nrf: disable interrupts before running wfi

In order to ensure we don't have any outstanding requests, disable
interrupts prior to issuing `WFI`.

As part of this process, check to see if there are any pending USB
requests, and only execute the `WFI` if there is no pending data.

This fixes #2855 on NRF.

Signed-off-by: Sean Cross <[email protected]>

Author: xobs

ports/nrf/supervisor/port.c

@@ -51,8 +51,11 @@
 #include "common-hal/rtc/RTC.h"
 #include "common-hal/neopixel_write/__init__.h"
 
+#include "shared-bindings/microcontroller/__init__.h"
 #include "shared-bindings/rtc/__init__.h"
 
+#include "lib/tinyusb/src/device/usbd.h"
+
 #ifdef CIRCUITPY_AUDIOBUSIO
 #include "common-hal/audiobusio/I2SOut.h"
 #endif
@@ -264,7 +267,15 @@ void port_sleep_until_interrupt(void) {
         sd_app_evt_wait();
     } else {
         // Call wait for interrupt ourselves if the SD isn't enabled.
-        __WFI();
+        // Note that `wfi` should be called with interrupts disabled,
+        // to ensure that the queue is properly drained.  The `wfi`
+        // instruction will returned as long as an interrupt is
+        // available, even though the actual handler won't fire until
+        // we re-enable interrupts.
+        common_hal_mcu_disable_interrupts();
+        if (!tud_task_event_ready())
+            __WFI();
+        common_hal_mcu_enable_interrupts();
     }
 }