fix(gptimer): race condition between start and stop

Merges https://github.com/espressif/esp-idf/pull/14767

components/driver/gptimer.c

@@ -377,14 +377,16 @@ esp_err_t gptimer_start(gptimer_handle_t timer)
         // the register used by the following LL functions are shared with other API,
         // which is possible to run along with this function, so we need to protect
         portENTER_CRITICAL_SAFE(&timer->spinlock);
-        timer_ll_enable_counter(timer->hal.dev, timer->timer_id, true);
         timer_ll_enable_alarm(timer->hal.dev, timer->timer_id, timer->flags.alarm_en);
+        // Note here, if the alarm target is set very close to the current counter value
+        // an alarm interrupt may be triggered very quickly after we start the timer
+        timer_ll_enable_counter(timer->hal.dev, timer->timer_id, true);
+        atomic_store(&timer->fsm, GPTIMER_FSM_RUN);
         portEXIT_CRITICAL_SAFE(&timer->spinlock);
     } else {
-        ESP_RETURN_ON_FALSE_ISR(false, ESP_ERR_INVALID_STATE, TAG, "timer is not enabled yet");
+        ESP_RETURN_ON_FALSE_ISR(false, ESP_ERR_INVALID_STATE, TAG, "timer is not ready for a new start");
     }
 
-    atomic_store(&timer->fsm, GPTIMER_FSM_RUN);
     return ESP_OK;
 }
 
@@ -398,12 +400,12 @@ esp_err_t gptimer_stop(gptimer_handle_t timer)
         portENTER_CRITICAL_SAFE(&timer->spinlock);
         timer_ll_enable_counter(timer->hal.dev, timer->timer_id, false);
         timer_ll_enable_alarm(timer->hal.dev, timer->timer_id, false);
+        atomic_store(&timer->fsm, GPTIMER_FSM_ENABLE);
         portEXIT_CRITICAL_SAFE(&timer->spinlock);
     } else {
         ESP_RETURN_ON_FALSE_ISR(false, ESP_ERR_INVALID_STATE, TAG, "timer is not running");
     }
 
-    atomic_store(&timer->fsm, GPTIMER_FSM_ENABLE);
     return ESP_OK;
 }
 

docs/en/api-reference/peripherals/gptimer.rst

@@ -84,7 +84,7 @@ Set up Alarm Action
 
 For most of the use cases of GPTimer, you should set up the alarm action before starting the timer, except for the simple wall-clock scenario, where a free running timer is enough. To set up the alarm action, you should configure several members of :cpp:type:`gptimer_alarm_config_t` based on how you make use of the alarm event:
 
--  :cpp:member:`gptimer_alarm_config_t::alarm_count` sets the target count value that will trigger the alarm event. You should also take the counting direction into consideration when setting the alarm value. Specially, :cpp:member:`gptimer_alarm_config_t::alarm_count` and :cpp:member:`gptimer_alarm_config_t::reload_count` cannot be set to the same value when :cpp:member:`gptimer_alarm_config_t::auto_reload_on_alarm` is true, as keeping reload with a target alarm count is meaningless.
+-  :cpp:member:`gptimer_alarm_config_t::alarm_count` sets the target count value that will trigger the alarm event. You should also take the counting direction into consideration when setting the alarm value. Specially, :cpp:member:`gptimer_alarm_config_t::alarm_count` and :cpp:member:`gptimer_alarm_config_t::reload_count` cannot be set to the same value when :cpp:member:`gptimer_alarm_config_t::auto_reload_on_alarm` is true, as keeping reload with a target alarm count is meaningless. Please also note, because of the interrupt latency, it's not recommended to set the alarm period smaller than 5 us.
 
 -  :cpp:member:`gptimer_alarm_config_t::reload_count` sets the count value to be reloaded when the alarm event happens. This configuration only takes effect when :cpp:member:`gptimer_alarm_config_t::auto_reload_on_alarm` is set to true.
 

docs/zh_CN/api-reference/peripherals/gptimer.rst

@@ -84,7 +84,7 @@
 
 对于大多数通用定时器使用场景而言，应在启动定时器之前设置警报动作，但不包括简单的挂钟场景，该场景仅需自由运行的定时器。设置警报动作，需要根据如何使用警报事件来配置 :cpp:type:`gptimer_alarm_config_t` 的不同参数：
 
--  :cpp:member:`gptimer_alarm_config_t::alarm_count` 设置触发警报事件的目标计数值。设置警报值时还需考虑计数方向。尤其是当 :cpp:member:`gptimer_alarm_config_t::auto_reload_on_alarm` 为 true 时，:cpp:member:`gptimer_alarm_config_t::alarm_count` 和 :cpp:member:`gptimer_alarm_config_t::reload_count` 不能设置为相同的值，因为警报值和重载值相同时没有意义。
+-  :cpp:member:`gptimer_alarm_config_t::alarm_count` 设置触发警报事件的目标计数值。设置警报值时还需考虑计数方向。当 :cpp:member:`gptimer_alarm_config_t::auto_reload_on_alarm` 为 ``true`` 时，:cpp:member:`gptimer_alarm_config_t::alarm_count` 和 :cpp:member:`gptimer_alarm_config_t::reload_count` 不能设置为相同的值，因为警报值和重载值相同时没有意义。请注意，由于中断延迟，不建议将警报周期设置为小于 5 微秒。
 
 -  :cpp:member:`gptimer_alarm_config_t::reload_count` 代表警报事件发生时要重载的计数值。此配置仅在 :cpp:member:`gptimer_alarm_config_t::auto_reload_on_alarm` 设置为 true 时生效。