test: Add a simple time test

Sometimes the time functions are incorrect due to bad time support on a
board. Add a unit test which tries to detect this.
Signed-off-by: NSimon Glass <sjg@chromium.org>

test/Kconfig

+config CMD_UT_TIME
+	bool "Unit tests for time functions"
+	help
+	  Enables the 'ut_time' command which tests that the time functions
+	  work correctly. The test is fairly simple and will not catch all
+	  problems. But if you are having problems with udelay() and the like,
+	  this is a good place to start.
+
 source "test/dm/Kconfig"

test/Makefile

@@ -6,3 +6,4 @@
 
 obj-$(CONFIG_SANDBOX) += command_ut.o
 obj-$(CONFIG_SANDBOX) += compression.o
+obj-$(CONFIG_CMD_UT_TIME) += time_ut.o

test/time_ut.c

+/*
+ * Copyright (c) 2015 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <command.h>
+#include <errno.h>
+
+static int test_get_timer(void)
+{
+	ulong base, start, next, diff;
+	int iter;
+
+	base = get_timer(0);
+	start = get_timer(0);
+	for (iter = 0; iter < 10; iter++) {
+		do {
+			next = get_timer(0);
+		} while (start == next);
+
+		if (start + 1 != next) {
+			printf("%s: iter=%d, start=%lu, next=%lu, expected a difference of 1\n",
+			       __func__, iter, start, next);
+			return -EINVAL;
+		}
+		start++;
+	}
+
+	/*
+	 * Check that get_timer(base) matches our elapsed time, allowing that
+	 * an extra millisecond may have passed.
+	 */
+	diff = get_timer(base);
+	if (diff != iter && diff != iter + 1) {
+		printf("%s: expected get_timer(base) to match elapsed time: diff=%lu, expected=%d\n",
+		       __func__, diff, iter);
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int test_timer_get_us(void)
+{
+	ulong prev, next, min = 1000000;
+	long delta;
+	int iter;
+
+	/* Find the minimum delta we can measure, in microseconds */
+	prev = timer_get_us();
+	for (iter = 0; iter < 100; ) {
+		next = timer_get_us();
+		if (next != prev) {
+			delta = next - prev;
+			if (delta < 0) {
+				printf("%s: timer_get_us() went backwards from %lu to %lu\n",
+				       __func__, prev, next);
+				return -EINVAL;
+			} else if (delta != 0) {
+				if (delta < min)
+					min = delta;
+				prev = next;
+				iter++;
+			}
+		}
+	}
+
+	if (min != 1) {
+		printf("%s: Minimum microsecond delta should be 1 but is %lu\n",
+		       __func__, min);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int test_time_comparison(void)
+{
+	ulong start_us, end_us, delta_us;
+	long error;
+	ulong start;
+
+	start = get_timer(0);
+	start_us = timer_get_us();
+	while (get_timer(start) < 1000)
+		;
+	end_us = timer_get_us();
+	delta_us = end_us - start_us;
+	error = delta_us - 1000000;
+	printf("%s: Microsecond time for 1 second: %lu, error = %ld\n",
+	       __func__, delta_us, error);
+	if (abs(error) > 1000)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int test_udelay(void)
+{
+	long error;
+	ulong start, delta;
+	int iter;
+
+	start = get_timer(0);
+	for (iter = 0; iter < 1000; iter++)
+		udelay(1000);
+	delta = get_timer(start);
+	error = delta - 1000;
+	printf("%s: Delay time for 1000 udelay(1000): %lu ms, error = %ld\n",
+	       __func__, delta, error);
+	if (abs(error) > 100)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int do_ut_time(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+{
+	int ret = 0;
+
+	ret |= test_get_timer();
+	ret |= test_timer_get_us();
+	ret |= test_time_comparison();
+	ret |= test_udelay();
+
+	printf("Test %s\n", ret ? "failed" : "passed");
+
+	return ret ? CMD_RET_FAILURE : CMD_RET_SUCCESS;
+}
+
+U_BOOT_CMD(
+	ut_time,	1,	1,	do_ut_time,
+	"Very basic test of time functions",
+	""
+);