debug: Added CPU usage callback

- Added a CPU load callback with threshold
- Changed cpu_load to use k_timer instead of k_work

Signed-off-by: Kristoffer Rist Skøien <kristoffer.skoien@nordicsemi.no>

include/zephyr/debug/cpu_load.h

@@ -8,6 +8,7 @@
 #define ZEPHYR_INCLUDE_DEBUG_CPU_LOAD_H_
 
 #include <stdbool.h>
+#include <stdint.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -48,6 +49,25 @@ int cpu_load_get(bool reset);
  */
 void cpu_load_log_control(bool enable);
 
+/* Optional callback for cpu_load_cb_reg
+ *
+ * This will be called from the k_timer expiry_fn used for periodic logging.
+ * CONFIG_CPU_LOAD_LOG_PERIODICALLY must be configured to a positive value.
+ * Time spent in this callback must be kept to a minimum.
+ */
+typedef void (*cpu_load_cb_t)(uint8_t percent);
+
+/** @brief Optional registration of callback when load is greater or equal to the threshold.
+ *
+ * @param cb Pointer to the callback function. NULL will cancel the callback.
+ * @param threshold_percent Threshold [0...100]. CPU load equal or greater that this
+ * will trigger the callback.
+ *
+ * @retval 0 - Callback registered/cancelled.
+ * @retval -EINVAL if the threshold is invalid.
+ */
+int cpu_load_cb_reg(cpu_load_cb_t cb, uint8_t threshold_percent);
+
 /**
  * @}
  */

subsys/debug/cpu_load.c

@@ -22,33 +22,49 @@ static uint32_t enter_ts;
 static uint32_t cyc_start;
 static uint32_t ticks_idle;
 
-static struct k_work_delayable cpu_load_log;
+static cpu_load_cb_t load_cb;
+static uint8_t cpu_load_threshold_percent;
+
+static void cpu_load_log_fn(struct k_timer *dummy)
+{
+	int load = cpu_load_get(true);
+	uint32_t percent = load / 10;
+	uint32_t fraction = load % 10;
+
+	LOG_INF("Load:%d.%03d%%", percent, fraction);
+	if (load_cb != NULL && percent >= cpu_load_threshold_percent) {
+		load_cb(percent);
+	}
+}
+
+K_TIMER_DEFINE(cpu_load_timer, cpu_load_log_fn, NULL);
 
 void cpu_load_log_control(bool enable)
 {
 	if (CONFIG_CPU_LOAD_LOG_PERIODICALLY == 0) {
 		return;
 	}
-
 	if (enable) {
-		(void)cpu_load_get(true);
-		k_work_schedule(&cpu_load_log, K_MSEC(CONFIG_CPU_LOAD_LOG_PERIODICALLY));
+		k_timer_start(&cpu_load_timer, K_MSEC(CONFIG_CPU_LOAD_LOG_PERIODICALLY),
+			      K_MSEC(CONFIG_CPU_LOAD_LOG_PERIODICALLY));
 	} else {
-		k_work_cancel_delayable(&cpu_load_log);
+		k_timer_stop(&cpu_load_timer);
 	}
 }
 
-#if CONFIG_CPU_LOAD_USE_COUNTER || CONFIG_CPU_LOAD_LOG_PERIODICALLY
-static void cpu_load_log_fn(struct k_work *work)
+int cpu_load_cb_reg(cpu_load_cb_t cb, uint8_t threshold_percent)
 {
-	int load = cpu_load_get(true);
-	uint32_t percent = load / 10;
-	uint32_t fraction = load % 10;
+	if (threshold_percent > 100) {
+		return -EINVAL;
+	}
 
-	LOG_INF("Load:%d.%03d%%", percent, fraction);
-	cpu_load_log_control(true);
+	cpu_load_threshold_percent = threshold_percent;
+	load_cb = cb;
+	return 0;
 }
 
+#if CONFIG_CPU_LOAD_USE_COUNTER || CONFIG_CPU_LOAD_LOG_PERIODICALLY
+
 static int cpu_load_init(void)
 {
 	if (IS_ENABLED(CONFIG_CPU_LOAD_USE_COUNTER)) {
@@ -59,8 +75,8 @@ static int cpu_load_init(void)
 	}
 
 	if (CONFIG_CPU_LOAD_LOG_PERIODICALLY > 0) {
-		k_work_init_delayable(&cpu_load_log, cpu_load_log_fn);
-		return k_work_schedule(&cpu_load_log, K_MSEC(CONFIG_CPU_LOAD_LOG_PERIODICALLY));
+		k_timer_start(&cpu_load_timer, K_MSEC(CONFIG_CPU_LOAD_LOG_PERIODICALLY),
+			      K_MSEC(CONFIG_CPU_LOAD_LOG_PERIODICALLY));
 	}
 
 	return 0;

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

@@ -94,6 +94,48 @@ ZTEST(cpu_load, test_periodic_report)
 	cpu_load_log_control(false);
 	log_backend_disable(&dummy);
 }
+
+void low_load_cb(uint8_t percent)
+{
+	/* Should never be called */
+	zassert_true(false, NULL);
+}
+
+static uint32_t num_load_callbacks;
+static uint8_t last_cpu_load_percent;
+
+void high_load_cb(uint8_t percent)
+{
+	last_cpu_load_percent = percent;
+	num_load_callbacks++;
+}
+
+ZTEST(cpu_load, test_callback_load_low)
+{
+	int ret = cpu_load_cb_reg(low_load_cb, 99);
+
+	zassert_equal(ret, 0);
+	k_msleep(CONFIG_CPU_LOAD_LOG_PERIODICALLY * 4);
+	zassert_equal(num_load_callbacks, 0);
+}
+
+ZTEST(cpu_load, test_callback_load_high)
+{
+	int ret = cpu_load_cb_reg(high_load_cb, 99);
+
+	zassert_equal(ret, 0);
+	k_busy_wait(CONFIG_CPU_LOAD_LOG_PERIODICALLY * 4 * 1000);
+	zassert_between_inclusive(last_cpu_load_percent, 99, 100);
+	zassert_between_inclusive(num_load_callbacks, 2, 7);
+
+	/* Reset the callback */
+	ret = cpu_load_cb_reg(NULL, 99);
+	num_load_callbacks = 0;
+	zassert_equal(ret, 0);
+	k_busy_wait(CONFIG_CPU_LOAD_LOG_PERIODICALLY * 4 * 1000);
+	zassert_equal(num_load_callbacks, 0);
+}
+
 #endif /* CONFIG_CPU_LOAD_LOG_PERIODICALLY > 0 */
 
 ZTEST_SUITE(cpu_load, NULL, NULL, NULL, NULL, NULL);

tests/subsys/debug/cpu_load/testcase.yaml

@@ -8,17 +8,21 @@ tests:
   debug.cpu_load:
     integration_platforms:
       - mps2/an385
+      - qemu_cortex_m3
   debug.cpu_load.counter:
     platform_allow:
       - nrf52840dk/nrf52840
       - nrf54h20dk/nrf54h20/cpuapp
+      - qemu_cortex_m3
     integration_platforms:
       - nrf52840dk/nrf52840
+      - qemu_cortex_m3
     extra_configs:
       - CONFIG_CPU_LOAD_USE_COUNTER=y
   debug.cpu_load.periodic_report:
     integration_platforms:
       - mps2/an385
+      - qemu_cortex_m3
     extra_configs:
       - CONFIG_CPU_LOAD_LOG_PERIODICALLY=50
       - CONFIG_LOG=y