RP2 - lightsleep() fails/does not exit when started from inside a thread - solution

[mungewell]

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• I've searched for existing issues matching this bug, and didn't find any.

Port, board and/or hardware

rp2 - official Pico (non-wifi)

MicroPython version

MicroPython v1.22.2 on 2024-02-22; Raspberry Pi Pico with RP2040

Reproduction

Run the attached script...

blink_thread.py.txt

Expected behaviour

When called within (only) a function, lightsleep() correct exits and the rest of the function are run.

MPY: soft reboot
Blink in thread test
CPU Freq 100000000
entering lightsleep
wake from sleep
CPU Freq 125000000

Observed behaviour

The lightsleep() call does not exit....

MPY: soft reboot
Blink in thread test
CPU Freq 100000000
entering lightsleep

...

Additional Information

No, I've provided everything above.

[mungewell]

I commented out various bits of the lightsleep() code, and noted that it DOES work from within a thread - if it does NOT call __wfi()

         scb_hw->scr |= M0PLUS_SCR_SLEEPDEEP_BITS;
+#if 0 //SDW
         __wfi();
+#endif //SDW
         scb_hw->scr &= ~M0PLUS_SCR_SLEEPDEEP_BITS;

So does this mean that the (previously set) timer interrupt does not occur, if running from within a thread? And if so, why?

[mungewell]

Seems that IRQs are NOT enabled, on the core that the code is running.... if we enable them, then the lightsleep() functions OK.

Patch (mixed in with my other stuff) is something like

@@ -165,18 +233,25 @@ STATIC void mp_machine_lightsleep(size_t n_args, const mp_obj_t *args) {
     } else {
         uint32_t sleep_en0 = clocks_hw->sleep_en0;
         uint32_t sleep_en1 = clocks_hw->sleep_en1;
-        clocks_hw->sleep_en0 = CLOCKS_SLEEP_EN0_CLK_RTC_RTC_BITS;
+        bool timer3_enabled = irq_is_enabled(3);
+        clocks_hw->sleep_en0 = req_sleep_en0 | CLOCKS_SLEEP_EN0_CLK_RTC_RTC_BITS;
         if (use_timer_alarm) {
             // Use timer alarm to wake.
-            clocks_hw->sleep_en1 = CLOCKS_SLEEP_EN1_CLK_SYS_TIMER_BITS;
+            clocks_hw->sleep_en1 = req_sleep_en1 | CLOCKS_SLEEP_EN1_CLK_SYS_TIMER_BITS;
+           // Make sure ALARM3/IRQ is enabled on _this_ core
+            timer_hw->inte |= 1 << 3;
+           if (timer3_enabled == false)
+               irq_set_enabled(3, true);
             timer_hw->alarm[3] = timer_hw->timerawl + delay_ms * 1000;
         } else {
             // TODO: Use RTC alarm to wake.
-            clocks_hw->sleep_en1 = 0;
+            clocks_hw->sleep_en1 = req_sleep_en1;
         }
         scb_hw->scr |= M0PLUS_SCR_SLEEPDEEP_BITS;
         __wfi();
         scb_hw->scr &= ~M0PLUS_SCR_SLEEPDEEP_BITS;
+       if (timer3_enabled == false)
+           irq_set_enabled(3, false);
         clocks_hw->sleep_en0 = sleep_en0;
         clocks_hw->sleep_en1 = sleep_en1;

[mungewell]

BTW I have PR with the Pico SDK for keeping some of the clocks running:
raspberrypi/pico-sdk#1672

[dpgeorge]

Fixed in 19844b4