esp-idf/components/esp_timer/src/esp_timer.c

/*
 * SPDX-FileCopyrightText: 2017-2022 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <sys/param.h>
#include <string.h>
#include "soc/soc.h"
#include "esp_types.h"
#include "esp_attr.h"
#include "esp_err.h"
#include "esp_task.h"
#include "esp_log.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/semphr.h"
#include "esp_ipc.h"
#include "esp_timer.h"
#include "esp_timer_impl.h"

#include "esp_private/startup_internal.h"
#include "esp_private/esp_timer_private.h"
#include "esp_private/system_internal.h"

#if CONFIG_IDF_TARGET_ESP32
#include "esp32/rtc.h"
#elif CONFIG_IDF_TARGET_ESP32S2
#include "esp32s2/rtc.h"
#elif CONFIG_IDF_TARGET_ESP32S3
#include "esp32s3/rtc.h"
#elif CONFIG_IDF_TARGET_ESP32C3
#include "esp32c3/rtc.h"
#elif CONFIG_IDF_TARGET_ESP32H4
#include "esp32h4/rtc.h"
#elif CONFIG_IDF_TARGET_ESP32C2
#include "esp32c2/rtc.h"
#elif CONFIG_IDF_TARGET_ESP32C6
#include "esp32c6/rtc.h"
#elif CONFIG_IDF_TARGET_ESP32H2
#include "esp32h2/rtc.h"
#endif

#include "sdkconfig.h"

#ifdef CONFIG_ESP_TIMER_PROFILING
#define WITH_PROFILING 1
#endif

#ifndef NDEBUG
// Enable built-in checks in queue.h in debug builds
#define INVARIANTS
#endif
#include "sys/queue.h"

#define EVENT_ID_DELETE_TIMER   0xF0DE1E1E

typedef enum {
    FL_ISR_DISPATCH_METHOD   = (1 << 0),  //!< 0=Callback is called from timer task, 1=Callback is called from timer ISR
    FL_SKIP_UNHANDLED_EVENTS = (1 << 1),  //!< 0=NOT skip unhandled events for periodic timers, 1=Skip unhandled events for periodic timers
} flags_t;

struct esp_timer {
    uint64_t alarm;
    uint64_t period:56;
    flags_t flags:8;
    union {
        esp_timer_cb_t callback;
        uint32_t event_id;
    };
    void* arg;
#if WITH_PROFILING
    const char* name;
    size_t times_triggered;
    size_t times_armed;
    size_t times_skipped;
    uint64_t total_callback_run_time;
#endif // WITH_PROFILING
    LIST_ENTRY(esp_timer) list_entry;
};

static inline bool is_initialized(void);
static esp_err_t timer_insert(esp_timer_handle_t timer, bool without_update_alarm);
static esp_err_t timer_remove(esp_timer_handle_t timer);
static bool timer_armed(esp_timer_handle_t timer);
static void timer_list_lock(esp_timer_dispatch_t timer_type);
static void timer_list_unlock(esp_timer_dispatch_t timer_type);

#if WITH_PROFILING
static void timer_insert_inactive(esp_timer_handle_t timer);
static void timer_remove_inactive(esp_timer_handle_t timer);
#endif // WITH_PROFILING

__attribute__((unused)) static const char* TAG = "esp_timer";

// lists of currently armed timers for two dispatch methods: ISR and TASK
static LIST_HEAD(esp_timer_list, esp_timer) s_timers[ESP_TIMER_MAX] = {
    [0 ... (ESP_TIMER_MAX - 1)] = LIST_HEAD_INITIALIZER(s_timers)
};
#if WITH_PROFILING
// lists of unarmed timers for two dispatch methods: ISR and TASK,
// used only to be able to dump statistics about all the timers
static LIST_HEAD(esp_inactive_timer_list, esp_timer) s_inactive_timers[ESP_TIMER_MAX] = {
    [0 ... (ESP_TIMER_MAX - 1)] = LIST_HEAD_INITIALIZER(s_timers)
};
#endif
// task used to dispatch timer callbacks
static TaskHandle_t s_timer_task;

// lock protecting s_timers, s_inactive_timers
static portMUX_TYPE s_timer_lock[ESP_TIMER_MAX] = {
    [0 ... (ESP_TIMER_MAX - 1)] = portMUX_INITIALIZER_UNLOCKED
};

#ifdef CONFIG_ESP_TIMER_SUPPORTS_ISR_DISPATCH_METHOD
// For ISR dispatch method, a callback function of the timer may require a context switch
static volatile BaseType_t s_isr_dispatch_need_yield = pdFALSE;
#endif // CONFIG_ESP_TIMER_SUPPORTS_ISR_DISPATCH_METHOD

esp_err_t esp_timer_create(const esp_timer_create_args_t* args,
                           esp_timer_handle_t* out_handle)
{
    if (!is_initialized()) {
        return ESP_ERR_INVALID_STATE;
    }
    if (args == NULL || args->callback == NULL || out_handle == NULL ||
        args->dispatch_method < 0 || args->dispatch_method >= ESP_TIMER_MAX) {
        return ESP_ERR_INVALID_ARG;
    }
    esp_timer_handle_t result = (esp_timer_handle_t) heap_caps_calloc(1, sizeof(*result), MALLOC_CAP_8BIT | MALLOC_CAP_INTERNAL);
    if (result == NULL) {
        return ESP_ERR_NO_MEM;
    }
    result->callback = args->callback;
    result->arg = args->arg;
    result->flags = (args->dispatch_method ? FL_ISR_DISPATCH_METHOD : 0) |
                    (args->skip_unhandled_events ? FL_SKIP_UNHANDLED_EVENTS : 0);
#if WITH_PROFILING
    result->name = args->name;
    esp_timer_dispatch_t dispatch_method = result->flags & FL_ISR_DISPATCH_METHOD;
    timer_list_lock(dispatch_method);
    timer_insert_inactive(result);
    timer_list_unlock(dispatch_method);
#endif
    *out_handle = result;
    return ESP_OK;
}

esp_err_t esp_timer_restart(esp_timer_handle_t timer, uint64_t timeout_us)
{
    esp_err_t ret = ESP_OK;

    if (timer == NULL) {
        return ESP_ERR_INVALID_ARG;
    }

    if (!is_initialized() || !timer_armed(timer)) {
        return ESP_ERR_INVALID_STATE;
    }

    esp_timer_dispatch_t dispatch_method = timer->flags & FL_ISR_DISPATCH_METHOD;
    timer_list_lock(dispatch_method);

    const int64_t now = esp_timer_impl_get_time();
    const uint64_t period = timer->period;

    /* We need to remove the timer to the list of timers and reinsert it at
     * the right position. In fact, the timers are sorted by their alarm value
     * (earliest first) */
    ret = timer_remove(timer);

    if (ret == ESP_OK) {
        /* Two cases here:
         * - if the alarm was a periodic one, i.e. `period` is not 0, the given timeout_us becomes the new period
         * - if the alarm was a one-shot one, i.e. `period` is 0, it remains non-periodic. */
        if (period != 0) {
            /* Remove function got rid of the alarm and period fields, restore them */
            const uint64_t new_period = MAX(timeout_us, esp_timer_impl_get_min_period_us());
            timer->alarm = now + new_period;
            timer->period = new_period;
        } else {
            /* The new one-shot alarm shall be triggered timeout_us after the current time */
            timer->alarm = now + timeout_us;
            timer->period = 0;
        }
        ret = timer_insert(timer, false);
    }

    timer_list_unlock(dispatch_method);

    return ret;
}

esp_err_t IRAM_ATTR esp_timer_start_once(esp_timer_handle_t timer, uint64_t timeout_us)
{
    if (timer == NULL) {
        return ESP_ERR_INVALID_ARG;
    }
    if (!is_initialized() || timer_armed(timer)) {
        return ESP_ERR_INVALID_STATE;
    }
    int64_t alarm = esp_timer_get_time() + timeout_us;
    esp_timer_dispatch_t dispatch_method = timer->flags & FL_ISR_DISPATCH_METHOD;
    timer_list_lock(dispatch_method);
    timer->alarm = alarm;
    timer->period = 0;
#if WITH_PROFILING
    timer->times_armed++;
#endif
    esp_err_t err = timer_insert(timer, false);
    timer_list_unlock(dispatch_method);
    return err;
}

esp_err_t IRAM_ATTR esp_timer_start_periodic(esp_timer_handle_t timer, uint64_t period_us)
{
    if (timer == NULL) {
        return ESP_ERR_INVALID_ARG;
    }
    if (!is_initialized() || timer_armed(timer)) {
        return ESP_ERR_INVALID_STATE;
    }
    period_us = MAX(period_us, esp_timer_impl_get_min_period_us());
    int64_t alarm = esp_timer_get_time() + period_us;
    esp_timer_dispatch_t dispatch_method = timer->flags & FL_ISR_DISPATCH_METHOD;
    timer_list_lock(dispatch_method);
    timer->alarm = alarm;
    timer->period = period_us;
#if WITH_PROFILING
    timer->times_armed++;
    timer->times_skipped = 0;
#endif
    esp_err_t err = timer_insert(timer, false);
    timer_list_unlock(dispatch_method);
    return err;
}

esp_err_t IRAM_ATTR esp_timer_stop(esp_timer_handle_t timer)
{
    if (timer == NULL) {
        return ESP_ERR_INVALID_ARG;
    }
    if (!is_initialized() || !timer_armed(timer)) {
        return ESP_ERR_INVALID_STATE;
    }
    return timer_remove(timer);
}

esp_err_t esp_timer_delete(esp_timer_handle_t timer)
{
    if (timer == NULL) {
        return ESP_ERR_INVALID_ARG;
    }
    if (timer_armed(timer)) {
        return ESP_ERR_INVALID_STATE;
    }
    // A case for the timer with ESP_TIMER_ISR:
    // This ISR timer was removed from the ISR list in esp_timer_stop() or in timer_process_alarm() -> LIST_REMOVE(it, list_entry)
    // and here this timer will be added to another the TASK list, see below.
    // We do this because we want to free memory of the timer in a task context instead of an isr context.
    int64_t alarm = esp_timer_get_time();
    timer_list_lock(ESP_TIMER_TASK);
    timer->flags &= ~FL_ISR_DISPATCH_METHOD;
    timer->event_id = EVENT_ID_DELETE_TIMER;
    timer->alarm = alarm;
    timer->period = 0;
    timer_insert(timer, false);
    timer_list_unlock(ESP_TIMER_TASK);
    return ESP_OK;
}

static IRAM_ATTR esp_err_t timer_insert(esp_timer_handle_t timer, bool without_update_alarm)
{
#if WITH_PROFILING
    timer_remove_inactive(timer);
#endif
    esp_timer_handle_t it, last = NULL;
    esp_timer_dispatch_t dispatch_method = timer->flags & FL_ISR_DISPATCH_METHOD;
    if (LIST_FIRST(&s_timers[dispatch_method]) == NULL) {
        LIST_INSERT_HEAD(&s_timers[dispatch_method], timer, list_entry);
    } else {
        LIST_FOREACH(it, &s_timers[dispatch_method], list_entry) {
            if (timer->alarm < it->alarm) {
                LIST_INSERT_BEFORE(it, timer, list_entry);
                break;
            }
            last = it;
        }
        if (it == NULL) {
            assert(last);
            LIST_INSERT_AFTER(last, timer, list_entry);
        }
    }
    if (without_update_alarm == false && timer == LIST_FIRST(&s_timers[dispatch_method])) {
        esp_timer_impl_set_alarm_id(timer->alarm, dispatch_method);
    }
    return ESP_OK;
}

static IRAM_ATTR esp_err_t timer_remove(esp_timer_handle_t timer)
{
    esp_timer_dispatch_t dispatch_method = timer->flags & FL_ISR_DISPATCH_METHOD;
    timer_list_lock(dispatch_method);
    esp_timer_handle_t first_timer = LIST_FIRST(&s_timers[dispatch_method]);
    LIST_REMOVE(timer, list_entry);
    timer->alarm = 0;
    timer->period = 0;
    if (timer == first_timer) { // if this timer was the first in the list.
        uint64_t next_timestamp = UINT64_MAX;
        first_timer = LIST_FIRST(&s_timers[dispatch_method]);
        if (first_timer) { // if after removing the timer from the list, this list is not empty.
            next_timestamp = first_timer->alarm;
        }
        esp_timer_impl_set_alarm_id(next_timestamp, dispatch_method);
    }
#if WITH_PROFILING
    timer_insert_inactive(timer);
#endif
    timer_list_unlock(dispatch_method);
    return ESP_OK;
}

#if WITH_PROFILING

static IRAM_ATTR void timer_insert_inactive(esp_timer_handle_t timer)
{
    /* May be locked or not, depending on where this is called from.
     * Lock recursively.
     */
    esp_timer_dispatch_t dispatch_method = timer->flags & FL_ISR_DISPATCH_METHOD;
    esp_timer_handle_t head = LIST_FIRST(&s_inactive_timers[dispatch_method]);
    if (head == NULL) {
        LIST_INSERT_HEAD(&s_inactive_timers[dispatch_method], timer, list_entry);
    } else {
        /* Insert as head element as this is the fastest thing to do.
         * Removal is O(1) anyway.
         */
        LIST_INSERT_BEFORE(head, timer, list_entry);
    }
}

static IRAM_ATTR void timer_remove_inactive(esp_timer_handle_t timer)
{
    LIST_REMOVE(timer, list_entry);
}

#endif // WITH_PROFILING

static IRAM_ATTR bool timer_armed(esp_timer_handle_t timer)
{
    return timer->alarm > 0;
}

static IRAM_ATTR void timer_list_lock(esp_timer_dispatch_t timer_type)
{
    portENTER_CRITICAL_SAFE(&s_timer_lock[timer_type]);
}

static IRAM_ATTR void timer_list_unlock(esp_timer_dispatch_t timer_type)
{
    portEXIT_CRITICAL_SAFE(&s_timer_lock[timer_type]);
}

#ifdef CONFIG_ESP_TIMER_SUPPORTS_ISR_DISPATCH_METHOD
static IRAM_ATTR bool timer_process_alarm(esp_timer_dispatch_t dispatch_method)
#else
static bool timer_process_alarm(esp_timer_dispatch_t dispatch_method)
#endif
{
    timer_list_lock(dispatch_method);
    bool processed = false;
    esp_timer_handle_t it;
    while (1) {
        it = LIST_FIRST(&s_timers[dispatch_method]);
        int64_t now = esp_timer_impl_get_time();
        if (it == NULL || it->alarm > now) {
            break;
        }
        processed = true;
        LIST_REMOVE(it, list_entry);
        if (it->event_id == EVENT_ID_DELETE_TIMER) {
            // It is handled only by ESP_TIMER_TASK (see esp_timer_delete()).
            // All the ESP_TIMER_ISR timers which should be deleted are moved by esp_timer_delete() to the ESP_TIMER_TASK list.
            // We want to free memory of the timer in a task context instead of an isr context.
            free(it);
            it = NULL;
        } else {
            if (it->period > 0) {
                int skipped = (now - it->alarm) / it->period;
                if ((it->flags & FL_SKIP_UNHANDLED_EVENTS) && (skipped > 1)) {
                    it->alarm = now + it->period;
#if WITH_PROFILING
                    it->times_skipped += skipped;
#endif
                } else {
                    it->alarm += it->period;
                }
                timer_insert(it, true);
            } else {
                it->alarm = 0;
#if WITH_PROFILING
                timer_insert_inactive(it);
#endif
            }
#if WITH_PROFILING
            uint64_t callback_start = now;
#endif
            esp_timer_cb_t callback = it->callback;
            void* arg = it->arg;
            timer_list_unlock(dispatch_method);
            (*callback)(arg);
            timer_list_lock(dispatch_method);
#if WITH_PROFILING
            it->times_triggered++;
            it->total_callback_run_time += esp_timer_impl_get_time() - callback_start;
#endif
        }
    } // while(1)
    if (it) {
        if (dispatch_method == ESP_TIMER_TASK || (dispatch_method != ESP_TIMER_TASK && processed == true)) {
            esp_timer_impl_set_alarm_id(it->alarm, dispatch_method);
        }
    } else {
        if (processed) {
            esp_timer_impl_set_alarm_id(UINT64_MAX, dispatch_method);
        }
    }
    timer_list_unlock(dispatch_method);
    return processed;
}

static void timer_task(void* arg)
{
    while (true){
        ulTaskNotifyTake(pdTRUE, portMAX_DELAY);
        // all deferred events are processed at a time
        timer_process_alarm(ESP_TIMER_TASK);
    }
}

#ifdef CONFIG_ESP_TIMER_SUPPORTS_ISR_DISPATCH_METHOD
IRAM_ATTR void esp_timer_isr_dispatch_need_yield(void)
{
    assert(xPortInIsrContext());
    s_isr_dispatch_need_yield = pdTRUE;
}
#endif

static void IRAM_ATTR timer_alarm_handler(void* arg)
{
    BaseType_t xHigherPriorityTaskWoken = pdFALSE;
    bool isr_timers_processed = false;

#ifdef CONFIG_ESP_TIMER_SUPPORTS_ISR_DISPATCH_METHOD
    // process timers with ISR dispatch method
    isr_timers_processed = timer_process_alarm(ESP_TIMER_ISR);
    xHigherPriorityTaskWoken = s_isr_dispatch_need_yield;
    s_isr_dispatch_need_yield = pdFALSE;
#endif

    if (isr_timers_processed == false) {
        vTaskNotifyGiveFromISR(s_timer_task, &xHigherPriorityTaskWoken);
    }
    if (xHigherPriorityTaskWoken == pdTRUE) {
        portYIELD_FROM_ISR();
    }
}

static IRAM_ATTR inline bool is_initialized(void)
{
    return s_timer_task != NULL;
}

esp_err_t esp_timer_early_init(void)
{
    esp_timer_impl_early_init();
#if CONFIG_ESP_TIME_FUNCS_USE_ESP_TIMER
    esp_timer_impl_init_system_time();
#endif
    return ESP_OK;
}

static esp_err_t init_timer_task(void)
{
    esp_err_t err = ESP_OK;
    if (is_initialized()) {
        ESP_EARLY_LOGE(TAG, "Task is already initialized");
        err = ESP_ERR_INVALID_STATE;
    } else {
        int ret = xTaskCreatePinnedToCore(
                    &timer_task, "esp_timer",
                    ESP_TASK_TIMER_STACK, NULL, ESP_TASK_TIMER_PRIO,
                    &s_timer_task, CONFIG_ESP_TIMER_TASK_AFFINITY);
        if (ret != pdPASS) {
            ESP_EARLY_LOGE(TAG, "Not enough memory to create timer task");
            err = ESP_ERR_NO_MEM;
        }
    }
    return err;
}

static void deinit_timer_task(void)
{
    if (s_timer_task) {
        vTaskDelete(s_timer_task);
        s_timer_task = NULL;
    }
}

esp_err_t esp_timer_init(void)
{
    esp_err_t err = ESP_OK;
#ifndef CONFIG_ESP_TIMER_ISR_AFFINITY_NO_AFFINITY
    err = init_timer_task();
#else
    /* This function will be run on all cores if CONFIG_ESP_TIMER_ISR_AFFINITY_NO_AFFINITY is enabled,
     * We do it that way because we need to allocate the timer ISR on MULTIPLE cores.
     * timer task will be created by CPU0.
     */
    if (xPortGetCoreID() == 0) {
        err = init_timer_task();
    }
#endif // CONFIG_ESP_TIMER_ISR_AFFINITY_NO_AFFINITY
    if (err == ESP_OK) {
        err = esp_timer_impl_init(&timer_alarm_handler);
        if (err != ESP_OK) {
            ESP_EARLY_LOGE(TAG, "ISR init failed");
            deinit_timer_task();
        }
    }
    return err;
}

ESP_SYSTEM_INIT_FN(esp_timer_startup_init, CONFIG_ESP_TIMER_ISR_AFFINITY, 100)
{
    return esp_timer_init();
}

esp_err_t esp_timer_deinit(void)
{
    if (!is_initialized()) {
        return ESP_ERR_INVALID_STATE;
    }

    /* Check if there are any active timers */
    for (esp_timer_dispatch_t dispatch_method = ESP_TIMER_TASK; dispatch_method < ESP_TIMER_MAX; ++dispatch_method) {
        if (!LIST_EMPTY(&s_timers[dispatch_method])) {
            return ESP_ERR_INVALID_STATE;
        }
    }

    /* We can only check if there are any timers which are not deleted if
     * profiling is enabled.
     */
#if WITH_PROFILING
    for (esp_timer_dispatch_t dispatch_method = ESP_TIMER_TASK; dispatch_method < ESP_TIMER_MAX; ++dispatch_method) {
        if (!LIST_EMPTY(&s_inactive_timers[dispatch_method])) {
            return ESP_ERR_INVALID_STATE;
        }
    }
#endif

    esp_timer_impl_deinit();
    deinit_timer_task();
    return ESP_OK;
}

static void print_timer_info(esp_timer_handle_t t, char** dst, size_t* dst_size)
{
#if WITH_PROFILING
    size_t cb;
    // name is optional, might be missed.
    if (t->name) {
        cb = snprintf(*dst, *dst_size, "%-20.20s  ", t->name);
    } else {
        cb = snprintf(*dst, *dst_size, "timer@%-10p  ", t);
    }
    cb += snprintf(*dst + cb, *dst_size + cb, "%-10lld  %-12lld  %-12d  %-12d  %-12d  %-12lld\n",
                    (uint64_t)t->period, t->alarm, t->times_armed,
                    t->times_triggered, t->times_skipped, t->total_callback_run_time);
    /* keep this in sync with the format string, used in esp_timer_dump */
#define TIMER_INFO_LINE_LEN 90
#else
    size_t cb = snprintf(*dst, *dst_size, "timer@%-14p  %-10lld  %-12lld\n", t, (uint64_t)t->period, t->alarm);
#define TIMER_INFO_LINE_LEN 46
#endif
    *dst += cb;
    *dst_size -= cb;
}


esp_err_t esp_timer_dump(FILE* stream)
{
    /* Since timer lock is a critical section, we don't want to print directly
     * to stdout, since that may cause a deadlock if stdout is interrupt-driven
     * (via the UART driver). Allocate sufficiently large chunk of memory first,
     * print to it, then dump this memory to stdout.
     */

    esp_timer_handle_t it;

    /* First count the number of timers */
    size_t timer_count = 0;
    for (esp_timer_dispatch_t dispatch_method = ESP_TIMER_TASK; dispatch_method < ESP_TIMER_MAX; ++dispatch_method) {
        timer_list_lock(dispatch_method);
        LIST_FOREACH(it, &s_timers[dispatch_method], list_entry) {
            ++timer_count;
        }
#if WITH_PROFILING
        LIST_FOREACH(it, &s_inactive_timers[dispatch_method], list_entry) {
            ++timer_count;
        }
#endif
        timer_list_unlock(dispatch_method);
    }

    /* Allocate the memory for this number of timers. Since we have unlocked,
     * we may find that there are more timers. There's no bulletproof solution
     * for this (can't allocate from a critical section), but we allocate
     * slightly more and the output will be truncated if that is not enough.
     */
    size_t buf_size = TIMER_INFO_LINE_LEN * (timer_count + 3);
    char* print_buf = calloc(1, buf_size + 1);
    if (print_buf == NULL) {
        return ESP_ERR_NO_MEM;
    }

    /* Print to the buffer */
    char* pos = print_buf;
    for (esp_timer_dispatch_t dispatch_method = ESP_TIMER_TASK; dispatch_method < ESP_TIMER_MAX; ++dispatch_method) {
        timer_list_lock(dispatch_method);
        LIST_FOREACH(it, &s_timers[dispatch_method], list_entry) {
            print_timer_info(it, &pos, &buf_size);
        }
#if WITH_PROFILING
        LIST_FOREACH(it, &s_inactive_timers[dispatch_method], list_entry) {
            print_timer_info(it, &pos, &buf_size);
        }
#endif
        timer_list_unlock(dispatch_method);
    }

    if (stream != NULL) {
        fprintf(stream, "Timer stats:\n");
#if WITH_PROFILING
        fprintf(stream, "%-20s  %-10s  %-12s  %-12s  %-12s  %-12s  %-12s\n",
                "Name", "Period", "Alarm", "Times_armed", "Times_trigg", "Times_skip", "Cb_exec_time");
#else
        fprintf(stream, "%-20s  %-10s  %-12s\n", "Name", "Period", "Alarm");
#endif

        /* Print the buffer */
        fputs(print_buf, stream);
    }

    free(print_buf);
    return ESP_OK;
}

int64_t IRAM_ATTR esp_timer_get_next_alarm(void)
{
    int64_t next_alarm = INT64_MAX;
    for (esp_timer_dispatch_t dispatch_method = ESP_TIMER_TASK; dispatch_method < ESP_TIMER_MAX; ++dispatch_method) {
        timer_list_lock(dispatch_method);
        esp_timer_handle_t it = LIST_FIRST(&s_timers[dispatch_method]);
        if (it) {
            if (next_alarm > it->alarm) {
                next_alarm = it->alarm;
            }
        }
        timer_list_unlock(dispatch_method);
    }
    return next_alarm;
}

int64_t IRAM_ATTR esp_timer_get_next_alarm_for_wake_up(void)
{
    int64_t next_alarm = INT64_MAX;
    for (esp_timer_dispatch_t dispatch_method = ESP_TIMER_TASK; dispatch_method < ESP_TIMER_MAX; ++dispatch_method) {
        timer_list_lock(dispatch_method);
        esp_timer_handle_t it = NULL;
        LIST_FOREACH(it, &s_timers[dispatch_method], list_entry) {
            // timers with the SKIP_UNHANDLED_EVENTS flag do not want to wake up CPU from a sleep mode.
            if ((it->flags & FL_SKIP_UNHANDLED_EVENTS) == 0) {
                if (next_alarm > it->alarm) {
                    next_alarm = it->alarm;
                }
                break;
            }
        }
        timer_list_unlock(dispatch_method);
    }
    return next_alarm;
}

esp_err_t IRAM_ATTR esp_timer_get_period(esp_timer_handle_t timer, uint64_t *period)
{
    if (timer == NULL || period == NULL) {
        return ESP_ERR_INVALID_ARG;
    }

    esp_timer_dispatch_t dispatch_method = timer->flags & FL_ISR_DISPATCH_METHOD;

    timer_list_lock(dispatch_method);
    *period = timer->period;
    timer_list_unlock(dispatch_method);

    return ESP_OK;
}

esp_err_t IRAM_ATTR esp_timer_get_expiry_time(esp_timer_handle_t timer, uint64_t *expiry)
{
    if (timer == NULL || expiry == NULL) {
        return ESP_ERR_INVALID_ARG;
    }

    if (timer->period > 0) {
        /* Return error for periodic timers */
        return ESP_ERR_NOT_SUPPORTED;
    }

    esp_timer_dispatch_t dispatch_method = timer->flags & FL_ISR_DISPATCH_METHOD;

    timer_list_lock(dispatch_method);
    *expiry = timer->alarm;
    timer_list_unlock(dispatch_method);

    return ESP_OK;
}

bool esp_timer_is_active(esp_timer_handle_t timer)
{
    return timer_armed(timer);
}