soc: nordic: add fn for setting constlat mode

Nordic SoCs implement an event system, for which the system can
optimize for low latency/high power or low power.

Add soc level implementation of reference counted API which will
optimize for low latency if any part of the system requires it.

Signed-off-by: Bjarki Arge Andreasen <bjarki.andreasen@nordicsemi.no>

soc/nordic/common/CMakeLists.txt

@@ -29,3 +29,5 @@ if(CONFIG_TFM_PARTITION_PLATFORM)
     $<TARGET_PROPERTY:tfm,TFM_BINARY_DIR>/api_ns/interface/include
   )
 endif()
+
+zephyr_library_sources_ifdef(CONFIG_NRF_SYS_EVENT nrf_sys_event.c)

soc/nordic/common/Kconfig

@@ -4,4 +4,8 @@
 config HAS_NORDIC_DMM
 	bool
 
+config NRF_SYS_EVENT
+	bool "nRF system event support"
+	select NRFX_POWER if !NRF_PLATFORM_HALTIUM
+
 rsource "vpr/Kconfig"

soc/nordic/common/nrf_sys_event.c

@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <nrf_sys_event.h>
+
+#if CONFIG_SOC_SERIES_NRF54HX
+
+/*
+ * The 54HX is not yet supported by an nrfx driver nor the system controller so
+ * we implement an ISR and concurrent access safe reference counting implementation
+ * here using the nrfx hal.
+ */
+
+#include <hal/nrf_lrcconf.h>
+
+static struct k_spinlock global_constlat_lock;
+static uint16_t global_constlat_count;
+
+int nrf_sys_event_request_global_constlat(void)
+{
+	K_SPINLOCK(&global_constlat_lock) {
+		if (global_constlat_count == 0) {
+#if CONFIG_SOC_NRF54H20_CPUAPP
+			nrf_lrcconf_task_trigger(NRF_LRCCONF010,
+						 NRF_LRCCONF_TASK_CONSTLAT_ENABLE);
+#elif CONFIG_SOC_NRF54H20_CPURAD
+			nrf_lrcconf_task_trigger(NRF_LRCCONF000,
+						 NRF_LRCCONF_TASK_CONSTLAT_ENABLE);
+			nrf_lrcconf_task_trigger(NRF_LRCCONF020,
+						 NRF_LRCCONF_TASK_CONSTLAT_ENABLE);
+#else
+#error "unsupported"
+#endif
+		}
+
+		global_constlat_count++;
+	}
+
+	return 0;
+}
+
+int nrf_sys_event_release_global_constlat(void)
+{
+	K_SPINLOCK(&global_constlat_lock) {
+		if (global_constlat_count == 1) {
+#if CONFIG_SOC_NRF54H20_CPUAPP
+			nrf_lrcconf_task_trigger(NRF_LRCCONF010,
+						 NRF_LRCCONF_TASK_CONSTLAT_DISABLE);
+#elif CONFIG_SOC_NRF54H20_CPURAD
+			nrf_lrcconf_task_trigger(NRF_LRCCONF000,
+						 NRF_LRCCONF_TASK_CONSTLAT_DISABLE);
+			nrf_lrcconf_task_trigger(NRF_LRCCONF020,
+						 NRF_LRCCONF_TASK_CONSTLAT_DISABLE);
+#else
+#error "unsupported"
+#endif
+		}
+
+		global_constlat_count--;
+	}
+
+	return 0;
+}
+
+#else
+
+/*
+ * The nrfx power driver already contains an ISR and concurrent access safe reference
+ * counting API so we just use it directly when available.
+ */
+
+#include <nrfx_power.h>
+
+int nrf_sys_event_request_global_constlat(void)
+{
+	nrfx_err_t err;
+
+	err = nrfx_power_constlat_mode_request();
+
+	return (err == NRFX_SUCCESS || err == NRFX_ERROR_ALREADY) ? 0 : -EAGAIN;
+}
+
+int nrf_sys_event_release_global_constlat(void)
+{
+	nrfx_err_t err;
+
+	err = nrfx_power_constlat_mode_free();
+
+	return (err == NRFX_SUCCESS || err == NRFX_ERROR_BUSY) ? 0 : -EAGAIN;
+}
+
+#endif

soc/nordic/common/nrf_sys_event.h

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+
+/**
+ * @brief Request lowest latency for system events
+ *
+ * @details System will be configured for lowest latency after first
+ * call to nrf_sys_event_request_global_constlat() and will remain
+ * configured for lowest latency until matching number of calls to
+ * nrf_sys_event_release_global_constlat() occur.
+ *
+ * @retval 0 if successful
+ * @retval -errno code otherwise
+ */
+int nrf_sys_event_request_global_constlat(void);
+
+/**
+ * @brief Release low latency request
+ *
+ * @see nrf_sys_event_request_global_constlat()
+ *
+ * @retval 0 if successful
+ * @retval -errno code otherwise
+ */
+int nrf_sys_event_release_global_constlat(void);