tests/xtimer_now_irq/: New test for xtimer_now() with irq_disable()

This test checks, if the timer returns the correct time (xtimer_now_usec() is called), when interrupts are disabled. Specifically tested is if the time is correct after a low-level timer overflow.

tests/xtimer_now_irq/Makefile

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+include ../Makefile.tests_common
+
+USEMODULE += xtimer
+
+TEST_ON_CI_BLACKLIST += all
+
+include $(RIOTBASE)/Makefile.include

tests/xtimer_now_irq/README.md

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+# README for xtimer_now_irq test
+
+This test checks, if the timer returns the correct time (xtimer_now_usec() is called), when interrupts are disabled. Specifically tested is if the time is correct after a low-level timer overflow.
+
+When the returned value is incorrect the test will print: "ERROR: wrong time with interrupts disabled".
+
+This test must be run over at least one full timer period. Meaning the test only finishes in reasonable short time on platforms with small timers up to 24 bit.
+This test does not work for 32 bit timers.

tests/xtimer_now_irq/main.c

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+/*
+ * Copyright (C) 2020 Freie Universität Berlin,
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     tests
+ * @{
+ *
+ * @file
+ * @brief       testing xtimer_now_usec function with irq disabled
+ *
+ *
+ * @author      Julian Holzwarth <julian.holzwarth@fu-berlin.de>
+ *
+ */
+
+#include <stdio.h>
+#include "xtimer.h"
+#include "irq.h"
+
+#define TEST_COUNT 4
+
+int main(void)
+{
+    puts("xtimer_now_irq test application.\n");
+
+    uint8_t count = TEST_COUNT;
+    while (count) {
+        unsigned int state = irq_disable();
+        uint32_t t1 = xtimer_now_usec();
+        xtimer_spin(xtimer_ticks((uint32_t)(~XTIMER_MASK) / 2));
+        uint32_t t2 = xtimer_now_usec();
+        irq_restore(state);
+        if (t2 < t1) {
+            puts("ERROR: wrong time with interrupts disabled");
+            return -1;
+        }
+        puts("OK");
+        count --;
+    }
+    puts("SUCCESS");
+    return 0;
+}

tests/xtimer_now_irq/tests/01-run.py

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+#!/usr/bin/env python3
+
+#  Copyright (C) 2020 Freie Universität Berlin,
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+
+# @author      Julian Holzwarth <julian.holzwarth@fu-berlin.de>
+
+import sys
+from testrunner import run
+
+TIMEOUT = 20
+
+
+def testfunc(child):
+    for _ in range(4):
+        child.expect_exact("OK", timeout=TIMEOUT)
+    child.expect_exact("SUCCESS")
+
+
+if __name__ == "__main__":
+    sys.exit(run(testfunc))