tests: debug: Add test for cpu_load

 Add test for CPU load.

Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>

Author: nordic-krch

tests/subsys/debug/cpu_load/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(debug_cpu_load)
+
+target_sources(app PRIVATE src/main.c)

tests/subsys/debug/cpu_load/boards/nrf52840dk_nrf52840.overlay

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+/ {
+	chosen {
+		zephyr,cpu-load-counter = &timer0;
+	};
+};
+
+&timer0 {
+	status = "okay";
+	prescaler = <0>;
+};

tests/subsys/debug/cpu_load/boards/nrf54h20dk_nrf54h20_cpuapp.overlay

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+/ {
+	chosen {
+		zephyr,cpu-load-counter = &timer130;
+	};
+};
+
+&timer130 {
+	status = "okay";
+	prescaler = <0>;
+};

tests/subsys/debug/cpu_load/prj.conf

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+CONFIG_ZTEST=y
+CONFIG_CPU_LOAD=y
+CONFIG_CPU_LOAD_USE_COUNTER=n

tests/subsys/debug/cpu_load/src/main.c

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+/*
+ * Copyright (c) 2024, Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+#include <zephyr/debug/cpu_load.h>
+#include <zephyr/ztest.h>
+#include <zephyr/logging/log_ctrl.h>
+#include <zephyr/logging/log_backend.h>
+
+#include <zephyr/drivers/counter.h>
+
+#define DELTA 30
+
+ZTEST(cpu_load, test_load)
+{
+	int load;
+	uint32_t t_ms = 100;
+
+	if (CONFIG_CPU_LOAD_LOG_PERIODICALLY > 0) {
+		cpu_load_log_control(false);
+	}
+
+	/* Reset the measurement */
+	(void)cpu_load_get(true);
+	k_busy_wait(t_ms * USEC_PER_MSEC);
+
+	/* Measurement is not reset. */
+	load = cpu_load_get(false);
+	/* Result in per mille */
+	zassert_within(load, 1000, DELTA);
+
+	k_msleep(t_ms);
+	load = cpu_load_get(false);
+	zassert_within(load, 500, DELTA);
+
+	/* Reset the measurement */
+	(void)cpu_load_get(true);
+	k_msleep(t_ms);
+	load = cpu_load_get(false);
+	zassert_within(load, 0, DELTA);
+}
+
+#if CONFIG_CPU_LOAD_LOG_PERIODICALLY > 0
+static int cpu_load_src_id;
+static atomic_t log_cnt;
+
+static void process(const struct log_backend *const backend,
+		union log_msg_generic *msg)
+{
+	ARG_UNUSED(backend);
+	const void *source = msg->log.hdr.source;
+	int source_id = log_const_source_id((const struct log_source_const_data *)source);
+
+	if (source_id == cpu_load_src_id) {
+		atomic_inc(&log_cnt);
+	}
+}
+
+static void init(const struct log_backend *const backend)
+{
+	ARG_UNUSED(backend);
+}
+
+const struct log_backend_api mock_log_backend_api = {
+	.process = process,
+	.init = init
+};
+
+LOG_BACKEND_DEFINE(dummy, mock_log_backend_api, false, NULL);
+
+ZTEST(cpu_load, test_periodic_report)
+{
+	log_backend_enable(&dummy, NULL, LOG_LEVEL_INF);
+	cpu_load_log_control(true);
+
+	cpu_load_src_id = log_source_id_get(STRINGIFY(cpu_load));
+	atomic_set(&log_cnt, 0);
+	k_msleep(3 * CONFIG_CPU_LOAD_LOG_PERIODICALLY);
+	zassert_within(log_cnt, 3, 1);
+
+	cpu_load_log_control(false);
+	k_msleep(1);
+	atomic_set(&log_cnt, 0);
+	k_msleep(3 * CONFIG_CPU_LOAD_LOG_PERIODICALLY);
+	zassert_equal(log_cnt, 0);
+
+	cpu_load_log_control(true);
+	k_msleep(3 * CONFIG_CPU_LOAD_LOG_PERIODICALLY);
+	zassert_within(log_cnt, 3, 1);
+
+	cpu_load_log_control(false);
+	log_backend_disable(&dummy);
+}
+#endif /* CONFIG_CPU_LOAD_LOG_PERIODICALLY > 0 */
+
+ZTEST_SUITE(cpu_load, NULL, NULL, NULL, NULL, NULL);

tests/subsys/debug/cpu_load/testcase.yaml

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+common:
+  tags: cpu_load
+  arch_allow: arm
+  filter: CONFIG_CPU_CORTEX_M
+tests:
+  debug.cpu_load:
+    integration_platforms:
+      - mps2/an385
+  debug.cpu_load.counter:
+    platform_allow:
+      - nrf52840dk/nrf52840
+      - nrf54h20dk/nrf54h20/cpuapp
+    integration_platforms:
+      - nrf52840dk/nrf52840
+    extra_configs:
+      - CONFIG_CPU_LOAD_USE_COUNTER=y
+  debug.cpu_load.periodic_report:
+    integration_platforms:
+      - mps2/an385
+    extra_configs:
+      - CONFIG_CPU_LOAD_LOG_PERIODICALLY=50
+      - CONFIG_LOG=y
+      - CONFIG_TEST_LOGGING_DEFAULTS=n
+      - CONFIG_LOG_PRINTK=n
+      - CONFIG_LOG_BACKEND_UART=n
+      - CONFIG_LOG_MODE_IMMEDIATE=y