Bluetooth: Controller: Tune aux offset calculation overhead assertion

Tune the aux offset calculation overhead assertion to use
EVENT_OVERHEAD_START_US; this is the correct maximum
overhead causing ISR latency for start of a radio event that
occurs thereafter.

Signed-off-by: Vinayak Kariappa Chettimada <[email protected]>

Author: cvinayak

subsys/bluetooth/controller/ll_sw/nordic/lll/lll_vendor.h

@@ -16,26 +16,26 @@
 /* Measurement based on drifting roles that can overlap leading to collision
  * resolutions that consume CPU time between radio events.
  * Value include max end, start and scheduling CPU usage times.
- * Measurements based on central_gatt_write and peripheral_gatt_write sample on
- * nRF52833 SoC.
+ * Measurements based on central_gatt_write, peripheral_gatt_write, observer and
+ * broadcaster_multiple samples on nRF52833 SoC.
  */
 #if defined(CONFIG_BT_CTLR_ADV_EXT)
 #if defined(CONFIG_BT_OBSERVER)
 #if defined(CONFIG_BT_CTLR_PHY_CODED)
-/* Active connection in peripheral role with extended scanning on 1M and Coded
- * PHY, scheduling and receiving auxiliary PDUs.
+/* Simultaneous 3 extended advertising sets with extended scanning on 1M and Coded PHY, scheduling
+ * and receiving auxiliary PDUs.
  */
 #define EVENT_OVERHEAD_START_US       733 /* 24 RTC ticks */
 #else /* !CONFIG_BT_CTLR_PHY_CODED */
-/* Active connection in peripheral role with extended scanning on 1M only,
- * scheduling and receiving auxiliary PDUs.
+/* Active connection in peripheral role with extended scanning on 1M only, scheduling and receiving
+ * auxiliary PDUs.
  */
 #define EVENT_OVERHEAD_START_US       428 /* 14 RTC ticks */
 #endif /* !CONFIG_BT_CTLR_PHY_CODED */
 #else /* !CONFIG_BT_OBSERVER */
-/* Active connection in peripheral role with legacy scanning on 1M.
+/* Simultaneous 3 extended advertising sets calculating aux offsets.
  */
-#define EVENT_OVERHEAD_START_US       275 /* 9 RTC ticks */
+#define EVENT_OVERHEAD_START_US       367 /* 12 RTC ticks */
 #endif /* !CONFIG_BT_OBSERVER */
 #else /* !CONFIG_BT_CTLR_ADV_EXT */
 /* Active connection in peripheral role with additional advertising state.

subsys/bluetooth/controller/ll_sw/ull_adv_aux.c

@@ -3179,21 +3179,26 @@ void ull_adv_aux_lll_auxptr_fill(struct pdu_adv *pdu, struct lll_adv *adv)
 }
 
 #else /* !CONFIG_BT_TICKER_EXT_EXPIRE_INFO */
+
+/* Maximum retries when ticks_current can change, example, when 3 extended advertising sets
+ * configured, and 1 advertising set is calculating the aux_offset, 2 other advertising sets and 2
+ * scanning instances can expire changing the ticks_current value while we are querying for
+ * aux_offset value.
+ */
+#define MAX_RETRY_TICKS_CURRENT_CHANGE ((CONFIG_BT_CTLR_ADV_AUX_SET) - 1U +  2U)
+
 static void mfy_aux_offset_get(void *param)
 {
 	struct pdu_adv_aux_ptr *aux_ptr;
 	struct lll_adv_aux *lll_aux;
 	struct ll_adv_aux_set *aux;
 	uint32_t ticks_to_expire;
-	uint32_t ticks_to_start;
 	uint8_t data_chan_count;
 	uint8_t *data_chan_map;
 	uint32_t ticks_current;
-	uint32_t ticks_elapsed;
 	struct ll_adv_set *adv;
 	uint16_t chan_counter;
 	struct pdu_adv *pdu;
-	uint32_t ticks_now;
 	uint32_t remainder = 0U;
 	uint32_t offset_us;
 	uint8_t ticker_id;
@@ -3209,7 +3214,7 @@ static void mfy_aux_offset_get(void *param)
 	id = TICKER_NULL;
 	ticks_to_expire = 0U;
 	ticks_current = adv->ticks_at_expire;
-	retry = 1U; /* Assert on first ticks_current change */
+	retry = MAX_RETRY_TICKS_CURRENT_CHANGE;
 	do {
 		uint32_t volatile ret_cb;
 		uint32_t ticks_previous;
@@ -3323,11 +3328,16 @@ static void mfy_aux_offset_get(void *param)
 					   data_chan_map, data_chan_count);
 
 	/* Assertion check for delayed aux_offset calculations */
+	uint32_t ticks_to_start;
+	uint32_t ticks_elapsed;
+	uint32_t ticks_now;
+
 	ticks_now = ticker_ticks_now_get();
-	ticks_elapsed = ticker_ticks_diff_get(ticks_now, ticks_current);
-	ticks_to_start = HAL_TICKER_US_TO_TICKS(EVENT_OVERHEAD_XTAL_US) -
-			 HAL_TICKER_US_TO_TICKS(EVENT_OVERHEAD_PREEMPT_MIN_US);
-	LL_ASSERT_ERR(ticks_elapsed < ticks_to_start);
+	ticks_elapsed = ticker_ticks_diff_get(ticks_now, adv->ticks_at_expire);
+	ticks_to_start = HAL_TICKER_US_TO_TICKS(EVENT_OVERHEAD_START_US);
+	LL_ASSERT_MSG((ticks_elapsed <= ticks_to_start), "%s: overhead = %u (%u) us.",
+		      __func__, HAL_TICKER_TICKS_TO_US(ticks_elapsed),
+		      HAL_TICKER_TICKS_TO_US(ticks_to_start));
 }
 
 static void ticker_op_cb(uint32_t status, void *param)