soc: nordic: common: force CONSTLAT kconfig

Add an option to force constant latency mode at application startup.

Signed-off-by: Jordan Yates <[email protected]>

Author: JordanYates

soc/nordic/common/CMakeLists.txt

@@ -39,4 +39,5 @@ if(CONFIG_TFM_PARTITION_PLATFORM)
 endif()
 
 zephyr_library_sources_ifdef(CONFIG_NRF_SYS_EVENT nrf_sys_event.c)
+zephyr_library_sources_ifdef(CONFIG_NRF_FORCE_CONSTANT_LATENCY nrf_constlat.c)
 zephyr_library_sources_ifdef(CONFIG_MRAM_LATENCY mram_latency.c)

soc/nordic/common/Kconfig

@@ -21,6 +21,13 @@ config NRF_SYS_EVENT
 	bool "nRF system event support"
 	select NRFX_POWER if !NRF_PLATFORM_HALTIUM
 
+config NRF_FORCE_CONSTANT_LATENCY
+	bool "Force constant latency mode in system ON"
+	depends on NRF_SYS_EVENT
+	help
+	  Forcing constant latency mode minimises CPU wakeup latency and PPI task
+	  response time, at the cost of increased power consumption.
+
 config MRAM_LATENCY
 	bool "MRAM latency manager"
 	depends on NRFS_HAS_MRAM_SERVICE

soc/nordic/common/nrf_constlat.c

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2025 Embeint Pty Ltd
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/init.h>
+
+#include <nrf_sys_event.h>
+
+static int nrf_const_lat(void)
+{
+	return nrf_sys_event_request_global_constlat();
+}
+
+/* Immediately after the SoC init functions */
+SYS_INIT(nrf_const_lat, PRE_KERNEL_1, 1);