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 EXPORT_SYMBOL(rtc_mips_set_time);
  42
  43 int __weak rtc_mips_set_mmss(unsigned long nowtime)
  44 {
  45         return rtc_mips_set_time(nowtime);
  46 }
  47
  48 int update_persistent_clock(struct timespec now)
  49 {
  50         return rtc_mips_set_mmss(now.tv_sec);
  51 }
  52
  53 /*
  54  * High precision timer functions for a R4k-compatible timer.
  55  */
  56 static cycle_t c0_hpt_read(void)
  57 {
  58         return read_c0_count();
  59 }
  60
  61 int (*mips_timer_state)(void);
  62
  63 int null_perf_irq(void)
  64 {
  65         return 0;
  66 }
  67
  68 EXPORT_SYMBOL(null_perf_irq);
  69
  70 int (*perf_irq)(void) = null_perf_irq;
  71
  72 EXPORT_SYMBOL(perf_irq);
  73
  74 /*
  75  * time_init() - it does the following things.
  76  *
  77  * 1) plat_time_init() -
  78  *      a) (optional) set up RTC routines,
  79  *      b) (optional) calibrate and set the mips_hpt_frequency
  80  *          (only needed if you intended to use cpu counter as timer interrupt
  81  *           source)
  82  * 2) calculate a couple of cached variables for later usage
  83  */
  84
  85 unsigned int mips_hpt_frequency;
  86
  87 static struct clocksource clocksource_mips = {
  88         .name           = "MIPS",
  89         .read           = c0_hpt_read,
  90         .mask           = CLOCKSOURCE_MASK(32),
  91         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  92 };
  93
  94 void __init clocksource_set_clock(struct clocksource *cs, unsigned int clock)
  95 {
  96         u64 temp;
  97         u32 shift;
  98
  99         /* Find a shift value */
 100         for (shift = 32; shift > 0; shift--) {
 101                 temp = (u64) NSEC_PER_SEC << shift;
 102                 do_div(temp, clock);
 103                 if ((temp >> 32) == 0)
 104                         break;
 105         }
 106         cs->shift = shift;
 107         cs->mult = (u32) temp;
 108 }
 109
 110 void __cpuinit clockevent_set_clock(struct clock_event_device *cd,
 111         unsigned int clock)
 112 {
 113         u64 temp;
 114         u32 shift;
 115
 116         /* Find a shift value */
 117         for (shift = 32; shift > 0; shift--) {
 118                 temp = (u64) clock << shift;
 119                 do_div(temp, NSEC_PER_SEC);
 120                 if ((temp >> 32) == 0)
 121                         break;
 122         }
 123         cd->shift = shift;
 124         cd->mult = (u32) temp;
 125 }
 126
 127 static void __init init_mips_clocksource(void)
 128 {
 129         /* Calclate a somewhat reasonable rating value */
 130         clocksource_mips.rating = 200 + mips_hpt_frequency / 10000000;
 131
 132         clocksource_set_clock(&clocksource_mips, mips_hpt_frequency);
 133
 134         clocksource_register(&clocksource_mips);
 135 }
 136
 137 void __init __weak plat_time_init(void)
 138 {
 139 }
 140
 141 /*
 142  * This function exists in order to cause an error due to a duplicate
 143  * definition if platform code should have its own implementation.  The hook
 144  * to use instead is plat_time_init.  plat_time_init does not receive the
 145  * irqaction pointer argument anymore.  This is because any function which
 146  * initializes an interrupt timer now takes care of its own request_irq rsp.
 147  * setup_irq calls and each clock_event_device should use its own
 148  * struct irqrequest.
 149  */
 150 void __init plat_timer_setup(void)
 151 {
 152         BUG();
 153 }
 154
 155 static __init int cpu_has_mfc0_count_bug(void)
 156 {
 157         switch (current_cpu_type()) {
 158         case CPU_R4000PC:
 159         case CPU_R4000SC:
 160         case CPU_R4000MC:
 161                 /*
 162                  * V3.0 is documented as suffering from the mfc0 from count bug.
 163                  * Afaik this is the last version of the R4000.  Later versions
 164                  * were marketed as R4400.
 165                  */
 166                 return 1;
 167
 168         case CPU_R4400PC:
 169         case CPU_R4400SC:
 170         case CPU_R4400MC:
 171                 /*
 172                  * The published errata for the R4400 upto 3.0 say the CPU
 173                  * has the mfc0 from count bug.
 174                  */
 175                 if ((current_cpu_data.processor_id & 0xff) <= 0x30)
 176                         return 1;
 177
 178                 /*
 179                  * I don't have erratas for newer R4400 so be paranoid.
 180                  */
 181                 return 1;
 182         }
 183
 184         return 0;
 185 }
 186
 187 void __init time_init(void)
 188 {
 189         plat_time_init();
 190
 191         if (mips_clockevent_init() || !cpu_has_mfc0_count_bug())
 192                 init_mips_clocksource();
 193 }