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 static unsigned int __init calibrate_hpt(void)
  95 {
  96         cycle_t frequency, hpt_start, hpt_end, hpt_count, hz;
  97
  98         const int loops = HZ / 10;
  99         int log_2_loops = 0;
 100         int i;
 101
 102         /*
 103          * We want to calibrate for 0.1s, but to avoid a 64-bit
 104          * division we round the number of loops up to the nearest
 105          * power of 2.
 106          */
 107         while (loops > 1 << log_2_loops)
 108                 log_2_loops++;
 109         i = 1 << log_2_loops;
 110
 111         /*
 112          * Wait for a rising edge of the timer interrupt.
 113          */
 114         while (mips_timer_state());
 115         while (!mips_timer_state());
 116
 117         /*
 118          * Now see how many high precision timer ticks happen
 119          * during the calculated number of periods between timer
 120          * interrupts.
 121          */
 122         hpt_start = clocksource_mips.read();
 123         do {
 124                 while (mips_timer_state());
 125                 while (!mips_timer_state());
 126         } while (--i);
 127         hpt_end = clocksource_mips.read();
 128
 129         hpt_count = (hpt_end - hpt_start) & clocksource_mips.mask;
 130         hz = HZ;
 131         frequency = hpt_count * hz;
 132
 133         return frequency >> log_2_loops;
 134 }
 135
 136 void __init clocksource_set_clock(struct clocksource *cs, unsigned int clock)
 137 {
 138         u64 temp;
 139         u32 shift;
 140
 141         /* Find a shift value */
 142         for (shift = 32; shift > 0; shift--) {
 143                 temp = (u64) NSEC_PER_SEC << shift;
 144                 do_div(temp, clock);
 145                 if ((temp >> 32) == 0)
 146                         break;
 147         }
 148         cs->shift = shift;
 149         cs->mult = (u32) temp;
 150 }
 151
 152 void __cpuinit clockevent_set_clock(struct clock_event_device *cd,
 153         unsigned int clock)
 154 {
 155         u64 temp;
 156         u32 shift;
 157
 158         /* Find a shift value */
 159         for (shift = 32; shift > 0; shift--) {
 160                 temp = (u64) clock << shift;
 161                 do_div(temp, NSEC_PER_SEC);
 162                 if ((temp >> 32) == 0)
 163                         break;
 164         }
 165         cd->shift = shift;
 166         cd->mult = (u32) temp;
 167 }
 168
 169 static void __init init_mips_clocksource(void)
 170 {
 171         /* Calclate a somewhat reasonable rating value */
 172         clocksource_mips.rating = 200 + mips_hpt_frequency / 10000000;
 173
 174         clocksource_set_clock(&clocksource_mips, mips_hpt_frequency);
 175
 176         clocksource_register(&clocksource_mips);
 177 }
 178
 179 void __init __weak plat_time_init(void)
 180 {
 181 }
 182
 183 /*
 184  * This function exists in order to cause an error due to a duplicate
 185  * definition if platform code should have its own implementation.  The hook
 186  * to use instead is plat_time_init.  plat_time_init does not receive the
 187  * irqaction pointer argument anymore.  This is because any function which
 188  * initializes an interrupt timer now takes care of its own request_irq rsp.
 189  * setup_irq calls and each clock_event_device should use its own
 190  * struct irqrequest.
 191  */
 192 void __init plat_timer_setup(void)
 193 {
 194         BUG();
 195 }
 196
 197 void __init time_init(void)
 198 {
 199         plat_time_init();
 200
 201         if (cpu_has_counter && (mips_hpt_frequency || mips_timer_state)) {
 202                 /* We know counter frequency.  Or we can get it.  */
 203                 if (!mips_hpt_frequency)
 204                         mips_hpt_frequency = calibrate_hpt();
 205
 206                 /* Report the high precision timer rate for a reference.  */
 207                 printk("Using %u.%03u MHz high precision timer.\n",
 208                        ((mips_hpt_frequency + 500) / 1000) / 1000,
 209                        ((mips_hpt_frequency + 500) / 1000) % 1000);
 210                 init_mips_clocksource();
 211         }
 212
 213         mips_clockevent_init();
 214 }