nimble/phy: nrf5x: Add continues tone test mode

Use BLE_PHY_CS_TEST_MODE_CONTINUES_TONE and
BLE_PHY_CS_TEST_MODE_CONTINUES_TONE when building an image to put
the radio into continuous tone transmission mode. Helpful for frequency
calibration.

Author: mkasenberg

nimble/drivers/nrf5x/pkg.yml

@@ -46,3 +46,6 @@ pkg.source_files.'MCU_TARGET=="nRF54L15"':
 
 pkg.source_files.'BLE_CHANNEL_SOUNDING':
     - "src/ble_phy_cs.c"
+
+pkg.init.'BLE_PHY_CS_TEST_MODE_CONTINUES_TONE':
+    ble_phy_cs_tx_continuous_tone: $after:ble_transport_ll_init

nimble/drivers/nrf5x/src/ble_phy_cs.c

@@ -804,4 +804,36 @@ ble_phy_cs_subevent_start(struct ble_phy_cs_transmission *transm,
 
     return 0;
 }
+
+#if MYNEWT_VAL(BLE_PHY_CS_TEST_MODE_CONTINUES_TONE)
+void
+ble_phy_cs_tx_continuous_tone(void)
+{
+    int rc = 0;
+
+    os_trace_isr_enter();
+
+    ble_phy_rfclk_enable();
+
+    phy_ppi_cs_mode_enable();
+    ble_phy_cs_radio_events_clear();
+
+    /* Make sure all interrupts are disabled */
+    nrf_radio_int_disable(NRF_RADIO, NRF_RADIO_IRQ_MASK_ALL);
+
+    NRF_RADIO->SHORTS = 0;
+    ble_phy_cs_rtt_set(NULL, 0);
+    ble_phy_cs_channel_set(MYNEWT_VAL(BLE_PHY_CS_TEST_MODE_CONTINUES_TONE_CHANNEL));
+    ble_phy_cs_tone_configure(80, BLE_PHY_CS_TONE_MODE_FM);
+    ble_phy_cs_tune_set();
+
+    NRF_RADIO->TASKS_TXEN = 1;
+
+    while (1);
+
+    os_trace_isr_exit();
+
+    return;
+}
+#endif
 #endif