Bluetooth: controller: split: Support Zero Latency IRQs

Add support for Zero Latency IRQs, which avoids any Zephyr
OS or application influenced ISR latencies on the
controller's ISRs.

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

Author: cvinayak

subsys/bluetooth/controller/Kconfig

@@ -516,7 +516,7 @@ config BT_CTLR_PHY_CODED
 
 config BT_CTLR_ZLI
 	bool "Use Zero Latency IRQs"
-	depends on ZERO_LATENCY_IRQS
+	depends on ZERO_LATENCY_IRQS && BT_LL_SW_SPLIT
 	help
 	  Enable support for use of Zero Latency IRQ feature. Note, applications
 	  shall not use Zero Latency IRQ themselves when this option is selected,

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

@@ -33,6 +33,12 @@
 #include "common/log.h"
 #include "hal/debug.h"
 
+#if defined(CONFIG_BT_CTLR_ZLI)
+#define IRQ_CONNECT_FLAGS IRQ_ZERO_LATENCY
+#else
+#define IRQ_CONNECT_FLAGS 0
+#endif
+
 static struct {
 	struct {
 		void              *param;
@@ -158,11 +164,11 @@ int lll_init(void)
 
 	/* Connect ISRs */
 	IRQ_DIRECT_CONNECT(RADIO_IRQn, CONFIG_BT_CTLR_LLL_PRIO,
-			   radio_nrf5_isr, 0);
+			   radio_nrf5_isr, IRQ_CONNECT_FLAGS);
 	IRQ_CONNECT(RTC0_IRQn, CONFIG_BT_CTLR_ULL_HIGH_PRIO,
 		    rtc0_nrf5_isr, NULL, 0);
 	IRQ_CONNECT(HAL_SWI_RADIO_IRQ, CONFIG_BT_CTLR_LLL_PRIO,
-		    swi_lll_nrf5_isr, NULL, 0);
+		    swi_lll_nrf5_isr, NULL, IRQ_CONNECT_FLAGS);
 #if defined(CONFIG_BT_CTLR_LOW_LAT) || \
 	(CONFIG_BT_CTLR_ULL_HIGH_PRIO != CONFIG_BT_CTLR_ULL_LOW_PRIO)
 	IRQ_CONNECT(HAL_SWI_JOB_IRQ, CONFIG_BT_CTLR_ULL_LOW_PRIO,

subsys/bluetooth/controller/ll_sw/ull.c

@@ -406,21 +406,36 @@ void ll_reset(void)
 
 	/* Reset LLL via mayfly */
 	{
-		u32_t retval;
-		struct k_sem sem;
 		static memq_link_t link;
 		static struct mayfly mfy = {0, 0, &link, NULL,
 					    perform_lll_reset};
+		u32_t retval;
+
+		/* NOTE: If Zero Latency Interrupt is used, then LLL context
+		 *       will be the highest priority IRQ in the system, hence
+		 *       mayfly_enqueue will be done running the callee inline
+		 *       (vector to the callee function) in this function. Else
+		 *       we use semaphore to wait for perform_lll_reset to
+		 *       complete.
+		 */
+
+#if !defined(CONFIG_BT_CTLR_ZLI)
+		struct k_sem sem;
 
 		k_sem_init(&sem, 0, 1);
 		mfy.param = &sem;
+#endif /* !CONFIG_BT_CTLR_ZLI */
+
 		retval = mayfly_enqueue(TICKER_USER_ID_THREAD,
 					TICKER_USER_ID_LLL, 0, &mfy);
 		LL_ASSERT(!retval);
+
+#if !defined(CONFIG_BT_CTLR_ZLI)
 		/* LLL reset must complete before returning - wait for
 		 * reset completion in LLL mayfly thread
 		 */
 		k_sem_take(&sem, K_FOREVER);
+#endif /* !CONFIG_BT_CTLR_ZLI */
 	}
 
 	/* Common to init and reset */
@@ -1210,7 +1225,9 @@ static void perform_lll_reset(void *param)
 	LL_ASSERT(!err);
 #endif /* CONFIG_BT_CONN */
 
+#if !defined(CONFIG_BT_CTLR_ZLI)
 	k_sem_give(param);
+#endif /* !CONFIG_BT_CTLR_ZLI */
 }
 
 static inline void *mark_set(void **m, void *param)