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[HAL/APIC] Make the real time clock more precise
The interval time is now calculated in 0.1ns precision and a running fraction on the 100ns interval is updated on each clock interrupt. Also adjust minimum, maximum and default clock rate to what Windows uses.
This commit is contained in:
Timo Kreuzer
parent
aa3ef4c632
commit
3e1454c739
1 changed files with 59 additions and 40 deletions
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@ -18,56 +18,62 @@
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/* GLOBALS ********************************************************************/
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BOOLEAN HalpClockSetMSRate;
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UCHAR HalpNextMSRate;
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UCHAR HalpCurrentRate = 9; /* Initial rate 9: 128 Hz / 7.8 ms */
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ULONG HalpCurrentTimeIncrement;
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static UCHAR RtcMinimumClockRate = 8; /* Minimum rate 8: 256 Hz / 3.9 ms */
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static UCHAR RtcMaximumClockRate = 12; /* Maximum rate 12: 16 Hz / 62.5 ms */
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static const UCHAR RtcMinimumClockRate = 6; /* Minimum rate 6: 1024 Hz / 0.97 ms */
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static const UCHAR RtcMaximumClockRate = 10; /* Maximum rate 10: 64 Hz / 15.6 ms */
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static UCHAR HalpCurrentClockRate = 10; /* Initial rate 10: 64 Hz / 15.6 ms */
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static ULONG HalpCurrentTimeIncrement;
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static ULONG HalpMinimumTimeIncrement;
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static ULONG HalpMaximumTimeIncrement;
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static ULONG HalpCurrentFractionalIncrement;
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static ULONG HalpRunningFraction;
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static BOOLEAN HalpSetClockRate;
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static UCHAR HalpNextClockRate;
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/*!
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\brief Converts the CMOS RTC rate into the time increment in 100ns intervals.
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Rate Freqency Interval (ms) Result
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-------------------------------------
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Rate Frequency Interval (ms) Precise increment (0.1ns)
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------------------------------------------------------
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0 disabled
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1 32768 0.03052 305
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2 16384 0.06103 610
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3 8192 0.12207 1221
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4 4096 0.24414 2441
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5 2048 0.48828 4883
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6 1024 0.97656 9766
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7 512 1.95313 19531
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8 256 3.90625 39063
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9 128 7.8125 78125
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10 64 15.6250 156250
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11 32 31.25 312500
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12 16 62.5 625000
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13 8 125 1250000
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14 4 250 2500000
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15 2 500 5000000
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1 32768 0.03052 305,175
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2 16384 0.06103 610,351
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3 8192 0.12207 1,220,703
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4 4096 0.24414 2,441,406
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5 2048 0.48828 4,882,812
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6 1024 0.97656 9,765,625 <- minimum
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7 512 1.95313 19,531,250
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8 256 3.90625 39,062,500
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9 128 7.8125 78,125,000
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10 64 15.6250 156,250,000 <- maximum / default
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11 32 31.25 312,500,000
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12 16 62.5 625,000,000
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13 8 125 1,250,000,000
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14 4 250 2,500,000,000
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15 2 500 5,000,000,000
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*/
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FORCEINLINE
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ULONG
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RtcClockRateToIncrement(UCHAR Rate)
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RtcClockRateToPreciseIncrement(UCHAR Rate)
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{
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/* Calculate frequency */
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ULONG Freqency = 32768 >> (Rate - 1);
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ULONG Frequency = 32768 >> (Rate - 1);
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/* Calculate interval in 100ns interval: Interval = (1 / Frequency) * 10000000
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This formula will round properly, instead of truncating. */
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return (10000000 + (Freqency/2)) / Freqency;
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/* Calculate interval in 0.1ns interval: Interval = (1 / Frequency) * 10,000,000,000 */
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return 10000000000ULL / Frequency;
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}
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VOID
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RtcSetClockRate(UCHAR ClockRate)
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{
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UCHAR RegisterA;
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ULONG PreciseIncrement;
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/* Update the global values */
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HalpCurrentRate = ClockRate;
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HalpCurrentTimeIncrement = RtcClockRateToIncrement(ClockRate);
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HalpCurrentClockRate = ClockRate;
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PreciseIncrement = RtcClockRateToPreciseIncrement(ClockRate);
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HalpCurrentTimeIncrement = PreciseIncrement / 1000;
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HalpCurrentFractionalIncrement = PreciseIncrement % 1000;
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/* Acquire CMOS lock */
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HalpAcquireCmosSpinLock();
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@ -113,14 +119,17 @@ HalpInitializeClock(VOID)
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HalpReleaseCmosSpinLock();
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/* Set initial rate */
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RtcSetClockRate(HalpCurrentRate);
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RtcSetClockRate(HalpCurrentClockRate);
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/* Restore interrupt state */
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__writeeflags(EFlags);
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/* Calculate minumum and maximum increment */
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HalpMinimumTimeIncrement = RtcClockRateToPreciseIncrement(RtcMinimumClockRate) / 1000;
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HalpMaximumTimeIncrement = RtcClockRateToPreciseIncrement(RtcMaximumClockRate) / 1000;
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/* Notify the kernel about the maximum and minimum increment */
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KeSetTimeIncrement(RtcClockRateToIncrement(RtcMaximumClockRate),
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RtcClockRateToIncrement(RtcMinimumClockRate));
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KeSetTimeIncrement(HalpMaximumTimeIncrement, HalpMinimumTimeIncrement);
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/* Enable the timer interrupt */
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HalEnableSystemInterrupt(APIC_CLOCK_VECTOR, CLOCK_LEVEL, Latched);
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@ -155,14 +164,22 @@ HalpClockInterruptHandler(IN PKTRAP_FRAME TrapFrame)
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/* Save increment */
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LastIncrement = HalpCurrentTimeIncrement;
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/* Check if the running fraction has accounted for 100 ns */
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HalpRunningFraction += HalpCurrentFractionalIncrement;
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if (HalpRunningFraction >= 1000)
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{
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LastIncrement++;
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HalpRunningFraction -= 1000;
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}
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/* Check if someone changed the time rate */
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if (HalpClockSetMSRate)
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if (HalpSetClockRate)
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{
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/* Set new clock rate */
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RtcSetClockRate(HalpNextMSRate);
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RtcSetClockRate(HalpNextClockRate);
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/* We're done */
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HalpClockSetMSRate = FALSE;
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HalpSetClockRate = FALSE;
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}
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/* Update the system time -- on x86 the kernel will exit this trap */
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@ -174,18 +191,20 @@ NTAPI
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HalSetTimeIncrement(IN ULONG Increment)
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{
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UCHAR Rate;
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ULONG CurrentIncrement;
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/* Lookup largest value below given Increment */
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for (Rate = RtcMinimumClockRate; Rate <= RtcMaximumClockRate; Rate++)
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{
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/* Check if this is the largest rate possible */
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if (RtcClockRateToIncrement(Rate + 1) > Increment) break;
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CurrentIncrement = RtcClockRateToPreciseIncrement(Rate + 1) / 1000;
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if (Increment > CurrentIncrement) break;
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}
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/* Set the rate and tell HAL we want to change it */
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HalpNextMSRate = Rate;
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HalpClockSetMSRate = TRUE;
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HalpNextClockRate = Rate;
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HalpSetClockRate = TRUE;
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/* Return the real increment */
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return RtcClockRateToIncrement(Rate);
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return RtcClockRateToPreciseIncrement(Rate) / 1000;
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}
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