arch/arm26/kernel/time.c

   1 /*
   2  *  linux/arch/arm26/kernel/time.c
   3  *
   4  *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
   5  *  Modifications for ARM (C) 1994-2001 Russell King
   6  *  Mods for ARM26 (C) 2003 Ian Molton
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  *
  12  *  This file contains the ARM-specific time handling details:
  13  *  reading the RTC at bootup, etc...
  14  *
  15  *  1994-07-02  Alan Modra
  16  *              fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
  17  *  1998-12-20  Updated NTP code according to technical memorandum Jan '96
  18  *              "A Kernel Model for Precision Timekeeping" by Dave Mills
  19  */
  20
  21 #include <linux/module.h>
  22 #include <linux/kernel.h>
  23 #include <linux/interrupt.h>
  24 #include <linux/time.h>
  25 #include <linux/init.h>
  26 #include <linux/smp.h>
  27 #include <linux/timex.h>
  28 #include <linux/errno.h>
  29 #include <linux/profile.h>
  30
  31 #include <asm/hardware.h>
  32 #include <asm/io.h>
  33 #include <asm/irq.h>
  34 #include <asm/ioc.h>
  35
  36 /* this needs a better home */
  37 DEFINE_SPINLOCK(rtc_lock);
  38
  39 /* change this if you have some constant time drift */
  40 #define USECS_PER_JIFFY (1000000/HZ)
  41
  42 static int dummy_set_rtc(void)
  43 {
  44         return 0;
  45 }
  46
  47 /*
  48  * hook for setting the RTC's idea of the current time.
  49  */
  50 int (*set_rtc)(void) = dummy_set_rtc;
  51
  52 /*
  53  * Get time offset based on IOCs timer.
  54  * FIXME - if this is called with interrutps off, why the shennanigans
  55  * below ?
  56  */
  57 static unsigned long gettimeoffset(void)
  58 {
  59         unsigned int count1, count2, status;
  60         long offset;
  61
  62         ioc_writeb (0, IOC_T0LATCH);
  63         barrier ();
  64         count1 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
  65         barrier ();
  66         status = ioc_readb(IOC_IRQREQA);
  67         barrier ();
  68         ioc_writeb (0, IOC_T0LATCH);
  69         barrier ();
  70         count2 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
  71
  72         offset = count2;
  73         if (count2 < count1) {
  74                 /*
  75                  * We have not had an interrupt between reading count1
  76                  * and count2.
  77                  */
  78                 if (status & (1 << 5))
  79                         offset -= LATCH;
  80         } else if (count2 > count1) {
  81                 /*
  82                  * We have just had another interrupt between reading
  83                  * count1 and count2.
  84                  */
  85                 offset -= LATCH;
  86         }
  87
  88         offset = (LATCH - offset) * (tick_nsec / 1000);
  89         return (offset + LATCH/2) / LATCH;
  90 }
  91
  92 static unsigned long next_rtc_update;
  93
  94 /*
  95  * If we have an externally synchronized linux clock, then update
  96  * CMOS clock accordingly every ~11 minutes.  set_rtc() has to be
  97  * called as close as possible to 500 ms before the new second
  98  * starts.
  99  */
 100 static inline void do_set_rtc(void)
 101 {
 102         if (!ntp_synced() || set_rtc == NULL)
 103                 return;
 104
 105 //FIXME - timespec.tv_sec is a time_t not unsigned long
 106         if (next_rtc_update &&
 107             time_before((unsigned long)xtime.tv_sec, next_rtc_update))
 108                 return;
 109
 110         if (xtime.tv_nsec < 500000000 - ((unsigned) tick_nsec >> 1) &&
 111             xtime.tv_nsec >= 500000000 + ((unsigned) tick_nsec >> 1))
 112                 return;
 113
 114         if (set_rtc())
 115                 /*
 116                  * rtc update failed.  Try again in 60s
 117                  */
 118                 next_rtc_update = xtime.tv_sec + 60;
 119         else
 120                 next_rtc_update = xtime.tv_sec + 660;
 121 }
 122
 123 #define do_leds()
 124
 125 void do_gettimeofday(struct timeval *tv)
 126 {
 127         unsigned long flags;
 128         unsigned long seq;
 129         unsigned long usec, sec;
 130
 131         do {
 132                 seq = read_seqbegin_irqsave(&xtime_lock, flags);
 133                 usec = gettimeoffset();
 134                 sec = xtime.tv_sec;
 135                 usec += xtime.tv_nsec / 1000;
 136         } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
 137
 138         /* usec may have gone up a lot: be safe */
 139         while (usec >= 1000000) {
 140                 usec -= 1000000;
 141                 sec++;
 142         }
 143
 144         tv->tv_sec = sec;
 145         tv->tv_usec = usec;
 146 }
 147
 148 EXPORT_SYMBOL(do_gettimeofday);
 149
 150 int do_settimeofday(struct timespec *tv)
 151 {
 152         if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
 153                 return -EINVAL;
 154
 155         write_seqlock_irq(&xtime_lock);
 156         /*
 157          * This is revolting. We need to set "xtime" correctly. However, the
 158          * value in this location is the value at the most recent update of
 159          * wall time.  Discover what correction gettimeofday() would have
 160          * done, and then undo it!
 161          */
 162         tv->tv_nsec -= 1000 * gettimeoffset();
 163
 164         while (tv->tv_nsec < 0) {
 165                 tv->tv_nsec += NSEC_PER_SEC;
 166                 tv->tv_sec--;
 167         }
 168
 169         xtime.tv_sec = tv->tv_sec;
 170         xtime.tv_nsec = tv->tv_nsec;
 171         ntp_clear();
 172         write_sequnlock_irq(&xtime_lock);
 173         clock_was_set();
 174         return 0;
 175 }
 176
 177 EXPORT_SYMBOL(do_settimeofday);
 178
 179 static irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 180 {
 181         do_timer(1);
 182 #ifndef CONFIG_SMP
 183         update_process_times(user_mode(regs));
 184 #endif
 185         do_set_rtc(); //FIME - EVERY timer IRQ?
 186         profile_tick(CPU_PROFILING, regs);
 187         return IRQ_HANDLED; //FIXME - is this right?
 188 }
 189
 190 static struct irqaction timer_irq = {
 191         .name   = "timer",
 192         .flags  = IRQF_DISABLED,
 193         .handler = timer_interrupt,
 194 };
 195
 196 extern void ioctime_init(void);
 197
 198 /*
 199  * Set up timer interrupt.
 200  */
 201 void __init time_init(void)
 202 {
 203         ioc_writeb(LATCH & 255, IOC_T0LTCHL);
 204         ioc_writeb(LATCH >> 8, IOC_T0LTCHH);
 205         ioc_writeb(0, IOC_T0GO);
 206
 207
 208         setup_irq(IRQ_TIMER, &timer_irq);
 209 }
 210