arch/ia64/kernel/time.c

   1 /*
   2  * linux/arch/ia64/kernel/time.c
   3  *
   4  * Copyright (C) 1998-2003 Hewlett-Packard Co
   5  *      Stephane Eranian <eranian@hpl.hp.com>
   6  *      David Mosberger <davidm@hpl.hp.com>
   7  * Copyright (C) 1999 Don Dugger <don.dugger@intel.com>
   8  * Copyright (C) 1999-2000 VA Linux Systems
   9  * Copyright (C) 1999-2000 Walt Drummond <drummond@valinux.com>
  10  */
  11
  12 #include <linux/cpu.h>
  13 #include <linux/init.h>
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/profile.h>
  17 #include <linux/sched.h>
  18 #include <linux/time.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/efi.h>
  21 #include <linux/timex.h>
  22 #include <linux/clocksource.h>
  23
  24 #include <asm/machvec.h>
  25 #include <asm/delay.h>
  26 #include <asm/hw_irq.h>
  27 #include <asm/ptrace.h>
  28 #include <asm/sal.h>
  29 #include <asm/sections.h>
  30 #include <asm/system.h>
  31
  32 #include "fsyscall_gtod_data.h"
  33
  34 static cycle_t itc_get_cycles(void);
  35
  36 struct fsyscall_gtod_data_t fsyscall_gtod_data = {
  37         .lock = SEQLOCK_UNLOCKED,
  38 };
  39
  40 struct itc_jitter_data_t itc_jitter_data;
  41
  42 volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
  43
  44 #ifdef CONFIG_IA64_DEBUG_IRQ
  45
  46 unsigned long last_cli_ip;
  47 EXPORT_SYMBOL(last_cli_ip);
  48
  49 #endif
  50
  51 static struct clocksource clocksource_itc = {
  52         .name           = "itc",
  53         .rating         = 350,
  54         .read           = itc_get_cycles,
  55         .mask           = CLOCKSOURCE_MASK(64),
  56         .mult           = 0, /*to be caluclated*/
  57         .shift          = 16,
  58         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  59 };
  60 static struct clocksource *itc_clocksource;
  61
  62 static irqreturn_t
  63 timer_interrupt (int irq, void *dev_id)
  64 {
  65         unsigned long new_itm;
  66
  67         if (unlikely(cpu_is_offline(smp_processor_id()))) {
  68                 return IRQ_HANDLED;
  69         }
  70
  71         platform_timer_interrupt(irq, dev_id);
  72
  73         new_itm = local_cpu_data->itm_next;
  74
  75         if (!time_after(ia64_get_itc(), new_itm))
  76                 printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
  77                        ia64_get_itc(), new_itm);
  78
  79         profile_tick(CPU_PROFILING);
  80
  81         while (1) {
  82                 update_process_times(user_mode(get_irq_regs()));
  83
  84                 new_itm += local_cpu_data->itm_delta;
  85
  86                 if (smp_processor_id() == time_keeper_id) {
  87                         /*
  88                          * Here we are in the timer irq handler. We have irqs locally
  89                          * disabled, but we don't know if the timer_bh is running on
  90                          * another CPU. We need to avoid to SMP race by acquiring the
  91                          * xtime_lock.
  92                          */
  93                         write_seqlock(&xtime_lock);
  94                         do_timer(1);
  95                         local_cpu_data->itm_next = new_itm;
  96                         write_sequnlock(&xtime_lock);
  97                 } else
  98                         local_cpu_data->itm_next = new_itm;
  99
 100                 if (time_after(new_itm, ia64_get_itc()))
 101                         break;
 102
 103                 /*
 104                  * Allow IPIs to interrupt the timer loop.
 105                  */
 106                 local_irq_enable();
 107                 local_irq_disable();
 108         }
 109
 110         do {
 111                 /*
 112                  * If we're too close to the next clock tick for
 113                  * comfort, we increase the safety margin by
 114                  * intentionally dropping the next tick(s).  We do NOT
 115                  * update itm.next because that would force us to call
 116                  * do_timer() which in turn would let our clock run
 117                  * too fast (with the potentially devastating effect
 118                  * of losing monotony of time).
 119                  */
 120                 while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
 121                         new_itm += local_cpu_data->itm_delta;
 122                 ia64_set_itm(new_itm);
 123                 /* double check, in case we got hit by a (slow) PMI: */
 124         } while (time_after_eq(ia64_get_itc(), new_itm));
 125         return IRQ_HANDLED;
 126 }
 127
 128 /*
 129  * Encapsulate access to the itm structure for SMP.
 130  */
 131 void
 132 ia64_cpu_local_tick (void)
 133 {
 134         int cpu = smp_processor_id();
 135         unsigned long shift = 0, delta;
 136
 137         /* arrange for the cycle counter to generate a timer interrupt: */
 138         ia64_set_itv(IA64_TIMER_VECTOR);
 139
 140         delta = local_cpu_data->itm_delta;
 141         /*
 142          * Stagger the timer tick for each CPU so they don't occur all at (almost) the
 143          * same time:
 144          */
 145         if (cpu) {
 146                 unsigned long hi = 1UL << ia64_fls(cpu);
 147                 shift = (2*(cpu - hi) + 1) * delta/hi/2;
 148         }
 149         local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
 150         ia64_set_itm(local_cpu_data->itm_next);
 151 }
 152
 153 static int nojitter;
 154
 155 static int __init nojitter_setup(char *str)
 156 {
 157         nojitter = 1;
 158         printk("Jitter checking for ITC timers disabled\n");
 159         return 1;
 160 }
 161
 162 __setup("nojitter", nojitter_setup);
 163
 164
 165 void __devinit
 166 ia64_init_itm (void)
 167 {
 168         unsigned long platform_base_freq, itc_freq;
 169         struct pal_freq_ratio itc_ratio, proc_ratio;
 170         long status, platform_base_drift, itc_drift;
 171
 172         /*
 173          * According to SAL v2.6, we need to use a SAL call to determine the platform base
 174          * frequency and then a PAL call to determine the frequency ratio between the ITC
 175          * and the base frequency.
 176          */
 177         status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
 178                                     &platform_base_freq, &platform_base_drift);
 179         if (status != 0) {
 180                 printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
 181         } else {
 182                 status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
 183                 if (status != 0)
 184                         printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
 185         }
 186         if (status != 0) {
 187                 /* invent "random" values */
 188                 printk(KERN_ERR
 189                        "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
 190                 platform_base_freq = 100000000;
 191                 platform_base_drift = -1;       /* no drift info */
 192                 itc_ratio.num = 3;
 193                 itc_ratio.den = 1;
 194         }
 195         if (platform_base_freq < 40000000) {
 196                 printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
 197                        platform_base_freq);
 198                 platform_base_freq = 75000000;
 199                 platform_base_drift = -1;
 200         }
 201         if (!proc_ratio.den)
 202                 proc_ratio.den = 1;     /* avoid division by zero */
 203         if (!itc_ratio.den)
 204                 itc_ratio.den = 1;      /* avoid division by zero */
 205
 206         itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
 207
 208         local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
 209         printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
 210                "ITC freq=%lu.%03luMHz", smp_processor_id(),
 211                platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
 212                itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
 213
 214         if (platform_base_drift != -1) {
 215                 itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
 216                 printk("+/-%ldppm\n", itc_drift);
 217         } else {
 218                 itc_drift = -1;
 219                 printk("\n");
 220         }
 221
 222         local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
 223         local_cpu_data->itc_freq = itc_freq;
 224         local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
 225         local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
 226                                         + itc_freq/2)/itc_freq;
 227
 228         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
 229 #ifdef CONFIG_SMP
 230                 /* On IA64 in an SMP configuration ITCs are never accurately synchronized.
 231                  * Jitter compensation requires a cmpxchg which may limit
 232                  * the scalability of the syscalls for retrieving time.
 233                  * The ITC synchronization is usually successful to within a few
 234                  * ITC ticks but this is not a sure thing. If you need to improve
 235                  * timer performance in SMP situations then boot the kernel with the
 236                  * "nojitter" option. However, doing so may result in time fluctuating (maybe
 237                  * even going backward) if the ITC offsets between the individual CPUs
 238                  * are too large.
 239                  */
 240                 if (!nojitter)
 241                         itc_jitter_data.itc_jitter = 1;
 242 #endif
 243         } else
 244                 /*
 245                  * ITC is drifty and we have not synchronized the ITCs in smpboot.c.
 246                  * ITC values may fluctuate significantly between processors.
 247                  * Clock should not be used for hrtimers. Mark itc as only
 248                  * useful for boot and testing.
 249                  *
 250                  * Note that jitter compensation is off! There is no point of
 251                  * synchronizing ITCs since they may be large differentials
 252                  * that change over time.
 253                  *
 254                  * The only way to fix this would be to repeatedly sync the
 255                  * ITCs. Until that time we have to avoid ITC.
 256                  */
 257                 clocksource_itc.rating = 50;
 258
 259         /* Setup the CPU local timer tick */
 260         ia64_cpu_local_tick();
 261
 262         if (!itc_clocksource) {
 263                 /* Sort out mult/shift values: */
 264                 clocksource_itc.mult =
 265                         clocksource_hz2mult(local_cpu_data->itc_freq,
 266                                                 clocksource_itc.shift);
 267                 clocksource_register(&clocksource_itc);
 268                 itc_clocksource = &clocksource_itc;
 269         }
 270 }
 271
 272 static cycle_t itc_get_cycles(void)
 273 {
 274         u64 lcycle, now, ret;
 275
 276         if (!itc_jitter_data.itc_jitter)
 277                 return get_cycles();
 278
 279         lcycle = itc_jitter_data.itc_lastcycle;
 280         now = get_cycles();
 281         if (lcycle && time_after(lcycle, now))
 282                 return lcycle;
 283
 284         /*
 285          * Keep track of the last timer value returned.
 286          * In an SMP environment, you could lose out in contention of
 287          * cmpxchg. If so, your cmpxchg returns new value which the
 288          * winner of contention updated to. Use the new value instead.
 289          */
 290         ret = cmpxchg(&itc_jitter_data.itc_lastcycle, lcycle, now);
 291         if (unlikely(ret != lcycle))
 292                 return ret;
 293
 294         return now;
 295 }
 296
 297
 298 static struct irqaction timer_irqaction = {
 299         .handler =      timer_interrupt,
 300         .flags =        IRQF_DISABLED | IRQF_IRQPOLL,
 301         .name =         "timer"
 302 };
 303
 304 void __devinit ia64_disable_timer(void)
 305 {
 306         ia64_set_itv(1 << 16);
 307 }
 308
 309 void __init
 310 time_init (void)
 311 {
 312         register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
 313         efi_gettimeofday(&xtime);
 314         ia64_init_itm();
 315
 316         /*
 317          * Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
 318          * tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
 319          */
 320         set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
 321 }
 322
 323 /*
 324  * Generic udelay assumes that if preemption is allowed and the thread
 325  * migrates to another CPU, that the ITC values are synchronized across
 326  * all CPUs.
 327  */
 328 static void
 329 ia64_itc_udelay (unsigned long usecs)
 330 {
 331         unsigned long start = ia64_get_itc();
 332         unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;
 333
 334         while (time_before(ia64_get_itc(), end))
 335                 cpu_relax();
 336 }
 337
 338 void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;
 339
 340 void
 341 udelay (unsigned long usecs)
 342 {
 343         (*ia64_udelay)(usecs);
 344 }
 345 EXPORT_SYMBOL(udelay);
 346
 347 /* IA64 doesn't cache the timezone */
 348 void update_vsyscall_tz(void)
 349 {
 350 }
 351
 352 void update_vsyscall(struct timespec *wall, struct clocksource *c)
 353 {
 354         unsigned long flags;
 355
 356         write_seqlock_irqsave(&fsyscall_gtod_data.lock, flags);
 357
 358         /* copy fsyscall clock data */
 359         fsyscall_gtod_data.clk_mask = c->mask;
 360         fsyscall_gtod_data.clk_mult = c->mult;
 361         fsyscall_gtod_data.clk_shift = c->shift;
 362         fsyscall_gtod_data.clk_fsys_mmio = c->fsys_mmio;
 363         fsyscall_gtod_data.clk_cycle_last = c->cycle_last;
 364
 365         /* copy kernel time structures */
 366         fsyscall_gtod_data.wall_time.tv_sec = wall->tv_sec;
 367         fsyscall_gtod_data.wall_time.tv_nsec = wall->tv_nsec;
 368         fsyscall_gtod_data.monotonic_time.tv_sec = wall_to_monotonic.tv_sec
 369                                                         + wall->tv_sec;
 370         fsyscall_gtod_data.monotonic_time.tv_nsec = wall_to_monotonic.tv_nsec
 371                                                         + wall->tv_nsec;
 372
 373         /* normalize */
 374         while (fsyscall_gtod_data.monotonic_time.tv_nsec >= NSEC_PER_SEC) {
 375                 fsyscall_gtod_data.monotonic_time.tv_nsec -= NSEC_PER_SEC;
 376                 fsyscall_gtod_data.monotonic_time.tv_sec++;
 377         }
 378
 379         write_sequnlock_irqrestore(&fsyscall_gtod_data.lock, flags);
 380 }
 381