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/**@file*/

#ifndef TSC_HPP
#define TSC_HPP

#include <intrin.h>
#include <stdint.h>

/**
 * @brief  Gets the processor timestamp
 * @return processor timestamp
 */
inline unsigned __int64 PLAT_rdtsc()
{
	return __rdtsc();
}

#define CLOCK_INFO_CPUID_LEAF	(0x15)
#define SYSTEM_CLOCK_24MHZ	(24000000)
#define MAX_MODEL_LIST_LEN	(2)

typedef struct
{
	short		model_list[MAX_MODEL_LIST_LEN+1];	// Terminate model list with -1
	uint32_t	clock_rate;				// clock_rate of 0 is invalid
}
ModelNumberSystemClockRateMapping;

static ModelNumberSystemClockRateMapping ModelNumberSystemClockRateMap[] =
{
	{{ 0x5E, 0x4E, -1 }, SYSTEM_CLOCK_24MHZ },
	{{ -1 }, 0 },
};

/**
* @brief  Gets the system clock frequency using CPU model number
* @param  model_query model number to look up
* @return System frequency, or 0 on error
*/
inline uint32_t FindFrequencyByModel(uint8_t model_query) {
	ModelNumberSystemClockRateMapping *map = ModelNumberSystemClockRateMap;
	uint32_t ret = 0;

	while (map->clock_rate != 0)
	{
		short *model = map->model_list;

		while (*model != -1)
		{
			if (*model == model_query) {
				ret = map->clock_rate;
				break;
			}
			++model;
		}
		++map;
	}

	return ret;
}


/**
 * @brief  Gets the TSC frequnecy
 * @param  builtin whether device is connected to the Intel bus (not PCIE)
 * @return TSC frequency, or 0 on error
 */
inline uint64_t getTSCFrequency( bool builtin ) {
	int max_cpuid_level;
	int tmp[4];
	BOOL is_windows_10;
	LARGE_INTEGER freq;

	// Find the max cpuid level, and if possible find clock info
	__cpuid(tmp, 0);
	max_cpuid_level = tmp[0];
	if (max_cpuid_level >= CLOCK_INFO_CPUID_LEAF)
		__cpuid(tmp, CLOCK_INFO_CPUID_LEAF);

	// Determine if the OS is Windows 10 or later.
	{
		OSVERSIONINFOEXW osvi = { sizeof(osvi), 0, 0, 0, 0, {0}, 0, 0 };
		DWORDLONG        const dwlConditionMask = VerSetConditionMask(0, VER_MAJORVERSION, VER_GREATER_EQUAL);
		osvi.dwMajorVersion = 10;

		// NOTE:  VerifyVersionInfo returns false when called by applications that do not have a compatibility manifest for Windows 10,
		//  even when the current operating system version is Windows 10.
		is_windows_10 = VerifyVersionInfoW(&osvi, VER_MAJORVERSION, dwlConditionMask) != FALSE;
	}

	// For pre-Win10 on 6th Generation or greater Intel CPUs the raw hardware
	// clock will be returned, *else* use QPC for everything else
	//
	// EAX (tmp[0]) must be >= 1, See Intel SDM 17.15.4 "Invariant Time-keeping"
	if (!is_windows_10 &&
		max_cpuid_level >= CLOCK_INFO_CPUID_LEAF &&
		tmp[0] >= 1 &&
		builtin )
	{
		SYSTEM_INFO info;

		GetSystemInfo(&info);

		// Look at processor model (upper byte of revision) number to determine clock rate
		return FindFrequencyByModel(info.wProcessorRevision >> 8);
	}

	if (QueryPerformanceFrequency(&freq))
		return freq.QuadPart;

	return 0;
}

#endif/*TSC_HPP*/
