arch/parisc/kernel/time.c

   1 /*
   2  *  linux/arch/parisc/kernel/time.c
   3  *
   4  *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
   5  *  Modifications for ARM (C) 1994, 1995, 1996,1997 Russell King
   6  *  Copyright (C) 1999 SuSE GmbH, (Philipp Rumpf, prumpf@tux.org)
   7  *
   8  * 1994-07-02  Alan Modra
   9  *             fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
  10  * 1998-12-20  Updated NTP code according to technical memorandum Jan '96
  11  *             "A Kernel Model for Precision Timekeeping" by Dave Mills
  12  */
  13 #include <linux/errno.h>
  14 #include <linux/module.h>
  15 #include <linux/sched.h>
  16 #include <linux/kernel.h>
  17 #include <linux/param.h>
  18 #include <linux/string.h>
  19 #include <linux/mm.h>
  20 #include <linux/interrupt.h>
  21 #include <linux/time.h>
  22 #include <linux/init.h>
  23 #include <linux/smp.h>
  24 #include <linux/profile.h>
  25
  26 #include <asm/uaccess.h>
  27 #include <asm/io.h>
  28 #include <asm/irq.h>
  29 #include <asm/param.h>
  30 #include <asm/pdc.h>
  31 #include <asm/led.h>
  32
  33 #include <linux/timex.h>
  34
  35 static unsigned long clocktick __read_mostly;   /* timer cycles per tick */
  36
  37 #ifdef CONFIG_SMP
  38 extern void smp_do_timer(struct pt_regs *regs);
  39 #endif
  40
  41 irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
  42 {
  43         unsigned long now;
  44         unsigned long next_tick;
  45         unsigned long cycles_elapsed;
  46         unsigned long cycles_remainder;
  47         unsigned int cpu = smp_processor_id();
  48
  49         /* gcc can optimize for "read-only" case with a local clocktick */
  50         unsigned long cpt = clocktick;
  51
  52         profile_tick(CPU_PROFILING, regs);
  53
  54         /* Initialize next_tick to the expected tick time. */
  55         next_tick = cpu_data[cpu].it_value;
  56
  57         /* Get current interval timer.
  58          * CR16 reads as 64 bits in CPU wide mode.
  59          * CR16 reads as 32 bits in CPU narrow mode.
  60          */
  61         now = mfctl(16);
  62
  63         cycles_elapsed = now - next_tick;
  64
  65         if ((cycles_elapsed >> 5) < cpt) {
  66                 /* use "cheap" math (add/subtract) instead
  67                  * of the more expensive div/mul method
  68                  */
  69                 cycles_remainder = cycles_elapsed;
  70                 while (cycles_remainder > cpt) {
  71                         cycles_remainder -= cpt;
  72                 }
  73         } else {
  74                 cycles_remainder = cycles_elapsed % cpt;
  75         }
  76
  77         /* Can we differentiate between "early CR16" (aka Scenario 1) and
  78          * "long delay" (aka Scenario 3)? I don't think so.
  79          *
  80          * We expected timer_interrupt to be delivered at least a few hundred
  81          * cycles after the IT fires. But it's arbitrary how much time passes
  82          * before we call it "late". I've picked one second.
  83          */
  84 /* aproximate HZ with shifts. Intended math is "(elapsed/clocktick) > HZ" */
  85 #if HZ == 1000
  86         if (cycles_elapsed > (cpt << 10) )
  87 #elif HZ == 250
  88         if (cycles_elapsed > (cpt << 8) )
  89 #elif HZ == 100
  90         if (cycles_elapsed > (cpt << 7) )
  91 #else
  92 #warn WTF is HZ set to anyway?
  93         if (cycles_elapsed > (HZ * cpt) )
  94 #endif
  95         {
  96                 /* Scenario 3: very long delay?  bad in any case */
  97                 printk (KERN_CRIT "timer_interrupt(CPU %d): delayed!"
  98                         " cycles %lX rem %lX "
  99                         " next/now %lX/%lX\n",
 100                         cpu,
 101                         cycles_elapsed, cycles_remainder,
 102                         next_tick, now );
 103         }
 104
 105         /* convert from "division remainder" to "remainder of clock tick" */
 106         cycles_remainder = cpt - cycles_remainder;
 107
 108         /* Determine when (in CR16 cycles) next IT interrupt will fire.
 109          * We want IT to fire modulo clocktick even if we miss/skip some.
 110          * But those interrupts don't in fact get delivered that regularly.
 111          */
 112         next_tick = now + cycles_remainder;
 113
 114         cpu_data[cpu].it_value = next_tick;
 115
 116         /* Skip one clocktick on purpose if we are likely to miss next_tick.
 117          * We want to avoid the new next_tick being less than CR16.
 118          * If that happened, itimer wouldn't fire until CR16 wrapped.
 119          * We'll catch the tick we missed on the tick after that.
 120          */
 121         if (!(cycles_remainder >> 13))
 122                 next_tick += cpt;
 123
 124         /* Program the IT when to deliver the next interrupt. */
 125         /* Only bottom 32-bits of next_tick are written to cr16.  */
 126         mtctl(next_tick, 16);
 127
 128
 129         /* Done mucking with unreliable delivery of interrupts.
 130          * Go do system house keeping.
 131          */
 132 #ifdef CONFIG_SMP
 133         smp_do_timer(regs);
 134 #else
 135         update_process_times(user_mode(regs));
 136 #endif
 137         if (cpu == 0) {
 138                 write_seqlock(&xtime_lock);
 139                 do_timer(regs);
 140                 write_sequnlock(&xtime_lock);
 141         }
 142
 143         /* check soft power switch status */
 144         if (cpu == 0 && !atomic_read(&power_tasklet.count))
 145                 tasklet_schedule(&power_tasklet);
 146
 147         return IRQ_HANDLED;
 148 }
 149
 150
 151 unsigned long profile_pc(struct pt_regs *regs)
 152 {
 153         unsigned long pc = instruction_pointer(regs);
 154
 155         if (regs->gr[0] & PSW_N)
 156                 pc -= 4;
 157
 158 #ifdef CONFIG_SMP
 159         if (in_lock_functions(pc))
 160                 pc = regs->gr[2];
 161 #endif
 162
 163         return pc;
 164 }
 165 EXPORT_SYMBOL(profile_pc);
 166
 167
 168 /*
 169  * Return the number of micro-seconds that elapsed since the last
 170  * update to wall time (aka xtime).  The xtime_lock
 171  * must be at least read-locked when calling this routine.
 172  */
 173 static inline unsigned long gettimeoffset (void)
 174 {
 175 #ifndef CONFIG_SMP
 176         /*
 177          * FIXME: This won't work on smp because jiffies are updated by cpu 0.
 178          *    Once parisc-linux learns the cr16 difference between processors,
 179          *    this could be made to work.
 180          */
 181         unsigned long now;
 182         unsigned long prev_tick;
 183         unsigned long next_tick;
 184         unsigned long elapsed_cycles;
 185         unsigned long usec;
 186         unsigned long cpuid = smp_processor_id();
 187         unsigned long cpt = clocktick;
 188
 189         next_tick = cpu_data[cpuid].it_value;
 190         now = mfctl(16);        /* Read the hardware interval timer.  */
 191
 192         prev_tick = next_tick - cpt;
 193
 194         /* Assume Scenario 1: "now" is later than prev_tick.  */
 195         elapsed_cycles = now - prev_tick;
 196
 197 /* aproximate HZ with shifts. Intended math is "(elapsed/clocktick) > HZ" */
 198 #if HZ == 1000
 199         if (elapsed_cycles > (cpt << 10) )
 200 #elif HZ == 250
 201         if (elapsed_cycles > (cpt << 8) )
 202 #elif HZ == 100
 203         if (elapsed_cycles > (cpt << 7) )
 204 #else
 205 #warn WTF is HZ set to anyway?
 206         if (elapsed_cycles > (HZ * cpt) )
 207 #endif
 208         {
 209                 /* Scenario 3: clock ticks are missing. */
 210                 printk (KERN_CRIT "gettimeoffset(CPU %ld): missing %ld ticks!"
 211                         " cycles %lX prev/now/next %lX/%lX/%lX  clock %lX\n",
 212                         cpuid, elapsed_cycles / cpt,
 213                         elapsed_cycles, prev_tick, now, next_tick, cpt);
 214         }
 215
 216         /* FIXME: Can we improve the precision? Not with PAGE0. */
 217         usec = (elapsed_cycles * 10000) / PAGE0->mem_10msec;
 218
 219         /* add in "lost" jiffies */
 220         usec += cpt * (jiffies - wall_jiffies);
 221         return usec;
 222 #else
 223         return 0;
 224 #endif
 225 }
 226
 227 void
 228 do_gettimeofday (struct timeval *tv)
 229 {
 230         unsigned long flags, seq, usec, sec;
 231
 232         /* Hold xtime_lock and adjust timeval.  */
 233         do {
 234                 seq = read_seqbegin_irqsave(&xtime_lock, flags);
 235                 usec = gettimeoffset();
 236                 sec = xtime.tv_sec;
 237                 usec += (xtime.tv_nsec / 1000);
 238         } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
 239
 240         /* Move adjusted usec's into sec's.  */
 241         while (usec >= USEC_PER_SEC) {
 242                 usec -= USEC_PER_SEC;
 243                 ++sec;
 244         }
 245
 246         /* Return adjusted result.  */
 247         tv->tv_sec = sec;
 248         tv->tv_usec = usec;
 249 }
 250
 251 EXPORT_SYMBOL(do_gettimeofday);
 252
 253 int
 254 do_settimeofday (struct timespec *tv)
 255 {
 256         time_t wtm_sec, sec = tv->tv_sec;
 257         long wtm_nsec, nsec = tv->tv_nsec;
 258
 259         if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
 260                 return -EINVAL;
 261
 262         write_seqlock_irq(&xtime_lock);
 263         {
 264                 /*
 265                  * This is revolting. We need to set "xtime"
 266                  * correctly. However, the value in this location is
 267                  * the value at the most recent update of wall time.
 268                  * Discover what correction gettimeofday would have
 269                  * done, and then undo it!
 270                  */
 271                 nsec -= gettimeoffset() * 1000;
 272
 273                 wtm_sec  = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
 274                 wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
 275
 276                 set_normalized_timespec(&xtime, sec, nsec);
 277                 set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
 278
 279                 ntp_clear();
 280         }
 281         write_sequnlock_irq(&xtime_lock);
 282         clock_was_set();
 283         return 0;
 284 }
 285 EXPORT_SYMBOL(do_settimeofday);
 286
 287 /*
 288  * XXX: We can do better than this.
 289  * Returns nanoseconds
 290  */
 291
 292 unsigned long long sched_clock(void)
 293 {
 294         return (unsigned long long)jiffies * (1000000000 / HZ);
 295 }
 296
 297
 298 void __init start_cpu_itimer(void)
 299 {
 300         unsigned int cpu = smp_processor_id();
 301         unsigned long next_tick = mfctl(16) + clocktick;
 302
 303         mtctl(next_tick, 16);           /* kick off Interval Timer (CR16) */
 304
 305         cpu_data[cpu].it_value = next_tick;
 306 }
 307
 308 void __init time_init(void)
 309 {
 310         static struct pdc_tod tod_data;
 311
 312         clocktick = (100 * PAGE0->mem_10msec) / HZ;
 313
 314         start_cpu_itimer();     /* get CPU 0 started */
 315
 316         if(pdc_tod_read(&tod_data) == 0) {
 317                 write_seqlock_irq(&xtime_lock);
 318                 xtime.tv_sec = tod_data.tod_sec;
 319                 xtime.tv_nsec = tod_data.tod_usec * 1000;
 320                 set_normalized_timespec(&wall_to_monotonic,
 321                                         -xtime.tv_sec, -xtime.tv_nsec);
 322                 write_sequnlock_irq(&xtime_lock);
 323         } else {
 324                 printk(KERN_ERR "Error reading tod clock\n");
 325                 xtime.tv_sec = 0;
 326                 xtime.tv_nsec = 0;
 327         }
 328 }
 329