[nrf fromlist] modules: hal_nordic: nrf_802154: enable constant latency

To ensure that the accesses to the radio peripheral are done with
predictable timings, the constant latency must be enabled.
The constant latency mode is enabled alongside the HFXO.

Upstream PR #: 85883

Signed-off-by: Rafał Kuźnia <[email protected]>

Author: e-rk

modules/hal_nordic/Kconfig

@@ -36,6 +36,12 @@ menuconfig NRF_802154_RADIO_DRIVER
 
 if NRF_802154_RADIO_DRIVER
 
+config NRF_802154_CONSTLAT_CONTROL
+	def_bool y
+	select NRF_SYS_EVENT if SOC_SERIES_NRF54LX && NRF_802154_SL_OPENSOURCE
+	help
+	  Allows the nRF 802.15.4 radio driver to manage the constant latency state.
+
 config NRF_802154_MULTIPROTOCOL_SUPPORT
 	bool
 	help

modules/hal_nordic/nrf_802154/sl_opensource/platform/nrf_802154_clock_zephyr.c

@@ -12,6 +12,7 @@
 #include <compiler_abstraction.h>
 #include <zephyr/kernel.h>
 #include <zephyr/drivers/clock_control/nrf_clock_control.h>
+#include <nrf_sys_event.h>
 
 static bool hfclk_is_running;
 
@@ -52,6 +53,14 @@ void nrf_802154_clock_hfclk_start(void)
 
 	sys_notify_init_callback(&hfclk_cli.notify, hfclk_on_callback);
 
+	/*
+	 * todo: replace constlat request with PM policy API when
+	 * controlling the event latency becomes possible.
+	 */
+	if (IS_ENABLED(NRF_802154_CONSTLAT_CONTROL)) {
+		nrf_sys_event_request_global_constlat();
+	}
+
 	int ret = onoff_request(mgr, &hfclk_cli);
 	__ASSERT_NO_MSG(ret >= 0);
 	(void)ret;
@@ -67,6 +76,11 @@ void nrf_802154_clock_hfclk_stop(void)
 	int ret = onoff_cancel_or_release(mgr, &hfclk_cli);
 	__ASSERT_NO_MSG(ret >= 0);
 	(void)ret;
+
+	if (IS_ENABLED(NRF_802154_CONSTLAT_CONTROL)) {
+		nrf_sys_event_release_global_constlat();
+	}
+
 	hfclk_is_running = false;
 }