rtc: Add functions and tests for time conversion

To implement rtc driver for some ec chips, we
need to convert between calandar date and seconds
(since epoch time, 01-01-1970 00:00:00).

Sicne these functions are HW-independent, let's add
common/rtc.c, include/rtc.h, and unit test for this.

BUG=b:63908519
BRANCH=none
TEST=make buildall test -j

Change-Id: Icb1e768d2b3674d5225b83e09475e984eb104d06
Signed-off-by: Philip Chen <philipchen@google.com>
Reviewed-on: https://chromium-review.googlesource.com/666985
Commit-Ready: Philip Chen <philipchen@chromium.org>
Tested-by: Philip Chen <philipchen@chromium.org>
Reviewed-by: Shawn N <shawnn@chromium.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>

1 files changed, 45 insertions, 0 deletions

diff --git a/include/rtc.h b/include/rtc.h
new file mode 100644
index 0000000000..fa56634c5b
--- /dev/null
+++ b/include/rtc.h
@@ -0,0 +1,45 @@
+/* Copyright 2017 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/* RTC cross-platform functions */
+
+#ifndef __CROS_EC_RTC_H
+#define __CROS_EC_RTC_H
+
+#include "common.h"
+
+#define SECS_PER_DAY        (60 * 60 * 24)
+#define SECS_PER_YEAR       (365 * SECS_PER_DAY)
+/* The seconds elapsed from 01-01-1970 to 01-01-2000 */
+#define SECS_TILL_YEAR_2K   (946684800)
+#define IS_LEAP_YEAR(x)     \
+	(((x) % 4 == 0) && (((x) % 100 != 0) || ((x) % 400 == 0)))
+
+struct calendar_date {
+	/* The number of years since A.D. 2000, i.e. year = 17 for y2017 */
+	uint8_t year;
+	/* 1-based indexing, i.e. sane values range from 1 to 12 */
+	uint8_t month;
+	/* 1-based indexing, i.e. sane values range from 1 to 31 */
+	uint8_t day;
+};
+
+/**
+ * Convert calendar date to seconds elapsed since epoch time.
+ *
+ * @param time  The calendar date (years, months, and days).
+ * @return the seconds elapsed since epoch time (01-01-1970 00:00:00).
+ */
+uint32_t date_to_sec(struct calendar_date time);
+
+/**
+ * Convert seconds elapsed since epoch time to calendar date
+ *
+ * @param sec  The seconds elapsed since epoch time (01-01-1970 00:00:00).
+ * @return the calendar date (years, months, and days).
+ */
+struct calendar_date sec_to_date(uint32_t sec);
+
+#endif /* __CROS_EC_RTC_H */