Bluetooth: Controller: Extended Advertising back-to-back chaining

Add LLL implementation to chain Extended Advertising PDUs
back-to-back.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>

subsys/bluetooth/controller/Kconfig.ll_sw_split

@@ -176,6 +176,22 @@ config BT_CTLR_ADV_PDU_LINK
 	  is required to enable advertising data trains (i.e. transmission of
 	  AUX_CHAIN_IND).
 
+config BT_CTLR_ADV_PDU_BACK2BACK
+	bool "Enable back-to-back transmission of extended advertising trains"
+	depends on BT_CTLR_ADV_EXT && BT_BROADCASTER
+	select BT_CTLR_ADV_PDU_LINK
+	help
+	  Enables transmission of AUX_CHAIN_IND in extended advertising train by
+	  sending each AUX_CHAIN_IND one after another back-to-back.
+
+config BT_CTLR_ADV_PDU_BACK2BACK_AFS
+	int "AUX Frame Space for back-to-back transmission of extended advertising trains"
+	depends on BT_CTLR_ADV_PDU_BACK2BACK
+	range 300 1000
+	help
+	  Specific AUX Frame Space to be used for back-to-back transmission of
+	  extended advertising trains. Time specified in microseconds.
+
 config BT_CTLR_ADV_SYNC_PDU_BACK2BACK
 	bool "Enable back-to-back transmission of periodic advertising trains"
 	depends on BT_CTLR_ADV_PERIODIC

subsys/bluetooth/controller/ll_sw/lll_adv.h

@@ -67,6 +67,9 @@ struct lll_adv_aux {
 	uint32_t ticks_offset;
 
 	struct lll_adv_pdu data;
+#if defined(CONFIG_BT_CTLR_ADV_PDU_LINK)
+	struct pdu_adv     *last_pdu;
+#endif /* CONFIG_BT_CTLR_ADV_PDU_LINK */
 
 #if defined(CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL)
 	int8_t tx_pwr_lvl;

subsys/bluetooth/controller/ll_sw/nordic/lll/lll_adv_aux.c

@@ -46,7 +46,10 @@
 static int init_reset(void);
 static int prepare_cb(struct lll_prepare_param *p);
 static void isr_done(void *param);
-static void isr_tx(void *param);
+#if defined(CONFIG_BT_CTLR_ADV_PDU_BACK2BACK)
+static void isr_tx_chain(void *param);
+#endif /* CONFIG_BT_CTLR_ADV_PDU_BACK2BACK */
+static void isr_tx_rx(void *param);
 static void isr_rx(void *param);
 static inline int isr_rx_pdu(struct lll_adv_aux *lll_aux,
 			     uint8_t devmatch_ok, uint8_t devmatch_id,
@@ -224,9 +227,21 @@ static int prepare_cb(struct lll_prepare_param *p)
 		ARG_UNUSED(upd);
 #endif /* !CONFIG_BT_CTLR_PRIVACY */
 
-		radio_isr_set(isr_tx, lll);
+		radio_isr_set(isr_tx_rx, lll);
 		radio_tmr_tifs_set(EVENT_IFS_US);
 		radio_switch_complete_and_rx(phy_s);
+
+#if defined(CONFIG_BT_CTLR_ADV_PDU_BACK2BACK)
+	} else if (sec_pdu->adv_ext_ind.ext_hdr_len &&
+		   sec_pdu->adv_ext_ind.ext_hdr.aux_ptr) {
+		lll->last_pdu = sec_pdu;
+
+		radio_isr_set(isr_tx_chain, lll);
+		radio_tmr_tifs_set(EVENT_B2B_MAFS_US);
+		radio_switch_complete_and_b2b_tx(phy_s, lll_adv->phy_flags,
+						 phy_s, lll_adv->phy_flags);
+#endif /* CONFIG_BT_CTLR_ADV_PDU_BACK2BACK */
+
 	} else {
 		radio_isr_set(isr_done, lll);
 		radio_switch_complete_and_disable();
@@ -290,7 +305,77 @@ static void isr_done(void *param)
 	lll_isr_cleanup(param);
 }
 
-static void isr_tx(void *param)
+#if defined(CONFIG_BT_CTLR_ADV_PDU_BACK2BACK)
+static void isr_tx_chain(void *param)
+{
+	struct lll_adv_aux *lll_aux;
+	struct lll_adv *lll;
+	struct pdu_adv *pdu;
+
+	if (IS_ENABLED(CONFIG_BT_CTLR_PROFILE_ISR)) {
+		lll_prof_latency_capture();
+	}
+
+	/* Clear radio tx status and events */
+	lll_isr_tx_status_reset();
+
+	lll_aux = param;
+	lll = lll_aux->adv;
+
+	/* FIXME: Use implementation defined channel index */
+	lll_chan_set(0);
+
+	pdu = lll_adv_pdu_linked_next_get(lll_aux->last_pdu);
+	LL_ASSERT(pdu);
+	lll_aux->last_pdu = pdu;
+
+	/* setup tIFS switching */
+	if (pdu->adv_ext_ind.ext_hdr_len && pdu->adv_ext_ind.ext_hdr.aux_ptr) {
+		radio_isr_set(isr_tx_chain, lll_aux);
+		radio_tmr_tifs_set(EVENT_B2B_MAFS_US);
+		radio_switch_complete_and_b2b_tx(lll->phy_s, lll->phy_flags,
+						 lll->phy_s, lll->phy_flags);
+	} else {
+		radio_isr_set(isr_done, lll_aux);
+		radio_switch_complete_and_disable();
+	}
+
+	radio_pkt_tx_set(pdu);
+
+	/* assert if radio packet ptr is not set and radio started rx */
+	LL_ASSERT(!radio_is_ready());
+
+	if (IS_ENABLED(CONFIG_BT_CTLR_PROFILE_ISR)) {
+		lll_prof_cputime_capture();
+	}
+
+	/* capture end of AUX_SYNC_IND/AUX_CHAIN_IND PDU, used for calculating
+	 * next PDU timestamp.
+	 */
+	radio_tmr_end_capture();
+
+#if defined(CONFIG_BT_CTLR_GPIO_LNA_PIN)
+	if (IS_ENABLED(CONFIG_BT_CTLR_PROFILE_ISR)) {
+		/* PA/LNA enable is overwriting packet end used in ISR
+		 * profiling, hence back it up for later use.
+		 */
+		lll_prof_radio_end_backup();
+	}
+
+	radio_gpio_lna_setup();
+	radio_gpio_pa_lna_enable(radio_tmr_tifs_base_get() + EVENT_B2B_MAFS_US -
+				 4 - radio_tx_chain_delay_get(lll->phy_s,
+							      lll->phy_flags) -
+				 CONFIG_BT_CTLR_GPIO_LNA_OFFSET);
+#endif /* CONFIG_BT_CTLR_GPIO_LNA_PIN */
+
+	if (IS_ENABLED(CONFIG_BT_CTLR_PROFILE_ISR)) {
+		lll_prof_send();
+	}
+}
+#endif /* CONFIG_BT_CTLR_ADV_PDU_BACK2BACK */
+
+static void isr_tx_rx(void *param)
 {
 	struct node_rx_pdu *node_rx_prof;
 	struct node_rx_pdu *node_rx;

subsys/bluetooth/controller/ll_sw/pdu.h

@@ -93,6 +93,8 @@
 #define EVENT_MAFS_US           300
 /* Standard allows 2 us timing uncertainty inside the event */
 #define EVENT_MAFS_MAX_US       (EVENT_MAFS_US + EVENT_CLOCK_JITTER_US)
+/* Controller defined back to back transmit MAFS */
+#define EVENT_B2B_MAFS_US       (CONFIG_BT_CTLR_ADV_PDU_BACK2BACK_AFS)
 /* Minimum Subevent Space timings */
 #define EVENT_MSS_US            150
 /* Standard allows 2 us timing uncertainty inside the event */

tests/bluetooth/init/prj_ctlr_dbg.conf

@@ -16,6 +16,7 @@ CONFIG_BT_CTLR_ADVANCED_FEATURES=y
 CONFIG_BT_CTLR_PHY_2M=y
 CONFIG_BT_CTLR_PHY_2M_NRF=y
 CONFIG_BT_CTLR_PHY_CODED=y
+CONFIG_BT_CTLR_ADV_PDU_BACK2BACK=y
 CONFIG_BT_CTLR_LLL_PRIO=0
 CONFIG_BT_CTLR_ULL_HIGH_PRIO=1
 CONFIG_BT_CTLR_XTAL_ADVANCED=n