extmod/modmachine: Provide common bindings for 6 bare-metal functions.

Minor changes for consistency are:
- nrf gains: unique_id(), freq() [they do nothing]
- samd: deepsleep() now resets after calling lightsleep()
- esp32: lightsleep()/deepsleep() no longer take kw arg "sleep", instead
  it's positional to match others.  also, passing 0 here will now do a 0ms
  sleep instead of acting like nothing was passed.
  reset_cause() no longer takes any args (before it would just ignore them)
- mimxrt: freq() with an argument and lightsleep() both raise
  NotImplementedError

Signed-off-by: Damien George <damien@micropython.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/ports/stm32/powerctrl.c b/ports/stm32/powerctrl.c
index 1bb66c978..712021edb 100644
--- a/ports/stm32/powerctrl.c
+++ b/ports/stm32/powerctrl.c
@@ -993,7 +993,7 @@ void powerctrl_enter_stop_mode(void) {
     enable_irq(irq_state);
 }
 
-void powerctrl_enter_standby_mode(void) {
+NORETURN void powerctrl_enter_standby_mode(void) {
     rtc_init_finalise();
 
     #if defined(MICROPY_BOARD_ENTER_STANDBY)
@@ -1114,5 +1114,7 @@ void powerctrl_enter_standby_mode(void) {
 
     // enter standby mode
     HAL_PWR_EnterSTANDBYMode();
-    // we never return; MCU is reset on exit from standby
+
+    // MCU is reset on exit from standby, but just in case it's not, do an explicit reset.
+    powerctrl_mcu_reset();
 }