WIP: rp2: Make GPIO wakeup from lightsleep consistent.

Before this commit:

- A Pin with an irq() trigger is a wakeup source only when
  machine.lightsleep(n) is used with a timeout, and only if an IRQ handler
  is set.

After this commit:

- A Pin with an irq() trigger is a wakeup source from both
  indefinite machine.lightsleep() and machine.lightsleep(n) with
  a timeout.

- A Pin with an irq() trigger is a wakeup source even if no handler
  function is set.

Issues at present:

- Waking RP2040 repeatedly from machine.lightsleep() with no timeout and
  USB causes the USB connection to misbehave and eventually the CPU hangs.

- This implementation doesn't match the machine.Pin docs re: irq(wake=)
  argument. However, I think only cc3200 port has actually implemented
  this argument as documented.

This work was funded through GitHub Sponsors.

Signed-off-by: Angus Gratton <[email protected]>

Author: projectgus

ports/rp2/machine_pin.c

@@ -134,6 +134,7 @@ void machine_pin_deinit(void) {
             continue;
         }
         gpio_set_irq_enabled(i, GPIO_IRQ_ALL, false);
+        gpio_set_dormant_irq_enabled(i, GPIO_IRQ_ALL, false);
     }
     irq_remove_handler(IO_IRQ_BANK0, gpio_irq);
 }
@@ -458,16 +459,19 @@ void mp_hal_pin_interrupt(mp_hal_pin_obj_t pin, mp_obj_t handler, mp_uint_t trig
 
     // Disable all IRQs while data is updated.
     gpio_set_irq_enabled(pin, GPIO_IRQ_ALL, false);
+    gpio_set_dormant_irq_enabled(pin, GPIO_IRQ_ALL, false);
 
     // Update IRQ data.
     irq->base.handler = handler;
     irq->base.ishard = hard;
     irq->flags = 0;
     irq->trigger = trigger;
 
-    // Enable IRQ if a handler is given.
-    if (handler != mp_const_none && trigger != MP_HAL_PIN_TRIGGER_NONE) {
+    if (trigger != MP_HAL_PIN_TRIGGER_NONE) {
+        // Enable IRQ even if no handler is set, so pin can wake CPU from WFI/WFE
         gpio_set_irq_enabled(pin, trigger, true);
+        // Also have the IRQ wake us from indefinite lightsleep
+        gpio_set_dormant_irq_enabled(pin, trigger, true);
     }
 }