From e0d0200aedd0609e9aa491014e397e95cd02691b Mon Sep 17 00:00:00 2001
From: KonstantinKondrashov <konstantin@espressif.com>
Date: Mon, 26 Oct 2020 18:07:34 +0800
Subject: [PATCH] esp_timer: Use Task Notification instead of semaphore

---
 components/esp_timer/src/esp_timer.c | 43 +++++-----------------------
 1 file changed, 7 insertions(+), 36 deletions(-)

diff --git a/components/esp_timer/src/esp_timer.c b/components/esp_timer/src/esp_timer.c
index 975bc6c3d9..e2d03f434d 100644
--- a/components/esp_timer/src/esp_timer.c
+++ b/components/esp_timer/src/esp_timer.c
@@ -22,7 +22,6 @@
 #include "esp_log.h"
 #include "freertos/FreeRTOS.h"
 #include "freertos/task.h"
-#include "freertos/semphr.h"
 #include "freertos/xtensa_api.h"
 #include "soc/spinlock.h"
 #include "esp_timer.h"
@@ -54,8 +53,6 @@
 
 #define EVENT_ID_DELETE_TIMER   0xF0DE1E1E
 
-#define TIMER_EVENT_QUEUE_SIZE      16
-
 struct esp_timer {
     uint64_t alarm;
     uint64_t period;
@@ -85,7 +82,7 @@ static void timer_insert_inactive(esp_timer_handle_t timer);
 static void timer_remove_inactive(esp_timer_handle_t timer);
 #endif // WITH_PROFILING
 
-static const char* TAG = "esp_timer";
+__attribute__((unused)) static const char* TAG = "esp_timer";
 
 // list of currently armed timers
 static LIST_HEAD(esp_timer_list, esp_timer) s_timers =
@@ -98,13 +95,6 @@ static LIST_HEAD(esp_inactive_timer_list, esp_timer) s_inactive_timers =
 #endif
 // task used to dispatch timer callbacks
 static TaskHandle_t s_timer_task;
-// counting semaphore used to notify the timer task from ISR
-static SemaphoreHandle_t s_timer_semaphore;
-
-#if CONFIG_SPIRAM_USE_MALLOC
-// memory for s_timer_semaphore
-static StaticQueue_t s_timer_semaphore_memory;
-#endif
 
 // lock protecting s_timers, s_inactive_timers
 static portMUX_TYPE s_timer_lock = portMUX_INITIALIZER_UNLOCKED;
@@ -338,20 +328,17 @@ static void timer_process_alarm(esp_timer_dispatch_t dispatch_method)
 static void timer_task(void* arg)
 {
     while (true){
-        int res = xSemaphoreTake(s_timer_semaphore, portMAX_DELAY);
-        assert(res == pdTRUE);
+        ulTaskNotifyTake(pdTRUE, portMAX_DELAY);
+        // all deferred events are processed at a time
         timer_process_alarm(ESP_TIMER_TASK);
     }
 }
 
 static void IRAM_ATTR timer_alarm_handler(void* arg)
 {
-    int need_yield;
-    if (xSemaphoreGiveFromISR(s_timer_semaphore, &need_yield) != pdPASS) {
-        ESP_EARLY_LOGD(TAG, "timer queue overflow");
-        return;
-    }
-    if (need_yield == pdTRUE) {
+    BaseType_t xHigherPriorityTaskWoken = pdFALSE;
+    vTaskNotifyGiveFromISR(s_timer_task, &xHigherPriorityTaskWoken);
+    if (xHigherPriorityTaskWoken == pdTRUE) {
         portYIELD_FROM_ISR();
     }
 }
@@ -368,17 +355,6 @@ esp_err_t esp_timer_init(void)
         return ESP_ERR_INVALID_STATE;
     }
 
-#if CONFIG_SPIRAM_USE_MALLOC
-    memset(&s_timer_semaphore_memory, 0, sizeof(StaticQueue_t));
-    s_timer_semaphore = xSemaphoreCreateCountingStatic(TIMER_EVENT_QUEUE_SIZE, 0, &s_timer_semaphore_memory);
-#else
-    s_timer_semaphore = xSemaphoreCreateCounting(TIMER_EVENT_QUEUE_SIZE, 0);
-#endif
-    if (!s_timer_semaphore) {
-        err = ESP_ERR_NO_MEM;
-        goto out;
-    }
-
     int ret = xTaskCreatePinnedToCore(&timer_task, "esp_timer",
             ESP_TASK_TIMER_STACK, NULL, ESP_TASK_TIMER_PRIO, &s_timer_task, PRO_CPU_NUM);
     if (ret != pdPASS) {
@@ -404,10 +380,7 @@ out:
         vTaskDelete(s_timer_task);
         s_timer_task = NULL;
     }
-    if (s_timer_semaphore) {
-        vSemaphoreDelete(s_timer_semaphore);
-        s_timer_semaphore = NULL;
-    }
+
     return ESP_ERR_NO_MEM;
 }
 
@@ -435,8 +408,6 @@ esp_err_t esp_timer_deinit(void)
 
     vTaskDelete(s_timer_task);
     s_timer_task = NULL;
-    vSemaphoreDelete(s_timer_semaphore);
-    s_timer_semaphore = NULL;
     return ESP_OK;
 }