https://git.reactos.org/?p=reactos.git;a=commitdiff;h=3e1454c739ca7f59d4ce68...
commit 3e1454c739ca7f59d4ce686a5b6a8aa9c22d0e7e Author: Timo Kreuzer timo.kreuzer@reactos.org AuthorDate: Fri Jul 16 11:42:45 2021 +0200 Commit: Timo Kreuzer timo.kreuzer@reactos.org CommitDate: Mon Jul 19 23:05:03 2021 +0200
[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. --- hal/halx86/apic/rtctimer.c | 99 +++++++++++++++++++++++++++------------------- 1 file changed, 59 insertions(+), 40 deletions(-)
diff --git a/hal/halx86/apic/rtctimer.c b/hal/halx86/apic/rtctimer.c index 4c0b27dbc06..50b50248366 100644 --- a/hal/halx86/apic/rtctimer.c +++ b/hal/halx86/apic/rtctimer.c @@ -18,56 +18,62 @@
/* GLOBALS ********************************************************************/
-BOOLEAN HalpClockSetMSRate; -UCHAR HalpNextMSRate; -UCHAR HalpCurrentRate = 9; /* Initial rate 9: 128 Hz / 7.8 ms */ -ULONG HalpCurrentTimeIncrement; -static UCHAR RtcMinimumClockRate = 8; /* Minimum rate 8: 256 Hz / 3.9 ms */ -static UCHAR RtcMaximumClockRate = 12; /* Maximum rate 12: 16 Hz / 62.5 ms */ +static const UCHAR RtcMinimumClockRate = 6; /* Minimum rate 6: 1024 Hz / 0.97 ms */ +static const UCHAR RtcMaximumClockRate = 10; /* Maximum rate 10: 64 Hz / 15.6 ms */ +static UCHAR HalpCurrentClockRate = 10; /* Initial rate 10: 64 Hz / 15.6 ms */ +static ULONG HalpCurrentTimeIncrement; +static ULONG HalpMinimumTimeIncrement; +static ULONG HalpMaximumTimeIncrement; +static ULONG HalpCurrentFractionalIncrement; +static ULONG HalpRunningFraction; +static BOOLEAN HalpSetClockRate; +static UCHAR HalpNextClockRate;
/*! \brief Converts the CMOS RTC rate into the time increment in 100ns intervals.
- Rate Freqency Interval (ms) Result - ------------------------------------- + Rate Frequency Interval (ms) Precise increment (0.1ns) + ------------------------------------------------------ 0 disabled - 1 32768 0.03052 305 - 2 16384 0.06103 610 - 3 8192 0.12207 1221 - 4 4096 0.24414 2441 - 5 2048 0.48828 4883 - 6 1024 0.97656 9766 - 7 512 1.95313 19531 - 8 256 3.90625 39063 - 9 128 7.8125 78125 - 10 64 15.6250 156250 - 11 32 31.25 312500 - 12 16 62.5 625000 - 13 8 125 1250000 - 14 4 250 2500000 - 15 2 500 5000000 + 1 32768 0.03052 305,175 + 2 16384 0.06103 610,351 + 3 8192 0.12207 1,220,703 + 4 4096 0.24414 2,441,406 + 5 2048 0.48828 4,882,812 + 6 1024 0.97656 9,765,625 <- minimum + 7 512 1.95313 19,531,250 + 8 256 3.90625 39,062,500 + 9 128 7.8125 78,125,000 + 10 64 15.6250 156,250,000 <- maximum / default + 11 32 31.25 312,500,000 + 12 16 62.5 625,000,000 + 13 8 125 1,250,000,000 + 14 4 250 2,500,000,000 + 15 2 500 5,000,000,000
*/ FORCEINLINE ULONG -RtcClockRateToIncrement(UCHAR Rate) +RtcClockRateToPreciseIncrement(UCHAR Rate) { /* Calculate frequency */ - ULONG Freqency = 32768 >> (Rate - 1); + ULONG Frequency = 32768 >> (Rate - 1);
- /* Calculate interval in 100ns interval: Interval = (1 / Frequency) * 10000000 - This formula will round properly, instead of truncating. */ - return (10000000 + (Freqency/2)) / Freqency; + /* Calculate interval in 0.1ns interval: Interval = (1 / Frequency) * 10,000,000,000 */ + return 10000000000ULL / Frequency; }
VOID RtcSetClockRate(UCHAR ClockRate) { UCHAR RegisterA; + ULONG PreciseIncrement;
/* Update the global values */ - HalpCurrentRate = ClockRate; - HalpCurrentTimeIncrement = RtcClockRateToIncrement(ClockRate); + HalpCurrentClockRate = ClockRate; + PreciseIncrement = RtcClockRateToPreciseIncrement(ClockRate); + HalpCurrentTimeIncrement = PreciseIncrement / 1000; + HalpCurrentFractionalIncrement = PreciseIncrement % 1000;
/* Acquire CMOS lock */ HalpAcquireCmosSpinLock(); @@ -113,14 +119,17 @@ HalpInitializeClock(VOID) HalpReleaseCmosSpinLock();
/* Set initial rate */ - RtcSetClockRate(HalpCurrentRate); + RtcSetClockRate(HalpCurrentClockRate);
/* Restore interrupt state */ __writeeflags(EFlags);
+ /* Calculate minumum and maximum increment */ + HalpMinimumTimeIncrement = RtcClockRateToPreciseIncrement(RtcMinimumClockRate) / 1000; + HalpMaximumTimeIncrement = RtcClockRateToPreciseIncrement(RtcMaximumClockRate) / 1000; + /* Notify the kernel about the maximum and minimum increment */ - KeSetTimeIncrement(RtcClockRateToIncrement(RtcMaximumClockRate), - RtcClockRateToIncrement(RtcMinimumClockRate)); + KeSetTimeIncrement(HalpMaximumTimeIncrement, HalpMinimumTimeIncrement);
/* Enable the timer interrupt */ HalEnableSystemInterrupt(APIC_CLOCK_VECTOR, CLOCK_LEVEL, Latched); @@ -155,14 +164,22 @@ HalpClockInterruptHandler(IN PKTRAP_FRAME TrapFrame) /* Save increment */ LastIncrement = HalpCurrentTimeIncrement;
+ /* Check if the running fraction has accounted for 100 ns */ + HalpRunningFraction += HalpCurrentFractionalIncrement; + if (HalpRunningFraction >= 1000) + { + LastIncrement++; + HalpRunningFraction -= 1000; + } + /* Check if someone changed the time rate */ - if (HalpClockSetMSRate) + if (HalpSetClockRate) { /* Set new clock rate */ - RtcSetClockRate(HalpNextMSRate); + RtcSetClockRate(HalpNextClockRate);
/* We're done */ - HalpClockSetMSRate = FALSE; + HalpSetClockRate = FALSE; }
/* Update the system time -- on x86 the kernel will exit this trap */ @@ -174,18 +191,20 @@ NTAPI HalSetTimeIncrement(IN ULONG Increment) { UCHAR Rate; + ULONG CurrentIncrement;
/* Lookup largest value below given Increment */ for (Rate = RtcMinimumClockRate; Rate <= RtcMaximumClockRate; Rate++) { /* Check if this is the largest rate possible */ - if (RtcClockRateToIncrement(Rate + 1) > Increment) break; + CurrentIncrement = RtcClockRateToPreciseIncrement(Rate + 1) / 1000; + if (Increment > CurrentIncrement) break; }
/* Set the rate and tell HAL we want to change it */ - HalpNextMSRate = Rate; - HalpClockSetMSRate = TRUE; + HalpNextClockRate = Rate; + HalpSetClockRate = TRUE;
/* Return the real increment */ - return RtcClockRateToIncrement(Rate); + return RtcClockRateToPreciseIncrement(Rate) / 1000; }
-
Timo Kreuzer