1 files changed, 121 insertions, 0 deletions
diff --git a/cpukit/libtest/t-test-busy-tick.c b/cpukit/libtest/t-test-busy-tick.c
new file mode 100644
index 0000000000..3613f8ed72
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+++ b/cpukit/libtest/t-test-busy-tick.c
@@ -0,0 +1,121 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+
+/**
+ * @file
+ *
+ * @ingroup RTEMSTestFrameworkImpl
+ *
+ * @brief Implementation of T_get_one_clock_tick_busy().
+ */
+
+/*
+ * Copyright (C) 2014, 2020 embedded brains GmbH (http://www.embedded-brains.de)
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <rtems/test.h>
+
+#include <rtems.h>
+
+static uint_fast32_t
+T_estimate_busy_loop_maximum(void)
+{
+	uint_fast32_t initial;
+	uint_fast32_t units;
+
+	initial = rtems_clock_get_ticks_since_boot();
+	units = 0;
+
+	while (initial == rtems_clock_get_ticks_since_boot()) {
+		++units;
+	}
+
+	return units;
+}
+
+static uint_fast32_t
+T_wait_for_tick_change(void)
+{
+	uint_fast32_t initial;
+	uint_fast32_t now;
+
+	initial = rtems_clock_get_ticks_since_boot();
+
+	do {
+		now = rtems_clock_get_ticks_since_boot();
+	} while (now == initial);
+
+	return now;
+}
+
+uint_fast32_t
+T_get_one_clock_tick_busy(void)
+{
+	uint_fast32_t last;
+	uint_fast32_t now;
+	uint_fast32_t a;
+	uint_fast32_t b;
+	uint_fast32_t m;
+
+	/* Choose a lower bound */
+	a = 1;
+
+	/* Estimate an upper bound */
+
+	T_wait_for_tick_change();
+	b = 2 * T_estimate_busy_loop_maximum();
+
+	while (true) {
+		last = T_wait_for_tick_change();
+		T_busy(b);
+		now = rtems_clock_get_ticks_since_boot();
+
+		if (now != last) {
+			break;
+		}
+
+		b *= 2;
+		last = now;
+	}
+
+	/* Find a good value */
+	do {
+		m = (a + b) / 2;
+
+		last = T_wait_for_tick_change();
+		T_busy(m);
+		now = rtems_clock_get_ticks_since_boot();
+
+		if (now != last) {
+			b = m;
+		} else {
+			a = m;
+		}
+	} while (b - a > 1);
+
+	return m;
+}