arch/x86/kernel/time_32.c

   1 /*
   2  *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
   3  *
   4  * This file contains the PC-specific time handling details:
   5  * reading the RTC at bootup, etc..
   6  * 1994-07-02    Alan Modra
   7  *      fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
   8  * 1995-03-26    Markus Kuhn
   9  *      fixed 500 ms bug at call to set_rtc_mmss, fixed DS12887
  10  *      precision CMOS clock update
  11  * 1996-05-03    Ingo Molnar
  12  *      fixed time warps in do_[slow|fast]_gettimeoffset()
  13  * 1997-09-10   Updated NTP code according to technical memorandum Jan '96
  14  *              "A Kernel Model for Precision Timekeeping" by Dave Mills
  15  * 1998-09-05    (Various)
  16  *      More robust do_fast_gettimeoffset() algorithm implemented
  17  *      (works with APM, Cyrix 6x86MX and Centaur C6),
  18  *      monotonic gettimeofday() with fast_get_timeoffset(),
  19  *      drift-proof precision TSC calibration on boot
  20  *      (C. Scott Ananian <cananian@alumni.princeton.edu>, Andrew D.
  21  *      Balsa <andrebalsa@altern.org>, Philip Gladstone <philip@raptor.com>;
  22  *      ported from 2.0.35 Jumbo-9 by Michael Krause <m.krause@tu-harburg.de>).
  23  * 1998-12-16    Andrea Arcangeli
  24  *      Fixed Jumbo-9 code in 2.1.131: do_gettimeofday was missing 1 jiffy
  25  *      because was not accounting lost_ticks.
  26  * 1998-12-24 Copyright (C) 1998  Andrea Arcangeli
  27  *      Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
  28  *      serialize accesses to xtime/lost_ticks).
  29  */
  30
  31 #include <linux/init.h>
  32 #include <linux/interrupt.h>
  33 #include <linux/time.h>
  34 #include <linux/mca.h>
  35
  36 #include <asm/arch_hooks.h>
  37 #include <asm/hpet.h>
  38 #include <asm/time.h>
  39
  40 #include "do_timer.h"
  41
  42 unsigned int cpu_khz;   /* Detected as we calibrate the TSC */
  43 EXPORT_SYMBOL(cpu_khz);
  44
  45 int timer_ack;
  46
  47 unsigned long profile_pc(struct pt_regs *regs)
  48 {
  49         unsigned long pc = instruction_pointer(regs);
  50
  51 #ifdef CONFIG_SMP
  52         if (!v8086_mode(regs) && SEGMENT_IS_KERNEL_CODE(regs->cs) &&
  53             in_lock_functions(pc)) {
  54 #ifdef CONFIG_FRAME_POINTER
  55                 return *(unsigned long *)(regs->bp + 4);
  56 #else
  57                 unsigned long *sp = (unsigned long *)&regs->sp;
  58
  59                 /* Return address is either directly at stack pointer
  60                    or above a saved flags. Eflags has bits 22-31 zero,
  61                    kernel addresses don't. */
  62                 if (sp[0] >> 22)
  63                         return sp[0];
  64                 if (sp[1] >> 22)
  65                         return sp[1];
  66 #endif
  67         }
  68 #endif
  69         return pc;
  70 }
  71 EXPORT_SYMBOL(profile_pc);
  72
  73 /*
  74  * This is the same as the above, except we _also_ save the current
  75  * Time Stamp Counter value at the time of the timer interrupt, so that
  76  * we later on can estimate the time of day more exactly.
  77  */
  78 irqreturn_t timer_interrupt(int irq, void *dev_id)
  79 {
  80         /* Keep nmi watchdog up to date */
  81         per_cpu(irq_stat, smp_processor_id()).irq0_irqs++;
  82
  83 #ifdef CONFIG_X86_IO_APIC
  84         if (timer_ack) {
  85                 /*
  86                  * Subtle, when I/O APICs are used we have to ack timer IRQ
  87                  * manually to reset the IRR bit for do_slow_gettimeoffset().
  88                  * This will also deassert NMI lines for the watchdog if run
  89                  * on an 82489DX-based system.
  90                  */
  91                 spin_lock(&i8259A_lock);
  92                 outb(0x0c, PIC_MASTER_OCW3);
  93                 /* Ack the IRQ; AEOI will end it automatically. */
  94                 inb(PIC_MASTER_POLL);
  95                 spin_unlock(&i8259A_lock);
  96         }
  97 #endif
  98
  99         do_timer_interrupt_hook();
 100
 101         if (MCA_bus) {
 102                 /* The PS/2 uses level-triggered interrupts.  You can't
 103                 turn them off, nor would you want to (any attempt to
 104                 enable edge-triggered interrupts usually gets intercepted by a
 105                 special hardware circuit).  Hence we have to acknowledge
 106                 the timer interrupt.  Through some incredibly stupid
 107                 design idea, the reset for IRQ 0 is done by setting the
 108                 high bit of the PPI port B (0x61).  Note that some PS/2s,
 109                 notably the 55SX, work fine if this is removed.  */
 110
 111                 u8 irq_v = inb_p( 0x61 );       /* read the current state */
 112                 outb_p( irq_v|0x80, 0x61 );     /* reset the IRQ */
 113         }
 114
 115         return IRQ_HANDLED;
 116 }
 117
 118 extern void (*late_time_init)(void);
 119 /* Duplicate of time_init() below, with hpet_enable part added */
 120 void __init hpet_time_init(void)
 121 {
 122         if (!hpet_enable())
 123                 setup_pit_timer();
 124         time_init_hook();
 125 }
 126
 127 /*
 128  * This is called directly from init code; we must delay timer setup in the
 129  * HPET case as we can't make the decision to turn on HPET this early in the
 130  * boot process.
 131  *
 132  * The chosen time_init function will usually be hpet_time_init, above, but
 133  * in the case of virtual hardware, an alternative function may be substituted.
 134  */
 135 void __init time_init(void)
 136 {
 137         tsc_init();
 138         late_time_init = choose_time_init();
 139 }