tests/ports/rp2: Add a test case for light sleeping from CPU1.

Not currently passing.

This work was funded through GitHub Sponsors.

Signed-off-by: Angus Gratton <angus@redyak.com.au>

tests/ports/rp2/rp2_lightsleep_thread.py

@@ -0,0 +1,54 @@
+# Verify that a thread running on CPU1 can go to lightsleep
+# and wake up in the expected timeframe
+import _thread
+import time
+import unittest
+from machine import lightsleep
+
+N_SLEEPS = 5
+SLEEP_MS = 250
+
+IDEAL_RUNTIME = N_SLEEPS * SLEEP_MS
+MAX_RUNTIME = (N_SLEEPS + 1) * SLEEP_MS
+MAX_DELTA = 20
+
+
+class LightSleepInThread(unittest.TestCase):
+    def thread_entry(self, is_thread=True):
+        for _ in range(N_SLEEPS):
+            lightsleep(SLEEP_MS)
+        if is_thread:
+            self.thread_done = True
+
+    def elapsed_ms(self):
+        return time.ticks_diff(time.ticks_ms(), self.t0)
+
+    def setUp(self):
+        self.thread_done = False
+        self.t0 = time.ticks_ms()
+
+    def test_cpu0_busy(self):
+        _thread.start_new_thread(self.thread_entry, ())
+        # CPU0 is busy-waiting not asleep itself
+        while not self.thread_done:
+            self.assertLessEqual(self.elapsed_ms(), MAX_RUNTIME)
+        self.assertAlmostEqual(self.elapsed_ms(), IDEAL_RUNTIME, delta=MAX_DELTA)
+
+    def test_cpu0_sleeping(self):
+        _thread.start_new_thread(self.thread_entry, ())
+        time.sleep_ms(MAX_RUNTIME)
+        self.assertTrue(self.thread_done)
+        self.assertAlmostEqual(self.elapsed_ms(), MAX_RUNTIME, delta=MAX_DELTA)
+
+    def test_cpu0_also_lightsleep(self):
+        _thread.start_new_thread(self.thread_entry, ())
+        time.sleep(0.050)  # account for any delay in starting the thread
+        self.thread_entry(False)  # does the same lightsleep loop, doesn't set the done flag
+        self.assertTrue(self.thread_done)
+        # only one thread can actually be in lightsleep at a time to avoid races, so the total
+        # runtime is doubled by doing it on both CPUs
+        self.assertAlmostEqual(self.elapsed_ms(), IDEAL_RUNTIME * 2, delta=IDEAL_RUNTIME)
+
+
+if __name__ == "__main__":
+    unittest.main()