arch/mips/kernel/time.c

   1 /*
   2  * Copyright 2001 MontaVista Software Inc.
   3  * Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
   4  * Copyright (c) 2003, 2004  Maciej W. Rozycki
   5  *
   6  * Common time service routines for MIPS machines.
   7  *
   8  * This program is free software; you can redistribute  it and/or modify it
   9  * under  the terms of  the GNU General  Public License as published by the
  10  * Free Software Foundation;  either version 2 of the  License, or (at your
  11  * option) any later version.
  12  */
  13 #include <linux/bug.h>
  14 #include <linux/clockchips.h>
  15 #include <linux/types.h>
  16 #include <linux/kernel.h>
  17 #include <linux/init.h>
  18 #include <linux/sched.h>
  19 #include <linux/param.h>
  20 #include <linux/time.h>
  21 #include <linux/timex.h>
  22 #include <linux/smp.h>
  23 #include <linux/spinlock.h>
  24 #include <linux/export.h>
  25
  26 #include <asm/cpu-features.h>
  27 #include <asm/cpu-type.h>
  28 #include <asm/div64.h>
  29 #include <asm/time.h>
  30
  31 /*
  32  * forward reference
  33  */
  34 DEFINE_SPINLOCK(rtc_lock);
  35 EXPORT_SYMBOL(rtc_lock);
  36
  37 int __weak rtc_mips_set_time(unsigned long sec)
  38 {
  39         return -ENODEV;
  40 }
  41
  42 int __weak rtc_mips_set_mmss(unsigned long nowtime)
  43 {
  44         return rtc_mips_set_time(nowtime);
  45 }
  46
  47 int update_persistent_clock(struct timespec now)
  48 {
  49         return rtc_mips_set_mmss(now.tv_sec);
  50 }
  51
  52 static int null_perf_irq(void)
  53 {
  54         return 0;
  55 }
  56
  57 int (*perf_irq)(void) = null_perf_irq;
  58
  59 EXPORT_SYMBOL(perf_irq);
  60
  61 /*
  62  * time_init() - it does the following things.
  63  *
  64  * 1) plat_time_init() -
  65  *      a) (optional) set up RTC routines,
  66  *      b) (optional) calibrate and set the mips_hpt_frequency
  67  *          (only needed if you intended to use cpu counter as timer interrupt
  68  *           source)
  69  * 2) calculate a couple of cached variables for later usage
  70  */
  71
  72 unsigned int mips_hpt_frequency;
  73 EXPORT_SYMBOL_GPL(mips_hpt_frequency);
  74
  75 static __init int cpu_has_mfc0_count_bug(void)
  76 {
  77         switch (current_cpu_type()) {
  78         case CPU_R4000PC:
  79         case CPU_R4000SC:
  80         case CPU_R4000MC:
  81                 /*
  82                  * V3.0 is documented as suffering from the mfc0 from count bug.
  83                  * Afaik this is the last version of the R4000.  Later versions
  84                  * were marketed as R4400.
  85                  */
  86                 return 1;
  87
  88         case CPU_R4400PC:
  89         case CPU_R4400SC:
  90         case CPU_R4400MC:
  91                 /*
  92                  * The published errata for the R4400 up to 3.0 say the CPU
  93                  * has the mfc0 from count bug.
  94                  */
  95                 if ((current_cpu_data.processor_id & 0xff) <= 0x30)
  96                         return 1;
  97
  98                 /*
  99                  * we assume newer revisions are ok
 100                  */
 101                 return 0;
 102         }
 103
 104         return 0;
 105 }
 106
 107 void __init time_init(void)
 108 {
 109         plat_time_init();
 110
 111         /*
 112          * The use of the R4k timer as a clock event takes precedence;
 113          * if reading the Count register might interfere with the timer
 114          * interrupt, then we don't use the timer as a clock source.
 115          * We may still use the timer as a clock source though if the
 116          * timer interrupt isn't reliable; the interference doesn't
 117          * matter then, because we don't use the interrupt.
 118          */
 119         if (mips_clockevent_init() != 0 || !cpu_has_mfc0_count_bug())
 120                 init_mips_clocksource();
 121 }