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/config.h>
  22 #include <linux/module.h>
  23 #include <linux/kernel.h>
  24 #include <linux/interrupt.h>
  25 #include <linux/time.h>
  26 #include <linux/init.h>
  27 #include <linux/smp.h>
  28 #include <linux/timex.h>
  29 #include <linux/errno.h>
  30 #include <linux/profile.h>
  31
  32 #include <asm/hardware.h>
  33 #include <asm/io.h>
  34 #include <asm/irq.h>
  35 #include <asm/ioc.h>
  36
  37 u64 jiffies_64 = INITIAL_JIFFIES;
  38
  39 EXPORT_SYMBOL(jiffies_64);
  40
  41 extern unsigned long wall_jiffies;
  42
  43 /* this needs a better home */
  44 DEFINE_SPINLOCK(rtc_lock);
  45
  46 /* change this if you have some constant time drift */
  47 #define USECS_PER_JIFFY (1000000/HZ)
  48
  49 static int dummy_set_rtc(void)
  50 {
  51         return 0;
  52 }
  53
  54 /*
  55  * hook for setting the RTC's idea of the current time.
  56  */
  57 int (*set_rtc)(void) = dummy_set_rtc;
  58
  59 /*
  60  * Get time offset based on IOCs timer.
  61  * FIXME - if this is called with interrutps off, why the shennanigans
  62  * below ?
  63  */
  64 static unsigned long gettimeoffset(void)
  65 {
  66         unsigned int count1, count2, status;
  67         long offset;
  68
  69         ioc_writeb (0, IOC_T0LATCH);
  70         barrier ();
  71         count1 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
  72         barrier ();
  73         status = ioc_readb(IOC_IRQREQA);
  74         barrier ();
  75         ioc_writeb (0, IOC_T0LATCH);
  76         barrier ();
  77         count2 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
  78
  79         offset = count2;
  80         if (count2 < count1) {
  81                 /*
  82                  * We have not had an interrupt between reading count1
  83                  * and count2.
  84                  */
  85                 if (status & (1 << 5))
  86                         offset -= LATCH;
  87         } else if (count2 > count1) {
  88                 /*
  89                  * We have just had another interrupt between reading
  90                  * count1 and count2.
  91                  */
  92                 offset -= LATCH;
  93         }
  94
  95         offset = (LATCH - offset) * (tick_nsec / 1000);
  96         return (offset + LATCH/2) / LATCH;
  97 }
  98
  99 /*
 100  * Scheduler clock - returns current time in nanosec units.
 101  */
 102 unsigned long long sched_clock(void)
 103 {
 104         return (unsigned long long)jiffies * (1000000000 / HZ);
 105 }
 106
 107 static unsigned long next_rtc_update;
 108
 109 /*
 110  * If we have an externally synchronized linux clock, then update
 111  * CMOS clock accordingly every ~11 minutes.  set_rtc() has to be
 112  * called as close as possible to 500 ms before the new second
 113  * starts.
 114  */
 115 static inline void do_set_rtc(void)
 116 {
 117         if (!ntp_synced() || set_rtc == NULL)
 118                 return;
 119
 120 //FIXME - timespec.tv_sec is a time_t not unsigned long
 121         if (next_rtc_update &&
 122             time_before((unsigned long)xtime.tv_sec, next_rtc_update))
 123                 return;
 124
 125         if (xtime.tv_nsec < 500000000 - ((unsigned) tick_nsec >> 1) &&
 126             xtime.tv_nsec >= 500000000 + ((unsigned) tick_nsec >> 1))
 127                 return;
 128
 129         if (set_rtc())
 130                 /*
 131                  * rtc update failed.  Try again in 60s
 132                  */
 133                 next_rtc_update = xtime.tv_sec + 60;
 134         else
 135                 next_rtc_update = xtime.tv_sec + 660;
 136 }
 137
 138 #define do_leds()
 139
 140 void do_gettimeofday(struct timeval *tv)
 141 {
 142         unsigned long flags;
 143         unsigned long seq;
 144         unsigned long usec, sec, lost;
 145
 146         do {
 147                 seq = read_seqbegin_irqsave(&xtime_lock, flags);
 148                 usec = gettimeoffset();
 149
 150                 lost = jiffies - wall_jiffies;
 151                 if (lost)
 152                         usec += lost * USECS_PER_JIFFY;
 153
 154                 sec = xtime.tv_sec;
 155                 usec += xtime.tv_nsec / 1000;
 156         } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
 157
 158         /* usec may have gone up a lot: be safe */
 159         while (usec >= 1000000) {
 160                 usec -= 1000000;
 161                 sec++;
 162         }
 163
 164         tv->tv_sec = sec;
 165         tv->tv_usec = usec;
 166 }
 167
 168 EXPORT_SYMBOL(do_gettimeofday);
 169
 170 int do_settimeofday(struct timespec *tv)
 171 {
 172         if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
 173                 return -EINVAL;
 174
 175         write_seqlock_irq(&xtime_lock);
 176         /*
 177          * This is revolting. We need to set "xtime" correctly. However, the
 178          * value in this location is the value at the most recent update of
 179          * wall time.  Discover what correction gettimeofday() would have
 180          * done, and then undo it!
 181          */
 182         tv->tv_nsec -= 1000 * (gettimeoffset() +
 183                         (jiffies - wall_jiffies) * USECS_PER_JIFFY);
 184
 185         while (tv->tv_nsec < 0) {
 186                 tv->tv_nsec += NSEC_PER_SEC;
 187                 tv->tv_sec--;
 188         }
 189
 190         xtime.tv_sec = tv->tv_sec;
 191         xtime.tv_nsec = tv->tv_nsec;
 192         ntp_clear();
 193         write_sequnlock_irq(&xtime_lock);
 194         clock_was_set();
 195         return 0;
 196 }
 197
 198 EXPORT_SYMBOL(do_settimeofday);
 199
 200 static irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 201 {
 202         do_timer(regs);
 203 #ifndef CONFIG_SMP
 204         update_process_times(user_mode(regs));
 205 #endif
 206         do_set_rtc(); //FIME - EVERY timer IRQ?
 207         profile_tick(CPU_PROFILING, regs);
 208         return IRQ_HANDLED; //FIXME - is this right?
 209 }
 210
 211 static struct irqaction timer_irq = {
 212         .name   = "timer",
 213         .flags  = SA_INTERRUPT,
 214         .handler = timer_interrupt,
 215 };
 216
 217 extern void ioctime_init(void);
 218
 219 /*
 220  * Set up timer interrupt.
 221  */
 222 void __init time_init(void)
 223 {
 224         ioc_writeb(LATCH & 255, IOC_T0LTCHL);
 225         ioc_writeb(LATCH >> 8, IOC_T0LTCHH);
 226         ioc_writeb(0, IOC_T0GO);
 227
 228
 229         setup_irq(IRQ_TIMER, &timer_irq);
 230 }
 231