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Bluetooth: controller: Handle peripheral CIS creation latency
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Instead of asserting, handle CIS creation latency for the peripheral by
finding next valid ISO event at which to start the CIG ticker.

Refactored calculations of the cig_offset to separate functions, to be
used also when calculating a new start offset.

Signed-off-by: Morten Priess <[email protected]>
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@mtpr-ot @carlescufi
mtpr-ot authored and carlescufi committed Jan 17, 2024
1 parent c4e48b6 commit 056d5a3
Showing 1 changed file with 87 additions and 39 deletions.
126 changes: 87 additions & 39 deletions subsys/bluetooth/controller/ll_sw/ull_conn_iso.c
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Original file line number Diff line number Diff line change
Expand Up @@ -775,28 +775,52 @@ void ull_conn_iso_ticker_cb(uint32_t ticks_at_expire, uint32_t ticks_drift,
ull_conn_iso_transmit_test_cig_interval(cig->lll.handle, ticks_at_expire);
}

static uint32_t cig_offset_calc(struct ll_conn_iso_group *cig, struct ll_conn_iso_stream *cis,
uint32_t cis_offset, uint32_t *ticks_at_expire, uint32_t remainder)
{
uint32_t acl_to_cig_ref_point;
uint32_t cis_offs_to_cig_ref;
uint32_t remainder_us;

remainder_us = remainder;
hal_ticker_remove_jitter(ticks_at_expire, &remainder_us);

cis_offs_to_cig_ref = cig->sync_delay - cis->sync_delay;

/* Establish the CIG reference point by adjusting ACL-to-CIS offset
* (cis->offset) by the difference between CIG- and CIS sync delays.
*/
acl_to_cig_ref_point = cis_offset - cis_offs_to_cig_ref;

/* Calculate the CIG reference point of first CIG event. This
* calculation is inaccurate. However it is the best estimate available
* until the first anchor point for the leading CIS is available.
*/
cig->cig_ref_point = isoal_get_wrapped_time_us(HAL_TICKER_TICKS_TO_US(*ticks_at_expire),
remainder_us +
EVENT_OVERHEAD_START_US +
acl_to_cig_ref_point);
/* Calculate initial ticker offset */
return remainder_us + acl_to_cig_ref_point;
}

void ull_conn_iso_start(struct ll_conn *conn, uint16_t cis_handle,
uint32_t ticks_at_expire, uint32_t remainder,
uint16_t instant_latency)
{
struct ll_conn_iso_group *cig;
struct ll_conn_iso_stream *cis;
uint32_t acl_to_cig_ref_point;
uint32_t cis_offs_to_cig_ref;
uint32_t ticks_remainder;
uint32_t ticks_periodic;
uint32_t ticker_status;
uint32_t remainder_us;
int32_t cig_offset_us;
uint32_t ticks_slot;
uint8_t ticker_id;

cis = ll_conn_iso_stream_get(cis_handle);
cig = cis->group;

cis_offs_to_cig_ref = cig->sync_delay - cis->sync_delay;

cis->lll.offset = cis_offs_to_cig_ref;
cis->lll.offset = cig->sync_delay - cis->sync_delay;
cis->lll.handle = cis_handle;

#if defined(CONFIG_BT_CTLR_LE_ENC)
Expand Down Expand Up @@ -868,25 +892,7 @@ void ull_conn_iso_start(struct ll_conn *conn, uint16_t cis_handle,

ticker_id = TICKER_ID_CONN_ISO_BASE + ll_conn_iso_group_handle_get(cig);

remainder_us = remainder;
hal_ticker_remove_jitter(&ticks_at_expire, &remainder_us);

/* Establish the CIG reference point by adjusting ACL-to-CIS offset
* (cis->offset) by the difference between CIG- and CIS sync delays.
*/
acl_to_cig_ref_point = cis->offset - cis_offs_to_cig_ref;

/* Calculate initial ticker offset */
cig_offset_us = remainder_us + acl_to_cig_ref_point;

/* Calculate the CIG reference point of first CIG event. This
* calculation is inaccurate. However it is the best estimate available
* until the first anchor point for the leading CIS is available.
*/
cig->cig_ref_point = isoal_get_wrapped_time_us(HAL_TICKER_TICKS_TO_US(ticks_at_expire),
remainder_us +
EVENT_OVERHEAD_START_US +
acl_to_cig_ref_point);
cig_offset_us = cig_offset_calc(cig, cis, cis->offset, &ticks_at_expire, remainder);

if (false) {

Expand All @@ -900,8 +906,6 @@ void ull_conn_iso_start(struct ll_conn *conn, uint16_t cis_handle,
*/
iso_interval_us_frac = EVENT_US_TO_US_FRAC(cig->iso_interval * ISO_INT_UNIT_US) -
cig->lll.window_widening_periodic_us_frac;
ticks_periodic = EVENT_US_FRAC_TO_TICKS(iso_interval_us_frac);
ticks_remainder = EVENT_US_FRAC_TO_REMAINDER(iso_interval_us_frac);

#if defined(CONFIG_BT_CTLR_PERIPHERAL_ISO_EARLY_CIG_START)
bool early_start = (cis->offset < EVENT_OVERHEAD_START_US);
Expand All @@ -914,22 +918,66 @@ void ull_conn_iso_start(struct ll_conn *conn, uint16_t cis_handle,
cig_offset_us += (conn->lll.interval * CONN_INT_UNIT_US);
cig->cig_ref_point = isoal_get_wrapped_time_us(cig->cig_ref_point,
conn->lll.interval * CONN_INT_UNIT_US);
} else {
LL_ASSERT(instant_latency == 1U);
} else if (instant_latency > 1U) {
/* We have passed the last possible event for a timely start. For
* early_start this means the latency is actually one less.
*/
instant_latency--;
}
} else {
/* FIXME: Handle latency due to skipped ACL events around the
* instant to start CIG
*/
LL_ASSERT(instant_latency == 0U);
}
#else /* CONFIG_BT_CTLR_PERIPHERAL_ISO_EARLY_CIG_START */
/* FIXME: Handle latency due to skipped ACL events around the
* instant to start CIG
*/
LL_ASSERT(instant_latency == 0U);
#endif /* CONFIG_BT_CTLR_PERIPHERAL_ISO_EARLY_CIG_START */

if (instant_latency > 0U) {
/* Try to start the CIG late by finding the CIG event relative to current
* ACL event, taking latency into consideration. Adjust ticker periodicity
* with increased window widening.
*/
uint32_t lost_cig_events;
uint32_t iso_interval_us;
uint32_t acl_latency_us;
uint32_t lost_payloads;
uint32_t cis_offset;

acl_latency_us = instant_latency * conn->lll.interval * CONN_INT_UNIT_US;
iso_interval_us = cig->iso_interval * ISO_INT_UNIT_US;

if (acl_latency_us > iso_interval_us) {
/* Latency is greater than the ISO interval - find the offset from
* this ACL event to the next active ISO event, and adjust the event
* counter accordingly.
*/
lost_cig_events = DIV_ROUND_UP(acl_latency_us - cis->offset,
iso_interval_us);
cis_offset = cis->offset + (lost_cig_events * iso_interval_us) -
acl_latency_us;
} else {
/* Latency is less than- or equal to one ISO interval - start at
* next ISO event.
*/
lost_cig_events = 1U;
cis_offset = cis->offset + iso_interval_us - acl_latency_us;
}

cis->lll.event_count += lost_cig_events;

lost_payloads = (lost_cig_events - (cis->lll.rx.ft - 1)) * cis->lll.rx.bn;
cis->lll.rx.payload_count += lost_payloads;

lost_payloads = (lost_cig_events - (cis->lll.tx.ft - 1)) * cis->lll.tx.bn;
cis->lll.tx.payload_count += lost_payloads;

/* Adjust for extra window widening */
iso_interval_us_frac = EVENT_US_TO_US_FRAC(cig->iso_interval *
ISO_INT_UNIT_US);
iso_interval_us_frac -= cig->lll.window_widening_periodic_us_frac *
instant_latency;
/* Calculate new offset */
cig_offset_us = cig_offset_calc(cig, cis, cis_offset, &ticks_at_expire,
remainder);
}

ticks_periodic = EVENT_US_FRAC_TO_TICKS(iso_interval_us_frac);
ticks_remainder = EVENT_US_FRAC_TO_REMAINDER(iso_interval_us_frac);
#endif /* CONFIG_BT_CTLR_PERIPHERAL_ISO */

} else if (IS_CENTRAL(cig)) {
Expand Down

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