hal/halx86/pc98/clock.c

   1 /*
   2  * PROJECT:     NEC PC-98 series HAL
   3  * LICENSE:     GPL-2.0-or-later (https://spdx.org/licenses/GPL-2.0-or-later)
   4  * PURPOSE:     PIT rollover tables
   5  * COPYRIGHT:   Copyright 2020 Dmitry Borisov (di.sean@protonmail.com)
   6  */
   7
   8 /* INCLUDES ******************************************************************/
   9
  10 #include <hal.h>
  11
  12 /* GLOBALS *******************************************************************/
  13
  14 #define LPT_STATUS         0x42
  15 #define SYSTEM_CLOCK_8_MHZ 0x20
  16
  17 ULONG PIT_FREQUENCY;
  18 HALP_ROLLOVER HalpRolloverTable[15];
  19
  20 /* Accuracy is 97.5% */
  21 static const HALP_ROLLOVER RolloverTable1[15] =
  22 {
  23     {1996, 9996}, /* 1 ms */
  24     {3993, 19997},
  25     {5990, 29998},
  26     {7987, 39999},
  27     {9984, 50000},
  28     {11980, 59996},
  29     {13977, 69997},
  30     {15974, 79998},
  31     {17971, 89999},
  32     {19968, 100000},
  33     {21964, 109996},
  34     {23961, 119997},
  35     {25958, 129998},
  36     {27955, 139999},
  37     {29951, 149995} /* 15 ms */
  38 };
  39 static const HALP_ROLLOVER RolloverTable2[15] =
  40 {
  41     {2463, 10022}, /* 1 ms */
  42     {4912, 19987},
  43     {7376, 30013},
  44     {9825, 39978},
  45     {12288, 50000},
  46     {14751, 60022},
  47     {17200, 69987},
  48     {19664, 80013},
  49     {22113, 89978},
  50     {24576, 100000},
  51     {27039, 110022},
  52     {29488, 119987},
  53     {31952, 130013},
  54     {34401, 139978},
  55     {36864, 150000} /* 15 ms */
  56 };
  57
  58 /* PRIVATE FUNCTIONS *********************************************************/
  59
  60 VOID
  61 NTAPI
  62 HalpInitializeClockPc98(VOID)
  63 {
  64     /* Obtain system clock value from the parallel port */
  65     if (__inbyte(LPT_STATUS) & SYSTEM_CLOCK_8_MHZ)
  66     {
  67         PIT_FREQUENCY = TIMER_FREQUENCY_1;
  68         RtlCopyMemory(HalpRolloverTable, RolloverTable1, sizeof(HALP_ROLLOVER) * 15);
  69     }
  70     else
  71     {
  72         PIT_FREQUENCY = TIMER_FREQUENCY_2;
  73         RtlCopyMemory(HalpRolloverTable, RolloverTable2, sizeof(HALP_ROLLOVER) * 15);
  74     }
  75 }