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/smtc_ipi.h>
  30 #include <asm/time.h>
  31
  32 /*
  33  * forward reference
  34  */
  35 DEFINE_SPINLOCK(rtc_lock);
  36 EXPORT_SYMBOL(rtc_lock);
  37
  38 int __weak rtc_mips_set_time(unsigned long sec)
  39 {
  40         return 0;
  41 }
  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 static int null_perf_irq(void)
  54 {
  55         return 0;
  56 }
  57
  58 int (*perf_irq)(void) = null_perf_irq;
  59
  60 EXPORT_SYMBOL(perf_irq);
  61
  62 /*
  63  * time_init() - it does the following things.
  64  *
  65  * 1) plat_time_init() -
  66  *      a) (optional) set up RTC routines,
  67  *      b) (optional) calibrate and set the mips_hpt_frequency
  68  *          (only needed if you intended to use cpu counter as timer interrupt
  69  *           source)
  70  * 2) calculate a couple of cached variables for later usage
  71  */
  72
  73 unsigned int mips_hpt_frequency;
  74
  75 /*
  76  * This function exists in order to cause an error due to a duplicate
  77  * definition if platform code should have its own implementation.  The hook
  78  * to use instead is plat_time_init.  plat_time_init does not receive the
  79  * irqaction pointer argument anymore.  This is because any function which
  80  * initializes an interrupt timer now takes care of its own request_irq rsp.
  81  * setup_irq calls and each clock_event_device should use its own
  82  * struct irqrequest.
  83  */
  84 void __init plat_timer_setup(void)
  85 {
  86         BUG();
  87 }
  88
  89 static __init int cpu_has_mfc0_count_bug(void)
  90 {
  91         switch (current_cpu_type()) {
  92         case CPU_R4000PC:
  93         case CPU_R4000SC:
  94         case CPU_R4000MC:
  95                 /*
  96                  * V3.0 is documented as suffering from the mfc0 from count bug.
  97                  * Afaik this is the last version of the R4000.  Later versions
  98                  * were marketed as R4400.
  99                  */
 100                 return 1;
 101
 102         case CPU_R4400PC:
 103         case CPU_R4400SC:
 104         case CPU_R4400MC:
 105                 /*
 106                  * The published errata for the R4400 up to 3.0 say the CPU
 107                  * has the mfc0 from count bug.
 108                  */
 109                 if ((current_cpu_data.processor_id & 0xff) <= 0x30)
 110                         return 1;
 111
 112                 /*
 113                  * we assume newer revisions are ok
 114                  */
 115                 return 0;
 116         }
 117
 118         return 0;
 119 }
 120
 121 void __init time_init(void)
 122 {
 123         plat_time_init();
 124
 125         /*
 126          * The use of the R4k timer as a clock event takes precedence;
 127          * if reading the Count register might interfere with the timer
 128          * interrupt, then we don't use the timer as a clock source.
 129          * We may still use the timer as a clock source though if the
 130          * timer interrupt isn't reliable; the interference doesn't
 131          * matter then, because we don't use the interrupt.
 132          */
 133         if (mips_clockevent_init() != 0 || !cpu_has_mfc0_count_bug())
 134                 init_mips_clocksource();
 135 }