cpu/esp_common: stop WiFi interface before sleep/reboot

The WiFi interface should be stopped before reboot or sleep. But stopping the WiFi interface disconnects an existing connection. Usually, esp_wifi_netdev tries to reconnect on an disconnect event. However, trying reconnect with a stopped WiFi interface may lead to a crash. Therefore, the stop event has to be handled.

cpu/esp32/periph/pm.c

@@ -34,6 +34,23 @@
 #include "soc/rtc.h"
 #include "soc/rtc_cntl_reg.h"
 
+static inline esp_sleep_wakeup_cause_t pm_get_wakeup_cause(void)
+{
+    return esp_sleep_get_wakeup_cause();
+}
+
+/* function that is required by pm_set if esp_now and esp_wifi are not used */
+esp_err_t __attribute__((weak)) esp_wifi_start(void)
+{
+    return ESP_OK;
+}
+
+/* function that is required by pm_set if esp_now and esp_wifi are not used */
+esp_err_t __attribute__((weak)) esp_wifi_stop(void)
+{
+    return ESP_OK;
+}
+
 static inline void pm_set_lowest_normal(void)
 {
     /* reset system watchdog timer */
@@ -65,6 +82,11 @@ void pm_reboot(void)
 {
     DEBUG ("%s\n", __func__);
 
+    if (IS_USED(MODULE_ESP_WIFI_ANY)) {
+        /* stop WiFi if necessary */
+        esp_wifi_stop();
+    }
+
     /* suspend and flush UARTs */
     for (int i = 0; i < 3; ++i) {
         REG_SET_BIT(UART_FLOW_CONF_REG(i), UART_FORCE_XOFF);
@@ -121,6 +143,10 @@ void pm_set(unsigned mode)
         UNREACHABLE();
     }
     else if (mode == ESP_PM_LIGHT_SLEEP) {
+        if (IS_USED(MODULE_ESP_WIFI_ANY)) {
+            /* stop WiFi if necessary */
+            esp_wifi_stop();
+        }
 
         esp_light_sleep_start();
 
@@ -130,6 +156,10 @@ void pm_set(unsigned mode)
 
         DEBUG ("%s exit from power mode %d @%u with reason %d\n", __func__,
                mode, system_get_time(), wakeup_reason);
+
+        /* restart WiFi if necessary */
+        if (IS_USED(MODULE_ESP_WIFI_ANY) && (esp_wifi_start() != ESP_OK)) {
+            LOG_ERROR("esp_wifi_start failed\n");
         }
     }
 }

cpu/esp_common/esp-wifi/esp_wifi_netdev.c

@@ -398,6 +398,8 @@ static const char *_esp_wifi_disc_reasons [] = {
     "HANDSHAKE_TIMEOUT"            /* 204 */
 };
 
+static unsigned _esp_wifi_started = 0;
+
 /*
  * Event handler for esp system events.
  */
@@ -412,6 +414,7 @@ static esp_err_t IRAM_ATTR _esp_system_event_handler(void *ctx, system_event_t *
 
     switch(event->event_id) {
         case SYSTEM_EVENT_STA_START:
+            _esp_wifi_started = 1;
             ESP_WIFI_DEBUG("WiFi started");
             result = esp_wifi_connect();
             if (result != ESP_OK) {
@@ -420,6 +423,11 @@ static esp_err_t IRAM_ATTR _esp_system_event_handler(void *ctx, system_event_t *
             }
             break;
 
+        case SYSTEM_EVENT_STA_STOP:
+            _esp_wifi_started = 0;
+            ESP_WIFI_DEBUG("WiFi stopped");
+            break;
+
         case SYSTEM_EVENT_SCAN_DONE:
             ESP_WIFI_DEBUG("WiFi scan done");
             break;
@@ -457,19 +465,20 @@ static esp_err_t IRAM_ATTR _esp_system_event_handler(void *ctx, system_event_t *
             _esp_wifi_dev.event_disc++;
             netdev_trigger_event_isr(&_esp_wifi_dev.netdev);
 
-            /* call disconnect to reset internal state */
-            result = esp_wifi_disconnect();
-            if (result != ESP_OK) {
-                ESP_WIFI_LOG_ERROR("esp_wifi_disconnect failed with "
-                                   "return value %d", result);
-                return result;
-            }
-
-            /* try to reconnect */
-            result = esp_wifi_connect();
-            if (result != ESP_OK) {
-               ESP_WIFI_LOG_ERROR("esp_wifi_connect failed with "
-                                  "return value %d", result);
+            if (reason != WIFI_REASON_ASSOC_LEAVE) {
+                /* call disconnect to reset internal state */
+                result = esp_wifi_disconnect();
+                if (result != ESP_OK) {
+                    ESP_WIFI_LOG_ERROR("esp_wifi_disconnect failed with "
+                                       "return value %d", result);
+                    return result;
+                }
+
+                /* try to reconnect */
+                if (_esp_wifi_started && ((result = esp_wifi_connect()) != ESP_OK)) {
+                   ESP_WIFI_LOG_ERROR("esp_wifi_connect failed with "
+                                      "return value %d", result);
+                }
             }
 
             break;