pm: fix entering light sleep in single core mode

Tickless idle/light sleep procedure had a bug in single core mode.
Consider the flow of events:
1. Idle task runs and calls vApplicationIdleHook
2. This calls esp_vApplicationIdleHook, which calls esp_pm_impl_idle_hook, and pm lock for RTOS on the current core is released.
3. Then esp_vApplicationIdleHook calls esp_pm_impl_waiti, which checks that s_entered_light_sleep[core_id]==false and goes into waiti state.
4. Some interrupt happens, calls esp_pm_impl_isr_hook, which takes pm lock for RTOS. PM state goes back to CPU_FREQ_MAX.
5. Once the interrupt is over, vApplicationIdleHook returns, and Idle task continues to run, finally reaching the call to vApplicationSleep.
6. vApplicationSleep does not enter light sleep, because esp_pm_impl_isr_hook has already changed PM state from IDLE to CPU_FREQ_MAX.

This didn’t happen in dual core mode, because waiti state of one CPU was interrupted by CCOMPARE update interrupt from the other CPU, in which case PM lock for FreeRTOS was not taken.

Fix by inverting the meaning of the flag (for convenience) and only setting it to true when vApplicationSleep actually fails to enter light sleep.

components/esp32/pm_esp32.c

@@ -81,11 +81,11 @@ static uint32_t s_ccount_div;
 static uint32_t s_ccount_mul;
 
 #if CONFIG_FREERTOS_USE_TICKLESS_IDLE
-/* Indicates if light sleep entry was successful for given CPU.
+/* Indicates if light sleep entry was skipped in vApplicationSleep for given CPU.
  * This in turn gets used in IDLE hook to decide if `waiti` needs
  * to be invoked or not.
  */
-static bool s_entered_light_sleep[portNUM_PROCESSORS];
+static bool s_skipped_light_sleep[portNUM_PROCESSORS];
 #endif // CONFIG_FREERTOS_USE_TICKLESS_IDLE
 
 /* Indicates to the ISR hook that CCOMPARE needs to be updated on the given CPU.
@@ -465,10 +465,14 @@ void esp_pm_impl_waiti()
 {
 #if CONFIG_FREERTOS_USE_TICKLESS_IDLE
     int core_id = xPortGetCoreID();
-    if (!s_entered_light_sleep[core_id]) {
+    if (s_skipped_light_sleep[core_id]) {
         asm("waiti 0");
-    } else {
-        s_entered_light_sleep[core_id] = false;
+        /* Interrupt took the CPU out of waiti and s_rtos_lock_handle[core_id]
+         * is now taken. However since we are back to idle task, we can release
+         * the lock so that vApplicationSleep can attempt to enter light sleep.
+         */
+        esp_pm_impl_idle_hook();
+        s_skipped_light_sleep[core_id] = false;
     }
 #else
     asm("waiti 0");
@@ -480,7 +484,11 @@ void esp_pm_impl_waiti()
 void IRAM_ATTR vApplicationSleep( TickType_t xExpectedIdleTime )
 {
     portENTER_CRITICAL(&s_switch_lock);
-    if (s_mode == PM_MODE_LIGHT_SLEEP && !s_is_switching) {
+    int core_id = xPortGetCoreID();
+    if (s_mode != PM_MODE_LIGHT_SLEEP || s_is_switching) {
+        s_skipped_light_sleep[core_id] = true;
+    } else {
+        s_skipped_light_sleep[core_id] = false;
         /* Calculate how much we can sleep */
         int64_t next_esp_timer_alarm = esp_timer_get_next_alarm();
         int64_t now = esp_timer_get_time();
@@ -494,7 +502,6 @@ void IRAM_ATTR vApplicationSleep( TickType_t xExpectedIdleTime )
             esp_sleep_pd_config(ESP_PD_DOMAIN_RTC_PERIPH, ESP_PD_OPTION_ON);
 #endif
             /* Enter sleep */
-            int core_id = xPortGetCoreID();
             ESP_PM_TRACE_ENTER(SLEEP, core_id);
             int64_t sleep_start = esp_timer_get_time();
             esp_light_sleep_start();
@@ -516,7 +523,6 @@ void IRAM_ATTR vApplicationSleep( TickType_t xExpectedIdleTime )
                     ;
                 }
             }
-            s_entered_light_sleep[core_id] = true;
         }
     }
     portEXIT_CRITICAL(&s_switch_lock);