src/system/kernel/arch/x86/timers/x86_pit.cpp

   1 /*
   2  * Copyright 2008, Dustin Howett, dustin.howett@gmail.com. All rights reserved.
   3  * Copyright 2005, Axel Dörfler, axeld@pinc-software.de. All rights reserved.
   4  * Distributed under the terms of the MIT License.
   5  *
   6  * Copyright 2001, Travis Geiselbrecht. All rights reserved.
   7  * Distributed under the terms of the NewOS License.
   8  */
   9
  10 #include <timer.h>
  11 #include <arch/x86/timer.h>
  12
  13 #include <arch/int.h>
  14 #include <arch/cpu.h>
  15
  16 #include "pit.h"
  17
  18 static bool sPITTimerInitialized = false;
  19
  20 struct timer_info gPITTimer = {
  21         "PIT",
  22         &pit_get_prio,
  23         &pit_set_hardware_timer,
  24         &pit_clear_hardware_timer,
  25         &pit_init
  26 };
  27
  28
  29 static int
  30 pit_get_prio(void)
  31 {
  32         return 1;
  33 }
  34
  35
  36 static int32
  37 pit_timer_interrupt(void *data)
  38 {
  39         return timer_interrupt();
  40 }
  41
  42
  43 static status_t
  44 pit_set_hardware_timer(bigtime_t relativeTimeout)
  45 {
  46         uint16 nextEventClocks;
  47
  48         if (relativeTimeout <= 0)
  49                 nextEventClocks = 2;
  50         else if (relativeTimeout < PIT_MAX_TIMER_INTERVAL)
  51                 nextEventClocks = relativeTimeout * PIT_CLOCK_RATE / 1000000;
  52         else
  53                 nextEventClocks = 0xffff;
  54
  55         out8(PIT_SELCH0 | PIT_RWBOTH | PIT_MD_INTON0, PIT_CTRL);
  56         out8(nextEventClocks & 0xff, PIT_CNT0);
  57         out8((nextEventClocks >> 8) & 0xff, PIT_CNT0);
  58
  59         arch_int_enable_io_interrupt(0);
  60         return B_OK;
  61 }
  62
  63
  64 static status_t
  65 pit_clear_hardware_timer(void)
  66 {
  67         arch_int_disable_io_interrupt(0);
  68         return B_OK;
  69 }
  70
  71
  72 static status_t
  73 pit_init(struct kernel_args *args)
  74 {
  75         if (sPITTimerInitialized) {
  76                 return B_OK;
  77         }
  78
  79         install_io_interrupt_handler(0, &pit_timer_interrupt, NULL, 0);
  80         pit_clear_hardware_timer();
  81
  82         sPITTimerInitialized = true;
  83
  84         return B_OK;
  85 }