+#if MYNEWT_VAL(BLE_LL_ISO_HCI_FEEDBACK_INTERVAL_MS)
+ if (fb_hci_ev) {
+ fb_hci_ev->length = sizeof(*fb_hci_ev_vs) + sizeof(*fb_hci_subev) +
+ fb_hci_subev->count * sizeof(fb_hci_subev->feedback[0]);
+ ble_transport_to_hs_evt(fb_hci_ev);
+ big->last_feedback = now;
+ }
+#endif
+
  big->sch.start_time = big->event_start;
  big->sch.remainder = big->event_start_us;
 
@@ -760,6 +812,8 @@ ble_ll_iso_big_event_sched_cb(struct ble_ll_sched_item *sch)
  ble_phy_mode_set(phy_mode, phy_mode);
 #endif
 
+ ble_ll_tx_power_set(g_ble_ll_tx_power);
+
  BLE_LL_ASSERT(!big->framed);
 
  /* XXX calculate this in advance at the end of previous event? */

nimble/controller/syscfg.yml

@@ -488,6 +488,23 @@ syscfg.defs:
  - BLE_LL_ISO if 1
  value: 0
  state: experimental
+ BLE_LL_ISO_HCI_FEEDBACK_INTERVAL_MS:
+ description: >
+ Enables ISO synchronization feedback using vendor-specific HCI event.
+ The event is sent at configured interval after completed ISO event
+ and contains BIG handle, number of expected SDUs per ISO interval
+ and difference between expected vs actual number of SDUs queued in
+ controller.
+ The expected number of SDUs queued after each event is number of
+ SDUs required for each ISO event (i.e. including pre-transmissions)
+ minus number of SDUs expected per each ISO interval.
+ The host can use feedback to e.g. adjust for jitter between audio
+ clock and LL clock.
+ Set to 0 to disable.
+ value: 0
+ experimental: 1
+ restrictions:
+ - BLE_LL_HCI_VS || BLE_LL_ISO_HCI_FEEDBACK_INTERVAL_MS == 0
 
  BLE_LL_SYSINIT_STAGE:
  description: >

nimble/include/nimble/hci_common.h

@@ -1611,6 +1611,18 @@ struct ble_hci_ev_vs_css_slot_changed {
  uint16_t slot_idx;
 };
 
+#define BLE_HCI_VS_SUBEV_ISO_HCI_FEEDBACK (0x03)
+struct feedback_pkt {
+ uint16_t handle;
+ uint8_t sdu_per_interval;
+ int8_t diff;
+} __attribute__((packed));
+struct ble_hci_vs_subev_iso_hci_feedback {
+ uint8_t big_handle;
+ uint8_t count;
+ struct feedback_pkt feedback[0];
+} __attribute__((packed));
+
 #define BLE_HCI_VS_SUBEV_ID_LLCP_TRACE (0x17)
 
 /* LE sub-event codes */