background tasks: Add, use port_wake_main_task

Some ports need an extra operation to ensure that the main task is
awoken so that a queued background task will execute during an ongoing
light sleep.

This removes the need to enable supervisor ticks while I2SOut is operating.

Closes: #3952

ports/esp32s2/common-hal/audiobusio/I2SOut.c

@@ -63,8 +63,6 @@ void common_hal_audiobusio_i2sout_construct(audiobusio_i2sout_obj_t* self,
     self->bit_clock = bit_clock;
     self->word_select = word_select;
     self->data = data;
-
-    supervisor_enable_tick();
 }
 
 bool common_hal_audiobusio_i2sout_deinited(audiobusio_i2sout_obj_t* self) {
@@ -95,8 +93,6 @@ void common_hal_audiobusio_i2sout_deinit(audiobusio_i2sout_obj_t* self) {
         port_i2s_reset_instance(self->peripheral.instance);
     }
     self->peripheral.instance = -1;
-
-    supervisor_disable_tick();
 }
 
 void common_hal_audiobusio_i2sout_play(audiobusio_i2sout_obj_t* self,

ports/esp32s2/supervisor/port.c

@@ -111,6 +111,12 @@ safe_mode_t port_init(void) {
     heap = NULL;
     never_reset_module_internal_pins();
 
+    #if defined(DEBUG)
+    // debug UART
+    common_hal_never_reset_pin(&pin_GPIO43);
+    common_hal_never_reset_pin(&pin_GPIO44);
+    #endif
+
     #if defined(DEBUG) || defined(ENABLE_JTAG)
     // JTAG
     common_hal_never_reset_pin(&pin_GPIO39);
@@ -291,10 +297,14 @@ void port_disable_tick(void) {
     esp_timer_stop(_tick_timer);
 }
 
-void sleep_timer_cb(void* arg) {
+void port_wake_main_task() {
     xTaskNotifyGive(circuitpython_task);
 }
 
+void sleep_timer_cb(void* arg) {
+    port_wake_main_task();
+}
+
 void port_interrupt_after_ticks(uint32_t ticks) {
     uint64_t timeout_us = ticks * 1000000ull / 1024;
     if (esp_timer_start_once(_sleep_timer, timeout_us) != ESP_OK) {

supervisor/port.h

@@ -99,4 +99,8 @@ void port_background_task(void);
 void port_start_background_task(void);
 void port_finish_background_task(void);
 
+// Some ports need special handling to wake the main task from an interrupt
+// context or other task.  The port must implement the necessary code in this
+// function.  A default weak implementation is provided that does nothing.
+void port_wake_main_task(void);
 #endif  // MICROPY_INCLUDED_SUPERVISOR_PORT_H

supervisor/shared/background_callback.c

@@ -38,6 +38,8 @@ STATIC volatile background_callback_t *callback_head, *callback_tail;
 #define CALLBACK_CRITICAL_BEGIN (common_hal_mcu_disable_interrupts())
 #define CALLBACK_CRITICAL_END (common_hal_mcu_enable_interrupts())
 
+MP_WEAK void port_wake_main_task(void) {}
+
 void background_callback_add_core(background_callback_t *cb) {
     CALLBACK_CRITICAL_BEGIN;
     if (cb->prev || callback_head == cb) {
@@ -55,6 +57,8 @@ void background_callback_add_core(background_callback_t *cb) {
     }
     callback_tail = cb;
     CALLBACK_CRITICAL_END;
+
+    port_wake_main_task();
 }
 
 void background_callback_add(background_callback_t *cb, background_callback_fun fun, void *data) {