https://git.reactos.org/?p=reactos.git;a=commitdiff;h=3bbcc16d8e76ecf4296bdfc57e461a18523198a6
commit 3bbcc16d8e76ecf4296bdfc57e461a18523198a6 Author: Timo Kreuzer <[email protected]> AuthorDate: Tue Dec 31 09:39:55 2019 +0100 Commit: Timo Kreuzer <[email protected]> CommitDate: Sun Sep 20 23:08:17 2020 +0200 [HAL] Fix calculation of timer increment --- hal/halx86/apic/rtctimer.c | 42 +++++++++++++++++++++++++++++++++++------- 1 file changed, 35 insertions(+), 7 deletions(-) diff --git a/hal/halx86/apic/rtctimer.c b/hal/halx86/apic/rtctimer.c index afd3d9dab5a..62318f724ba 100644 --- a/hal/halx86/apic/rtctimer.c +++ b/hal/halx86/apic/rtctimer.c @@ -4,7 +4,9 @@ * FILE: hal/halx86/apic/rtctimer.c * PURPOSE: HAL APIC Management and Control Code * PROGRAMMERS: Timo Kreuzer ([email protected]) - * REFERENCES: + * REFERENCES: https://wiki.osdev.org/RTC + * https://forum.osdev.org/viewtopic.php?f=13&t=20825&start=0 + * http://www.bioscentral.com/misc/cmosmap.htm */ /* INCLUDES *******************************************************************/ @@ -24,16 +26,42 @@ BOOLEAN HalpClockSetMSRate; UCHAR HalpNextMSRate; UCHAR HalpCurrentRate = 9; /* Initial rate 9: 128 Hz / 7.8 ms */ ULONG HalpCurrentTimeIncrement; -static UCHAR RtcMinimumClockRate = 6; /* Minimum rate 6: 16 Hz / 62.5 ms */ -static UCHAR RtcMaximumClockRate = 10; /* Maximum rate 10: 256 Hz / 3.9 ms */ - - +static UCHAR RtcMinimumClockRate = 8; /* Minimum rate 8: 256 Hz / 3.9 ms */ +static UCHAR RtcMaximumClockRate = 12; /* Maximum rate 12: 16 Hz / 62.5 ms */ + +/*! + \brief Converts the CMOS RTC rate into the time increment in 100ns intervals. + + Rate Freqency Interval (ms) Result + ------------------------------------- + 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 + +*/ FORCEINLINE ULONG RtcClockRateToIncrement(UCHAR Rate) { - ULONG Freqency = ((32768 << 1) >> Rate); - return (1000000 + (Freqency/2)) / Freqency; + /* Calculate frequency */ + ULONG Freqency = 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; } VOID
