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/module.h>
  25
  26 #include <asm/cpu-features.h>
  27 #include <asm/div64.h>
  28 #include <asm/smtc_ipi.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 0;
  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
  74 void __init clocksource_set_clock(struct clocksource *cs, unsigned int clock)
  75 {
  76         u64 temp;
  77         u32 shift;
  78
  79         /* Find a shift value */
  80         for (shift = 32; shift > 0; shift--) {
  81                 temp = (u64) NSEC_PER_SEC << shift;
  82                 do_div(temp, clock);
  83                 if ((temp >> 32) == 0)
  84                         break;
  85         }
  86         cs->shift = shift;
  87         cs->mult = (u32) temp;
  88 }
  89
  90 void __cpuinit clockevent_set_clock(struct clock_event_device *cd,
  91         unsigned int clock)
  92 {
  93         u64 temp;
  94         u32 shift;
  95
  96         /* Find a shift value */
  97         for (shift = 32; shift > 0; shift--) {
  98                 temp = (u64) clock << shift;
  99                 do_div(temp, NSEC_PER_SEC);
 100                 if ((temp >> 32) == 0)
 101                         break;
 102         }
 103         cd->shift = shift;
 104         cd->mult = (u32) temp;
 105 }
 106
 107 /*
 108  * This function exists in order to cause an error due to a duplicate
 109  * definition if platform code should have its own implementation.  The hook
 110  * to use instead is plat_time_init.  plat_time_init does not receive the
 111  * irqaction pointer argument anymore.  This is because any function which
 112  * initializes an interrupt timer now takes care of its own request_irq rsp.
 113  * setup_irq calls and each clock_event_device should use its own
 114  * struct irqrequest.
 115  */
 116 void __init plat_timer_setup(void)
 117 {
 118         BUG();
 119 }
 120
 121 static __init int cpu_has_mfc0_count_bug(void)
 122 {
 123         switch (current_cpu_type()) {
 124         case CPU_R4000PC:
 125         case CPU_R4000SC:
 126         case CPU_R4000MC:
 127                 /*
 128                  * V3.0 is documented as suffering from the mfc0 from count bug.
 129                  * Afaik this is the last version of the R4000.  Later versions
 130                  * were marketed as R4400.
 131                  */
 132                 return 1;
 133
 134         case CPU_R4400PC:
 135         case CPU_R4400SC:
 136         case CPU_R4400MC:
 137                 /*
 138                  * The published errata for the R4400 upto 3.0 say the CPU
 139                  * has the mfc0 from count bug.
 140                  */
 141                 if ((current_cpu_data.processor_id & 0xff) <= 0x30)
 142                         return 1;
 143
 144                 /*
 145                  * we assume newer revisions are ok
 146                  */
 147                 return 0;
 148         }
 149
 150         return 0;
 151 }
 152
 153 void __init time_init(void)
 154 {
 155         plat_time_init();
 156
 157         if (!mips_clockevent_init() || !cpu_has_mfc0_count_bug())
 158                 init_mips_clocksource();
 159 }