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. See
   7  * Documentation/mips/time.README.
   8  *
   9  * This program is free software; you can redistribute  it and/or modify it
  10  * under  the terms of  the GNU General  Public License as published by the
  11  * Free Software Foundation;  either version 2 of the  License, or (at your
  12  * option) any later version.
  13  */
  14 #include <linux/bug.h>
  15 #include <linux/clockchips.h>
  16 #include <linux/types.h>
  17 #include <linux/kernel.h>
  18 #include <linux/init.h>
  19 #include <linux/sched.h>
  20 #include <linux/param.h>
  21 #include <linux/profile.h>
  22 #include <linux/time.h>
  23 #include <linux/timex.h>
  24 #include <linux/smp.h>
  25 #include <linux/kernel_stat.h>
  26 #include <linux/spinlock.h>
  27 #include <linux/interrupt.h>
  28 #include <linux/module.h>
  29 #include <linux/kallsyms.h>
  30
  31 #include <asm/bootinfo.h>
  32 #include <asm/cache.h>
  33 #include <asm/compiler.h>
  34 #include <asm/cpu.h>
  35 #include <asm/cpu-features.h>
  36 #include <asm/div64.h>
  37 #include <asm/sections.h>
  38 #include <asm/smtc_ipi.h>
  39 #include <asm/time.h>
  40
  41 #include <irq.h>
  42
  43 /*
  44  * forward reference
  45  */
  46 DEFINE_SPINLOCK(rtc_lock);
  47 EXPORT_SYMBOL(rtc_lock);
  48
  49 int __weak rtc_mips_set_time(unsigned long sec)
  50 {
  51         return 0;
  52 }
  53 EXPORT_SYMBOL(rtc_mips_set_time);
  54
  55 int __weak rtc_mips_set_mmss(unsigned long nowtime)
  56 {
  57         return rtc_mips_set_time(nowtime);
  58 }
  59
  60 int update_persistent_clock(struct timespec now)
  61 {
  62         return rtc_mips_set_mmss(now.tv_sec);
  63 }
  64
  65 /*
  66  * Null high precision timer functions for systems lacking one.
  67  */
  68 static cycle_t null_hpt_read(void)
  69 {
  70         return 0;
  71 }
  72
  73 /*
  74  * High precision timer functions for a R4k-compatible timer.
  75  */
  76 static cycle_t c0_hpt_read(void)
  77 {
  78         return read_c0_count();
  79 }
  80
  81 int (*mips_timer_state)(void);
  82
  83 /*
  84  * local_timer_interrupt() does profiling and process accounting
  85  * on a per-CPU basis.
  86  *
  87  * In UP mode, it is invoked from the (global) timer_interrupt.
  88  *
  89  * In SMP mode, it might invoked by per-CPU timer interrupt, or
  90  * a broadcasted inter-processor interrupt which itself is triggered
  91  * by the global timer interrupt.
  92  */
  93 void local_timer_interrupt(int irq, void *dev_id)
  94 {
  95         profile_tick(CPU_PROFILING);
  96         update_process_times(user_mode(get_irq_regs()));
  97 }
  98
  99 int null_perf_irq(void)
 100 {
 101         return 0;
 102 }
 103
 104 EXPORT_SYMBOL(null_perf_irq);
 105
 106 int (*perf_irq)(void) = null_perf_irq;
 107
 108 EXPORT_SYMBOL(perf_irq);
 109
 110 /*
 111  * time_init() - it does the following things.
 112  *
 113  * 1) plat_time_init() -
 114  *      a) (optional) set up RTC routines,
 115  *      b) (optional) calibrate and set the mips_hpt_frequency
 116  *          (only needed if you intended to use cpu counter as timer interrupt
 117  *           source)
 118  * 2) calculate a couple of cached variables for later usage
 119  */
 120
 121 unsigned int mips_hpt_frequency;
 122
 123 static unsigned int __init calibrate_hpt(void)
 124 {
 125         cycle_t frequency, hpt_start, hpt_end, hpt_count, hz;
 126
 127         const int loops = HZ / 10;
 128         int log_2_loops = 0;
 129         int i;
 130
 131         /*
 132          * We want to calibrate for 0.1s, but to avoid a 64-bit
 133          * division we round the number of loops up to the nearest
 134          * power of 2.
 135          */
 136         while (loops > 1 << log_2_loops)
 137                 log_2_loops++;
 138         i = 1 << log_2_loops;
 139
 140         /*
 141          * Wait for a rising edge of the timer interrupt.
 142          */
 143         while (mips_timer_state());
 144         while (!mips_timer_state());
 145
 146         /*
 147          * Now see how many high precision timer ticks happen
 148          * during the calculated number of periods between timer
 149          * interrupts.
 150          */
 151         hpt_start = clocksource_mips.read();
 152         do {
 153                 while (mips_timer_state());
 154                 while (!mips_timer_state());
 155         } while (--i);
 156         hpt_end = clocksource_mips.read();
 157
 158         hpt_count = (hpt_end - hpt_start) & clocksource_mips.mask;
 159         hz = HZ;
 160         frequency = hpt_count * hz;
 161
 162         return frequency >> log_2_loops;
 163 }
 164
 165 struct clocksource clocksource_mips = {
 166         .name           = "MIPS",
 167         .mask           = CLOCKSOURCE_MASK(32),
 168         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 169 };
 170
 171 void __init clocksource_set_clock(struct clocksource *cs, unsigned int clock)
 172 {
 173         u64 temp;
 174         u32 shift;
 175
 176         /* Find a shift value */
 177         for (shift = 32; shift > 0; shift--) {
 178                 temp = (u64) NSEC_PER_SEC << shift;
 179                 do_div(temp, clock);
 180                 if ((temp >> 32) == 0)
 181                         break;
 182         }
 183         cs->shift = shift;
 184         cs->mult = (u32) temp;
 185 }
 186
 187 void __cpuinit clockevent_set_clock(struct clock_event_device *cd,
 188         unsigned int clock)
 189 {
 190         u64 temp;
 191         u32 shift;
 192
 193         /* Find a shift value */
 194         for (shift = 32; shift > 0; shift--) {
 195                 temp = (u64) clock << shift;
 196                 do_div(temp, NSEC_PER_SEC);
 197                 if ((temp >> 32) == 0)
 198                         break;
 199         }
 200         cd->shift = shift;
 201         cd->mult = (u32) temp;
 202 }
 203
 204 static void __init init_mips_clocksource(void)
 205 {
 206         if (!mips_hpt_frequency || clocksource_mips.read == null_hpt_read)
 207                 return;
 208
 209         /* Calclate a somewhat reasonable rating value */
 210         clocksource_mips.rating = 200 + mips_hpt_frequency / 10000000;
 211
 212         clocksource_set_clock(&clocksource_mips, mips_hpt_frequency);
 213
 214         clocksource_register(&clocksource_mips);
 215 }
 216
 217 void __init __weak plat_time_init(void)
 218 {
 219 }
 220
 221 /*
 222  * This function exists in order to cause an error due to a duplicate
 223  * definition if platform code should have its own implementation.  The hook
 224  * to use instead is plat_time_init.  plat_time_init does not receive the
 225  * irqaction pointer argument anymore.  This is because any function which
 226  * initializes an interrupt timer now takes care of its own request_irq rsp.
 227  * setup_irq calls and each clock_event_device should use its own
 228  * struct irqrequest.
 229  */
 230 void __init plat_timer_setup(struct irqaction *irq)
 231 {
 232         BUG();
 233 }
 234
 235 void __init time_init(void)
 236 {
 237         plat_time_init();
 238
 239         /* Choose appropriate high precision timer routines.  */
 240         if (!cpu_has_counter && !clocksource_mips.read)
 241                 /* No high precision timer -- sorry.  */
 242                 clocksource_mips.read = null_hpt_read;
 243         else if (!mips_hpt_frequency && !mips_timer_state) {
 244                 /* A high precision timer of unknown frequency.  */
 245                 if (!clocksource_mips.read)
 246                         /* No external high precision timer -- use R4k.  */
 247                         clocksource_mips.read = c0_hpt_read;
 248         } else {
 249                 /* We know counter frequency.  Or we can get it.  */
 250                 if (!clocksource_mips.read) {
 251                         /* No external high precision timer -- use R4k.  */
 252                         clocksource_mips.read = c0_hpt_read;
 253                 }
 254                 if (!mips_hpt_frequency)
 255                         mips_hpt_frequency = calibrate_hpt();
 256
 257                 /* Report the high precision timer rate for a reference.  */
 258                 printk("Using %u.%03u MHz high precision timer.\n",
 259                        ((mips_hpt_frequency + 500) / 1000) / 1000,
 260                        ((mips_hpt_frequency + 500) / 1000) % 1000);
 261         }
 262
 263         init_mips_clocksource();
 264         mips_clockevent_init();
 265 }