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