Fix ESP32 system restart problems

[mikee47]

See #2500 for discussion.

[mikee47]

The cause of the WDT is because the call to esp_wifi_stop() hangs waiting on a queued message to be handled. Because the call originates from the same task which handles the message queue, a deadlock occurs. That means a regular IDF application would behave the same way if esp_wifi_stop() were called from within an event handler (not yet confirmed, but easy enough to test).

The problem can be avoided by calling esp_restart() in the context of another task:

esp_ipc_call(0, esp_ipc_func_t(esp_restart), nullptr);

The following demonstrates that the cause is indeed in esp_wifi_stop as it too succeeds:

esp_ipc_call(0, esp_ipc_func_t(esp_wifi_stop), nullptr);
esp_restart();

[slaff]

@kmihaylov can you test if this change is fixing the restart issue for you?

[kmihaylov]

Sure, just need to do some daily tasks and I'll try it in the afternoon.

[kmihaylov]

It looks like Mike's patch is working!

I'm updating Sming this way:

git fetch origin pull/2543/head:pr/2543
git checkout pr/2543
make dist-clean
make Sming-clean

Here is the code:

#include <SmingCore.h>
#include "esp_wifi.h"
#include <esp_ipc.h>

Timer testTimer;

void wifiInit() {
	esp_wifi_deinit();
	esp_netif_create_default_wifi_sta();
	wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
	ESP_ERROR_CHECK(esp_wifi_init(&cfg));
	esp_wifi_set_mode(WIFI_MODE_STA);
	wifi_config_t wifiCfg;
	esp_wifi_set_config(WIFI_IF_STA, &wifiCfg);
	esp_wifi_start();
}

void shutdown() {
	//esp_ipc_call(0, esp_ipc_func_t(esp_wifi_stop), nullptr);
	//esp_wifi_stop();
	System.restart();
}

void init()
{
	wifiInit();
	testTimer.initializeMs(5000, shutdown).startOnce();
}

This code successfully restarts the app. If I use the esp_wifi_stop() then WDT occurs. Calling it in the context of another task (alone; w/o System.restart()) doesn't trigger the WDT. Calling both esp_wifi_stop() (in another task) and then System.restart() triggers WDT, but I think this might be expected...?

[mikee47]

Note that with IDF 4.4 (#2612) IPC is no longer available for single-core SOCs, so instead the call can be handled by the esp_timer task (see #2371).

const esp_timer_create_args_t create_args = {
  .callback = esp_timer_cb_t(esp_restart),
  .dispatch_method = ESP_TIMER_TASK,
};
esp_timer_handle_t handle{nullptr};
esp_timer_create(&create_args, &handle);
esp_timer_start_once(handle, 100);