/* $Id: time-r0drv-linux.c 109033 2016-07-22 18:27:37Z bird $ */
/** @file
 * IPRT - Time, Ring-0 Driver, Linux.
 */

/*
 * Copyright (C) 2006-2016 Oracle Corporation
 *
 * This file is part of VirtualBox Open Source Edition (OSE), as
 * available from http://www.virtualbox.org. This file is free software;
 * you can redistribute it and/or modify it under the terms of the GNU
 * General Public License (GPL) as published by the Free Software
 * Foundation, in version 2 as it comes in the "COPYING" file of the
 * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
 *
 * The contents of this file may alternatively be used under the terms
 * of the Common Development and Distribution License Version 1.0
 * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
 * VirtualBox OSE distribution, in which case the provisions of the
 * CDDL are applicable instead of those of the GPL.
 *
 * You may elect to license modified versions of this file under the
 * terms and conditions of either the GPL or the CDDL or both.
 */

/*********************************************************************************************************************************
*   Header Files                                                                                                                 *
*********************************************************************************************************************************/
#define LOG_GROUP RTLOGGROUP_TIME
#include "the-linux-kernel.h"
#include "internal/iprt.h"
#include <iprt/time.h>
#include <iprt/asm.h>

DECLINLINE(uint64_t) rtTimeGetSystemNanoTS(void)
{
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 16)	/* This must match timer-r0drv-linux.c! */
	/*
	 * Use ktime_get_ts, this is also what clock_gettime(CLOCK_MONOTONIC,) is using.
	 */
	uint64_t u64;
	struct timespec Ts;
	ktime_get_ts(&Ts);
	u64 = Ts.tv_sec * RT_NS_1SEC_64 + Ts.tv_nsec;
	return u64;

#elif LINUX_VERSION_CODE >= KERNEL_VERSION(2, 5, 60)
	/*
	 * Seems there is no way of getting to the exact source of
	 * sys_clock_gettime(CLOCK_MONOTONIC, &ts) here, I think. But
	 * 64-bit jiffies adjusted for the initial value should be pretty
	 * much the same I hope.
	 */
	uint64_t u64 = get_jiffies_64();
# ifdef INITIAL_JIFFIES
	u64 += INITIAL_JIFFIES;
# endif
	u64 *= TICK_NSEC;
	return u64;

#else /* < 2.5.60 */
# if BITS_PER_LONG >= 64
	/*
	 * This is the same as above, except that there is no get_jiffies_64()
	 * here and we rely on long, and therefor jiffies, being 64-bit instead.
	 */
	uint64_t u64 = jiffies;
# ifdef INITIAL_JIFFIES
	u64 += INITIAL_JIFFIES;
# endif
	u64 *= TICK_NSEC;
	return u64;

# else /* 32 bit jiffies */
	/*
	 * We'll have to try track jiffy rollovers here or we'll be
	 * in trouble every time it flips.
	 *
	 * The high dword of the s_u64Last is the rollover count, the
	 * low dword is the previous jiffies.  Updating is done by
	 * atomic compare & exchange of course.
	 */
	static uint64_t volatile s_u64Last = 0;
	uint64_t u64;

	for (;;) {
		uint64_t u64NewLast;
		int32_t iDelta;
		uint32_t cRollovers;
		uint32_t u32LastJiffies;

		/* sample the values */
		unsigned long ulNow = jiffies;
		uint64_t u64Last = s_u64Last;
		if (ulNow != jiffies)
			continue;	/* try again */
#  ifdef INITIAL_JIFFIES
		ulNow += INITIAL_JIFFIES;
#  endif

		u32LastJiffies = (uint32_t) u64Last;
		cRollovers = u64Last >> 32;

		/*
		 * Check for rollover and update the static last value.
		 *
		 * We have to make sure we update it successfully to rule out
		 * an underrun because of racing someone.
		 */
		iDelta = ulNow - u32LastJiffies;
		if (iDelta < 0) {
			cRollovers++;
			u64NewLast = RT_MAKE_U64(ulNow, cRollovers);
			if (!ASMAtomicCmpXchgU64
			    (&s_u64Last, u64NewLast, u64Last))
				continue;	/* race, try again */
		} else {
			u64NewLast = RT_MAKE_U64(ulNow, cRollovers);
			ASMAtomicCmpXchgU64(&s_u64Last, u64NewLast, u64Last);
		}

		/* calculate the return value */
		u64 = ulNow;
		u64 *= TICK_NSEC;
		u64 += cRollovers * (_4G * TICK_NSEC);
		break;
	}

	return u64;
# endif	/* 32 bit jiffies */
#endif /* < 2.5.60 */
}

RTDECL(uint64_t) RTTimeNanoTS(void)
{
	return rtTimeGetSystemNanoTS();
}

RT_EXPORT_SYMBOL(RTTimeNanoTS);

RTDECL(uint64_t) RTTimeMilliTS(void)
{
	return rtTimeGetSystemNanoTS() / RT_NS_1MS;
}

RT_EXPORT_SYMBOL(RTTimeMilliTS);

RTDECL(uint64_t) RTTimeSystemNanoTS(void)
{
	return rtTimeGetSystemNanoTS();
}

RT_EXPORT_SYMBOL(RTTimeSystemNanoTS);

RTDECL(uint64_t) RTTimeSystemMilliTS(void)
{
	return rtTimeGetSystemNanoTS() / RT_NS_1MS;
}

RT_EXPORT_SYMBOL(RTTimeSystemMilliTS);

RTDECL(PRTTIMESPEC) RTTimeNow(PRTTIMESPEC pTime)
{
	IPRT_LINUX_SAVE_EFL_AC();
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 16)
	struct timespec Ts;
	ktime_get_real_ts(&Ts);
	IPRT_LINUX_RESTORE_EFL_AC();
	return RTTimeSpecSetTimespec(pTime, &Ts);

#else /* < 2.6.16 */
	struct timeval Tv;
	do_gettimeofday(&Tv);
	IPRT_LINUX_RESTORE_EFL_AC();
	return RTTimeSpecSetTimeval(pTime, &Tv);
#endif
}

RT_EXPORT_SYMBOL(RTTimeNow);
