tsc.h File Reference

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Macros
#define	NUM_SAMPLES   4
#define	MSR_RDTSC   0x10
#define	KiGetIdtEntry(Pcr, Vector)   &((Pcr)->IDT[Vector])

Functions
void __cdecl	TscCalibrationISR (void)
VOID NTAPI	HalpInitializeTsc (void)

Variables
LARGE_INTEGER	HalpCpuClockFrequency

Macro Definition Documentation

KiGetIdtEntry

#define KiGetIdtEntry	(		Pcr,
			Vector
	)		&((Pcr)->IDT[Vector])

Definition at line 17 of file tsc.h.

MSR_RDTSC

#define MSR_RDTSC   0x10

Definition at line 6 of file tsc.h.

NUM_SAMPLES

#define NUM_SAMPLES   4

Definition at line 5 of file tsc.h.

Function Documentation

HalpInitializeTsc()

VOID NTAPI HalpInitializeTsc

(

void

)

Definition at line 56 of file tsc.c.

{
    ULONG_PTR Flags;
    KIDTENTRY OldIdtEntry, *IdtPointer;
    PKPCR Pcr = KeGetPcr();
    UCHAR RegisterA, RegisterB;

    /* Check if the CPU supports RDTSC */
    if (!(KeGetCurrentPrcb()->FeatureBits & KF_RDTSC))
    {
        KeBugCheck(HAL_INITIALIZATION_FAILED);
    }

     /* Save flags and disable interrupts */
    Flags = __readeflags();
    _disable();

    /* Enable the periodic interrupt in the CMOS */
    RegisterB = HalpReadCmos(RTC_REGISTER_B);
    HalpWriteCmos(RTC_REGISTER_B, RegisterB | RTC_REG_B_PI);

    /* Modify register A to RTC_MODE to get SAMPLE_FREQENCY */
    RegisterA = HalpReadCmos(RTC_REGISTER_A);
    RegisterA = (RegisterA & 0xF0) | RTC_MODE;
    HalpWriteCmos(RTC_REGISTER_A, RegisterA);

    /* Save old IDT entry */
    IdtPointer = KiGetIdtEntry(Pcr, HalpRtcClockVector);
    OldIdtEntry = *IdtPointer;

    /* Set the calibration ISR */
    KeRegisterInterruptHandler(HalpRtcClockVector, TscCalibrationISR);

    /* Reset TSC value to 0 */
    __writemsr(MSR_RDTSC, 0);

    /* Enable the timer interrupt */
    HalEnableSystemInterrupt(HalpRtcClockVector, CLOCK_LEVEL, Latched);

    /* Read register C, so that the next interrupt can happen */
    HalpReadCmos(RTC_REGISTER_C);

    /* Wait for completion */
    _enable();
    while (TscCalibrationPhase < NUM_SAMPLES) _ReadWriteBarrier();
    _disable();

    /* Disable the periodic interrupt in the CMOS */
    HalpWriteCmos(RTC_REGISTER_B, RegisterB & ~RTC_REG_B_PI);

    /* Disable the timer interrupt */
    HalDisableSystemInterrupt(HalpRtcClockVector, CLOCK_LEVEL);

    /* Restore old IDT entry */
    *IdtPointer = OldIdtEntry;

    /* Calculate an average, using simplified linear regression */
    HalpCpuClockFrequency.QuadPart = DoLinearRegression(NUM_SAMPLES - 1,
                                                        TscCalibrationArray);

    /* Restore flags */
    __writeeflags(Flags);

}

Referenced by HalpCalibrateStallExecution().

TscCalibrationISR()

void __cdecl TscCalibrationISR

(

void

)

Referenced by HalpInitializeTsc().

Variable Documentation

HalpCpuClockFrequency

LARGE_INTEGER HalpCpuClockFrequency

Definition at line 17 of file tsc.c.

Referenced by HalpCalibrateStallExecution(), HalpInitializeTsc(), and KeQueryPerformanceCounter().