// SPDX-License-Identifier: BSD-2-Clause
/*
 * Copyright 2022 Microchip
 */

#include <assert.h>
#include <drivers/rtc.h>

/* Time fields shift values to fit date in a 64bit word */
#define RTC_CMP_YEAR_SHIFT	U(36)
#define RTC_CMP_MONTH_SHIFT	U(32)
#define RTC_CMP_DAY_SHIFT	U(27)
#define RTC_CMP_HOUR_SHIFT	U(22)
#define RTC_CMP_MINUTES_SHIFT	U(16)
#define RTC_CMP_SECONDS_SHIFT	U(10)

struct rtc *rtc_device;

static const uint8_t rtc_months_days[] = {
	31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};

static unsigned long long rtc_time_to_ms(struct optee_rtc_time *time)
{
	uint64_t time_ms = 0;
	unsigned int n = 0;
	uint64_t days = 0;
	uint64_t year = 0;

	if (!time->tm_mday || time->tm_year < rtc_device->range_min.tm_year ||
	    time->tm_year > rtc_device->range_max.tm_year)
		panic();

	/* Elapsed milliseconds since midnight */
	time_ms = time->tm_ms;
	time_ms += time->tm_sec * MS_PER_SEC;
	time_ms += time->tm_min * MS_PER_MIN;
	time_ms += time->tm_hour * MS_PER_HOUR;

	/* Elapsed days in current month and in past months of current year */
	days = time->tm_mday - 1;
	for (n = 0; n < time->tm_mon; n++)
		days += rtc_get_month_days(n, time->tm_year);

	/* Elapsed days pasted years */
	year = time->tm_year;
	days += (year * 365) + (year / 4) - (year / 100) + (year / 400);

	/* Accumulate the elapsed days */
	time_ms += days * MS_PER_DAY;

	return time_ms;
}

bool rtc_is_a_leap_year(uint32_t year)
{
	return !(year % 4) && ((year % 100) || !(year % 400));
}

uint8_t rtc_get_month_days(uint32_t month, uint32_t year)
{
	if (rtc_is_a_leap_year(year) && month == 1)
		return rtc_months_days[month] + 1;
	else
		return rtc_months_days[month];
}

int rtc_timecmp(struct optee_rtc_time *a, struct optee_rtc_time *b)
{
	uint64_t tm_a = 0;
	uint64_t tm_b = 0;

	tm_a = SHIFT_U64(a->tm_year, RTC_CMP_YEAR_SHIFT) +
	       SHIFT_U64(a->tm_mon, RTC_CMP_MONTH_SHIFT) +
	       SHIFT_U64(a->tm_mday, RTC_CMP_DAY_SHIFT) +
	       SHIFT_U64(a->tm_hour, RTC_CMP_HOUR_SHIFT) +
	       SHIFT_U64(a->tm_min, RTC_CMP_MINUTES_SHIFT) +
	       SHIFT_U64(a->tm_sec, RTC_CMP_SECONDS_SHIFT) +
	       a->tm_ms;
	tm_b = SHIFT_U64(b->tm_year, RTC_CMP_YEAR_SHIFT) +
	       SHIFT_U64(b->tm_mon, RTC_CMP_MONTH_SHIFT) +
	       SHIFT_U64(b->tm_mday, RTC_CMP_DAY_SHIFT) +
	       SHIFT_U64(b->tm_hour, RTC_CMP_HOUR_SHIFT) +
	       SHIFT_U64(b->tm_min, RTC_CMP_MINUTES_SHIFT) +
	       SHIFT_U64(b->tm_sec, RTC_CMP_SECONDS_SHIFT) +
	       b->tm_ms;

	return CMP_TRILEAN(tm_a, tm_b);
}

signed long long rtc_diff_calendar_ms(struct optee_rtc_time *ref1,
				      struct optee_rtc_time *ref2)
{
	signed long long res = 0;

	if (SUB_OVERFLOW(rtc_time_to_ms(ref1), rtc_time_to_ms(ref2), &res)) {
		DMSG("Overflow while computing time diff in milliseconds");
		return LLONG_MAX;
	}

	return res;
}

signed long long rtc_diff_calendar_tick(struct optee_rtc_time *ref1,
					struct optee_rtc_time *ref2,
					unsigned long long tick_rate)
{
	signed long long diff_ms = rtc_diff_calendar_ms(ref1, ref2);
	signed long long res = 0;

	if (diff_ms == LLONG_MAX || MUL_OVERFLOW(diff_ms, tick_rate, &res)) {
		DMSG("Overflow while computing calendar diff in ticks");
		return LLONG_MAX;
	}

	return res / MS_PER_SEC;
}

void rtc_register(struct rtc *rtc)
{
	/* One RTC is supported only */
	assert(!rtc_device);

	/* RTC should *at least* allow to get the time */
	assert(rtc && rtc->ops && rtc->ops->get_time);

	rtc_device = rtc;
}