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>

7 files changed, 240 insertions, 0 deletions

diff --git a/common/build.mk b/common/build.mk
index 7f73c885fa..1600bcfbea 100644
--- a/common/build.mk
+++ b/common/build.mk
@@ -64,6 +64,7 @@ common-$(CONFIG_FMAP)+=fmap.o
 common-$(CONFIG_GESTURE_SW_DETECTION)+=gesture.o
 common-$(CONFIG_HOSTCMD_EVENTS)+=host_event_commands.o
 common-$(CONFIG_HOSTCMD_PD)+=host_command_master.o
+common-$(CONFIG_HOSTCMD_RTC)+=rtc.o
 common-$(CONFIG_I2C_MASTER)+=i2c_master.o
 common-$(CONFIG_I2C_SLAVE)+=i2c_slave.o
 common-$(CONFIG_I2C_VIRTUAL_BATTERY)+=virtual_battery.o
diff --git a/common/rtc.c b/common/rtc.c
new file mode 100644
index 0000000000..8a2fbc7139
--- /dev/null
+++ b/common/rtc.c
@@ -0,0 +1,67 @@
+/* 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 code for Chrome EC */
+/* TODO(chromium:733844): Move this conversion to kernel rtc-cros-ec driver */
+
+#include "rtc.h"
+
+static uint16_t days_since_year_start[12] = {
+0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};
+
+/* Conversion between calendar date and seconds eclapsed since 1970-01-01 */
+uint32_t date_to_sec(struct calendar_date time)
+{
+	int i;
+	uint32_t sec;
+
+	sec = time.year * SECS_PER_YEAR;
+	for (i = 0; i < time.year; i++) {
+		if (IS_LEAP_YEAR(i))
+			sec += SECS_PER_DAY;
+	}
+
+	sec += (days_since_year_start[time.month - 1] +
+		(IS_LEAP_YEAR(time.year) && time.month > 2) +
+		(time.day - 1)) * SECS_PER_DAY;
+
+	/* add the accumulated time in seconds from 1970 to 2000 */
+	return sec + SECS_TILL_YEAR_2K;
+}
+
+struct calendar_date sec_to_date(uint32_t sec)
+{
+	struct calendar_date time;
+	int day_tmp; /* for intermediate calculation */
+	int i;
+
+	/* RTC time must be after year 2000. */
+	sec = (sec > SECS_TILL_YEAR_2K) ? (sec - SECS_TILL_YEAR_2K) : 0;
+
+	day_tmp = sec / SECS_PER_DAY;
+	time.year = day_tmp / 365;
+	day_tmp %= 365;
+	for (i = 0; i < time.year; i++) {
+		if (IS_LEAP_YEAR(i))
+			day_tmp -= 1;
+	}
+	day_tmp++;
+	if (day_tmp <= 0) {
+		time.year -= 1;
+		day_tmp += IS_LEAP_YEAR(time.year) ? 366 : 365;
+	}
+	for (i = 1; i < 12; i++) {
+		if (days_since_year_start[i] +
+		    (IS_LEAP_YEAR(time.year) && (i >= 2)) >= day_tmp)
+			break;
+	}
+	time.month = i;
+
+	day_tmp -= days_since_year_start[time.month - 1] +
+		   (IS_LEAP_YEAR(time.year) && (time.month > 2));
+	time.day = day_tmp;
+
+	return time;
+}
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 */
diff --git a/test/build.mk b/test/build.mk
index ba4a2c6966..20a55fb3fc 100644
--- a/test/build.mk
+++ b/test/build.mk
@@ -66,6 +66,7 @@ test-list-host += queue
 test-list-host += rma_auth
 test-list-host += rsa
 test-list-host += rsa3
+test-list-host += rtc
 test-list-host += sbs_charging_v2
 test-list-host += sha256
 test-list-host += sha256_unrolled
@@ -116,6 +117,7 @@ queue-y=queue.o
 rma_auth-y=rma_auth.o
 rsa-y=rsa.o
 rsa3-y=rsa.o
+rtc-y=rtc.o
 sbs_charging-y=sbs_charging.o
 sbs_charging_v2-y=sbs_charging_v2.o
 sha256-y=sha256.o
diff --git a/test/rtc.c b/test/rtc.c
new file mode 100644
index 0000000000..5d16d3008c
--- /dev/null
+++ b/test/rtc.c
@@ -0,0 +1,104 @@
+/* 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.
+ *
+ * Tests for rtc time conversions
+ */
+
+#include "console.h"
+#include "common.h"
+#include "rtc.h"
+#include "test_util.h"
+#include "util.h"
+
+/* Known conversion pairs of date and epoch time. */
+static struct {
+	struct calendar_date time;
+	uint32_t sec;
+} test_case[] = {
+	{{8, 3, 1}, 1204329600},
+	{{17, 10, 1}, 1506816000},
+};
+
+static int calendar_time_comp(struct calendar_date time_1,
+			   struct calendar_date time_2)
+{
+	return (time_1.year == time_2.year &&
+		time_1.month == time_2.month &&
+		time_1.day == time_2.day);
+}
+
+static int test_time_conversion(void)
+{
+	struct calendar_date time_1;
+	struct calendar_date time_2;
+	uint32_t sec;
+	int i;
+
+	/* The seconds elapsed from 01-01-1970 to 01-01-2000 */
+	sec = SECS_TILL_YEAR_2K;
+	time_1.year = 0;
+	time_1.month = 1;
+	time_1.day = 1;
+
+	/* Test from year 2000 to 2050 */
+	for (i = 0; i <= 50; i++) {
+		/* Test Jan. 1 */
+		time_1.year = i;
+		time_1.month = 1;
+		time_1.day = 1;
+
+		TEST_ASSERT(date_to_sec(time_1) == sec);
+		time_2 = sec_to_date(sec);
+		TEST_ASSERT(calendar_time_comp(time_1, time_2));
+
+		/* Test the day boundary between Jan. 1 and Jan. 2 */
+		time_2 = sec_to_date(sec + SECS_PER_DAY - 1);
+		TEST_ASSERT(calendar_time_comp(time_1, time_2));
+
+		time_1.day = 2;
+
+		TEST_ASSERT(date_to_sec(time_1) == sec + SECS_PER_DAY);
+		time_2 = sec_to_date(sec + SECS_PER_DAY);
+		TEST_ASSERT(calendar_time_comp(time_1, time_2));
+
+		/*
+		 * Test the month boundary and leap year:
+		 * Is the 60th day of a year Mar. 1 or Feb. 29?
+		 */
+		time_2 = sec_to_date(sec + 59 * SECS_PER_DAY);
+		if (IS_LEAP_YEAR(i))
+			TEST_ASSERT(time_2.month == 2 && time_2.day == 29);
+		else
+			TEST_ASSERT(time_2.month == 3 && time_2.day == 1);
+
+		/* Test the year boundary on Dec. 31 */
+		sec += SECS_PER_YEAR - (IS_LEAP_YEAR(i) ? 0 : SECS_PER_DAY);
+		time_1.month = 12;
+		time_1.day = 31;
+
+		TEST_ASSERT(date_to_sec(time_1) == sec);
+		time_2 = sec_to_date(sec);
+		TEST_ASSERT(calendar_time_comp(time_1, time_2));
+
+		sec += SECS_PER_DAY;
+		time_2 = sec_to_date(sec - 1);
+		TEST_ASSERT(calendar_time_comp(time_1, time_2));
+	}
+
+	/* Verify known test cases */
+	for (i = 0; i < ARRAY_SIZE(test_case); i++) {
+		TEST_ASSERT(date_to_sec(test_case[i].time) == test_case[i].sec);
+		time_1 = sec_to_date(test_case[i].sec);
+		TEST_ASSERT(calendar_time_comp(time_1, test_case[i].time));
+	}
+
+	return EC_SUCCESS;
+}
+
+void run_test(void)
+{
+	RUN_TEST(test_time_conversion);
+
+	test_print_result();
+}
diff --git a/test/rtc.tasklist b/test/rtc.tasklist
new file mode 100644
index 0000000000..e76178ba0a
--- /dev/null
+++ b/test/rtc.tasklist
@@ -0,0 +1,17 @@
+/* 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.
+ */
+
+/**
+ * List of enabled tasks in the priority order
+ *
+ * The first one has the lowest priority.
+ *
+ * For each task, use the macro TASK_TEST(n, r, d, s) where :
+ * 'n' in the name of the task
+ * 'r' in the main routine of the task
+ * 'd' in an opaque parameter passed to the routine at startup
+ * 's' is the stack size in bytes; must be a multiple of 8
+ */
+#define CONFIG_TEST_TASK_LIST
diff --git a/test/test_config.h b/test/test_config.h
index 31d5679d05..23d836ffd9 100644
--- a/test/test_config.h
+++ b/test/test_config.h
@@ -230,6 +230,10 @@ enum nvmem_vars {
 #define CONFIG_FLASH_NVMEM_VARS_USER_SIZE 600
 #endif	/* TEST_NVMEM_VARS */
 
+#ifdef TEST_RTC
+#define CONFIG_HOSTCMD_RTC
+#endif
+
 #ifdef TEST_VBOOT
 #define CONFIG_RWSIG
 #define CONFIG_SHA256