Bluetooth: controller: nRF5: Back-to-Back Radio Tx interface

Add Radio interface to perform back-to-back transmit of PDU
with a configurable inter frame spacing.

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

subsys/bluetooth/controller/ll_sw/nordic/hal/nrf5/radio/radio.c

@@ -489,28 +489,55 @@ void *radio_pkt_decrypt_get(void)
 #endif
 
 #if !defined(CONFIG_BT_CTLR_TIFS_HW)
+
+#define SW_SWITCH_PREV_RX 0
+#define SW_SWITCH_NEXT_RX 0
+#define SW_SWITCH_PREV_TX 1
+#define SW_SWITCH_NEXT_TX 1
+#define SW_SWITCH_PREV_PHY_1M 0
+#define SW_SWITCH_PREV_FLAGS_DONTCARE 0
+#define SW_SWITCH_NEXT_FLAGS_DONTCARE 0
+
 static uint8_t sw_tifs_toggle;
 
-static void sw_switch(uint8_t dir, uint8_t phy_curr, uint8_t flags_curr, uint8_t phy_next,
- uint8_t flags_next)
+static inline void sw_switch(uint8_t dir_curr, uint8_t dir_next,
+ uint8_t phy_curr, uint8_t flags_curr,
+ uint8_t phy_next, uint8_t flags_next)
 {
  uint8_t ppi = HAL_SW_SWITCH_RADIO_ENABLE_PPI(sw_tifs_toggle);
  uint8_t cc = SW_SWITCH_TIMER_EVTS_COMP(sw_tifs_toggle);
  uint32_t delay;
 
  hal_radio_sw_switch_setup(cc, ppi, sw_tifs_toggle);
 
- if (dir) {
+ /* NOTE: As constants are passed to dir_curr and dir_next, the
+ * compiler should optimize out the redundant code path as
+ * this is an inline function.
+ */
+ if (dir_next) {
  /* TX */
 
- /* Calculate delay with respect to current (RX) and next
- * (TX) PHY. If RX PHY is LE Coded, assume S8 coding scheme.
+ /* Calculate delay with respect to current and next PHY.
  */
- delay = HAL_RADIO_NS2US_ROUND(
- hal_radio_tx_ready_delay_ns_get(phy_next, flags_next) +
- hal_radio_rx_chain_delay_ns_get(phy_curr, 1));
-
- hal_radio_txen_on_sw_switch(ppi);
+ if (dir_curr) {
+ delay = HAL_RADIO_NS2US_ROUND(
+ hal_radio_tx_ready_delay_ns_get(phy_next,
+ flags_next) +
+ hal_radio_tx_chain_delay_ns_get(phy_curr,
+ flags_curr));
+
+ hal_radio_b2b_txen_on_sw_switch(ppi);
+ } else {
+ /* If RX PHY is LE Coded, calculate for S8 coding.
+ * Assumption being, S8 has higher delay.
+ */
+ delay = HAL_RADIO_NS2US_ROUND(
+ hal_radio_tx_ready_delay_ns_get(phy_next,
+ flags_next) +
+ hal_radio_rx_chain_delay_ns_get(phy_curr, 1));
+
+ hal_radio_txen_on_sw_switch(ppi);
+ }
 
 #if defined(CONFIG_BT_CTLR_PHY_CODED)
 #if defined(CONFIG_HAS_HW_NRF_RADIO_BLE_CODED)
@@ -520,7 +547,7 @@ static void sw_switch(uint8_t dir, uint8_t phy_curr, uint8_t flags_curr, uint8_t
  HAL_SW_SWITCH_GROUP_TASK_DISABLE_PPI(
  sw_tifs_toggle);
 
- if (phy_curr & PHY_CODED) {
+ if (!dir_curr && (phy_curr & PHY_CODED)) {
  /* Switching to TX after RX on LE Coded PHY. */
 
  uint8_t cc_s2 =
@@ -544,7 +571,8 @@ static void sw_switch(uint8_t dir, uint8_t phy_curr, uint8_t flags_curr, uint8_t
 
  hal_radio_sw_switch_coded_tx_config_set(ppi_en, ppi_dis,
  cc_s2, sw_tifs_toggle);
- } else {
+
+ } else if (!dir_curr) {
  /* Switching to TX after RX on LE 1M/2M PHY */
 
  hal_radio_sw_switch_coded_config_clear(ppi_en,
@@ -613,12 +641,19 @@ void radio_switch_complete_and_rx(uint8_t phy_rx)
 #else /* !CONFIG_BT_CTLR_TIFS_HW */
  NRF_RADIO->SHORTS = RADIO_SHORTS_READY_START_Msk |
  RADIO_SHORTS_END_DISABLE_Msk;
- sw_switch(0, 0, 0, phy_rx, 0);
+
+ /* NOTE: As Tx chain delays are negligible constant values (~1 us)
+ * across nRF5x radios, sw_switch assumes the 1M chain delay for
+ * calculations.
+ */
+ sw_switch(SW_SWITCH_PREV_TX, SW_SWITCH_NEXT_RX,
+ SW_SWITCH_PREV_PHY_1M, SW_SWITCH_PREV_FLAGS_DONTCARE,
+ phy_rx, SW_SWITCH_NEXT_FLAGS_DONTCARE);
 #endif /* !CONFIG_BT_CTLR_TIFS_HW */
 }
 
-void radio_switch_complete_and_tx(uint8_t phy_rx, uint8_t flags_rx, uint8_t phy_tx,
- uint8_t flags_tx)
+void radio_switch_complete_and_tx(uint8_t phy_rx, uint8_t flags_rx,
+ uint8_t phy_tx, uint8_t flags_tx)
 {
 #if defined(CONFIG_BT_CTLR_TIFS_HW)
  NRF_RADIO->SHORTS = RADIO_SHORTS_READY_START_Msk |
@@ -627,7 +662,25 @@ void radio_switch_complete_and_tx(uint8_t phy_rx, uint8_t flags_rx, uint8_t phy_
 #else /* !CONFIG_BT_CTLR_TIFS_HW */
  NRF_RADIO->SHORTS = RADIO_SHORTS_READY_START_Msk |
  RADIO_SHORTS_END_DISABLE_Msk;
- sw_switch(1, phy_rx, flags_rx, phy_tx, flags_tx);
+
+ sw_switch(SW_SWITCH_PREV_RX, SW_SWITCH_NEXT_TX,
+ phy_rx, flags_rx, phy_tx, flags_tx);
+#endif /* !CONFIG_BT_CTLR_TIFS_HW */
+}
+
+void radio_switch_complete_and_b2b_tx(uint8_t phy_curr, uint8_t flags_curr,
+ uint8_t phy_next, uint8_t flags_next)
+{
+#if defined(CONFIG_BT_CTLR_TIFS_HW)
+ NRF_RADIO->SHORTS = RADIO_SHORTS_READY_START_Msk |
+ RADIO_SHORTS_END_DISABLE_Msk |
+ RADIO_SHORTS_DISABLED_TXEN_Msk;
+#else /* !CONFIG_BT_CTLR_TIFS_HW */
+ NRF_RADIO->SHORTS = RADIO_SHORTS_READY_START_Msk |
+ RADIO_SHORTS_END_DISABLE_Msk;
+
+ sw_switch(SW_SWITCH_PREV_TX, SW_SWITCH_NEXT_TX,
+ phy_curr, flags_curr, phy_next, flags_next);
 #endif /* !CONFIG_BT_CTLR_TIFS_HW */
 }
 

subsys/bluetooth/controller/ll_sw/nordic/hal/nrf5/radio/radio.h

@@ -48,6 +48,8 @@ void *radio_pkt_decrypt_get(void);
 void radio_switch_complete_and_rx(uint8_t phy_rx);
 void radio_switch_complete_and_tx(uint8_t phy_rx, uint8_t flags_rx, uint8_t phy_tx,
  uint8_t flags_tx);
+void radio_switch_complete_and_b2b_tx(uint8_t phy_curr, uint8_t flags_curr,
+ uint8_t phy_next, uint8_t flags_next);
 void radio_switch_complete_and_disable(void);
 
 void radio_rssi_measure(void);

subsys/bluetooth/controller/ll_sw/nordic/hal/nrf5/radio/radio_nrf5_dppi.h

@@ -469,6 +469,21 @@ static inline void hal_radio_txen_on_sw_switch(uint8_t ppi)
  nrf_radio_subscribe_set(NRF_RADIO, NRF_RADIO_TASK_TXEN, ppi);
 }
 
+static inline void hal_radio_b2b_txen_on_sw_switch(uint8_t ppi)
+{
+ /* NOTE: Calling radio_tmr_start/radio_tmr_start_us/radio_tmr_start_now
+ * after the radio_switch_complete_and_b2b_tx() call would have
+ * changed the PPI channel to HAL_RADIO_ENABLE_ON_TICK_PPI as we
+ * cannot double buffer the subscribe buffer. Hence, lets have
+ * both DPPI channel enabled (other one was enabled by the DPPI
+ * group when the Radio End occurred) so that when both timer
+ * trigger one of the DPPI is correct in the radio tx
+ * subscription.
+ */
+ nrf_radio_subscribe_set(NRF_RADIO, NRF_RADIO_TASK_TXEN, ppi);
+ nrf_dppi_channels_enable(NRF_DPPIC, BIT(ppi));
+}
+
 static inline void hal_radio_rxen_on_sw_switch(uint8_t ppi)
 {
  nrf_radio_subscribe_set(NRF_RADIO, NRF_RADIO_TASK_RXEN, ppi);

subsys/bluetooth/controller/ll_sw/nordic/hal/nrf5/radio/radio_nrf5_ppi.h

@@ -479,6 +479,16 @@ static inline void hal_radio_txen_on_sw_switch(uint8_t ppi)
  HAL_SW_SWITCH_RADIO_ENABLE_PPI_TASK_TX);
 }
 
+static inline void hal_radio_b2b_txen_on_sw_switch(uint8_t ppi)
+{
+ /* NOTE: As independent PPI are used to trigger the Radio Tx task,
+ * double buffers implementation works for sw_switch using PPIs,
+ * simply reuse the hal_radio_txen_on_sw_switch() functon to set
+ * the next PPIs task to be Radio Tx enable.
+ */
+ hal_radio_txen_on_sw_switch(ppi);
+}
+
 static inline void hal_radio_rxen_on_sw_switch(uint8_t ppi)
 {
  nrf_ppi_task_endpoint_setup(